Bio

Bio


Branimir I. (Brandy) Sikic, M. D., is Professor of Medicine in the Division of Oncology at Stanford University School of Medicine. He is Co-director of the Stanford University Center for Clinical and Translational Education and Research (Spectrum) and Director of the Stanford Clinical and Translational Research Unit (CTRU). He received his undergraduate education at Georgetown University, and an M. D. from the University of Chicago. He returned to Georgetown for his residency in internal medicine, and performed a research fellowship in cancer pharmacology at the National Cancer Institute and in medical oncology at Georgetown prior to his appointment to the Stanford University faculty in 1979. He has authored more than 230 publications, edited two books, and is the inventor of two U.S. patents. He has served on several advisory committees of the National Institutes of Health, including as chairman of the Experimental Therapeutics I Study Section. In 2005-6 he chaired the Scientific Program Committee for the American Society of Clinical Oncology (ASCO), and in 2008-9 was co-chair of the Program Committee of the American Association for Cancer Research (AACR). In 2010 he was awarded the Katarina Zrinska medal for science and medicine by the president of Croatia. Dr. Sikic is a leader in the pharmacology of anticancer drugs and the development of new cancer therapies. His research spans the spectrum from molecular and genetic approaches in cancer cells to clinical trials in cancer patients. Dr. Sikic's laboratory studies mechanisms of drug resistance in cancer cells and the development of more effective cancer therapies. He has made major contributions to understanding the problem of multidrug resistance in cancer cells. Current molecular and genetic studies of drug resistance in cellular and murine models include epithelial to mesenchymal transition (EMT), tubulin dynamicity, IAP inhibitors, and the CCLS/CCR2 pathway. Active clinical trials of new anticancer drugs include kinase inhibitors, and antibodies activating the T-cell regulating CD27 pathway and the macrophage regulating CD47 pathway.

Clinical Focus


  • Cancer > Sarcoma
  • Medical Oncology
  • New Drug Studies

Academic Appointments


Administrative Appointments


  • Co-Director, Stanford Center for Clinical and Translational Education and Research, Stanford University (2008 - Present)
  • Director, Clinical and Translational Research Unit, Stanford University (2008 - Present)
  • Scientific Program Committee Chair, American Society of Clinical Oncology (2005 - 2006)

Honors & Awards


  • Presidential Medal for Science and Medicine, Government of Croatia (2010)
  • Statesman Award, American Society of Clinical Oncology (2010)
  • John H. Blaffer Visiting Professor, M.D. Anderson Cancer Center (2003)
  • Best Doctors in America, "Best Doctors" annual survey (2002-13)
  • Oncology Teaching Award, Oncology Division, Stanford (2000)
  • Plenary lecturer in drug resistanc e, Netherlands Cancer Institute (1999)
  • 70th Anniversary of the CRC lecture, British Association of Cancer Research (1993)
  • Pfizer Visiting Professor in Clinical Pharmacology, Dartmouth University (1992)

Professional Education


  • Fellowship:Georgetown University Hospital (1979) DC
  • Residency:Georgetown University Hospital (1975) DC
  • Board Recertification, Medical Oncology, American Board of Internal Medicine (2010)
  • Board Certification: Medical Oncology, American Board of Internal Medicine (1979)
  • Fellowship:National Cancer Institute (1978) MD
  • Board Certification: Internal Medicine, American Board of Internal Medicine (1975)
  • Internship:Georgetown University Hospital (1973) DC
  • Medical Education:University of Chicago School of Medicine (1972) IL
  • B.S., Georgetown University, Biology (1968)
  • M.D., University of Chicago, Medicine (1972)

Community and International Work


  • Central European Oncology Congress, Opatija, Croatia

    Topic

    Oncology continuing education

    Populations Served

    Central and Eastern Europe

    Location

    International

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    No

Research & Scholarship

Current Research and Scholarly Interests


Our goals are to understand mechanisms of drug resistance in cancer cells and to develop more effective therapies. Current research ranges from biochemical and molecular studies in cellular models to Phase I, II and III clinical trials of new inhibitors of drug resistance and novel therapies such as multi-targeted tyrosine kinase inhibitors and activators of TRAIL signaling. We are developing approaches to personalized therapies of ovarian cancer using biomarkers to select individualized treatments for patients.

Laboratory projects include studies of the multidrug transporter P-glycoprotein, regulation of the MDR1 gene, the role of beta tubulin gene expression in resistance to taxanes and vinca alkaloids, and the use of gene expression profiling in discovering molecular and genetic determinants of outcomes in cancer treatment in various cancers, particularly ovarian, colorectal, and acute myeloid leukemias.

Clinical investigations include the prognostic significance of resistance gene expression in cancers, pharmacokinetic consequences of MDR modulation, development of new modulators of drug resistance, and new targeted drugs, including kinase inhibitors and inhibitors of apoptosis. We are performing pharmacogenetic and pharmacogenomic studies to investigate determinants of response and toxicities in these patients.

Clinical Trials


  • Genome, Proteome and Tissue Microarray in Childhood Acute Leukemia Recruiting

    We will study gene and protein expression in leukemia cells of children diagnosed with acute leukemia. We hope to identify genes or proteins which can help us grade leukemia at diagnosis in order to: (a) develop better means of diagnosis and (b) more accurately choose the best therapy for each patient.

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  • Cisplatin and ZD1839 + Re-Irradiation in Recurrent Squamous Cell Cancer of the Head and Neck Not Recruiting

    To determine safety profile of the epidermal growth factor receptor (EGFR) antagonist, ZD1839 in combination with cisplatin and radiation therapy in patients with local-regional recurrent squamous cell cancer of the head and neck. To study the effects of ZD1839 combined with either cisplatin or radiotherapy on signal transduction pathway gene expression in tumor cells in patients with local-regional recurrent squamous cell cancer of the head and neck using micro array analysis from tumor samples taken at the time of relapse and during treatment.

    Stanford is currently not accepting patients for this trial. For more information, please contact Priscilla Wong, (650) 725 - 4777.

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  • coBRIM: A Phase 3 Study Comparing GDC-0973 (Cobimetinib), a MEK Inhibitor, in Combination With Vemurafenib vs Vemurafenib Alone in Patients With Metastatic Melanoma Not Recruiting

    This multicenter, randomized, double-blind, placebo-controlled phase 3 study will evaluate the safety and efficacy of vemurafenib alone and vemurafenib in combination with GDC-0973 (cobimetinib), a MEK inhibitor, in previously untreated BRAF V600 mutation-positive patients with unresectable locally advanced or metastatic melanoma. Patients will be randomized to one of two treatment arms, Arm A: vemurafenib 960 mg twice a day (days 1-28 of each cycle) and placebo (days 1-21 of each cycle); Arm B: vemurafenib 960 mg twice a day (days 1-28 of each cycle) and GDC-0973 (cobimetinib) 60 mg once daily (days 1-21 of each cycle). Patients will receive treatment until disease progression, unacceptable toxicity or withdrawal of consent.

    Stanford is currently not accepting patients for this trial. For more information, please contact Jennifer Vargas, 650-723-0371.

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  • A Phase 1/2 Study of HKI-272 (Neratinib) in Combination With Paclitaxel (Taxol) in Subjects With Solid Tumors and Breast Cancer Not Recruiting

    The purpose of this study is to learn whether it is safe and effective to administer HKI-272 (neratinib) in combination with paclitaxel in patients with breast cancer.

    Stanford is currently not accepting patients for this trial. For more information, please contact Mary Chen, (650) 723 - 8686.

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  • A Study of CDX-1127 in Patients With Select Solid Tumor Types or Hematologic Cancers Recruiting

    This is a study of CDX-1127, a therapy that targets the immune system and may act to promote anti-cancer effects. The study enrolls patients with hematologic cancers (certain leukemias and lymphomas), as well as patients with select types of solid tumors.

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  • A Phase 1 Study of MPDL3280A (an Engineered Anti-PDL1 Antibody) in Patients With Locally Advanced or Metastatic Solid Tumors Not Recruiting

    This Phase I, multicenter, first in human, open-label, dose escalation study will evaluate the safety, tolerability, and pharmacokinetics of MPDL3280A administered as single agent by intravenous (IV) infusion to patients with locally advanced or metastatic solid malignancies or hematologic malignancies.

    Stanford is currently not accepting patients for this trial. For more information, please contact Rajapaksa Amanda, 650-725-6301.

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  • BRIM8: A Study of Vemurafenib Adjuvant Therapy in Patients With Resected Cutaneous BRAF Mutant Melanoma Recruiting

    This multi-center, randomized, double-blind, placebo-controlled study will evaluate the efficacy and safety of vemurafenib in patients with completely resected, cutaneous BRAF-mutation positive melanoma at high risk for recurrence. Patients will be randomized to receive oral doses of vemurafenib 960 mg twice daily or matching placebo. The anticipated time on study treatment is 52 weeks.

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Teaching

2013-14 Courses


Publications

Journal Articles


  • Clinical trial designs for testing biomarker-based personalized therapies CLINICAL TRIALS Lai, T. L., Lavori, P. W., Shih, M. I., Sikic, B. I. 2012; 9 (2): 141-154

    Abstract

    Advances in molecular therapeutics in the past decade have opened up new possibilities for treating cancer patients with personalized therapies, using biomarkers to determine which treatments are most likely to benefit them, but there are difficulties and unresolved issues in the development and validation of biomarker-based personalized therapies. We develop a new clinical trial design to address some of these issues. The goal is to capture the strengths of the frequentist and Bayesian approaches to address this problem in the recent literature and to circumvent their limitations.We use generalized likelihood ratio tests of the intersection null and enriched strategy null hypotheses to derive a novel clinical trial design for the problem of advancing promising biomarker-guided strategies toward eventual validation. We also investigate the usefulness of adaptive randomization (AR) and futility stopping proposed in the recent literature.Simulation studies demonstrate the advantages of testing both the narrowly focused enriched strategy null hypothesis related to validating a proposed strategy and the intersection null hypothesis that can accommodate to a potentially successful strategy. AR and early termination of ineffective treatments offer increased probability of receiving the preferred treatment and better response rates for patients in the trial, at the expense of more complicated inference under small-to-moderate total sample sizes and some reduction in power.The binary response used in the development phase may not be a reliable indicator of treatment benefit on long-term clinical outcomes. In the proposed design, the biomarker-guided strategy (BGS) is not compared to 'standard of care', such as physician's choice that may be informed by patient characteristics. Therefore, a positive result does not imply superiority of the BGS to 'standard of care'. The proposed design and tests are valid asymptotically. Simulations are used to examine small-to-moderate sample properties.Innovative clinical trial designs are needed to address the difficulties and issues in the development and validation of biomarker-based personalized therapies. The article shows the advantages of using likelihood inference and interim analysis to meet the challenges in the sample size needed and in the constantly evolving biomarker landscape and genomic and proteomic technologies.

    View details for DOI 10.1177/1740774512437252

    View details for Web of Science ID 000302636500001

    View details for PubMedID 22397801

  • NFKBIA Deletion in Glioblastomas. NEW ENGLAND JOURNAL OF MEDICINE Bredel, M., Scholtens, D. M., Yadav, A. K., Alvarez, A. A., Renfrow, J. J., Chandler, J. P., Yu, I. L., Carro, M. S., Dai, F., Tagge, M. J., Ferrarese, R., Bredel, C., Phillips, H. S., Lukac, P. J., Robe, P. A., Weyerbrock, A., Vogel, H., Dubner, S., Mobley, B., He, X., Scheck, A. C., Sikic, B. I., Aldape, K. D., Chakravarti, A., Harsh, G. R. 2011; 364 (7): 627-637

    Abstract

    Amplification and activating mutations of the epidermal growth factor receptor (EGFR) oncogene are molecular hallmarks of glioblastomas. We hypothesized that deletion of NFKBIA (encoding nuclear factor of ?-light polypeptide gene enhancer in B-cells inhibitor-?), an inhibitor of the EGFR-signaling pathway, promotes tumorigenesis in glioblastomas that do not have alterations of EGFR.We analyzed 790 human glioblastomas for deletions, mutations, or expression of NFKBIA and EGFR. We studied the tumor-suppressor activity of NFKBIA in tumor-cell culture. We compared the molecular results with the outcome of glioblastoma in 570 affected persons.NFKBIA is often deleted but not mutated in glioblastomas; most deletions occur in nonclassical subtypes of the disease. Deletion of NFKBIA and amplification of EGFR show a pattern of mutual exclusivity. Restoration of the expression of NFKBIA attenuated the malignant phenotype and increased the vulnerability to chemotherapy of cells cultured from tumors with NFKBIA deletion; it also reduced the viability of cells with EGFR amplification but not of cells with normal gene dosages of both NFKBIA and EGFR. Deletion and low expression of NFKBIA were associated with unfavorable outcomes. Patients who had tumors with NFKBIA deletion had outcomes that were similar to those in patients with tumors harboring EGFR amplification. These outcomes were poor as compared with the outcomes in patients with tumors that had normal gene dosages of NFKBIA and EGFR. A two-gene model that was based on expression of NFKBIA and O(6)-methylguanine DNA methyltransferase was strongly associated with the clinical course of the disease.Deletion of NFKBIA has an effect that is similar to the effect of EGFR amplification in the pathogenesis of glioblastoma and is associated with comparatively short survival.

    View details for DOI 10.1056/NEJMoa1006312

    View details for Web of Science ID 000287406000008

    View details for PubMedID 21175304

  • Expression and Silencing of the Microtubule-Associated Protein Tau in Breast Cancer Cells MOLECULAR CANCER THERAPEUTICS Spicakova, T., O'Brien, M. M., Duran, G. E., Sweet-Cordero, A., Sikic, B. I. 2010; 9 (11): 2970-2981

    Abstract

    The microtubule-associated protein Tau has been reported to be a predictive factor for clinical response to taxanes in metastatic breast cancer. We generated a panel of eight taxane-resistant variants from four human breast cancer cell lines (MCF-7, T-47D, MDA-MB-231, and BT-549). Four variants had higher levels of Tau compared with their T-47D and MDA-MB-231 parental cells. Using isoform-specific primers, we found that Tau 0N, 1N, 2N, 3R, and 4R isoforms are overexpressed in the resistant variants, as is Tau exon 6 but not exons 4A or 8. To determine whether Tau overexpression produces resistance to taxanes, we derived three independent T-47D clones stably overexpressing Tau 3R and 4R isoforms. Tau overexpression did not result in taxane resistance compared with parental cells transfected with vector alone. We then knocked down Tau expression in three cell lines that expressed Tau constitutively (MCF-7 and ZR-75-1 breast cancer cells, and OVCAR-3 ovarian cancer cells). Lentivirus-mediated silencing of Tau expression in MCF-7 and OVCAR-3 cells did not result in increased taxane sensitivity compared with luciferase short hairpin RNA-infected cells and uninfected parental cells. Transient silencing using Tau-specific small interfering RNAs also did not alter taxane sensitivity relative to nontargeting controls in both MCF-7 and ZR-75-1 cells. These results show that neither overexpression nor depletion of Tau modulates cellular sensitivity to taxanes. Although Tau overexpression has been reported to be a predictive marker of taxane resistance, it is not likely to be a direct mechanism of taxane resistance in breast cancer.

    View details for DOI 10.1158/1535-7163.MCT-10-0780

    View details for Web of Science ID 000283998200012

    View details for PubMedID 21062914

  • A Network Model of a Cooperative Genetic Landscape in Brain Tumors JAMA-JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION Bredel, M., Scholtens, D. M., Harsh, G. R., Bredel, C., Chandler, J. P., Renfrow, J. J., Yadav, A. K., Vogel, H., Scheck, A. C., Tibshirani, R., Sikic, B. I. 2009; 302 (3): 261-275

    Abstract

    Gliomas, particularly glioblastomas, are among the deadliest of human tumors. Gliomas emerge through the accumulation of recurrent chromosomal alterations, some of which target yet-to-be-discovered cancer genes. A persistent question concerns the biological basis for the coselection of these alterations during gliomagenesis.To describe a network model of a cooperative genetic landscape in gliomas and to evaluate its clinical relevance.Multidimensional genomic profiles and clinical profiles of 501 patients with gliomas (45 tumors in an initial discovery set collected between 2001 and 2004 and 456 tumors in validation sets made public between 2006 and 2008) from multiple academic centers in the United States and The Cancer Genome Atlas Pilot Project (TCGA).Identification of genes with coincident genetic alterations, correlated gene dosage and gene expression, and multiple functional interactions; association between those genes and patient survival.Gliomas select for a nonrandom genetic landscape-a consistent pattern of chromosomal alterations-that involves altered regions ("territories") on chromosomes 1p, 7, 8q, 9p, 10, 12q, 13q, 19q, 20, and 22q (false-discovery rate-corrected P<.05). A network model shows that these territories harbor genes with putative synergistic, tumor-promoting relationships. The coalteration of the most interactive of these genes in glioblastoma is associated with unfavorable patient survival. A multigene risk scoring model based on 7 landscape genes (POLD2, CYCS, MYC, AKR1C3, YME1L1, ANXA7, and PDCD4) is associated with the duration of overall survival in 189 glioblastoma samples from TCGA (global log-rank P = .02 comparing 3 survival curves for patients with 0-2, 3-4, and 5-7 dosage-altered genes). Groups of patients with 0 to 2 (low-risk group) and 5 to 7 (high-risk group) dosage-altered genes experienced 49.24 and 79.56 deaths per 100 person-years (hazard ratio [HR], 1.63; 95% confidence interval [CI], 1.10-2.40; Cox regression model P = .02), respectively. These associations with survival are validated using gene expression data in 3 independent glioma studies, comprising 76 (global log-rank P = .003; 47.89 vs 15.13 deaths per 100 person-years for high risk vs low risk; Cox model HR, 3.04; 95% CI, 1.49-6.20; P = .002) and 70 (global log-rank P = .008; 83.43 vs 16.14 deaths per 100 person-years for high risk vs low risk; HR, 3.86; 95% CI, 1.59-9.35; P = .003) high-grade gliomas and 191 glioblastomas (global log-rank P = .002; 83.23 vs 34.16 deaths per 100 person-years for high risk vs low risk; HR, 2.27; 95% CI, 1.44-3.58; P<.001).The alteration of multiple networking genes by recurrent chromosomal aberrations in gliomas deregulates critical signaling pathways through multiple, cooperative mechanisms. These mutations, which are likely due to nonrandom selection of a distinct genetic landscape during gliomagenesis, are associated with patient prognosis.

    View details for Web of Science ID 000267948100020

    View details for PubMedID 19602686

  • A Phase II Study of Gefitinib, 5-Fluorouracil, Leucovorin, and Oxaliplatin in Previously Untreated Patients with Metastatic Colorectal Cancer CLINICAL CANCER RESEARCH Fischer, G., Kuo, T., Ramsey, M., Schwartz, E., Rouse, R., Cho, C. D., Halsey, J., Sikic, B. I. 2008; 14 (21): 7074-7079

    Abstract

    We investigated the gefitinib, 5-fluorouracil (5-FU), leucovorin and oxaliplatin (IFOX) regimen as first-line therapy in patients with metastatic colorectal cancer.Eligible patients had stage IV colorectal adenocarcinoma, and had not received prior chemotherapy for metastatic disease. Each cycle consisted of 14 days. Cycle 1 consisted of oxaliplatin, leucovorin, and 5-FU (FOLFOX-4). All subsequent cycles consisted of FOLFOX-4 with gefitinib at 500 mg orally daily throughout the 14-day cycle.Forty-five patients were enrolled and were assessable for toxicity. Forty-three patients were assessable for response. Thirty-one of the 43 patients (72%) had either a complete or partial response by the Response Evaluation Criteria in Solid Tumors. Median overall survival was 20.5 months. Median time to progression was 9.3 months. Commonly encountered grade 3 or 4 toxicities included diarrhea in 67% of patients and neutropenia in 60%. Grade 2 acneiform skin rash typical of gefitinib occurred in 60% of patients.IFOX is an active first-line regimen in patients with metastatic colorectal adenocarcinoma, showing higher response rates but also increased toxicities compared with FOLFOX-4 alone in a similar patient population.

    View details for DOI 10.1158/1078-0432.CCR-08-1014

    View details for Web of Science ID 000260732200044

    View details for PubMedID 18981005

  • Differential gene expression patterns and interaction networks in BCR-ABL-positive and -negative adult acute lymphoblastic leukemias JOURNAL OF CLINICAL ONCOLOGY Juric, D., Lacayo, N. J., Ramsey, M. C., Racevskis, J., Wiernik, P. H., Rowe, J. M., Goldstone, A. H., O'Dwyer, P. J., Paietta, E., Sikic, B. I. 2007; 25 (11): 1341-1349

    Abstract

    To identify gene expression patterns and interaction networks related to BCR-ABL status and clinical outcome in adults with acute lymphoblastic leukemia (ALL).DNA microarrays were used to profile a set of 54 adult ALL specimens from the Medical Research Council UKALL XII/Eastern Cooperative Oncology Group E2993 trial (21 p185BCR-ABL-positive, 16 p210BCR-ABL-positive and 17 BCR-ABL-negative specimens).Using supervised and unsupervised analysis tools, we detected significant transcriptomic changes in BCR-ABL-positive versus -negative specimens, and assessed their validity in an independent cohort of 128 adult ALL specimens. This set of 271 differentially expressed genes (including GAB1, CIITA, XBP1, CD83, SERPINB9, PTP4A3, NOV, LOX, CTNND1, BAALC, and RAB21) is enriched for genes involved in cell death, cellular growth and proliferation, and hematologic system development and function. Network analysis demonstrated complex interaction patterns of these genes, and identified FYN and IL15 as the hubs of the top-scoring network. Within the BCR-ABL-positive subgroups, we identified genes overexpressed (PILRB, STS-1, SPRY1) or underexpressed (TSPAN16, ADAMTSL4) in p185BCR-ABL-positive ALL relative to p210BCR-ABL-positive ALL. Finally, we constructed a gene expression- and interaction-based outcome predictor consisting of 27 genes (including GRB2, GAB1, GLI1, IRS1, RUNX2, and SPP1), which correlated with overall survival in BCR-ABL-positive adult ALL (P = .0001), independent of age (P = .25) and WBC count at presentation (P = .003).We identified prominent molecular features of BCR-ABL-positive adult ALL, which may be useful for developing novel therapeutic targets and prognostic markers in this disease.

    View details for DOI 10.1200/JCO.2006.09.3534

    View details for Web of Science ID 000245851900009

    View details for PubMedID 17312329

  • Regional activation of chromosomal arm 7q with and without gene amplification in taxane-selected human ovarian cancer cell lines GENES CHROMOSOMES & CANCER Wang, Y. C., Juric, D., Francisco, B., Yu, R. X., Duran, G. E., Chen, G. K., Chen, X., Sikic, B. I. 2006; 45 (4): 365-374

    Abstract

    Taxanes are important drugs in the treatment of ovarian and other cancers, but their efficacy is limited by intrinsic and acquired drug resistance. Expression of the multidrug transporter P-glycoprotein, encoded by the MDR1 (ABCB1) gene, is one of the causes of clinical drug resistance to taxanes. To study the mechanisms of MDR1 activation related to taxanes, we established 11 multidrug-resistant variants from six ovarian cancer cell lines by continuous exposure to either paclitaxel or docetaxel. We profiled gene expression and gene copy number alterations in these cell lines using cDNA microarrays and identified a cluster of genes coactivated with MDR1 in 7q21.11-13. Regional activation was evident in nine resistant variants displaying a coexpression pattern of up to 22 genes over an 8-Mb area, including SRI, MGC4175, CLDN12, CROT, and CDK6. In six of these variants, regional activation was driven by gene copy number alterations, with low-level gains or high-level amplifications spanning the involved region. However, three variants displayed regional increases in gene expression even without concomitant gene copy number changes. These results suggest that regional gene activation may be a fundamental mechanism for acquired drug resistance, with or without changes in gene dosage. In addition to numerical and structural chromosomal changes driven by genome instability in cancer cells, other mechanisms might be involved in MDR1 regional activation, such as chromatin remodeling and DNA or histone modifications of the 7q21 region.

    View details for DOI 10.1002/gcc.20300

    View details for Web of Science ID 000235743400006

    View details for PubMedID 16382445

  • Phase I study of gefitinib, oxaliplatin, 5-fluorouracil, and leucovorin (IFOX) in patients with advanced solid malignancies INVESTIGATIONAL NEW DRUGS Cho, C. D., Fisher, G. A., Halsey, J., Sikic, B. I. 2006; 24 (2): 117-123

    Abstract

    Aphase 1 study of gefitinib in combination with oxaliplatin, 5-fluorouracil and leucovorin (IFOX)was conducted to evaluate the safety and feasibility of this regimen.Patients with advanced solid malignancies were treated with escalating doses of gefitinib (250 mg or 500 mg once daily) in combination with FOLFOX (oxaliplatin, 5-fluorouracil, and leucovorin). The initial dose of oxaliplatin was 70 mg/m2 with sequential dose escalation to 85 mg/m2.Sixteen patients received a total of 138 14-day courses of daily gefitinib in combination with FOLFOX. Escalation of gefitinib from 250 mg/d to 500 mg/d with FOLFOX was well-tolerated. In addition, no severe toxicities precluded subsequent dose escalation of oxaliplatin from 70 mg/m2 to 85 mg/m2 at which no dose-limiting toxicity was seen. No further dose escalation was performed as this represented the oxaliplatin dose administered in the standard FOLFOX-4 regimen. The most predominant toxicity was diarrhea, which was well controlled with oral antidiarrheal agents. Four partial remissions occurred in patients with metastatic colorectal cancer.Gefitinib as a 500 mg daily continuous dose was well tolerated in combination with full doses of FOLFOX-4.

    View details for DOI 10.1007/s10637-006-2032-7

    View details for Web of Science ID 000236793800003

    View details for PubMedID 16683204

  • Tumor necrosis factor-alpha-induced protein 3 as a putative regulator of nuclear factor-kappa B-mediated resistance to O-6-alkylating agents in human glioblastomas JOURNAL OF CLINICAL ONCOLOGY Bredel, M., Bredel, C., Juric, D., Duran, G. E., Yu, R. X., Harsh, G. R., Vogel, H., Recht, L. D., Scheck, A. C., Sikic, B. I. 2006; 24 (2): 274-287

    Abstract

    Pre-existing and acquired drug resistance are major obstacles to the successful treatment of glioblastomas.We used an integrated resistance model and genomics tools to globally explore molecular factors and cellular pathways mediating resistance to O6-alkylating agents in glioblastoma cells.We identified a transcriptomic signature that predicts a common in vitro and in vivo resistance phenotype to these agents, a proportion of which is imprinted recurrently by gene dosage changes in the resistant glioblastoma genome. This signature was highly enriched for genes with functions in cell death, compromise, and survival. Modularity was a predominant organizational principle of the signature, with functions being carried out by groups of interacting molecules in overlapping networks. A highly significant network was built around nuclear factor-kappaB (NF-kappaB), which included the persistent alterations of various NF-kappaB pathway elements. Tumor necrosis factor-alpha-induced protein 3 (TNFAIP3) was identified as a new regulatory component of a putative cytoplasmic signaling cascade that mediates NF-kappaB activation in response to DNA damage caused by O6-alkylating agents. Expression of the corresponding zinc finger protein A20 closely mirrored the expression of the TNFAIP3 transcript, and was inversely related to NF-kappaB activation status in the resistant cells. A prediction model based on the resistance signature enabled the subclassification of an independent, validation cohort of 31 glioblastomas into two outcome groups (P = .037) and revealed TNFAIP3 as part of an optimized four-gene predictor associated significantly with patient survival (P = .022).Our results offer strong evidence for TNFAIP3 as a key regulator of the cytoplasmic signaling to activate NF-kappaB en route to O6-alkylating agent resistance in glioblastoma cells. This pathway may be an attractive target for therapeutic modulation of glioblastomas.

    View details for DOI 10.1200/JCO.2005.02.9405

    View details for Web of Science ID 000234741700008

    View details for PubMedID 16365179

  • Gene expression profiling differentiates germ cell tumors from other cancers and defines subtype-specific signatures PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Juric, D., Sale, S., Hromas, R. A., Yu, R., Wang, Y., Duran, G. E., Tibshirari, R., Einhorn, L. H., Sikic, B. I. 2005; 102 (49): 17763-17768

    Abstract

    Germ cell tumors (GCTs) of the testis are the predominant cancer among young men. We analyzed gene expression profiles of 50 GCTs of various subtypes, and we compared them with 443 other common malignant tumors of epithelial, mesenchymal, and lymphoid origins. Significant differences in gene expression were found among major histological subtypes of GCTs, and between them and other malignancies. We identified 511 genes, belonging to several critical functional groups such as cell cycle progression, cell proliferation, and apoptosis, to be significantly differentially expressed in GCTs compared with other tumor types. Sixty-five genes were sufficient for the construction of a GCT class predictor of high predictive accuracy (100% training set, 96% test set), which might be useful in the diagnosis of tumors of unknown primary origin. Previously described diagnostic and prognostic markers were found to be expressed by the appropriate GCT subtype (AFP, POU5F1, POV1, CCND2, and KIT). Several additional differentially expressed genes were identified in teratomas (EGR1 and MMP7), yolk sac tumors (PTPN13 and FN1), and seminomas (NR6A1, DPPA4, and IRX1). Dynamic computation of interaction networks and mapping to existing pathways knowledge databases revealed a potential role of EGR1 in p21-induced cell cycle arrest and intrinsic chemotherapy resistance of mature teratomas.

    View details for DOI 10.1073/pnas.0509082102

    View details for Web of Science ID 000233849000041

    View details for PubMedID 16306258

  • Genetic and epigenetic modeling of the origins of multidrug-resistant cells in a human sarcoma cell line CANCER RESEARCH Chen, K. G., Wang, Y. C., Schaner, M. E., Francisco, B., Duran, G. E., Juric, D., Huff, L. M., Padilla-Nash, H., Ried, T., Fojo, T., Sikic, B. I. 2005; 65 (20): 9388-9397

    Abstract

    The origin of drug-resistant cells in human cancers has been a fundamental problem of cancer pharmacology. Two major contrasting hypotheses (genetics versus epigenetics) have been proposed to elucidate the mechanisms of acquired drug resistance. In this study, we answer these fundamental questions through investigation of the genetic and epigenetic pathways that control the origin of ABCB1 (MDR1) gene activation with acquired multidrug resistance in drug-sensitive human sarcoma (MES-SA cells). The genetic and epigenetic bases of this selected activation involve the initiation of transcription at a site 112 kb upstream of the ABCB1 proximal promoter (P1) in the drug-resistant cells. This activation was associated with a chromatin-remodeling process characterized by an increase in acetylated histone H3 within a 968-bp region 5' of the ABCB1 upstream promoter. These alterations provide both genetic and epigenetic susceptibility for ABCB1 expression in drug-resistant cells. Complete activation of the ABCB1 gene through the coding region was proposed by interactions of selected trans-alterations or epigenetic changes on the ABCB1 proximal promoter, which occurred during initial drug exposure. Thus, our data provide evidence for a major genomic alteration that changes the chromatin structure of the ABCB1 upstream promoter via acetylation of histone H3 initiating ABCB1 activation, further elucidating the genetic and epigenetic bases that determine chemotherapeutic response in drug-resistant derivatives of MES-SA cells.

    View details for DOI 10.1158/0008-5472.CAN-04-4133

    View details for Web of Science ID 000232566800041

    View details for PubMedID 16230402

  • Functional network analysis reveals extended gliomagenesis pathway maps and three novel MYC-interacting genes in human gliomas CANCER RESEARCH Bredel, M., Bredel, C., Juric, D., Harsh, G. R., Vogel, H., Recht, L. D., Sikic, B. I. 2005; 65 (19): 8679-8689

    Abstract

    Gene expression profiling has proven useful in subclassification and outcome prognostication for human glial brain tumors. The analysis of biological significance of the hundreds or thousands of alterations in gene expression found in genomic profiling remains a major challenge. Moreover, it is increasingly evident that genes do not act as individual units but collaborate in overlapping networks, the deregulation of which is a hallmark of cancer. Thus, we have here applied refined network knowledge to the analysis of key functions and pathways associated with gliomagenesis in a set of 50 human gliomas of various histogenesis, using cDNA microarrays, inferential and descriptive statistics, and dynamic mapping of gene expression data into a functional annotation database. Highest-significance networks were assembled around the myc oncogene in gliomagenesis and around the integrin signaling pathway in the glioblastoma subtype, which is paradigmatic for its strong migratory and invasive behavior. Three novel MYC-interacting genes (UBE2C, EMP1, and FBXW7) with cancer-related functions were identified as network constituents differentially expressed in gliomas, as was CD151 as a new component of a network that mediates glioblastoma cell invasion. Complementary, unsupervised relevance network analysis showed a conserved self-organization of modules of interconnected genes with functions in cell cycle regulation in human gliomas. This approach has extended existing knowledge about the organizational pattern of gene expression in human gliomas and identified potential novel targets for future therapeutic development.

    View details for DOI 10.1158/0008-5472

    View details for Web of Science ID 000232199400018

    View details for PubMedID 16204036

  • Phase II study of gefitinib, fluorouracil, leucovorin, and oxaliplatin therapy in previously treated patients with metastatic colorectal cancer JOURNAL OF CLINICAL ONCOLOGY Kuo, T., Cho, C. D., Halsey, J., Wakelee, H. A., Advani, R. H., Ford, J. M., Fisher, G. A., Sikic, B. I. 2005; 23 (24): 5613-5619

    Abstract

    To investigate the gefitinib, fluorouracil (FU), leucovorin, and oxaliplatin regimen (IFOX) in previously treated patients with metastatic colorectal cancer.Eligible patients had stage IV colorectal adenocarcinoma and had demonstrated progression or intolerance to a prior chemotherapy regimen not including oxaliplatin. Each cycle consisted of 14 days. Cycle 1 consisted of oxaliplatin 85 mg/m2 intravenously (IV) during 2 hours on day 1, hours 0 to 2; leucovorin 200 mg/m2 IV on days 1 and 2, hours 0 to 2; FU 400 mg/m2 IV push on days 1 and 2; and FU 600 mg/m2 IV on days 1 and 2, hours 2 to 24 (FOLFOX-4). All subsequent cycles consisted of FOLFOX-4 with gefitinib at 500 mg/d administered orally throughout the 14-day cycle.Twenty-seven patients were enrolled onto the study. The median number of prior chemotherapy regimens was two, and 74% of all patients received prior irinotecan. Nine of the 27 patients (33%) and six of the 20 patients (30%) who had prior FU and irinotecan had a partial response by Response Evaluation Criteria in Solid Tumors Group criteria. Median overall survival was 12.0 months. Median event-free survival was 5.4 months. Grade 3 to 4 toxicities included neutropenia (48%), diarrhea (48%), nausea (22%), and vomiting (15%).IFOX is an active regimen in patients with previously treated metastatic colorectal adenocarcinoma, demonstrating higher response rates than those reported with FOLFOX-4 alone in a similar patient population.

    View details for DOI 10.1200/JCO.2005.08.359

    View details for Web of Science ID 000231371700034

    View details for PubMedID 16110021

  • High-resolution genome-wide mapping of genetic alterations in human glial brain tumors CANCER RESEARCH Bredel, M., Bredel, C., Juric, D., Harsh, G. R., Vogel, H., Recht, L. D., Sikic, B. I. 2005; 65 (10): 4088-4096

    Abstract

    High-resolution genome-wide mapping of exact boundaries of chromosomal alterations should facilitate the localization and identification of genes involved in gliomagenesis and may characterize genetic subgroups of glial brain tumors. We have done such mapping using cDNA microarray-based comparative genomic hybridization technology to profile copy number alterations across 42,000 mapped human cDNA clones, in a series of 54 gliomas of varying histogenesis and tumor grade. This gene-by-gene approach permitted the precise sizing of critical amplicons and deletions and the detection of multiple new genetic aberrations. It has also revealed recurrent patterns of occurrence of distinct chromosomal aberrations as well as their interrelationships and showed that gliomas can be clustered into distinct genetic subgroups. A subset of detected alterations was shown predominantly associated with either astrocytic or oligodendrocytic tumor phenotype. Finally, five novel minimally deleted regions were identified in a subset of tumors, containing putative candidate tumor suppressor genes (TOPORS, FANCG, RAD51, TP53BP1, and BIK) that could have a role in gliomagenesis.

    View details for Web of Science ID 000229062000015

    View details for PubMedID 15899798

  • Gene expression profiles at diagnosis in de novo childhood AML patients identify FLT3 mutations with good clinical outcomes BLOOD Lacayo, N. J., Meshinchi, S., Kinnunen, P., Yu, R., Wang, Y., Stuber, C. M., Douglas, L., Wahab, R., Becton, D. L., Weinstein, H., Chang, M. N., Willman, C. L., Radich, J. P., Tibshirani, R., Ravindranath, Y., Sikic, B. I., Dahl, G. V. 2004; 104 (9): 2646-2654

    Abstract

    Fms-like tyrosine kinase 3 (FLT3) mutations are associated with unfavorable outcomes in children with acute myeloid leukemia (AML). We used DNA microarrays to identify gene expression profiles related to FLT3 status and outcome in childhood AML. Among 81 diagnostic specimens, 36 had FLT3 mutations (FLT3-MUs), 24 with internal tandem duplications (ITDs) and 12 with activating loop mutations (ALMs). In addition, 8 of 19 specimens from patients with relapses had FLT3-MUs. Predictive analysis of microarrays (PAM) identified genes that differentiated FLT3-ITD from FLT3-ALM and FLT3 wild-type (FLT3-WT) cases. Among the 42 specimens with FLT3-MUs, PAM identified 128 genes that correlated with clinical outcome. Event-free survival (EFS) in FLT3-MU patients with a favorable signature was 45% versus 5% for those with an unfavorable signature (P = .018). Among FLT3-MU specimens, high expression of the RUNX3 gene and low expression of the ATRX gene were associated with inferior outcome. The ratio of RUNX3 to ATRX expression was used to classify FLT3-MU cases into 3 EFS groups: 70%, 37%, and 0% for low, intermediate, and high ratios, respectively (P < .0001). Thus, gene expression profiling identified AML patients with divergent prognoses within the FLT3-MU group, and the RUNX3 to ATRX expression ratio should be a useful prognostic indicator in these patients.

    View details for DOI 10.1182/blood-2004-12-4449

    View details for Web of Science ID 000224795700014

    View details for PubMedID 15251987

  • CCAAT/enhancer-binding protein beta (nuclear factor for interleukin 6) transactivates the human MDR1 gene by interaction with an inverted CCAAT box in human cancer cells MOLECULAR PHARMACOLOGY Chen, G. K., Sale, S., Tan, T., Ermoian, R. P., Sikic, B. I. 2004; 65 (4): 906-916

    Abstract

    We investigated the mechanisms of MDR1 gene activation by CCAAT/enhancer binding protein beta (C/EBPbeta, or nuclear factor for interleukin 6) in human cancer cells. Transfection of the breast cancer cell line MCF-7 and its doxorubicin-selected variant MCF-7/ADR by either C/EBPbeta or C/EBPbeta-LIP (a dominant-negative form of C/EBPbeta) confirmed their roles in the activation or repression of the endogenous, chromosomally embedded MDR1 gene. Cotransfection experiments with promoter constructs revealed a C/EBPbeta interaction on the MDR1 promoter via the region within -128 to -75. Deletions within the putative AP-1 box (-123 to -111) increased MDR1 promoter activity when stimulated by C/EBPbeta, suggesting that the AP-1 site negatively regulates MDR1 activation by C/EBPbeta. Mutations within the inverted CCAAT box (Y box) (-82 to -73) abolished the C/EBPbeta-stimulated MDR1 promoter activity, indicating that the Y box is required for MDR1 activation by C/EBPbeta. Chromatin immunoprecipitation (ChIP) revealed that C/EBPbeta precipitates a transcription complex containing C/EBPbeta, the MDR1 promoter sequences (-250 to +54), and the hBrm protein. In conclusion, alteration of expression or function of C/EBPbeta plays an important role in MDR1 gene regulation. C/EBPbeta activates the endogenous MDR1 gene of MCF-7 cells, and this activation was associated with a novel C/EBPbeta interaction region within the proximal MDR1 promoter (-128 to -75). The mechanisms of MDR1 activation by C/EBPbeta include C/EBPbeta binding of the chromatin of the MDR1 gene and interactions of C/EBPbeta with the Y box and Y box-associated proteins.

    View details for Web of Science ID 000220450200012

    View details for PubMedID 15044620

  • Modulation of resistance to idarubicin by the cyclosporin PSC 833 (valspodar) in multidrug-resistant cells. Journal of experimental therapeutics & oncology Lacayo, N. J., Duran, G. E., Sikic, B. I. 2003; 3 (3): 127-135

    Abstract

    Idarubicin (IDA) is an anthracycline anticancer drug utilized in the treatment of acute leukemias. There are conflicting data published with regard to the cross-resistance of IDA in multidrug-resistant (MDR) cells expressing P-glycoprotein (P-gp). We evaluated the cytotoxicity and cellular accumulation of IDA in a panel of anthracycline-selected MDR cell lines. Leukemia K562/R7 cells and sarcoma MES-SA/Dx5 cells expressing high levels of the MDR1 (ABCB1) gene were resistant to IDA (42-fold and 150-fold, respectively). In both of these cell lines, resistance to IDA was equivalent to that for doxorubicin, the drug used to select for the MDR variants. The P-gp inhibitor PSC 833 (valspodar) at 2 microM completely restored sensitivity to IDA. IDA accumulation was decreased 12-fold in MES-SA/Dx5 cells vs parental cell line, and drug uptake was restored to control levels by PSC 833. Reduced intracellular IDA was correlated with P-gp content by flow cytometry. Experiments in NIH3T3 murine cells transfected with the human MDR1 gene substantiated the findings of cross-resistance to IDA and reversal of resistance by PSC 833. Our data indicate that IDA is a high-affinity substrate for P-gp.

    View details for PubMedID 14641819

  • Preferential expression of a mutant allele of the amplified MDR1 (ABCB1) gene in drug-resistant variants of a human sarcoma GENES CHROMOSOMES & CANCER Chen, G. K., Lacayo, N. J., Duran, G. E., Wang, Y., Bangs, C. D., Rea, S., Kovacs, M., Cherry, A. M., Brown, J. M., Sikic, B. I. 2002; 34 (4): 372-383

    Abstract

    Activation of the MDR1 (ABCB1) gene is a common event conferring multidrug resistance (MDR) in human cancers. We investigated MDR1 activation in MDR variants of a human sarcoma line, some of which express a mutant MDR1, which facilitated the study of allelic gene expression. Structural alterations of MDR1, gene copy numbers, and allelic expression were analyzed by cytogenetic karyotyping, oligonucleotide hybridization, Southern blotting, polymerase chain reaction, and DNA heteroduplex assays. Both chromosome 7 alterations and several cytogenetic changes involving the 7q21 locus are associated with the development of MDR in these sarcoma cells. Multistep-selected cells and their revertants contain three- to six-fold MDR1 gene amplification compared with that of the drug-sensitive parental cell line MES-SA and single-step doxorubicin-selected mutants. MDR1 gene amplification precedes the emergence of a mutant allele in cells that were coselected with doxorubicin and a cyclosporin inhibitor of P-glycoprotein (P-gp). Allele-specific oligonucleotide hybridization showed that the endogenous mutant allele was present as a single copy, with multiple copies of the normal allele. Reselection of revertant cells with doxorubicin in either the presence or the absence of the P-gp inhibitor resulted in exclusive reexpression of the mutant MDR1 allele, regardless of the presence of multiple wild-type MDR1 alleles. These data provide new insights into how multiple alleles are regulated in the amplicon of drug-resistant cancer cells and indicate that increased expression of an amplified gene can result from selective transcription of a single mutant allele of the gene.

    View details for DOI 10.1002/gcc.10067

    View details for Web of Science ID 000176495400004

    View details for PubMedID 12112526

  • MDR1 activation is the predominant resistance mechanism selected by vinblastine in MES-SA cells BRITISH JOURNAL OF CANCER Chen, G. K., Duran, G. E., Mangili, A., Beketic-Oreskovic, L., Sikic, B. 2000; 83 (7): 892-898

    Abstract

    Single-step selection with vinblastine was performed in populations of the human sarcoma cell line MES-SA, to assess cellular mechanisms of resistance to the drug and mutation rates via fluctuation analysis. At a stringent selection with 20 nM vinblastine, resulting in 5-6 logs of cell killing, the mutation rate was 7 x 10(-7)per cell generation. Analysis of variance supported the hypothesis of spontaneous mutations conferring vinblastine resistance, rather than induction of adaptive response elements. Surviving clones displayed a stable multidrug resistance phenotype over a 3-month period. All propagated clones demonstrated high levels of resistance to vinblastine and paclitaxel, and lower cross-resistance to doxorubicin and etoposide. Activation of MDR 1 gene expression and P-glycoprotein function was demonstrable in all clones. No elevation was found in the expression of the mrp gene, the LRP-56 major vault protein and beta-tubulin isotypes (M40, beta4, 5beta, and beta9) in these mutants. We conclude that initial-step resistant mechanism in these vinblastine-selected mutants commonly arises from a stochastic mutation event with activation of the MDR 1 gene.

    View details for Web of Science ID 000089389600010

    View details for PubMedID 10970691

  • Loss of cyclosporin and azidopine binding are associated with altered ATPase activity by a mutant p-glycoprotein with deleted Phe(335) MOLECULAR PHARMACOLOGY Chen, G. K., Lacayo, N. J., Duran, G. E., Cohen, D., Sikic, B. I. 2000; 57 (4): 769-777

    Abstract

    In this study, we further characterize a mutant P-glycoprotein (P-gp) that has a deletion of Phe(335) and is resistant to inhibition by cyclosporins. Photoaffinity labeling with [(3)H]cyclosporine and [(3)H]azidopine revealed markedly decreased binding to the mutant P-gp compared with wild-type P-gp. Expression of the mutant P-gp in multidrug-resistant variant cell line MES-SA/DxP (DxP) cells was associated with a 2-fold higher basal ATPase activity relative to multidrug-resistant cell line MES-SA/Dx5 (Dx5) cells with wild-type P-gp. Cyclosporine inhibited ATPase activity in both cell types, whereas the cyclosporin D analog valspodar (PSC 833), vinblastine, and dactinomycin stimulated ATPase activity in Dx5 but not in mutant DxP cells. Moreover, the cell lines differed in their responses to verapamil, which produced greater stimulation of ATPase in Dx5 than DxP cells. Verapamil significantly reversed the [(3)H]daunorubicin accumulation defect in wild-type Dx5 cells, but it had no significant effect on [(3)H]daunorubicin accumulation in the mutant DxP cells. Verapamil was not transported by cells expressing either mutant or wild-type P-gp. Vanadate trapping of azido-ATP was markedly impaired in mutant P-gp. In conclusion, our data demonstrate that Phe(335) of transmembrane 6 is an important amino acid residue for the formation of cyclosporine and azidopine drug-binding site(s). Phe(335) also plays a role in the coupling of verapamil binding and modulation of daunorubicin intracellular accumulation in wild-type P-gp. In addition, Phe(335) in transmembrane 6 may play a role in coupling drug binding to ATPase activity. The deletion of Phe(335) results in a significant increase in the basal ATPase activity with a concomitant decrease in its ability to trap ATP and transport some P-gp substrates.

    View details for Web of Science ID 000086066500017

    View details for PubMedID 10727524

  • Modulation of multidrug resistance: A paradigm for translational clinical research ONCOLOGY-NEW YORK Sikic, B. I. 1999; 13 (5A): 183-187

    Abstract

    Resistance of cancer cells is the major limitation to the success of chemotherapy. Although many mechanisms of cellular resistance to anticancer drugs have been defined, the best understood of these is multidrug resistance (MDR), caused by the multidrug transporter, P-glycoprotein (P-gp), the product of the MDR1 gene. New drugs developed specifically to inhibit P-gp and modulate MDR, such as valspodar (PSC 833 [Amdray]), are currently undergoing clinical testing. Moreover, agents designed to inhibit other mechanisms of drug resistance are currently in development, and concurrent blockade of multiple mechanisms of resistance appears to be a promising approach. Coadministration of MDR1-related chemotherapeutic drugs with an MDR modulator may enhance the bioavailability of these agents sufficiently to enable oral dosing, which would potentially be more convenient and less toxic.

    View details for Web of Science ID 000165178200008

    View details for PubMedID 10370927

  • Modulation and prevention of multidrug resistance by inhibitors of P-glycoprotein CANCER CHEMOTHERAPY AND PHARMACOLOGY Sikic, B. I., Fisher, G. A., Lum, B. L., Halsey, J., BEKETICORESKOVIC, L., Chen, G. 1997; 40: S13-S19

    Abstract

    Intrinsic and acquired multidrug resistance (MDR) in many human cancers may be due to expression of the multidrug transporter P-glycoprotein (Pgp), which is encoded by the mdr1 gene. There is substantial evidence that Pgp is expressed both as an acquired mechanism (e.g., in leukemias, lymphomas, myeloma, and breast and ovarian carcinomas) and constitutively (e.g., in colorectal and renal cancers) and that its expression is of prognostic significance in many types of cancer. Clinical trials of MDR modulation are complicated by the presence of multiple-drug-resistance mechanisms in human cancers, the pharmacokinetic interactions that result from the inhibition of Pgp in normal tissues, and, until recently, the lack of potent and specific inhibitors of Pgp. A large number of clinical trials of reversal of MDR have been undertaken with drugs that are relatively weak inhibitors and produce limiting toxicities at doses below those necessary to inhibit Pgp significantly. The advent of newer drugs such as the cyclosporin PSC 833 (PSC) provides clinicians with more potent and specific inhibitors for MDR modulation trials. Understanding how modulators of Pgp such as PSC 833 affect the toxicity and pharmacokinetics of cytotoxic agents is fundamental for the design of therapeutic trials of MDR modulation. Our studies of combinations of high-dose cyclosporin (CsA) or PSC 833 with etoposide, doxorubicin, or paclitaxel have produced data regarding the role of Pgp in the clinical pharmacology of these agents. Major pharmacokinetic interactions result from the coadministration of CsA or PSC 833 with MDR-related anticancer agents (e.g., doxorubicin, daunorubicin, etoposide, paclitaxel, and vinblastine). These include increases in the plasma area under the curve and half-life and decreases in the clearance of these cytotoxic drugs, consistent with Pgp modulation at the biliary lumen and renal tubule, blocking excretion of drugs into the bile and urine. The biological and medical implications of our studies include the following. First, Pgp is a major organic cation transporter in tissues responsible for the excretion of xenobiotics (both drugs and toxins) by the biliary tract and proximal tubule of the kidney. Our clinical data are supported by recent studies in mdr-gene-knockout mice. Second, modulation of Pgp in tumors is likely to be accompanied by altered Pgp function in normal tissues, with pharmacokinetic interactions manifesting as inhibition of the disposition of MDR-related cytotoxins (which are transport substrates for Pgp). Third, these pharmacokinetic interactions of Pgp modulation are predictable if one defines the pharmacology of the modulating agent and the combination. The interactions lead to increased toxicities such as myelosuppression unless doses are modified to compensate for the altered disposition of MDR-related cytotoxins. Fourth, in serial studies where patients are their own controls and clinical resistance is established, remissions are observed when CsA or PSC 833 is added to therapy, even when doses of the cytotoxin are reduced by as much as 3-fold. This reversal of clinical drug resistance occurs particularly when the tumor cells express the mdr1 gene. Thus, tumor regression can be obtained without apparent increases in normal tissue toxicities. In parallel with these trials, we have recently demonstrated in the laboratory that PSC 833 decreases the mutation rate for resistance to doxorubicin and suppresses activation of mdr1 and the appearance of MDR mutants. These findings suggest that MDR modulation may delay the emergence of clinical drug resistance and support the concept of prevention of drug resistance in the earlier stages of disease and the utilization of time to progression as an important endpoint in clinical trials. Pivotal phase III trials to test these concepts with PSC 833 as an MDR modulator are under way or planned for patients with acute myeloid leukemias, multiple myeloma, and ovarian carcinoma.

    View details for Web of Science ID A1997XR32900004

    View details for PubMedID 9272128

  • Multidrug-resistant human sarcoma cells with a mutant P-glycoprotein, altered phenotype, and resistance to cyclosporins JOURNAL OF BIOLOGICAL CHEMISTRY Chen, G., Duran, G. E., Steger, K. A., Lacayo, N. J., Jaffrezou, J. P., Dumontet, C., Sikic, B. I. 1997; 272 (9): 5974-5982

    Abstract

    A variant of the multidrug-resistant human sarcoma cell line Dx5 was derived by co-selection with doxorubicin and the cyclosporin D analogue PSC 833, a potent inhibitor of the multidrug transporter P-glycoprotein. The variant DxP cells manifest an altered phenotype compared with Dx5, with decreased cross-resistance to Vinca alkaloids and no resistance to dactinomycin. Resistance to doxorubicin and paclitaxel is retained. The multidrug resistance phenotype of DxP cells is not modulated by 2 microM PSC 833 or cyclosporine. DxP cells manifest a decreased ability to transport [3H]cyclosporine. DNA heteroduplex analysis and sequencing reveal a mutant mdr1 gene (deletion of a phenylalanine at amino acid residue 335) in the DxP cell line. The mutant P-glycoprotein has a decreased affinity for PSC 833 and vinblastine and a decreased ability to transport rhodamine 123. Transfection of the mutant mdr1 gene into drug-sensitive MES-SA sarcoma cells confers resistance to both doxorubicin and PSC 833. Our study demonstrates that survival of cells exposed to doxorubicin and PSC 833 in a multistep selection occurred as a result of a P-glycoprotein mutation in transmembrane region 6. These data suggest that Phe335 is an important binding site on P-glycoprotein for substrates such as dactinomycin and vinblastine and for inhibitors such as cyclosporine and PSC 833.

    View details for Web of Science ID A1997WK74700086

    View details for PubMedID 9038218

  • Resistance mechanisms in human sarcoma mutants derived by single-step exposure to paclitaxel (Taxol) CANCER RESEARCH Dumontet, C., Duran, G. E., Steger, K. A., BEKETICORESKOVIC, L., Sikic, B. I. 1996; 56 (5): 1091-1097

    Abstract

    A fluctuation analysis experiment was performed by exposing 15 expanded populations of MES-SA sarcoma cells to paclitaxel (Taxol) at a concentration of 10 nM for 7 days. The mutation rate was approximately 8 multiplied by 10(-7)/cell generation. ANOVA supports a stochastic cell survival mechanism of spontaneous mutation rather than induction of an adaptive response under these selection conditions. Surviving colonies were found in 12 populations, 9 of which had clones that remained resistant to paclitaxel after a 2-month period of propagation. Analysis of mdr1 gene expression by reverse transcription PCR demonstrated positive clones in 4 of the 9 populations with stable resistance. Accumulation of [(3)H]paclitaxel was decreased in these clones but not in the mdr1-negative clones compared with parental cells. A high degree of resistance to paclitaxel (36- to 93-fold) was selected by this single drug exposure in all 9 stably resistant mutants. Those with mdr1 activation demonstrated a broad cross-resistance to vinblastine, doxorubicin, and etoposide, whereas the other 6 mutants were cross-resistant only to the Vinca alkaloids. Because tubulins are the target molecules for paclitaxel cytotoxicity, we evaluated total tubulin content by immunoblotting and performed semiquantitative reverse transcription PCR analysis for expression of the alpha-tubulin isotypes B alpha 1, K alpha 1 and H alpha 44, the beta-tubulin isotypes M40, beta9, 5beta, beta2 and beta4, and gamma-tubulin. Total tubulin content was decreased significantly in one of the single-step mutants. All surviving clones, both resistant and sensitive to paclitaxel, displayed reduced expression of the 5beta and beta 4 beta-tubulin isotype transcripts in comparison with the parental cell line. These data suggest that stringent exposure to paclitaxel selected clones with reduced transcript levels of 5beta and beta4 beta-tubulin isotypes, but that these reduced levels were not directly involved in the resistance of the clones to paclitaxel. The results suggest an important role for non-multidrug-resistant mechanisms of resistance to paclitaxel. These mechanisms do not involve reduced drug accumulation and provide cross-resistance among both paclitaxel and tubulin depolymerizing agents.

    View details for Web of Science ID A1996TX17300027

    View details for PubMedID 8640766

  • DECREASED MUTATION-RATE FOR CELLULAR-RESISTANCE TO DOXORUBICIN AND SUPPRESSION OF MDR1 GENE ACTIVATION BY THE CYCLOSPORINE PSC-833 JOURNAL OF THE NATIONAL CANCER INSTITUTE BEKETICORESKOVIC, L., Duran, G. E., Chen, G., Dumontet, C., Sikic, B. I. 1995; 87 (21): 1593-1602

    Abstract

    Various mechanisms can contribute to cellular resistance to doxorubicin. These include expression of the multidrug transporter P-glycoprotein (product of the mdr1 gene [also known as PGY1], Mrp (multidrug resistance-associated protein), the p110 major vault protein, altered glutathione metabolism, and altered levels or activity of topoisomerase II (Topo II). We reported recently that single-step treatment of human MES-SA sarcoma cells with 40 nM doxorubicin resulted in selection of spontaneous mutants at a rate of 1.8 x 10(-6) per cell generation. All individually selected mutants manifested the multidrug-resistant phenotype, related to activation of the mdr1 gene.Luria and Delbrück fluctuation analysis was performed with MES-SA cells to determine the mutation rate and the nature and mechanisms of resistance after single-step selection with doxorubicin in the presence of the cyclosporin PSC 833, a potent modulator of multidrug resistance.Ten flasks were seeded with 2000 cells/flask and grown to confluent populations of approximately 8 x 10(6) cells. After reseeding in 96-well plates, the populations were treated with 40 nM doxorubicin and 2 microM PSC 833 for 3 weeks. Surviving colonies were scored, individually harvested, and propagated. The drug-resistant phenotype was assessed by the tetrazolium dye (MTT) cytotoxicity assay and by monitoring cellular glutathione content and radiolabeled drug accumulation. Coupled reverse transcription-polymerase chain reaction (RT-PCR) was used to evaluate mdr1, MRP, Topo II alpha, and Topo II beta gene expression. Topo II, P-glycoprotein, and p110 levels were examined by immunoblotting or immunocytochemistry. Topo II activity was assessed by decatenation of kinetoplast DNA, and etoposide-induced cleavable complex formation was studied by the potassium-sodium dodecyl sulfate precipitation assay.Mutations were detected at a rate of 2.5 x 10(-7) per cell generation. Analysis of variance indicates that spontaneous mutations, rather than changes in cellular function, conferred resistance to doxorubicin and PSC 833. None of the isolated clones expressed mdr1 messenger RNA or P-glycoprotein, and none exhibited an increase in MRP expression. No alterations were found in cellular glutathione content, intracellular accumulations of daunorubicin and etoposide, levels of p110 protein, or levels of Topo II beta transcripts. However, a significant decrease in Topo II alpha messenger RNA and protein was found in all examined clones, as well as decreased Topo II catalytic activity and reduced cleavable complex formation in the presence of etoposide.PSC 833 co-selection reduced the mutation rate for doxorubicin-selected resistance by 10-fold and suppressed the emergence of mdr1 mutants. Survival of cells exposed to doxorubicin and PSC 833 occurs by selection of spontaneously arising mutants that exhibit altered Topo II alpha expression.Our results suggest that treatment with multidrug resistance modulators such as PSC 833 together with multidrug resistance-related cytotoxins may suppress the activation of mdr1 and prevent the emergence of resistant cancer cell clones with the multidrug-resistant phenotype.

    View details for Web of Science ID A1995TB16200009

    View details for PubMedID 7563202

  • The reversal of multidrug resistance. Cancer treatment and research Fisher, G. A., Lum, B. L., Sikic, B. I. 1995; 78: 45-70

    View details for PubMedID 8595147

  • PREVALENCE OF MULTIDRUG-RESISTANCE RELATED TO ACTIVATION OF THE MDR1 GENE IN HUMAN SARCOMA MUTANTS DERIVED BY SINGLE-STEP DOXORUBICIN SELECTION CANCER RESEARCH Chen, G., Jaffrezou, J. P., Fleming, W. H., Duran, G. E., Sikic, B. I. 1994; 54 (18): 4980-4987

    Abstract

    Fluctuation analysis experiments were performed in the human sarcoma cell line MES-SA to assess whether selection or induction mechanisms determine resistance to doxorubicin (DOX), mutation rates, and the nature of the surviving clones. Thirteen flasks were seeded with 2000 cells/flask and grown to confluent populations of approximately 3.3 x 10(6) cells. After reseeding in 96-well plates, each population was treated with 40 nM DOX for 2 weeks. Surviving colonies were scored and harvested. Clones were propagated and analyzed for drug resistance phenotype. Expression of the mdr1, mrp, and topoisomerase II alpha and II beta genes was analyzed by reverse transcription-polymerase chain reaction. Accumulation of the P-glycoprotein substrate rhodamine-123 was measured by flow cytometry, with and without the cyclosporin D analogue SDZ PSC 833. Cellular glutathione levels were measured by flow cytometry, and M(r) 110,000 vesicular protein (p110) expression was detected by immunohistochemistry. Analysis of variance supported the hypothesis of spontaneous mutations rather than induction conferring DOX resistance. At this stringent level (5-6 log cell killing) of drug exposure, the mutation rate was estimated at 1.8 x 10(-6) per cell generation. All 30 propagated clones demonstrated cross-resistance to vinblastine, etoposide, and paclitaxel (Taxol), but not to cisplatin or bleomycin. Increased mRNA levels of mdr1 were observed in all 27 clones tested, including at least 1 from each of the 13 populations. No alterations were found in expression or level of topoisomerase II alpha or II beta, mrp, glutathione, and p110. Expression of P-glycoprotein was confirmed by flow cytometry using the monoclonal antibody UIC2. In almost all tested clones, decreased intracellular rhodamine-123 accumulation was modulated by 2 microM SDZ PSC 833, and the vinblastine resistance in all examined clones was completely reversed by SDZ PSC 833 and verapamil. Our study demonstrates that survival of cells exposed to DOX in a single step occurs as a result of a stochastic process consistent with mutational events. Activation of the mdr1 gene is the predominant mechanism selected by DOX in these resistant clones.

    View details for Web of Science ID A1994PF79100023

    View details for PubMedID 7915196

  • MUTATION-RATES AND MECHANISMS OF RESISTANCE TO ETOPOSIDE DETERMINED FROM FLUCTUATION ANALYSIS JOURNAL OF THE NATIONAL CANCER INSTITUTE Jaffrezou, J. P., Chen, G., Duran, G. E., Kuhl, J. S., Sikic, B. I. 1994; 86 (15): 1152-1158

    Abstract

    The major known mechanisms of resistance to etoposide include altered expression of its target enzyme, topoisomerase II (Topo II), and the multidrug-resistant phenotypes encoded by the mdr1 and MRP (multidrug resistance-associated protein) genes. There is little information regarding the distribution, frequency, and origin of these mechanisms in cancer cells.We performed fluctuation analysis experiments with the human sarcoma cell line, MES-SA, to assess 1) if selection or induction mechanisms are involved in resistance to etoposide, 2) mutation rates for cellular resistance to etoposide, and 3) the nature of the single-step selected surviving clones.Three groups of 10 flasks were seeded with more than 2000 cells each and allowed to grow to near confluence (approximately 3 x 10(6) cells per flask). After reseeding, each group received etoposide for 1 week at a final concentration of 0.5 microM (group A), 1.0 microM (group B), and 5.0 microM (group C). Surviving colonies in each of the 30 populations were scored and individually harvested.Mutation rates were estimated at 2.9 x 10(-6) (group A), 5.7 x 10(-7) (group B), and 1.7 x 10(-7) (group C) per cell generation. Of 61 propagated colonies, four of 26 from group A, five of 19 from group B, and none of 16 from group C were stably resistant. Analysis of variance supported the hypothesis of spontaneous mutations rather than induction, conferring etoposide resistance in groups A and B. Five of the stably resistant clones were cross-resistant to doxorubicin. Analysis by polymerase chain reaction failed to detect the expression of the multidrug-resistant gene mdr1 messenger RNA (mRNA) in any of the clones. No increase in expression of the MRP gene was observed. However, a significant decrease in both Topo II alpha and II beta mRNA (30%-70%) was found in six of seven stably resistant and six of six unstably resistant mutants.Our study demonstrates that resistance to etoposide arises spontaneously, with most clones surviving either stochastically or through very labile mechanisms of resistance. The experimental design has derived a set of resistant mutants from a single-step selection. In those clones, decreased expression of Topo II is the predominant mechanism selected.These findings suggest that stable resistance to etoposide chemotherapy may be acquired by selection of spontaneously arising mutants rather than induction by drug exposure. The stably resistant clones may represent descendants from a single mutational event in each population.

    View details for Web of Science ID A1994NZ23500011

    View details for PubMedID 8028036

  • PHASE-I TRIAL OF DOXORUBICIN WITH CYCLOSPORINE AS A MODULATOR OF MULTIDRUG-RESISTANCE JOURNAL OF CLINICAL ONCOLOGY Bartlett, N. L., Lum, B. L., Fisher, G. A., BROPHY, N. A., EHSAN, M. N., Halsey, J., Sikic, B. I. 1994; 12 (4): 835-842

    Abstract

    To study the effects of cyclosporine (CsA), a modulator of multidrug resistance (MDR), on the pharmacokinetics and toxicities of doxorubicin.Nineteen patients with incurable malignancies entered this phase I trial. Initially patients received doxorubicin alone (60 or 75 mg/m2) as a 48-hour continuous intravenous (i.v.) infusion. Patients whose tumors did not respond received CsA as a 2-hour loading dose of 6 mg/kg and a 48-hour continuous infusion of 18 mg/kg/d with doxorubicin. Target CsA levels were 3,000 to 4,800 ng/mL (2.5 to 4.0 mumol/L). Doxorubicin doses were reduced to 40% of the prior dose without CsA, and then escalated until myelosuppression equivalent to that resulting from doxorubicin alone was observed. Doxorubicin pharmacokinetics were analyzed with and without CsA.Thirteen patients received both doxorubicin alone and the combination of doxorubicin and CsA. Mean CsA levels were more than 2,000 ng/mL for all cycles and more than 3,000 ng/mL for 68% of cycles. Dose escalation of doxorubicin with CsA was stopped at 60% of the doxorubicin alone dose, as four of five patients at this dose level had WBC nadirs equivalent to those seen with doxorubicin alone. Nonhematologic toxicities were mild. Reversible hyperbilirubinemia occurred in 68% of doxorubicin/CsA courses. The addition of CsA to doxorubicin increased grade 1 and 2 nausea (87% v 47%) and vomiting (50% v 10%) compared with doxorubicin alone. There was no significant nephrotoxicity. Paired pharmacokinetics were studied in 12 patients. The addition of CsA increased the dose-adjusted area under the curve (AUC) of doxorubicin by 55%, and of its metabolite doxorubicinol by 350%.CsA inhibits the clearance of both doxorubicin and doxorubicinol. Equivalent myelosuppression was observed when the dose of doxorubicin with CsA was 60% of the dose of doxorubicin without CsA. Understanding these pharmacokinetic interactions is essential for the design and interpretation of clinical trials of MDR modulation, and should be studied with more potent MDR modulators.

    View details for Web of Science ID A1994NG39500028

    View details for PubMedID 8151326

  • MODULATION OF MULTIDRUG-RESISTANCE - AT THE THRESHOLD JOURNAL OF CLINICAL ONCOLOGY Sikic, B. I. 1993; 11 (9): 1629-1635

    View details for Web of Science ID A1993LW36900001

    View details for PubMedID 8355032

  • PHASE-I TRIAL OF ETOPOSIDE WITH CYCLOSPORINE AS A MODULATOR OF MULTIDRUG RESISTANCE JOURNAL OF CLINICAL ONCOLOGY Yahanda, A. M., ADLER, K. M., Fisher, G. A., BROPHY, N. A., Halsey, J., Hardy, R. I., Gosland, M. P., Lum, B. L., Sikic, B. I. 1992; 10 (10): 1624-1634

    Abstract

    To determine the maximum-tolerated dose (MTD) of cyclosporine (CsA) infusion administered with etoposide for 3 days in patients with cancer.Of the 72 registered patients, 26 were treated initially with CsA and etoposide. Forty-six received etoposide alone until disease progression, and 31 of these proceeded to CsA and etoposide. CsA was administered as a 2-hour loading dose (LD) and as a 3-day continuous infusion (CI); doses were escalated from 2 to 8 mg/kg LD and 5 to 24 mg/kg/d CI.Fifty-seven patients were treated with 113 cycles of CsA with etoposide. Steady-state serum CsA levels (nonspecific immunoassay) more than 2,000 ng/mL were achieved in 91% of the cycles at CsA doses > or = 5 mg/kg LD and > or = 15 mg/kg/d CI. The major dose-related toxicity of CsA was reversible hyperbilirubinemia, which occurred in 78% of the courses with CsA levels > 2,000 ng/mL. Myelosuppression and nausea were more severe with CsA and etoposide. Other CsA toxicities included hypomagnesemia, 60%; hypertension, 29%; and headache, 21%. Nephrotoxicity was mild in 12% and severe in 2% of the cycles. Tumor regressions occurred in four patients after the addition of CsA (one non-Hodgkin's lymphoma, one Hodgkin's disease, and two ovarian carcinomas). Biopsy procedures for tumors from three of the four patients who responded were performed, and the results were positive for mdr1 expression.Serum CsA levels of up to 4 mumol/L (4,800 ng/mL) are achievable during a short-term administration with acceptable toxicities when administered in combination with etoposide. The CsA dose that is recommended in adults is a LD of 5 to 6 mg/kg, followed by a CI of 15 to 18 mg/kg/d for 60 hours. CsA blood levels should be monitored and the doses should be adjusted to achieve CsA levels of 2.5 to 4 mumol/L (3,000 to 4,800 ng/mL). Reversible hyperbilirubinemia may be a useful marker of inhibition by CsA of P-glycoprotein function. When used with high-dose CsA, etoposide doses should be reduced by approximately 50% to compensate for the pharmacokinetic effects of CsA on etoposide (Lum et al, J Clin Oncol, 10:1635-1642, 1992).

    View details for Web of Science ID A1992JQ71900018

    View details for PubMedID 1403040

  • ALTERATION OF ETOPOSIDE PHARMACOKINETICS AND PHARMACODYNAMICS BY CYCLOSPORINE IN A PHASE-I TRIAL TO MODULATE MULTIDRUG RESISTANCE JOURNAL OF CLINICAL ONCOLOGY Lum, B. L., Kaubisch, S., Yahanda, A. M., ADLER, K. M., JEW, L., EHSAN, M. N., BROPHY, N. A., Halsey, J., Gosland, M. P., Sikic, B. I. 1992; 10 (10): 1635-1642

    Abstract

    To determine the effects of high-dose cyclosporine (CsA) infusion on the pharmacokinetics of etoposide in patients with cancer.Sixteen patients were administered 20 paired courses of etoposide and CsA/etoposide. Etoposide was administered daily for three days, alone or with CsA, which was delivered by a loading dose and 3-day infusion. Etoposide was measured by high-performance liquid chromatography (HPLC) and serum CsA by nonspecific immunoassay. Etoposide pharmacokinetics included area under the concentration-time curve (AUC), total and renal clearance (CL), half-life (T1/2), and volume of distribution at steady state (Vss).CsA concentrations more than 2,000 ng/mL produced an increase in etoposide AUC of 80% (P less than .001), a 38% decrease in total CL (P < .01), a > twofold increase in T1/2 (P < .01), and a 46% larger Vss (P = .01) compared with etoposide alone. CsA levels ranged from 297 to 5,073 ng/mL. Higher CsA levels (< 2,000 ng/mL v > 2,000 ng/mL) resulted in greater changes in etoposide kinetics: Vss (1.4% v 46%) and T1/2 (40% v 108%). CsA produced a 38% decrease in renal and a 52% decrease in nonrenal CL of etoposide. Etoposide with CsA levels > 2,000 ng/mL produced a lower WBC count nadir (900/mm3 v 1,600/mm3) compared with baseline etoposide cycles.High-dose CsA produces significant increases in etoposide systemic exposure and leukopenia. These pharmacokinetic changes are consistent with inhibition by CsA of the multidrug transporter P-glycoprotein in normal tissues. Etoposide doses should be reduced by 50% when used with high-dose CsA in patients with normal renal and liver function. Alterations in the disposition of other multidrug resistance (MDR)-related drugs should be expected to occur with modulation of P-glycoprotein function in clinical trials.

    View details for Web of Science ID A1992JQ71900019

    View details for PubMedID 1403041

  • MULTIDRUG RESISTANCE (MDR1) GENE-EXPRESSION IN ADULT ACUTE LEUKEMIAS - CORRELATIONS WITH TREATMENT OUTCOME AND INVITRO DRUG SENSITIVITY BLOOD Marie, J. P., Zittoun, R., Sikic, B. I. 1991; 78 (3): 586-592

    Abstract

    Resistance to multiple chemotherapeutic agents has been related to the production of P-glycoprotein, a trans-membrane drug efflux pump that is encoded by the multidrug resistance (MDR) gene mdr1. To investigate whether mdr1 could be involved in clinical resistance to chemotherapy in acute leukemias, we have analyzed retrospectively the RNA from adult acute leukemia cells by slot-blot hybridization with a human mdr1 probe. Units of mdr1 expression were defined by reference to drug-sensitive human sarcoma and K562 leukemia cell lines (1 U) and the highly resistant doxorubicin selected leukemia cells K562/R7 (50 U). We studied 41 adult patients with acute leukemias: 5 acute lymphoblastic leukemias, 23 acute myeloid leukemias, and 13 secondary leukemias or blast crisis of chronic myelogenous leukemia. Expression of 10 U or more of mdr1 was found in 6 of 31 (19%) leukemias at diagnosis, versus 5 of 10 (50%) after relapse from therapy, P = .06. The complete remission rate and in vitro sensitivity to daunorubicin were both correlated with low expression (1 U, v 2 U or more) of mdr1. Among 36 evaluable attempts to induce remission, the complete remission rate was 67% (8 of 12) for patients with undetectable or minimal mdr1 expression (1 U), versus 29% (7 of 24) in patients with 2 U or more of expression, P = .03. In vitro resistance to daunorubicin or other MDR-related drugs was associated with expression of 2 U or more of mdr1 in 11 of 11 cases, while specimens that were sensitive to these agents were negative for mdr1 expression in 5 of 11 cases, P = .03. These data suggest that mdr1 expression contributes to chemoresistance in acute leukemia. Determination of mdr1 gene expression may be useful in designing therapy for patients with leukemia.

    View details for Web of Science ID A1991FZ56600007

    View details for PubMedID 1859877

  • MULTIDRUG (PLEIOTROPIC) RESISTANCE IN DOXORUBICIN-SELECTED VARIANTS OF THE HUMAN SARCOMA CELL-LINE MES-SA CANCER RESEARCH Harker, W. G., Sikic, B. I. 1985; 45 (9): 4091-4096

    Abstract

    The emergence of drug-resistant tumor cells is a major limiting factor in cancer chemotherapy. There is little information about the nature of such resistant variants among human cancer cell populations. Doxorubicin (DOX)-resistant sublines of the human sarcoma cell line MES-SA were selected by continuous in vitro exposure to DOX. Stepwise increases in DOX concentration produced variants which were 25- and 100-fold resistant to DOX. These sublines displayed marked cross-resistance to daunorubicin, dactinomycin, mitoxantrone, colchicine, vincristine, vinblastine, and etoposide and moderate resistance to mitomycin C and melphalan. Cross-resistance was not observed, however, to methotrexate, 5-fluorouracil, bleomycin, carmustine, or cisplatin. DOX resistance in these cell lines appeared to be stable despite long periods of growth in drug-free medium. Two additional marker chromosomes were identified in the 100-fold resistant variant, which indicated clonal selection during drug exposure, but no double minute chromosomes or homogeneously staining regions were noted. Doxorubicin accumulation in the DOX-resistant cells was reduced by approximately 50% compared to that of the sensitive MES-SA cells, as a result of enhanced efflux of DOX from the resistant cells. There was no evidence of appreciable DOX metabolism by either the sensitive or resistant cells. These studies demonstrate marked DOX resistance and multidrug resistance arising in a human sarcoma line during exposure to DOX. The pleiotropic nature of this resistance is similar to that described in other models. Decreased drug accumulation due to enhanced drug efflux is identified as a major mechanism of resistance in these cells, although other factors may also be involved.

    View details for Web of Science ID A1985APR5700018

    View details for PubMedID 4028002

  • DISSOCIATION OF ANTITUMOR POTENCY FROM ANTHRACYCLINE CARDIOTOXICITY IN A DOXORUBICIN ANALOG SCIENCE Sikic, B. I., EHSAN, M. N., Harker, W. G., FRIEND, N. F., Brown, B. W., Newman, R. A., Hacker, M. P., ACTON, E. M. 1985; 228 (4707): 1544-1546

    Abstract

    The search for new congeners of the leading anticancer drug doxorubicin has led to an analog that is approximately 1000 times more potent, noncardiotoxic at therapeutic dose levels, and non-cross-resistant with doxorubicin. The new anthracycline, 3'-deamino-3'-(3-cyano-4-morpholinyl)doxorubicin (MRA-CN), is produced by incorporation of the 3' amino group of doxorubicin in a new cyanomorpholinyl ring. The marked increase in potency was observed against human ovarian and breast carcinomas in vitro; it was not accompanied by an increase in cardiotoxicity in fetal mouse heart cultures. Doxorubicin and MRA-CN both produced typical cardiac ultrastructural and biochemical changes, but at equimolar concentrations. In addition, MRA-CN was not cross-resistant with doxorubicin in a variant of the human sarcoma cell line MES-SA selected for resistance to doxorubicin. Thus antitumor efficacy was dissociated from both cardiotoxicity and cross-resistance by this modification of anthracycline structure.

    View details for Web of Science ID A1985AKM5200037

    View details for PubMedID 4012308

  • DEVELOPMENT AND CHARACTERIZATION OF A HUMAN SARCOMA CELL-LINE, MES-SA, SENSITIVE TO MULTIPLE-DRUGS CANCER RESEARCH Harker, W. G., MacKintosh, F. R., Sikic, B. I. 1983; 43 (10): 4943-4950

    Abstract

    A cell line designated MES-SA has been developed from a uterine sarcoma. Cells from the surgical tumor specimen were grown in a soft-agar clonogenic assay, with a relatively high plating efficiency of 0.5% and sensitivity to multiple drugs. Histologically, the surgical specimen and tumors developing after MES-SA inoculation into nude mice were identical, consisting of sheets of anaplastic sarcoma cells amid scant hyalinized stroma. The nonepithelial origin of this line was supported by ultrastructural analysis and negative mucin staining. Growth in monolayer was established by seeding colonies from soft agar into liquid media and has been maintained for over 21 months (greater than 100 passages), with a population-doubling time for the cell line of 22 hr. The MES-SA line readily forms colonies in soft agar with plating efficiencies ranging from 10 to 20%. Tumor cell inoculation s.c. into nude mice produces tumors within 2 to 3 weeks and subsequent tumor volume-doubling times of 7 to 10 days. MES-SA has a modal chromosome number of 45. Karyotypic abnormalities include: monosomic forms of chromosomes 5, 6, and 7; a 5q, 6p translocation; and one marker chromosome. In vitro sensitivities to doxorubicin, dactinomycin, mitomycin C, and bleomycin have been demonstrated by clonogenic assay. These drug sensitivities remain stable over long periods of monolayer growth and after passage in nude mice.

    View details for Web of Science ID A1983RH70800069

    View details for PubMedID 6883344

  • IMPROVED THERAPEUTIC INDEX OF BLEOMYCIN WHEN ADMINISTERED BY CONTINUOUS INFUSION IN MICE CANCER TREATMENT REPORTS Sikic, B. I., Collins, J. M., Mimnaugh, E. G., Gram, T. E. 1978; 62 (12): 2011-2017

    Abstract

    The effects of three different dosage schedules on both therapeutic effect and pulmonary toxicity of bleomycin were studied in mice. Therapy was assessed by both survival and decreased tumor size in mice bearing Lewis lung carcinoma. Lung toxicity was estimated in nontumored mice as increases in lung collagen content by measuring lung hydroxyproline concentrations. In the first set of experiments, bleomycin injections twice daily (low-dose, high-frequency) produced a significant (34%) increase in lifespan over controls, whereas the same total dose given twice weekly did not result in increased survival. Both schedules produced pulmonary toxicity. Continuous sc infusion of bleomycin via an osmotic minipump was compared to these two schedules of intermittent injection. Identical total doses of drug were administered in all three schedules. Continuous infusion for 7 days produced marked inhibition of tumor growth (T/C = 16%), which was significantly better than twice weekly or ten-times weekly injection of the same total dose. Furthermore, at a total dose of 40 mg/kg of bleomycin, continuous infusion did not result in measurable pulmonary toxicity, whereas both schedules of bolus injection produced significant increases in lung collagen content. Thus, continuous infusion of bleomycin improved its therapeutic effect against Lewis lung carcinoma and also reduced its pulmonary toxicity.

    View details for Web of Science ID A1978GN70800004

    View details for PubMedID 87269

  • QUANTIFICATION OF BLEOMYCIN PULMONARY TOXICITY IN MICE BY CHANGES IN LUNG HYDROXYPROLINE CONTENT AND MORPHOMETRIC HISTOPATHOLOGY CANCER RESEARCH Sikic, B. I., Young, D. M., Mimnaugh, E. G., Gram, T. E. 1978; 38 (3): 787-792

    Abstract

    Bleomycin treatment produced dose-dependent changes in lung collagen content and in several measurable histopathological parameters. NIH/Swiss mice were treated twice weekly for 6 weeks with bleomycin, 0, 1, 20, or 40 mg/kg s.c. The two highest doses produced mortalities of 35 and 100%, respectively, as well as loss of body weight and increase in lung wet weight. Lung hydroxyproline content, an index of collagen, increased to 40 to 50% above control levels at 6 and 8 weeks after initiation of treatment with bleomycin 20 mg/kg. Morphometric analysis was applied to the following parameters at light microscopy: number of intraalveolar macrophages and leukocytes, total pulmonary cell count, alveolar wall thickness, and percentage of consolidation of lung parenchyma. The two highest doses produced increases in all of these parameters as compared to controls. The most marked changes occurred in the number of intraalveolar cells, which in the group given 20 mg/kg rose to 150, 190, and 210% of controls at 4, 6, and 8 weeks. The lowest dose of bleomycin, 1 mg/kg twice weekly for 6 weeks, evoked no pulmonary or other toxicity by the parameters examined. This model of chronic pulmonary toxicity may be useful in analog development, in testing potential antidotes, and in examining the effects of other factors that might modify the pulmonary toxicity of bleomycin.

    View details for Web of Science ID A1978EN67300054

    View details for PubMedID 75060

  • Phase I trial of ixabepilone administered as three oral doses each separated by 6 hours every 3 weeks in patients with advanced solid tumors INVESTIGATIONAL NEW DRUGS Kunz, P. L., He, A. R., Colevas, A. D., Pishvaian, M. J., Hwang, J. J., Clemens, P. L., Messina, M., Kaleta, R., Abrahao, F., Sikic, B. I., Marshall, J. L. 2012; 30 (6): 2364-2370

    Abstract

    Ixabepilone, which stabilizes microtubules, has low susceptibility to drug resistance mediated by P-glycoprotein or ?III-tubulin.This study was designed to determine the maximum tolerated dose (MTD) of oral ixabepilone when administered every 6 h for three doses, every 3 weeks, to patients with refractory advanced cancers. Eighteen patients were treated with escalating doses of ixabepilone: three at cohort 1 (30 mg/dose; 90 mg on Day 1), nine at cohort 2 (40 mg/dose; 120 mg on Day 1), and six at cohort 3 (50 mg/dose; 150 mg on Day 1). Serial plasma samples were collected during cycle 1 for pharmacokinetic (PK) measurements.Of the 18 treated patients, eight were male and ten were female. The median age was 59 years, and most had an excellent performance status (KPS 90-100; 61%). There were two dose limiting toxicities (DLT): Grade 4 febrile neutropenia at the 120 mg dose and Grade 4 neutropenic sepsis at the 150 mg dose. Because of the severity and duration of neutropenic sepsis at level 3, level 2 (120 mg) was defined as the MTD and this cohort was expanded to nine patients. High inter-individual variability in plasma drug concentrations was observed during the study, with particularly high levels in two patients with DLT.On the basis of this safety profile, the MTD of oral ixabepilone was defined as 120 mg given as three 40 mg doses each separated by 6 h on Day 1 of a 3-week cycle. However, the PK variability observed makes further development of this oral formulation unlikely.

    View details for DOI 10.1007/s10637-012-9800-3

    View details for Web of Science ID 000310470100028

    View details for PubMedID 22331549

  • A phase I trial of vandetanib combined with capecitabine, oxaliplatin and bevacizumab for the first-line treatment of metastatic colorectal cancer INVESTIGATIONAL NEW DRUGS Cabebe, E. C., Fisher, G. A., Sikic, B. I. 2012; 30 (3): 1082-1087

    Abstract

    Vandetanib is a tyrosine kinase inhibitor of both the vascular endothelial growth factor (VEGFR) and epidermal growth factor (EGFR) receptors. The primary objectives of this study were to determine the maximum tolerated dose of vandetanib with capecitabine and oxaliplatin, without and with bevacizumab, for the first line treatment of metastatic colorectal cancer (mCRC), and to define the dose limiting toxicities.Three cohorts of patients were studied, with capecitabine at 1,000 mg/m(2) twice daily p.o. on days 1-14 of a 3 week cycle, with oxaliplatin i.v. at 130 mg/m(2) on day 1. Vandetanib dosing was 100 mg/day in cohort 1 and 300 mg/day in cohorts 2 and 3. Bevacizumab was added in cohort 3 at 7.5 mg/kg i.v. on day 1 every 3 weeks.Thirteen patients were enrolled and received from one to eight cycles per patient. Grade 4 dermatitis developed in one patient in the first cohort, and the cohort was expanded to six patients with no further dose limiting toxicities (DLT). The second cohort of 3 patients was well tolerated. The third cohort resulted in grade 3 diarrhea, requiring several days of hospitalization and i.v. hydration, in 3 of the 4 patients. Given the severity and duration of diarrhea, each of these was considered a DLT, and therefore cohort 3 was considered to be above the maximum tolerated dose. Six of the 13 patients achieved a partial or complete remission (46%). The time to progression ranged from 2 to 14 months.Vandetanib at doses of 100 mg and 300 mg daily in combination with capecitabine and oxaliplatin was well tolerated. However, the addition of bevacizumab resulted in severe diarrhea in three out of four patients. Bevacizumab was not well tolerated with vandetanib and XELOX in combination.

    View details for DOI 10.1007/s10637-011-9656-y

    View details for Web of Science ID 000303878700023

    View details for PubMedID 21404105

  • Phase I trial of oblimersen (GenasenseA (R)) and gemcitabine in refractory and advanced malignancies INVESTIGATIONAL NEW DRUGS Galatin, P. S., Advani, R. H., Fisher, G. A., Francisco, B., Julian, T., Losa, R., Sierra, M. I., Sikic, B. I. 2011; 29 (5): 971-977

    Abstract

    Overexpression of Bcl-2 is associated with worse prognosis for a number of cancer types. The present study was designed to determine the maximum tolerated dose (MTD) of oblimersen (antisense Bcl-2) and gemcitabine when administered to patients with refractory malignancies.Sixteen patients with advanced solid tumors refractory to standard therapies were treated with escalating doses of oblimersen continuous, 120-h intravenous infusion given every 14 days, with a fixed-dose-rate intravenous infusion of gemcitabine administered on day 5 of each cycle. Serial plasma samples were collected to calculate the pharmacokinetics of oblimersen and gemcitabine, and also to measure the effect of oblimersen on Bcl-2 expression.7 women and 9 men, median age 55 years (range 35-74 years), received a 5-day infusion of oblimersen at dose levels of 5 mg/kg/day (n = 4) or 7 mg/kg/day (n = 12). On the 5th day of the infusion, gemcitabine was given at 10 mg/m(2)/h for a total dose of 1,000 mg/m(2) (n = 7; cohorts I and II), 1,200 mg/m(2) (n = 3; cohort III), or 1,500 mg/m(2) (n = 6; cohort IV). Edema was the dose-limiting toxicity (DLT), necessitating expansion of cohort IV. No subsequent DLTs were noted. Thus, the maximum planned doses were well tolerated, and a formal MTD was not determined. Most hematologic toxicities were grade 1 or 2. There was low-grade fatigue, nausea/vomiting, and myalgias/arthralgias. Oblimersen C(ss) and AUC increased in relation to the dose escalation, but gemcitabine triphosphate levels did not correlate well with dose. There were no objective responses, though 5 patients had stable disease. A >75% reduction in Bcl-2 expression in peripheral blood mononuclear leucocytes was seen more frequently in patients who achieved stable disease than in progressing patients.The maximal planned dose levels of oblimersen and gemcitabine in combination were well tolerated. Only one DLT (edema) occurred. There was a correlation between Bcl-2 reduction and stable disease. The recommended doses of the drugs for future studies are 7 mg/kg/day of oblimersen on days 1-5, and gemcitabine 1,500 mg/m(2) on day 5, every two weeks.

    View details for DOI 10.1007/s10637-010-9416-4

    View details for Web of Science ID 000294223500027

    View details for PubMedID 20349264

  • Phase I Study of Valspodar (PSC-833) With Mitoxantrone and Etoposide in Refractory and Relapsed Pediatric Acute Leukemia: A Report From the Children's Oncology Group PEDIATRIC BLOOD & CANCER O'Brien, M. M., Lacayo, N. J., Lum, B. L., Kshirsagar, S., Buck, S., Ravindranath, Y., Bernstein, M., Weinstein, H., Chang, M. N., Arceci, R. J., Sikic, B. I., Dahl, G. V. 2010; 54 (5): 694-702

    Abstract

    Valspodar, a non-immunosuppressive analog of cylosporine, is a potent P-glycoprotein (MDR1) inhibitor. As MDR1-mediated efflux of chemotherapeutic agents from leukemic blasts may contribute to drug resistance, a phase 1 study of valspodar combined with mitoxantrone and etoposide in pediatric patients with relapsed or refractory leukemias was performed.Patients received a valspodar-loading dose (2 mg/kg) followed by a 5-day continuous valspodar infusion (8, 10, 12.5, or 15 mg/kg/day) combined with lower than standard doses of mitoxantrone and etoposide. The valspodar dose was escalated using a standard 3 + 3 phase I design.Twenty-one patients were evaluable for toxicity and 20 for response. The maximum tolerated dose (MTD) of valspodar was 12.5 mg/kg/day, combined with 50% dose-reduced mitoxantrone and etoposide. The clearance of mitoxantrone and etoposide was decreased by 64% and 60%, respectively, when combined with valspodar. Dose-limiting toxicities included stomatitis, ataxia, and bone marrow aplasia. Three of 11 patients with acute lymphoblastic leukemia (ALL) had complete responses while no patient with acute myeloid leukemia (AML) had an objective response. In vitro studies demonstrated P-glycoprotein expression on the blasts of 5 of 14 patients, although only 1 had inhibition of rhodamine efflux by valspodar.While this regimen was tolerable, responses in this heavily pretreated population were limited to a subset of patients with ALL.

    View details for DOI 10.1002/pbc.22366

    View details for Web of Science ID 000275935700009

    View details for PubMedID 20209646

  • Phase I and pharmacokinetic study of lexatumumab (HGS-ETR2) given every 2 weeks in patients with advanced solid tumors ANNALS OF ONCOLOGY Wakelee, H. A., Patnaik, A., Sikic, B. I., Mita, M., Fox, N. L., Miceli, R., Ullrich, S. J., Fisher, G. A., Tolcher, A. W. 2010; 21 (2): 376-381

    Abstract

    Lexatumumab (HGS-ETR2) is a fully human agonistic mAb to the tumor necrosis factor-related apoptosis-inducing ligand receptor 2 that activates the extrinsic apoptosis pathway and has potent preclinical antitumor activity. Materials and methods: This phase 1, dose escalation study assessed the safety, tolerability, pharmacokinetics (PKs) and immunogenicity of lexatumumab administered i.v. every 14 days in patients with advanced solid tumors.Thirty-one patients received lexatumumab over five dose levels (0.1-10 mg/kg). Most (26 of 31) received four or more cycles of treatment. One patient at 10 mg/kg experienced a possibly related dose-limiting toxicity of grade 3 hyperamylasemia. Nine patients achieved stable disease. One patient with chemotherapy-refractive Hodgkin's disease experienced a mixed response. Lexatumumab PKs were linear up to 10 mg/kg. At the 10 mg/kg dose, the mean (+/-standard deviation) t(1/2b) was 13.67 +/- 4.07 days, clearance was 4.95 +/- 1.93 ml/day/kg, V(1) was 45.55 ml/kg and V(ss) was 79.08 ml/kg, indicating that lexatumumab distributes outside the plasma compartment. No human antihuman antibodies were detected.Lexatumumab can be safely administered every 14 days at 10 mg/kg. The PK profile supports this schedule. Further evaluation of lexatumumab at this dose schedule is warranted, including combination trials with other agents.

    View details for DOI 10.1093/annonc/mdp292

    View details for Web of Science ID 000274087600029

    View details for PubMedID 19633048

  • Analysis of phase II studies on targeted agents and subsequent phase III trials: What are the predictors for success? JOURNAL OF CLINICAL ONCOLOGY Chan, J. K., Ueda, S. M., Sugiyama, V. E., Stave, C. D., Shin, J. Y., Monk, B. J., Sikic, B. I., Osann, K., Kapp, D. S. 2008; 26 (9): 1511-1518

    Abstract

    To identify the characteristics of phase II studies that predict for subsequent "positive" phase III trials (those that reached the proposed primary end points of study or those wherein the study drug was superior to the standard regimen investigating targeted agents in advanced tumors.We identified all phase III clinical trials of targeted therapies against advanced cancers published from 1985 to 2005. Characteristics of the preceding phase II studies were reviewed to identify predictive factors for success of the subsequent phase III trial. Data were analyzed using the chi(2) test and logistic regression models.Of 351 phase II studies, 167 (47.6%) subsequent phase III trials were positive and 184 (52.4%) negative. Phase II studies from multiple rather than single institutions were more likely to precede a successful trial (60.4% v 39.4%; P < .001). Positive phase II results were more likely to lead to a successful phase III trial (50.8% v 22.5%; P = .003). The percentage of successful trials from pharmaceutical companies was significantly higher compared with academic, cooperative groups, and research institutes (89.5% v 44.2%, 45.2%, and 46.3%, respectively; P = .002). On multivariate analysis, these factors and shorter time interval between publication of phase II results and III study publication were independent predictive factors for a positive phase III trial.In phase II studies of targeted agents, multiple- versus single-institution participation, positive phase II trial, pharmaceutical company-based trials, and shorter time period between publication of phase II to phase III trial were independent predictive factors of success in a phase III trial. Investigators should be cognizant of these factors in phase II studies before designing phase III trials.

    View details for DOI 10.1200/JCO.2007.14.8874

    View details for Web of Science ID 000254178600020

    View details for PubMedID 18285603

  • Integrated high-resolution genome-wide analysis of gene dosage and gene expression in human brain tumors. Methods in molecular biology (Clifton, N.J.) Juric, D., Bredel, C., Sikic, B. I., Bredel, M. 2007; 377: 187-202

    Abstract

    A hallmark genomic feature of human brain tumors is the presence of multiple complex structural and numerical chromosomal aberrations that result in altered gene dosages. These genetic alterations lead to widespread, genome-wide gene expression changes. Both gene expression as well as gene copy number profiles can be assessed on a large scale using microarray methodology. The integration of genetic data with gene expression data provides a particularly effective approach for cancer gene discovery. Utilizing an array of bioinformatics tools, we describe an analysis algorithm that allows for the integration of gene copy number and gene expression profiles as a first-pass means of identifying potential cancer gene targets in human (brain) tumors. This strategy combines circular binary segmentation for the identification of gene copy number alterations, and gene copy number and gene expression data integration with a modification of signal-to-noise ratio computation and random permutation testing. We have evaluated this approach and confirmed its efficacy in the human glioma genome.

    View details for PubMedID 17634618

  • A pilot phase II trial of valspodar modulation of multidrug resistance to paclitaxel in the treatment of metastatic carcinoma of the breast (E1195): A trial of the eastern cooperative oncology group CANCER INVESTIGATION Carlson, R. W., O'Neill, A. M., Goldstein, L. J., Sikic, B. I., Abramson, N., Stewart, J. A., Davidson, N. E., Wood, W. C. 2006; 24 (7): 677-681

    Abstract

    To assess the activity and toxicity of valspodar (PSC-833) in combination with paclitaxel in women with anthracycline refractory, metastatic breast cancer.Limited, multi-institutional, Phase II trial of valspodar at 5 mg/kg/dose orally every 6 hours for 12 doses in combination with paclitaxel 70 mg/m2 administered intravenously as a 3-hour infusion beginning 4 hours after the fifth dose of valspodar, every 3 weeks. Eligible patients had bi-dimensionally measurable metastatic carcinoma of the breast, prior anthracycline therapy or a medical contraindication to anthracycline therapy, no more than one prior chemotherapy for recurrent or metastatic breast cancer, and adequate organ function. Treatment was continued until disease progression or unacceptable toxicity.Thirty-four patients are evaluable for response and 37 for toxicity. Two (6 percent) patients achieved a complete response and 5 (15 percent) a partial response for an objective response rate of 21 percent (95 percent confidence interval of 9 to 38 percent). Median duration of response was 9.7 months (95 percent confidence interval 8.0-17.2 months), median time to progression was 3.3 months (95 percent confidence interval 2.0-4.2 months), and median survival was 12 months (95 percent confidence interval 8.1-17.3 months). The toxicity experienced was acceptable.Combination valspodar plus paclitaxel is an active regimen and has acceptable toxicity. The combination is not clearly more active than single agent paclitaxel.

    View details for DOI 10.1080/07357900600981349

    View details for Web of Science ID 000242207700003

    View details for PubMedID 17118777

  • Multidrug resistance and stem cells in acute myeloid leukemia CLINICAL CANCER RESEARCH Sikic, B. I. 2006; 12 (11): 3231-3232
  • A phase I trial of liposomal doxorubicin, paclitaxel and valspodar (PSC-833), an inhibitor of multidrug resistance ANNALS OF ONCOLOGY Advani, R., Lum, B. L., Fisher, G. A., Halsey, J., Chin, D. L., Jacobs, C. D., Sikic, B. I. 2005; 16 (12): 1968-1973

    Abstract

    The aim of this study was to determine (i) the maximum tolerated dose (MTD) of liposomal doxorubicin (L-DOX) and paclitaxel (DP), (ii) the MTD of DP plus valspodar (DPV) and (iii) pharmacokinetic (PK) interactions of valspodar with L-DOX and paclitaxel.Twenty-three patients with metastatic cancers received DP, followed 4 weeks later by DPV. Dose levels of DP were (mg/m2 for L-DOX/paclitaxel): 30/135 (n = 7), 30/150 (n = 4), 35/150 (n = 8) and 40/150 (n = 4). Dose levels of DPV were 15/70 (n = 10) and 15/60 (n = 10). Serial, paired PK studies were performed.The MTD of DP was 40/150. For DPV at 15/70, five of 10 patients experienced grade 4 neutropenia. In the next cohort, a reduced dose of 15/60 was well tolerated. Valspodar produced reversible grade 3 ataxia in seven patients, requiring dose reduction from 5 to 4 mg/kg. Paired PK studies indicated no interaction between L-DOX and valspodar, and a 49% increase in the median half-life of paclitaxel. Two partial and one minor remissions were noted.The use of valspodar necessitated dose reductions of DP, with neutropenia being dose limiting. Valspodar PK interactions were observed with paclitaxel but not L-DOX.

    View details for DOI 10.1093/annonc/mdi396

    View details for Web of Science ID 000233489600018

    View details for PubMedID 16126736

  • A phase I trial of aprinocarsen (ISIS 3521/LY900003), an antisense inhibitor of protein kinase C-alpha administered as a 24-hour weekly infusion schedule in patients with advanced cancer INVESTIGATIONAL NEW DRUGS Advani, R., Lum, B. L., Fisher, G. A., Halsey, J., Geary, R. S., Holmlund, J. T., Kwoh, T. J., DORR, F. A., Sikic, B. I. 2005; 23 (5): 467-477

    Abstract

    A phase I study was performed to determine the maximum tolerated dose (MTD), safety profile and pharmacology of aprinocarsen (ISIS 3521), an antisense oligonucleotide to protein kinase C-alpha, in patients with refractory solid tumors.Fourteen patients were treated in sequential cohorts of aprinocarsen by 24-hour continuous infusion (CIV), weekly, at doses of 6, 12, 18 and 24 mg/kg.One grade 4 toxicity was observed, transient grade 4 neutropenia at 18 mg/kg. Grade 3 toxicities included neutropenia at 12 mg/kg, fever and hemorrhage at 18 mg/kg, and neutropenia, nausea, and chills at 24 mg/kg. Grade 2 toxicities included thrombocytopenia myalgias, chills, headache, fatigue, fever and nausea/vomiting. Mean prothrombin times and activated partial thromboplastin times (aPTT) increased by 10% and 29% from baseline (p = 0.006 and 0.005). Mean complement split products (Bb and C3a) increased 1.6-fold and 3.6-fold (from p = 0.014 and 0.004, respectively). These changes correlated with dose and were transient with recovery to baseline by day 7. Steady state plasma concentrations (Css) of aprinocarsen were achieved within four hours. Css better described changes in aPTT than dose. Clinical evidence of complement activation was not observed.In contrast to 21-day protracted infusion schedules, delivery of aprinocarsen over a 24-hour infusion schedule showed concentration-dependent effects on coagulation and complement, which are consistent with nonclinical toxicology studies performed in the phosphorothioate DNA antisense drug class. These coagulation and complement changes resulted in a maximum tolerated dose 24 mg/kg.

    View details for DOI 10.1007/s10637-005-2906-0

    View details for Web of Science ID 000231245000008

    View details for PubMedID 16133798

  • Activity of novel cytotoxic agents in lung cancer: Epothilones and topoisomerase I inhibitors CLINICAL LUNG CANCER Wakelee, H. A., Sikic, B. I. 2005; 7: S6-S12

    Abstract

    The treatment of lung cancer--small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC)--is a significant challenge in oncology. The best reported median survival remains near 1 year in advanced NSCLC despite several decades of steady improvement and extensive research with traditional chemotherapy drugs and novel compounds targeted to different aspects of tumor cell growth and function (such as the epidermal growth factor receptor). Extensive-stage SCLC survival is only slightly better. Novel "targeted" therapeutic agents hold promise, but cytotoxic therapy remains the backbone of treatment. Many new cytotoxic agents are currently in development. In this review, we will focus on 2 classes of cytotoxins: epothilones and topoisomerase I inhibitors. Epothilones are microtubule stabilizers with a mechanism of action similar to that of the taxanes, with preclinical activity superior to that of the taxanes. Phase I trials have been completed for patupilone and ixabepilone, and there are encouraging phase II data with ixabepilone in NSCLC. A phase II trial of patupilone is ongoing. The camptothecins, which are topoisomerase I inhibitors, have a long history in the treatment of lung cancer, but the currently available drugs, topotecan and irinotecan, have limitations. Gimatecan and other novel camptothecins have superior preclinical activity and promising phase I/II data in NSCLC and SCLC.

    View details for Web of Science ID 000242719700002

    View details for PubMedID 16159420

  • Amplification of whole tumor genomes and geneby-gene mapping of genomic aberrations from limited sources of fresh-frozen and paraffin-embedded DNA JOURNAL OF MOLECULAR DIAGNOSTICS Bredel, M., Bredel, C., Juric, D., Kim, Y., Vogel, H., Harsh, G. R., Recht, L. D., Pollack, J. R., Sikic, B. I. 2005; 7 (2): 171-182

    Abstract

    Sufficient quantity of genomic DNA can be a bottleneck in genome-wide analysis of clinical tissue samples. DNA polymerase Phi29 can be used for the random-primed amplification of whole genomes, although the amplification may introduce bias in gene dosage. We have performed a detailed investigation of this technique in archival fresh-frozen and formalin-fixed/paraffin-embedded tumor DNA by using cDNA microarray-based comparative genomic hybridization. Phi29 amplified DNA from matched pairs of fresh-frozen and formalin-fixed/paraffin-embedded tumor samples with similar efficiency. The distortion in gene dosage representation in the amplified DNA was nonrandom and reproducibly involved distinct genomic loci. Regional amplification efficiency was significantly linked to regional GC content of the template genome. The biased gene representation in amplified tumor DNA could be effectively normalized by using amplified reference DNA. Our data suggest that genome-wide gene dosage alterations in clinical tumor samples can be reliably assessed from a few hundred tumor cells. Therefore, this amplification method should lend itself to high-throughput genetic analyses of limited sources of tumor, such as fine-needle biopsies, laser-microdissected tissue, and small paraffin-embedded specimens.

    View details for Web of Science ID 000228736900004

    View details for PubMedID 15858140

  • A method for detecting and correcting feature misidentification on expression microarrays BMC GENOMICS Tu, I. P., Schaner, M., Diehn, M., Sikic, B. I., Brown, P. O., Botstein, D., Fero, M. J. 2004; 5

    Abstract

    Much of the microarray data published at Stanford is based on mouse and human arrays produced under controlled and monitored conditions at the Brown and Botstein laboratories and at the Stanford Functional Genomics Facility (SFGF). Nevertheless, as large datasets based on the Stanford Human array began to accumulate, a small but significant number of discrepancies were detected that required a serious attempt to track down the original source of error. Due to a controlled process environment, sufficient data was available to accurately track the entire process leading to up to the final expression data. In this paper, we describe our statistical methods to detect the inconsistencies in microarray data that arise from process errors, and discuss our technique to locate and fix these errors.To date, the Brown and Botstein laboratories and the Stanford Functional Genomics Facility have together produced 40,000 large-scale (10-50,000 feature) cDNA microarrays. By applying the heuristic described here, we have been able to check most of these arrays for misidentified features, and have been able to confidently apply fixes to the data where needed. Out of the 265 million features checked in our database, problems were detected and corrected on 1.3 million of them.Process errors in any genome scale high throughput production regime can lead to subsequent errors in data analysis. We show the value of tracking multi-step high throughput operations by using this knowledge to detect and correct misidentified data on gene expression microarrays.

    View details for DOI 10.1186/1471-2164-5-64

    View details for Web of Science ID 000224203400001

    View details for PubMedID 15357875

  • Resistance to microtubule-targeted cytotoxins in a K562 leukemia cell variant associated with altered tubulin expression and polymerization. Bulletin du cancer Dumontet, C., Jaffrezou, J., Tsuchiya, E., Duran, G. E., Chen, G., Derry, W. B., Wilson, L., Jordan, M. A., Sikic, B. I. 2004; 91 (5): E81-112

    Abstract

    A vinblastine resistant cell line, KCVB2, was established by co-selecting the parental erythroleukemic cell line K562 with step-wise increased concentrations of vinblastine (Velban) in the presence of the cyclosporin D analogue PSC 833 (2 microM), a potent modulator of the multidrug resistance phenotype. KCVB2 cells are 8-fold resistant to the selecting agent, vinblastine, but also exhibit significant resistance to other vinca alkaloids, including 14-fold resistance to vinorelbine, as well as 6-fold cross-resistance to paclitaxel. Doubling time and morphology were similar to the parental K562 cells. Rt-PCR analysis revealed no alterations in the expression of the mdr1 and MRP genes. Intracellular vinblastine accumulation was unchanged. Disruption of the mitotic spindles and multiple mitotic asters occurred in both cell lines but required higher concentrations of vinblastine in KCVB2 cells than in K562 cells. Significant differences were observed in the tubulin content of KCVB2 cells: reduction of total tubulin content, increased polymerized fraction of total tubulin, and overexpression of class III beta-tubulin which is expressed at very low levels in the parental K562 cells. K562 cells transfected with murine class III beta-tubulin did not display the resistance pattern observed in KCVB2 cells. Revertants of KCVB2 manifested reversion to parental drug sensitivity, an increase in total tubulin level, and a decrease in polymerized tubulin. In conclusion, the KCVB2 cell line displays a novel mechanism of resistance to both depolymerizing and stabilizing microtubule-targeted cytotoxins which does not involve altered cellular drug accumulation, but corresponds to alterations in the total tubulin content and polymerization status, and may involve an effect on microtubule dynamics.

    View details for PubMedID 15568225

  • Mitoxantrone, etoposide, and cytarabine with or without valspodar in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome: A phase III trial (E2995) JOURNAL OF CLINICAL ONCOLOGY Greenberg, P. L., Lee, S. J., Advani, R., Tallman, M. S., Sikic, B. I., Letendre, L., Dugan, K., Lum, B., Chin, D. L., Dewald, G., Paietta, E., Bennett, J. M., Rowe, J. M. 2004; 22 (6): 1078-1086

    Abstract

    To determine whether adding the multidrug resistance gene-1 (MDR-1) modulator valspodar (PSC 833; Novartis Pharmaceuticals, Hanover, NJ) to chemotherapy provided clinical benefit to patients with poor-risk acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS).A phase III randomized study was performed using valspodar plus mitoxantrone, etoposide, and cytarabine (PSC-MEC; n=66) versus MEC (n=63) to treat patients with relapsed or refractory AML and high-risk MDS.For the PSC-MEC versus MEC arms, complete response (CR) was achieved in 17% versus 25% of patients, respectively (P=not significant). For patients who had not received prior intensive chemotherapy (ie, with secondary AML or high-risk MDS), the CR rate was increased--35% versus 15% for the remaining patients (P=.018); CR rates did not differ between treatment arms. The median disease-free survival in those achieving CR was similar in the two arms (10 versus 9.3 months) as was the patients' overall survival (4.6 versus 5.4 months). The CR rates in MDR+ (69% of patients) versus MDR- patients were similar for those receiving either chemotherapy regimen (16% versus 24%). The CR rate for unfavorable cytogenetic patients (45% of patients) was 13% compared to the remainder, 28% (P=.09). Population pharmacokinetic analysis demonstrated that the clearances of mitoxantrone and etoposide were decreased by 59% and 50%, respectively, supporting the empiric dose reductions in the PSC-MEC arm designed in anticipation of drug interactions between valspodar and the chemotherapeutic agents.CR rates and overall survival were not improved by using PSC-MEC compared to MEC chemotherapy alone in patients with poor-risk AML or high-risk MDS.

    View details for DOI 10.1200/JCO.2004.07.048

    View details for Web of Science ID 000220287900017

    View details for PubMedID 15020609

  • Genomics-based hypothesis generation: a novel approach to unravelling drug resistance in brain tumours? LANCET ONCOLOGY Bredel, M., Bredel, C., Sikic, B. I. 2004; 5 (2): 89-100

    Abstract

    No currently available chemotherapy seems likely to substantially improve outcome in most patients with brain tumours. Several resistance-associated cellular factors, which were discovered in other cancer models, have also been identified in brain tumours. Although these mechanisms play some part in resistance in brain tumours, they are not sufficient to explain the poor clinical response to chemotherapy. There could be other brain-tumour-specific genetic profiles that are associated with tumour sensitivity to chemotherapy. There is increasing awareness that drug resistance in brain tumours is not a result of changes in single molecular pathways but is likely to involve a complex network of regulatory dynamics. Further insights into chemoresistance in brain tumours could come with comprehensive characterisation of their gene expression, as well as the genetic changes occurring in response to chemotherapy. Recent progress in high-throughput bioanalytical methods for genome-wide studies has made possible a novel research model of initial hypothesis generation followed by functional testing of the generated hypothesis.

    View details for Web of Science ID 000188816600018

    View details for PubMedID 14761812

  • A phase II trial of aprinocarsen, an antisense oligonucleotide inhibitor of protein kinase C alpha, administered as a 21-day infusion to patients with advanced ovarian carcinoma CANCER Advani, R., Peethambaram, P., Lum, B. L., Fisher, G. A., Hartmann, L., Long, H. J., Halsey, J., Holmlund, J. T., Dorr, A., Sikic, B. I. 2004; 100 (2): 321-326

    Abstract

    It has been postulated that protein kinase C alpha (PKC-alpha) plays a pivotal role in signal transduction in tumor cancer cells. Aprinocarsen, a 20-base antisense oligonucleotide, has shown ability to inhibit PKC-alpha protein expression and inhibit tumor growth in human xenograft models. In a previous Phase I trial, the authors demonstrated the safety and some evidence of activity in ovarian carcinoma of aprinocarsen administered as a 21-day, continuous, intravenous infusion.In this Phase II trial, 36 patients with advanced ovarian carcinoma were treated with aprinocarsen at a dose of 2 mg/kg per day delivered as a 21-day, continuous, intravenous infusion. The primary objective was to determine the antitumor response, and the secondary objectives were to evaluate toxicity and to evaluate effects on quality of life (QOL).Between September 1997 and December 1999, 36 patients (median age, 58 years) were enrolled in this trial. Patients were stratified into 2 groups: a platinum-sensitive group (n = 12 patients) and a platinum-resistant group (n = 24 patients). All 36 patients were evaluable for toxicity, and 27 patients were fully assessable for antitumor response after 2 cycles of therapy. All patients had received prior treatments. No objective responses were noted in the platinum-sensitive group. In the platinum-resistant group, 1 patient had some evidence of antitumor activity indicated by a decrease in serum CA 125 and stable disease on imaging studies for 8 months. No changes were noted in overall patient ratings for any of the five QOL domains.When it was administered as a single agent, aprinocarsen did not have significant clinical activity in patients with advanced ovarian carcinoma. Further study may be warranted in combination with platinum-based regimens.

    View details for DOI 10.1002/cncr.11909

    View details for Web of Science ID 000188610500016

    View details for PubMedID 14716767

  • Phase I and pharmacokinetic study of BMS-188797, a new taxane analog, administered on a weekly schedule in patients with advanced malignancies CLINICAL CANCER RESEARCH Advani, R., Fisher, G. A., Lum, B. L., Jambalos, C., Cho, C. D., Cohen, M., Gollerkeri, A., Sikic, B. I. 2003; 9 (14): 5187-5194

    Abstract

    The purpose of this study was to establish the maximum tolerated dose (MTD), dose-limiting toxicities (DLTs), and preliminary activity of BMS-188797 administered weekly.Patients with advanced malignancies were treated with escalating doses of BMS-188797 on a weekly schedule as a 1-h i.v. infusion. Plasma sampling was performed to characterize the pharmacokinetics of BMS-188797.Eighteen patients with advanced malignancies were enrolled at three dose levels ranging from 35 to 65 mg/m(2). The number of patients evaluated at each dose level was as follows: 35 mg/m(2) (n = 3); 50 mg/m(2) (n = 9); and 65 mg/m(2) (n = 6). At 65 mg/m(2), three of six patients had a DLT (one had grade 4 neutropenia lasting >7 days, and two had grade 3 diarrhea). Expansion of the 50-mg/m(2) dose cohort to nine patients established this dose as the MTD, with one patient experiencing a DLT (grade 4 neutropenia with fever). Two partial responses were observed (lung cancer, 7+ months; ovarian cancer, 6+ months durations), as well as two minor responses (esophageal cancer, 5 months; ovarian cancer, 5 months). Both patients with partial responses had been clinically resistant to paclitaxel. Plasma pharmacokinetic mean values of maximum concentration (C(max)) and area under the curve (AUC(0-48)) increased in a dose-dependent manner within the range of doses used in this study, and in three of four patients, the DLTs correlated with AUC.The MTD and the recommended Phase II dose of weekly BMS-188797 is 50 mg/m(2). The drug demonstrates antitumor activity in taxane-refractory solid tumors and is now being evaluated in combination with carboplatin.

    View details for Web of Science ID 000186558400017

    View details for PubMedID 14613998

  • Gene expression patterns in ovarian carcinomas MOLECULAR BIOLOGY OF THE CELL Schaner, M. E., Ross, D. T., Ciaravino, G., Sorlie, T., Troyanskaya, O., Diehn, M., Wang, Y. C., Duran, G. E., Sikic, T. L., Caldeira, S., Skomedal, H., Tu, I. P., Hernandez-Boussard, T., Johnson, S. W., O'Dwyer, P. J., Fero, M. J., Kristensen, G. B., Borresen-Dale, A. L., Hastie, T., Tibshirani, R., van de Rijn, M., Teng, N. N., Longacre, T. A., Botstein, D., Brown, P. O., Sikic, B. I. 2003; 14 (11): 4376-4386

    Abstract

    We used DNA microarrays to characterize the global gene expression patterns in surface epithelial cancers of the ovary. We identified groups of genes that distinguished the clear cell subtype from other ovarian carcinomas, grade I and II from grade III serous papillary carcinomas, and ovarian from breast carcinomas. Six clear cell carcinomas were distinguished from 36 other ovarian carcinomas (predominantly serous papillary) based on their gene expression patterns. The differences may yield insights into the worse prognosis and therapeutic resistance associated with clear cell carcinomas. A comparison of the gene expression patterns in the ovarian cancers to published data of gene expression in breast cancers revealed a large number of differentially expressed genes. We identified a group of 62 genes that correctly classified all 125 breast and ovarian cancer specimens. Among the best discriminators more highly expressed in the ovarian carcinomas were PAX8 (paired box gene 8), mesothelin, and ephrin-B1 (EFNB1). Although estrogen receptor was expressed in both the ovarian and breast cancers, genes that are coregulated with the estrogen receptor in breast cancers, including GATA-3, LIV-1, and X-box binding protein 1, did not show a similar pattern of coexpression in the ovarian cancers.

    View details for Web of Science ID 000186738300005

    View details for PubMedID 12960427

  • Phase I trial of uracil-ftorafur, leucovorin, and etoposide: an active all-oral regimen for metastatic breast cancer BREAST CANCER RESEARCH AND TREATMENT Hartman, A. R., Grekowicz, A., Lum, B. L., Carlson, R. W., Schurman, C., Sikic, B. I., Shapiro, R., Stockdale, F. E. 2003; 82 (1): 61-69

    Abstract

    To determine the maximum tolerated doses, toxicities, and therapeutic effect of an oral chemotherapy regimen consisting of uracil-ftorafur, etoposide, and leucovorin for metastatic breast cancer.The regimen consists of 28-day cycles of uracil-ftorafur, etoposide, and leucovorin administered orally on days 1-14. The dose of etoposide was fixed at 50 mg/m2/day, and uracil-ftorafur was escalated in 50 mg/m2/day increments from 200 to 350 mg/m2. Leucovorin, was used at a dose of 90 mg/day. Eligibility criteria required prior treatment with a taxane or anthracycline.A total of 23 patients were enrolled. Twenty patients are assessable for toxicity and 16 patients are assessable for response. All non-hematologic toxicities were grade 1 or 2. Three hematologic dose-limiting toxicities (DLTs) were observed. Partial responses were seen in 6 of 16 (37.5%, 95% confidence interval 15%, 85%) of assessable patients with durations ranging from 4 to 20 months. Stable disease was observed in 4 of 16 (25%) of patients with durations from 4 to 12 months. Median time to progression was 10.5 months. An intent to treat analysis revealed a response of 26%.The recommended dose and schedule of this combination is uracil-ftorafur 350 mg/m2, leucovorin 90 mg/day, and etoposide 50 mg/m2 for two consecutive weeks in a 4-week cycle. This all-oral regimen is well tolerated and demonstrates encouraging efficacy in a cohort of heavily pretreated patient with metastatic breast cancer.

    View details for Web of Science ID 000186609000008

    View details for PubMedID 14672404

  • Rapid determination of PEGylated liposomal doxorubicin and its major metabolite in human plasma by ultraviolet-visible high-performance liquid chromatography JOURNAL OF CHROMATOGRAPHY B-ANALYTICAL TECHNOLOGIES IN THE BIOMEDICAL AND LIFE SCIENCES Chin, D. L., Lum, B. L., Sikic, B. I. 2002; 779 (2): 259-269

    Abstract

    A high-performance liquid chromatographic method was developed for the quantification of doxorubicin derived from PEGylated liposomal doxorubicin (Doxil) and its major metabolite in human plasma. This method utilizes Triton X-100 to disperse the liposome, followed by a protein precipitation step with 5-sulfosalicylic acid. Analytes in the resultant supernatant are separated on a Discovery RP amide C(16) column (250 x 3 mm I.D., 5 microm) using an isocratic elution with a mobile phase consisting of 0.05 M sodium acetate (pH 4.0) and acetonitrile (72:28). The retention times for doxorubicin and the internal standard daunorubicin were 4.8 and 10.1 min, respectively. The column eluate was monitored by UV-visible detection at 487 nm. The determination of doxorubicin was found to be linear in the range of 1.0 ng/mL to 25 microg/mL, with intra-day and inter-day coefficients of variation and percent error < or =10%. The recovery of doxorubicin from plasma was >69.3%, with a liposomal dispersion efficiency of >95.7%. Our analytical method for free and PEGylated doxorubicin in human plasma is rapid, avoids organic extractions, and maintains sensitivity for the parent compound and its major metabolite, doxorubicinol.

    View details for Web of Science ID 000178936700011

    View details for PubMedID 12361740

  • Re: Genetic analysis of the beta-tubulin gene, TUBB, in non-small-cell lung cancer JOURNAL OF THE NATIONAL CANCER INSTITUTE Sale, S., Oefner, P. J., Sikic, B. I. 2002; 94 (10): 776-777

    View details for Web of Science ID 000175623400019

    View details for PubMedID 12011233

  • Pharmacokinetic interactions of cyclosporine with etoposide and mitoxantrone in children with acute myeloid leukemia LEUKEMIA Lacayo, N. J., Lum, B. L., Becton, D. L., Weinstein, H., Ravindranath, Y., Chang, M. N., Bomgaars, L., Lauer, S. J., Sikic, B. I., Dahl, G. V. 2002; 16 (5): 920-927

    Abstract

    The purpose of this study was to assess the effect of the multidrug resistance modulator cyclosporine (CsA) on the pharmacokinetics of etoposide and mitoxantrone in children with de novo acute myeloid leukemia (AML). Serial blood samples for pharmacokinetic studies were obtained in 38 children over a 24-h period following cytotoxin treatment with or without CsA on days 1 and 4. Drug concentrations were quantitated using validated HPLC methods, and pharmacokinetic parameters were determined using compartmental modeling with an iterative two-stage approach, implemented on ADAPT II software. Etoposide displayed a greater degree of interindividual variability in clearance and systemic exposure than mitoxantrone. With CsA treatment, etoposide and mitoxantrone mean clearance declined by 71% and 42%, respectively. These effects on clearance, in combination with the empiric 40% dose reduction for either cytotoxin, resulted in a 47% and 12% increases in the mean AUC for etoposide and mitoxantrone, respectively. There were no differences in the rates of stomatitis or infection between the two groups. CsA treatment resulted in an increased incidence of hyperbilrubinemia, which rapidly reversed upon conclusion of drug therapy. The variability observed in clearance, combined with the empiric 40% dose reduction of the cytotoxins, resulted in statistically similar systemic exposure and similar toxicity.

    View details for DOI 10.1038/sj/leu/2402455

    View details for Web of Science ID 000175631200020

    View details for PubMedID 11986955

  • Conservation of the class I beta-tubulin gene in human populations and lack of mutations in lung cancers and paclitaxel-resistant ovarian cancers MOLECULAR CANCER THERAPEUTICS Sale, S., Sung, R., Shen, P. D., Yu, K., Wang, Y., Duran, G. E., Kim, J. H., Fojo, T., Oefner, P. J., Sikic, B. I. 2002; 1 (3): 215-225

    Abstract

    The goal of this study was to determine the prevalence of sequence variants in the class I beta-tubulin (clone m40) gene and their occurrence in human tumors and cancer cell lines. DNA was isolated from 93 control individuals representing a wide variety of ethnicities, 49 paclitaxel-naive specimens (16 ovarian cancers, 17 non-small cell lung cancers, and 16 ovarian cancer cell lines), and 30 paclitaxel-resistant specimens (9 ovarian cancers, 9 ovarian cancer cell lines, and 12 ovarian cancer xenografts in nude mice). Denaturing high-performance liquid chromatography and direct sequence analysis detected two silent polymorphisms in exon 4, Leu217Leu (CTG/CTA) and Gly400Gly (GGC/GGT), with minor allele frequencies of 17 and 0.5%, respectively. Five nucleotide substitutions and one single-base deletion were detected in introns 1, 2, and 3 and in the 3' untranslated region. Analysis of 49 paclitaxel-naive and 30 paclitaxel-resistant specimens revealed no additional polymorphisms in the coding region. In addition, no amino acid replacements were found in chimpanzee, gorilla, and orangutan in comparison to human. Our data demonstrate a very high degree of sequence conservation in class I beta-tubulin, suggesting that all residues are important in tubulin structure and function. Individual variation in response to treatment with paclitaxel is not likely to be caused by genetic variations in the beta-tubulin drug target. Moreover, acquired mutations in class I beta-tubulin are unlikely to be a clinically relevant cause of drug resistance.

    View details for Web of Science ID 000178736700007

    View details for PubMedID 12467216

  • Motexafin gadolinium: A redox active drug that enhances the efficacy of bleomycin and doxorubicin CLINICAL CANCER RESEARCH MILLER, R. A., Woodburn, K. W., Fan, Q., Lee, I., Miles, D., Duran, G., Sikic, B., Magda, D. 2001; 7 (10): 3215-3221

    Abstract

    The effect of motexafin gadolinium (MGd), a redox mediator, on tumor response to doxorubicin (Dox) and bleomycin (Bleo) was investigated in vitro and in vivo. MES-SA human uterine sarcoma cells were studied in vitro using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay. Rif-1, a murine fibrosarcoma cell line, was studied using a clonogenic survival assay. Tumor growth delay assays were performed using the EMT-6 murine mammary sarcoma cell line in BALB/c mice. MGd (25-100 microM) produced dose-dependent enhancement of Bleo cytotoxicity to MES-SA cells. The IC(50) for Bleo was reduced by approximately 10-fold using 100 microM MGd. In clonogenic assays using Rif-1 cells, MGd enhanced the activity of Bleo approximately 1000-fold. This effect was shown to be mediated, in part, by MGd inhibition of potentially lethal damage repair. MGd enhanced the tumor response to bleomycin and Dox in vivo. MGd had no significant effect on the systemic exposure to Dox (expressed in terms of the plasma area under the curve, 0-24 h) and did not increase Dox myelosuppression. MGd enhanced the effectiveness of the redox active drugs, Bleo and Dox.

    View details for Web of Science ID 000171574600037

    View details for PubMedID 11595717

  • Dominant effector genetics in mammalian cells NATURE GENETICS Xu, X., Leo, C., Jang, Y. J., Chan, E., Padilla, D., Huang, B. C., Lin, T., Gururaja, T., Hitoshi, Y., Lorens, J. B., Anderson, D. C., Sikic, B., Luo, Y., Payan, D. G., Nolan, G. P. 2001; 27 (1): 23-29

    Abstract

    We have expressed libraries of peptides in mammalian cells to select for trans-dominant effects on intracellular signaling systems. As an example-and to reveal pharmacologically relevant points in pathways that lead to Taxol resistance-we selected for peptide motifs that confer resistance to Taxol-induced cell death. Of several peptides selected, one, termed RGP8.5, was linked to upregulation of expression of the gene ABCB1 (also known as MDR1, for multiple drug resistance) in HeLa cells. Our data indicate that trans-dominant effector peptides can point to potential mechanisms by which signaling systems operate. Such tools may be useful in functional genomic analysis of signaling pathways in mammalian disease processes.

    View details for Web of Science ID 000166187900011

    View details for PubMedID 11137994

  • Clinical studies of antisense therapy in cancer FRONTIERS IN BIOSCIENCE Yuen, A. R., Sikic, B. I. 2000; 5: D588-D593

    Abstract

    The ability to target and inhibit individual gene expression with antisense oligonucleotides has shown promising activity in preclinical cancer models. Recent clinical studies have tested antisense compounds directed against seven cancer related genes including p53, bcl-2, c-raf, H-ras, protein kinase C-alpha, and protein kinase A. Class specific effects of the phosphorothioate backbone common to the first generation of antisense compounds have dominated the side effects of these oligonucleotides. Inhibition of target gene expression has been modest at most, and clinical activity has been primarily anecdotal. Combinations of the antisense compounds with chemotherapy and second-generation oligonucleotides offer promise that these agents might become a standard part of future cancer therapy.

    View details for Web of Science ID 000089664000003

    View details for PubMedID 10833467

  • Mitoxantrone, etoposide, and cyclosporine therapy in pediatric patients with recurrent or refractory acute myeloid leukemia JOURNAL OF CLINICAL ONCOLOGY Dahl, G. V., Lacayo, N. J., Brophy, N., Dunussi-Joannopoulos, K., Weinstein, H. J., Chang, M. R., Sikic, B. I., Arceci, R. J. 2000; 18 (9): 1867-1875

    Abstract

    To determine the remission rate and toxicity of mitoxantrone, etoposide, and cyclosporine (MEC) therapy, multidrug resistance-1 (MDR1) status, and steady-state cyclosporine (CSA) levels in children with relapsed and/or refractory acute myeloid leukemia.MEC therapy consisted of mitoxantrone 6 mg/m(2)/d for 5 days, etoposide 60 mg/m(2)/d for 5 days, and CSA 10 mg/kg for 2 hours followed by 30 mg/kg/d as a continuous infusion for 98 hours. Because of pharmacokinetic interactions, drug doses were decreased to 60% of those found to be effective without coadministration of CSA. MDR1 expression was evaluated by reverse transcriptase polymerase chain reaction, flow cytometry, and the ability of CSA at 2.5 micromol/L to increase intracellular accumulation of (3)H-daunomycin in blasts from bone marrow specimens.The remission rate was 35% (n = 23 of 66). Overall, 35% of patients (n = 23) achieved complete remission (CR), 12% of patients (n = 8) achieved partial remission, and 9% of patients (n = 6) died of infection. Exposure to CSA levels of greater than 2,400 ng/mL was achieved in 95% of patients (n = 56 of 59). Toxicities included infection, cardiotoxicity, myelosuppression, stomatitis, and reversible increases in serum creatinine and bilirubin. In most who had relapsed while receiving therapy or whose induction therapy had failed, response was not significantly different for MDR1-positive and MDR1-negative patients.Serum levels of CSA capable of reversing multidrug resistance are achievable in children with acceptable toxicity. The CR rate of 35% achieved in this study is comparable to previously reported results using standard doses of mitoxantrone and etoposide. The use of CSA may have improved the response rate for the MDR1-positive patients so that it was not different from that for the MDR1-negative patients.

    View details for Web of Science ID 000086873900008

    View details for PubMedID 10784627

  • Decreased cortisol secretion by adrenal glands perfused with the P-glycoprotein inhibitor valspodar and mitotane or doxorubicin ANTI-CANCER DRUGS Cufer, T., Pfeifer, M., Vrhovec, I., Frangez, R., Kosec, M., Mrhar, A., Grabnar, I., Golouh, R., Vogric, S., Sikic, B. I. 2000; 11 (4): 303-309

    Abstract

    The aim of this study was to investigate the role of P-glycoprotein (P-gp) in the adrenal gland. It has been presumed that P-gp, rather than being involved in physiological cortisol secretion, plays a role in protecting the adrenacortical cells from xenobiotics. To explore this a study was performed on perfused bovine adrenal glands. Individual experimental groups were perfused with either a selective P-gp blocker (valspodar) alone, with a xenobiotic (mitotane or doxorubicin) alone or with both valspodar and a xenobiotic. The cumulative amounts of cortisol secreted in each individual group were calculated and the two-sample t-test was used to compare the mean values of cumulative amounts. The mean value of cortisol secreted from the group of adrenals perfused with the P-gp blocker was not significantly different from that of the control group. Treatment with either mitotane or doxorubicin decreased the amount of cortisol secreted but not significantly when compared to the amount of cortisol secreted in basal conditions. However, treatment with the P-gp blocker valspodar in addition to either mitotane or doxorubicin significantly decreased cortisol secreted compared to the amount of cortisol secreted by the glands treated with either mitotane (p=0.009) or doxorubicin (p=0.017) alone. The regressive changes discovered in all experimental groups were most prominent when valspodar was used with either mitotane or doxorubicin. We found that P-gp blockade increases by xenobiotic (mitotane and doxorubicin)-induced damage of adrenocortical cells, which points to a role of P-gp in the protection of adrenal gland from xenobiotics.

    View details for Web of Science ID 000087531300012

    View details for PubMedID 10898547

  • Effect of high-dose cyclosporine on etoposide pharmacodynamics in a trial to reverse P-glycoprotein (MDR1 gene) mediated drug resistance CANCER CHEMOTHERAPY AND PHARMACOLOGY Lum, B. L., Kaubisch, S., Fisher, G. A., Brown, B. W., Sikic, B. I. 2000; 45 (4): 305-311

    Abstract

    The consequences of using cyclosporine (CsA) therapy to modulate P-glycoprotein-mediated multidrug resistance include increased myelosuppression, hyperbilirubinemia, and altered disposition of the cytotoxin. The purpose of this study was to analyze further the relationship between the degree of leukopenia, and etoposide pharmacokinetic factors.Each patient initially received intravenously-administered etoposide alone (150-200 mg/m2/d x 3). Later it was given in combination with CsA administered at escalating loading doses (range 2-7 mg/kg) as a 2 hour intravenous (IV) infusion followed by a 3 day continuous infusion, at doses ranging from 5 to 21 mg/ kg/day. Serial plasma etoposide concentration-time samples were assayed by high-performance liquid chromatography (HPLC). The area under the curve (AUC) of unbound etoposide was calculated from the total plasma etoposide AUC using a previous published equation [22] where % unbound etoposide = (1.4 x total bilirubin) - (6.8 x serum albumin) + 34.4. The percent decrease in white blood cell (WBC) count and the total or unbound etoposide AUC relationship was fitted to a sigmoid Emax model adapted for paired observations, where: % Decrease in WBC count =E(max) x PDRV(H+Z x delta)/(PDRV50 + Z x beta) + PDRVH + Z x delta In this equation, Z was the variable describing the two treatment groups (0 = no CsA and 1 = CsA). The fitted parameters were PDRV50, the pharmacodynamic response variable (PDRV) producing 50% of the maximal response; parameter beta, which describes the effect of the treatment group on the PDRV50; parameter H (Hill constant), which defines the slope of the response curve and parameter delta, which describes the effect of the treatment group on parameter H.CsA at a median concentration of 1,938 microg/ml resulted in a median increase in the total plasma etoposide AUC by 103% and the calculated unbound plasma etoposide AUC by 104%. This paralleled a 12% greater median percent decrease in WBC count during etoposide + CsA treatment (72% vs. 84%, P = 0.03). The percent decrease in WBC count and total or unbound etoposide AUC relationship was fitted to the sigmoid Emax model. The model using the unbound etoposide AUC described the data adequately (r = 0.790) and was precise, with a mean absolute error of 6.4% (95% confidence interval: -4.9, 7.8). The fitted parameter-estimates suggested that at equivalent unbound etoposide AUC values above 10 microg x h/ml, the sigmoid Emax model predicted a 5% greater WBC count suppression when CsA was added to the treatment regimen.These findings suggest that a small degree of the enhanced myelosuppression observed with CsA combined with etoposide might be attributable to inhibition of P-glycoprotein in bone marrow precursor cells. However, the majority of the effect observed appears to be due to pharmacokinetic interactions, which result in increases in unbound etoposide.

    View details for Web of Science ID 000086159200007

    View details for PubMedID 10755319

  • Phase I study of an antisense oligonucleotide to protein kinase C-alpha (ISIS 3521/CGP 64128A) in patients with cancer CLINICAL CANCER RESEARCH Yuen, A. R., Halsey, J., Fisher, G. A., Holmlund, J. T., Geary, R. S., Kwoh, T. J., Dorr, A., Sikic, B. I. 1999; 5 (11): 3357-3363

    Abstract

    Protein kinase C (PKC) is an attractive target in cancer therapy. It is overexpressed in a variety of cancers, and nonspecific inhibitors of PKC have demonstrated antitumor activity. Antisense oligonucleotides targeted against PKC-alpha, which have high specificity, can inhibit mRNA and protein expression as well as the growth of tumors in vitro and in vivo. This Phase I study sought to characterize the safety profile and to determine the maximum tolerated dose of antisense to PKC-alpha when administered by continuous infusion in patients. Patients with incurable malignancies received ISIS 3521, a 20-length phosphorothioate oligodeoxynucleotide specific for PKC-alpha. Treatment was delivered over a period of 21 days by continuous i.v. infusion followed by a 7-day rest period. Doses were increased from 0.5 to 3.0 mg/kg/day. Patients continued on the study until evidence of disease progression or unacceptable toxicity was detected. Between August 1996 and September 1997, 21 patients were treated in five patient cohorts. The maximum tolerated dose was 2.0 mg/kg/day. The dose-limiting toxicities were thrombocytopenia and fatigue at a dose of 3.0 mg/kg/day. Pharmacokinetic measurements showed rapid plasma clearance and dose-dependent steady-state concentrations of ISIS 3521. Evidence of tumor response lasting up to 11 months was observed in three of four patients with ovarian cancer. The recommended dose of ISIS 3521 for Phase II studies is 2.0 mg/kg/day when given over a period of 21 days. Side effects are modest and consist of thrombocytopenia and fatigue. Evidence of antitumor activity provides the rationale for Phase II studies in ovarian cancer and other malignancies.

    View details for Web of Science ID 000083853200005

    View details for PubMedID 10589745

  • Mechanisms of action of and resistance to antitubulin agents: Microtubule dynamics, drug transport, and cell death JOURNAL OF CLINICAL ONCOLOGY Dumontet, C., Sikic, B. I. 1999; 17 (3): 1061-1070

    Abstract

    To analyze the available data concerning mechanisms of action of and mechanisms of resistance to the antitubulin agents, vinca alkaloids and taxanes, and more recently described compounds.We conducted a review of the literature on classic and recent antitubulin agents, focusing particularly on the relationships between antitubulin agents and their intracellular target, the soluble tubulin/microtubule complex.Although it is widely accepted that antitubulin agents block cell division by inhibition of the mitotic spindle, the mechanism of action of antitubulin agents on microtubules remains to be determined. The classic approach is that vinca alkaloids depolymerize microtubules, thereby increasing the soluble tubulin pool, whereas taxanes stabilize microtubules and increase the microtubular mass. More recent data suggest that both classes of agents have a similar mechanism of action, involving the inhibition of microtubule dynamics. These data suggest that vinca alkaloids and taxanes may act synergistically as antitumor agents and may be administered as combination chemotherapy in the clinic. However, enhanced myeloid and neurologic toxicity, as well as a strong dependence on the sequence of administration, presently exclude these combinations outside the context of clinical trials. Although the multidrug resistance phenotype mediated by Pgp appears to be an important mechanism of resistance to these agents, alterations of microtubule structure resulting in altered microtubule dynamics and/or altered binding of antitubulin agents may constitute a significant mechanism of drug resistance.

    View details for Web of Science ID 000078972800042

    View details for PubMedID 10071301

  • Treatment of refractory and relapsed acute myelogenous leukemia with combination chemotherapy plus the multidrug resistance modulator PSC833 (Valspodar) BLOOD Advani, R., Saba, H. I., Tallman, M. S., Rowe, J. M., Wiernik, P. H., Ramek, J., Dugan, K., Lum, B., Villena, J., Davis, E., Paietta, E., Litchman, M., Sikic, B. I., Greenberg, P. L. 1999; 93 (3): 787-795

    Abstract

    A potential mechanism of chemotherapy resistance in acute myeloid leukemia (AML) is the multidrug resistance (MDR-1) gene product P-glycoprotein (P-gp), which is often overexpressed in myeloblasts from refractory or relapsed AML. In a multicenter phase II clinical trial, 37 patients with these poor risk forms of AML were treated with PSC 833 (Valspodar; Novartis Pharmaceutical Corporation, East Hanover, NJ), a potent inhibitor of the MDR-1 efflux pump, plus mitoxantrone, etoposide, and cytarabine (PSC-MEC). Pharmacokinetic (PK) interactions of etoposide and mitoxantrone with PSC were anticipated, measured in comparison with historical controls without PSC, and showed a 57% decrease in etoposide clearance (P =.001) and a 1.8-fold longer beta half-life for mitoxantrone in plasma (P <.05). The doses of mitoxantrone and etoposide were substantially reduced to compensate for these interactions and clinical toxicity and in Cohort II were well tolerated at dose levels of 4 mg/m2 mitoxantrone, 40 mg/m2 etoposide, and 1 g/m2 C daily for 5 days. Overall, postchemotherapy marrow hypoplasia was achieved in 33 patients. Twelve patients (32%) achieved complete remission, four achieved partial remission, and 21 failed therapy. The PK observations correlated with enhanced toxicity. The probability of an infectious early death was 36% (4 of 11) in patients with high PK parameters for either drug versus 5% (1 of 20) in those with lower PK parameters (P =.04). P-gp function was assessed in 19 patients using rhodamine-123 efflux and its inhibition by PSC. The median percentage of blasts expressing P-gp was increased (49%) for leukemic cells with PSC-inhibitable rhodamine efflux compared with 17% in cases lacking PSC-inhibitable efflux (P =.004). PSC-MEC was relatively well tolerated in these patients with poor-risk AML, and had encouraging antileukemic effects. The Eastern Cooperative Oncology Group is currently testing this regimen versus standard MEC chemotherapy in a phase III trial, E2995, in a similar patient population.

    View details for Web of Science ID 000078319100003

    View details for PubMedID 9920827

  • Interaction of anti-HIV protease inhibitors with the multidrug transporter P-glycoprotein (P-gp) in human cultured cells JOURNAL OF ACQUIRED IMMUNE DEFICIENCY SYNDROMES Washington, C. B., Duran, G. E., Man, M. C., Sikic, B. I., Blaschke, T. F. 1998; 19 (3): 203-209

    Abstract

    The anti-HIV protease inhibitors represent a new class of agents for treatment of HIV infection. Saquinavir, ritonavir, indinavir, and nelfinavir are the first drugs approved in this class and significantly reduce HIV RNA copy number with minimal adverse effects. They are all substrates of cytochrome P450 3A4, and are incompletely bioavailable. The drug transporting protein, P-glycoprotein (P-gp), which is highly expressed in the intestinal mucosa, could be responsible for the low oral bioavailability of these and other drugs which are substrates for this transporter. To determine whether these protease inhibitors are modulators of P-gp, we studied them in cell lines which do and do not express P-gp. Saquinavir, ritonavir and nelfinavir significantly inhibited the efflux of [3H]paclitaxel and [3H]vinblastine in P-gp-positive cells, resulting in an increase in intracellular accumulation of these drugs. However, similar concentrations of indinavir did not affect the accumulation of these anticancer agents. In photoaffinity labeling studies, saquinavir and ritonavir displaced [3H]azidopine, a substrate for P-gp, in a dose-dependent manner. These data suggest that saquinavir, ritonavir, and nelfinavir are inhibitors and possibly substrates of P-gp. Because saquinavir has a low bioavailability, its interaction with P-gp may be involved in limiting its absorption.

    View details for Web of Science ID 000076693700001

    View details for PubMedID 9803961

  • Effect of the multidrug resistance modulator valspodar on serum cortisol levels in rabbits CANCER CHEMOTHERAPY AND PHARMACOLOGY Cufer, T., Vrhovec, I., Pfeifer, M., Skrk, J., Borstnar, S., Sikic, B. I. 1998; 41 (6): 517-521

    Abstract

    To contribute to a better understanding of the physiological role of P-glycoprotein (P-gp) in the adrenal gland, we initiated our studies in rabbits. The aim of our study was to explore the effect of the selective multidrug resistance (MDR) modulator PSC 833 (valspodar) on serum cortisol in rabbits.Baseline and corticotropin-stimulated serum cortisol levels were measured before and after valspodar treatment in adult male rabbits. Seven rabbits were treated with 50 mg/kg per dose and seven, with 75 mg/kg per dose of valspodar subcutaneously. Serum cortisol levels were determined by radioimmunoassay adjusted for expected values.Serum cortisol levels (baseline as well as corticotropin-stimulated) increased after both valspodar treatment regimens. The increase was dose-dependent and was higher for the baseline than for the corticotropin-stimulated values. Serum valspodar levels exceeding 1000 ng/ml were achieved in all except one animal in each group. We hypothesize that the increased serum cortisol levels were due to increased adrenocorticotropic hormone (ACTH) secretion after valspodar treatment, but, unfortunately, we could not measure ACTH properly in rabbits by means of the commercially available kits.Our study indicates that P-gp is not involved in steroid hormone secretion in the adrenal gland. This is evident from observations that serum cortisol levels were found to have increased rather than decreased in rabbits treated with a P-gp blocker and that the treated animals appeared healthy and normal. Since P-gp was found to play an important role in protection against xenobiotics in some other organs, further studies to explore the protective role of P-gp in the adrenal gland are warranted.

    View details for Web of Science ID 000073172000014

    View details for PubMedID 9554598

  • Pharmacologic approaches to reversing multidrug resistance SEMINARS IN HEMATOLOGY Sikic, B. I. 1997; 34 (4): 40-47

    Abstract

    The rationale for modulation of multidrug resistance (MDR) by inhibitors of the multidrug transporter, P-glycoprotein (P-gp) includes the following: (1) P-gp is expressed by human cancers, either at diagnosis or after failure of chemotherapy; (2) P-gp expression at diagnosis has been associated with a poor prognosis in some types of cancer; (3) MDR related to P-gp expression can be reversed by modulators, resulting in enhanced therapeutic efficacy in cellular and animal models of drug resistance; and (4) the emergence of MDR related to P-gp expression can be prevented in cellular models by co-administration of MDR-related cytotoxins and modulators. Clinical trials of modulation of MDR have been limited by two major factors: inability to achieve adequate levels of the modulators to reverse drug resistance in patients and the presence of other mechanisms of resistance in tumor cells in addition to P-gp. The former limitation will hopefully be overcome by new, more potent and specific inhibitors of P-gp such as PSC 833. The latter will require further understanding of various alternative cellular mechanisms of resistance and the development of approaches to overcome or circumvent these mechanisms. PSC 833 is associated with significant drug interactions with MDR-related cytotoxic agents, which require dose reduction of the cytotoxins to achieve a dose exposure and toxicity similar to the chemotherapy agents without a modulator. These drug interactions are predictable and are at least in part due to inhibition of P-gp in normal tissues such as the liver and kidneys, where P-gp is known to play a role in drug excretion. Data from knockout mice, which lack P-gp expression, support the concept that P-gp is an important factor in MDR-related drug disposition. Early data from phase I and II trials with PSC 833 indicate that substantial inhibition of P-gp can be achieved in patients at clinically tolerable doses of both modulator and cytotoxins. The ultimate therapeutic benefit of MDR modulation with PSC 833 is currently being tested in phase III clinical trials in acute myeloid leukemias (AMLs) and multiple myeloma.

    View details for Web of Science ID 000070965700007

    View details for PubMedID 9408960

  • Validation of a limited sampling model to determine etoposide area under the curve PHARMACOTHERAPY Lum, B. L., LANE, K. J., Synold, T. W., Goram, A., Charnick, S. B., Sikic, B. I. 1997; 17 (5): 887-890

    Abstract

    To validate the utility of a previously reported 3-point limited sampling model (LSM) for determining etoposide area under the curve to infinity (AUC(infinity)).Secondary analysis of data from two clinical trials of etoposide.University medical center clinical research center.Thirty-four patients with different malignancies.Etoposide was administered as a 2-hour infusion to 34 patients. Serial plasma samples were drawn over 24 hours after the infusion and analyzed for etoposide by high-performance liquid chromatography.The 3-point LSM AUC was compared with a 14-point actual AUC calculated by the linear trapezoidal rule. Actual and predicted AUC(infinity) by the LSM were highly correlated (r=0.97, p<0.0001). The LSM predictions had a mean absolute error of 10.9% (95% CI -14.1, -5.3) and a mean error of -9.7% (95% CI 6.9, 14.9). Nine patients with poor AUC(infinity) estimations by the LSM (error > 12%) tended to have abnormally low or high peak concentrations.Our findings suggest the development of more robust LSM using other techniques, such as pharmacostatistical models, that can accommodate a greater degree of pharmacokinetic variability.

    View details for Web of Science ID A1997XX70400006

    View details for PubMedID 9324178

  • Treatment of angioimmunoblastic T-cell lymphoma with cyclosporine ANNALS OF ONCOLOGY Advani, R., Warnke, R., Sikic, B. I., Horning, S. 1997; 8 (6): 601-603

    View details for Web of Science ID A1997XN79200022

    View details for PubMedID 9261530

  • Spontaneous overexpression of the long form of the bcl-X protein in a highly resistant P388 leukaemia BRITISH JOURNAL OF CANCER Kuhl, J. S., Krajewski, S., Duran, G. E., Reed, J. C., Sikic, B. I. 1997; 75 (2): 268-274

    Abstract

    A novel resistant variant of murine P388 leukaemia, P388/SPR, was identified by de novo resistance to doxorubicin (DOX) in vivo. This mutant displayed a similar level of cross-resistance to etoposide (VP-16) and other topoisomerase II (topo II) inhibitors. Further analysis of the phenotype revealed a broad cross-resistance to vinca alkaloids, alkylating agents, antimetabolites, aphidicolin and UV light. Low-level expression of mdr1 and P-glycoprotein (P-gp), as well as a modest impairment of cellular drug accumulation and partial reversion of resistance to DOX and VP-16 by cyclosporine, confirmed a moderate role of P-gp in conferring drug resistance in P388/SPR cells. Consistent changes in neither topo II expression or activity nor glutathione metabolism could be detected. Induction of apoptosis was significantly reduced in P388/SPR cells, as indicated by minimal DNA fragmentation. Analysis of oncogenes regulating apoptotic cell death revealed a marked decrease of bcl-2 in combination with a moderate reduction of bax protein, but a striking overexpression of the long form of the bcl-X protein. Transfection of human bcl-X-L into P388 cells conferred drug resistance similar to that of P388/SPR cells. The data suggest that overexpression of bcl-X-L results in an unusual phenotype with broad cross-resistance to non-MDR-related cytotoxins in vitro, and provide an interesting example of spontaneous overexpression of another member of the bcl-2 gene family in cancer.

    View details for Web of Science ID A1997WC76300019

    View details for PubMedID 9010037

  • Differential single- versus double-strand DNA breakage produced by doxorubicin and its morpholinyl analogues CANCER CHEMOTHERAPY AND PHARMACOLOGY Duran, G. E., Lau, D. H., Lewis, A. D., Kuhl, J. S., Bammler, T. K., Sikic, B. I. 1996; 38 (3): 210-216

    Abstract

    The morpholinyl analogues of doxorubicin (DOX) have previously been reported to be non-cross-resistant in multidrug resistant (MDR) cells due to a lower affinity for P-glycoprotein relative to the parent compound. In order to further investigate the mechanisms of action of these morpholinyl anthracyclines, we examined their ability to cause DNA single- and double-strand breaks (SSB, DSB) and their interactions with topoisomerases. Alkaline elution curves were determined after 2-h drug treatment at 0.5, 2 and 5 microM, while neutral elution was conducted at 5, 10 and 25 microM in a human ovarian cell line, ES-2. A pulse-field gel electrophoresis assay was used to confirm the neutral elution data under the same conditions. Further, K-SDS precipitation and topoisomerase drug inhibition assays were used to determine the effects of DOX and the morpholinyl analogues on topoisomerase (Topo) I and II. Under deproteinated elution conditions (pH 12.1), DOX, morpholinyl DOX (MRA), methoxy-morpholinyl DOX (MMDX) and morpholinyl oxaunomycin (MX2) were equipotent at causing SSB in the human ovarian carcinoma cell line, ES-2. However, neutral elution (pH 9.6) under deproteinated conditions revealed marked differences in the degree of DNA DSB. After 2-h drug exposures at 10 microM, DSBs were 3300 rad equivalents for MX2, 1500 for DOX and 400 for both MRA and MMDX in the ES-2 cell line. Pulse-field data substantiated these differences in DSBs, with breaks easily detected after MX2 and DOX treatment, but not with MRA and MMDX. DOX and MX2 thus cause DNA strand breaks selectively through interaction with Topo II, but not Topo I. In contrast, MRA and MMDX cause DNA breaks through interactions with both topoisomerases with a predominant inhibition of Topo I.

    View details for Web of Science ID A1996UR19100002

    View details for PubMedID 8646794

  • Pharmacological considerations in the modulation of multidrug resistance EUROPEAN JOURNAL OF CANCER Fisher, G. A., Lum, B. L., Hausdorff, J., Sikic, B. I. 1996; 32A (6): 1082-1088

    View details for Web of Science ID A1996UT29600020

    View details for PubMedID 8763350

  • Doxorubicin selection for MDR1/P-glycoprotein reduces swelling-activated K+ and Cl- currents in MES-SA cells AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY Luckie, D. B., Krouse, M. E., Law, T. C., Sikic, B. I., Wine, J. J. 1996; 270 (4): C1029-C1036

    Abstract

    To test the hypothesis that P-glycoprotein enhances swelling currents through regulation of volume-sensitive Cl- channels [recently termed VSOAC (volume-sensitive osmolyte and anion channel)], a human uterine sarcoma cell line (MES-SA) and its doxorubicin-selected counterpart (Dx5) were studied. P-glycoprotein mRNA and protein levels were detected only in Dx5 cells. However, whole cell patch-clamp experiments showed that swollen Dx5 cells (n = 5) produced smaller VSOAC currents than MES-SA cells (n = 4; 106 +/- 26 pA/pF vs. 232 +/- 76 pA/pF at 90 mV). In radioisotopic efflux experiments, both swelling-activated 125I (Cl-) currents (n = 15) and 86Rb (K+) currents (n = 8) were found to be two-to fourfold smaller in the Dx5 (high P-glycoprotein) cells. Inhibitors of P-glycoprotein showed no specificity for the doxorubicin-selected cells (Dx5). Dideoxyforskolin (100 microM) blocked swelling-activated 125I efflux equally in both cell lines, whereas 100 microM verapamil had no effect. Thus, in this cell line, selection for P-glycoprotein expression is associated with reduced swelling currents. These findings suggest that P-glycoprotein expression does not directly facilitate VSOAC.

    View details for Web of Science ID A1996UD60600008

    View details for PubMedID 8928730

  • Differential expression of tubulin isotypes during the cell cycle CELL MOTILITY AND THE CYTOSKELETON Dumontet, C., Duran, G. E., Steger, K. A., Murphy, G. L., Sussman, H. H., Sikic, B. I. 1996; 35 (1): 49-58

    Abstract

    Microtubules play an essential role in cell division. Little is known about possible variations of total tubulin and tubulin isotype expression during the cell cycle. We analyzed the total tubulin content, tubulin polymerization status and tubulin isotype content in resting and dividing human K562 leukemic cells and human MES-SA sarcoma cells. Although the total cellular tubulin content increases as the cells progress toward mitosis, the total tubulin/total protein ratio is stable during the cell cycle. Reverse transcriptase-polymerase chain reaction was applied to analyze the levels of expression of alpha, beta, and gamma-tubulin isotypes. Whereas alpha-tubulin isotype and gamma-tubulin transcripts were found to be expressed at constant levels throughout the cell cycle, some of the beta-tubulin isotype transcripts were found to be more highly expressed in dividing then in resting cells. Both of the class IV beta-tubulin isotype transcripts (human 5 beta and beta 2, Class IVa and IVb, respectively) were expressed in dividing K562 and MES-SA cells at twice the levels found in resting cells. Increased expression of the class IV isotype proteins in dividing cells was confirmed by immunoblotting, both in K562 and in MES-SA cells. A larger fraction of total cell tubulin was found to be polymerized in dividing cells (36-40%) than in resting cells (27-30%). The degree of polymerization of class IV tubulin in dividing and resting cells was similar to that of total tubulin. These results show that total tubulin is expressed as constant levels throughout the cell cycle but that the degree of polymerization is increased as cells are committed to division. The relative overexpression of the two class IV beta-tubulin isotypes in dividing cells suggests functional specificity for these isotypes and a regulatory role of these isotypes on the microtubule network during mitosis.

    View details for Web of Science ID A1996VE88700004

    View details for PubMedID 8874965

  • Effect of different mathematical methods on etoposide area under the curve estimations and pharmacodynamic: Response predictions CANCER CHEMOTHERAPY AND PHARMACOLOGY McCauley, D. L., Lum, B. L., Sikic, B. I. 1996; 37 (3): 286-288

    Abstract

    Different methods to calculate interval area under the curve (AUC) data may produce substantial error. The purpose of this study was to compare methods of calculating etoposide AUC and determine the effect of these values on white blood cell (WBC) count nadir predictions calculated from a previously reported equation. Three AUC calculation methods were used: (1) the linear trapezoidal method, (2) a combination of the linear and logarithmic trapezoidal methods, and (3) the Lagrange method. Since none of the methods for determining the AUC could be considered the standard, the methods were evaluated by comparing differences between pairs of calculated AUC values by each method. The 95% CI for differences between all pairs of AUC values were greater than zero (no difference) indicating significance. Consistent with the smoother fitting function between data points, the Lagrange method tended to produce a larger AUC, lower clearance values, and lower WBC nadir count predictions than the other methods. The largest difference encountered was between the Lagrange and the linear-log AUC methods with a mean value of 16.9 micrograms h/ml (95% CI 9.4-24.3) This difference would account for approximately 11% of the total AUC. Using a previously published equation, where WBC nadir = -0.057 +0.048 x etoposide clearance, with clearance determined as dose/AUC, mean differences in calculated WBC nadir count values between the three AUC methods ranged from 80 to 220 cells/microliters, which would be expected to be of little clinical consequence. The precision of this equation, using data derived from linear trapezoidal AUC calculations, had a mean absolute error of 0.93 x 10(3)/microliters (95% CI 0.53-1.32). Our findings suggest that any of the three mathematical methods studied would produce similar etoposide AUC values and pharmacodynamic predictions. Further, these findings also suggest that the major limitation in predicting etoposide leukopenia lies with the imprecision of the pharmacodynamic model more so than the ability to accurately determine the AUC. However, our findings may not be applicable if other factors intervene which dramatically alter the shape of the etoposide concentration-time curve.

    View details for Web of Science ID A1996TJ73100014

    View details for PubMedID 8529291

  • GLUTATHIONE-S-TRANSFERASE-PI, GLUTATHIONE-S-TRANSFERASE-ALPHA, GLUTATHIONE-S-TRANSFERASE-MU AND GLUTATHIONE-S-TRANSFERASE-MDR1 MESSENGER-RNA EXPRESSION IN NORMAL LYMPHOCYTES AND CHRONIC LYMPHOCYTIC-LEUKEMIA LEUKEMIA Marie, J. P., Simonin, G., Legrand, O., Delmer, A., Faussat, A. M., Lewis, A. D., Sikic, B. I., Zittoun, R. 1995; 9 (10): 1742-1747

    Abstract

    Chronic B cell lymphoproliferative disorders are frequently sensitive to alkylating agents. To assess the glutathione-S-transferases (GSTs) gene expression in B tumoral lymphocytes, possibly responsible for this sensitivity, we developed a sensitive RT-PCR assay for the three isoenzymes GST pi, GST mu and GST alpha mRNA. Normal B and T lymphocytes from 11 blood donors were separated by magnetic beads and tested with this assay. The GST pi was the most abundant transferase, and was detected in all B and T cell samples. GST mu was undetectable ('null' phenotype) in 6/11 normal donors, either in B or T cells. GST alpha was very stable from donor to donor, and was highly correlated between B and T cells of the same individual (P < 0.0001). There is no correlation between the three isoenzymes, and between each isoenzyme and mdr1 gene expression. Twenty-three B lymphoproliferative disorders (20 B-CLL, 3 CD5- chronic lymphoproliferative syndromes) were tested with the same technique. An average decrease of 57% of the GST pi expression was noted in the mononuclear cells of these patients (P < 0.02), with no differences between the untreated and treated cases. The GST alpha and mdr1 mRNA levels did not differ from normal B lymphocytes, but the proportion of patients with no detectable expression of GST mu is lower than in the control (13%). Interestingly, the low content of GST pi in B-CLL could explain the frequent sensitivity of this disease to alkylating agents.

    View details for Web of Science ID A1995TA83500022

    View details for PubMedID 7564519

  • CYCLOSPORINE-A INCREASES SERUM CORTISOL-LEVELS IN RABBITS ANTI-CANCER DRUGS Cufer, T., Vrhovec, I., Skrk, J., Pfeifer, M., Pajk, B., Zakotnik, B., Filipic, B., Rode, B., Sikic, B. I. 1995; 6 (4): 615-618

    Abstract

    P-glycoprotein (P-gp), a membrane protein that was originally found to be involved in the efflux of cytotoxic drugs out of the tumor cells, is also present in a variety of normal human and animal tissues, such as the adrenal cortex. The function of P-gp in the adrenal cortex has not been defined yet. The aim of our study was to determine whether the blockade of P-gp by cyclosporine A (CsA) dissolved in Cremophor EL (Crem) inhibits cortisol secretion in rabbits. In 14 rabbits, the baseline and ACTH stimulated serum cortisol levels were measured before and after CsA treatment. Seven rabbits were treated with 2 x 30 mg/kg CsA and seven with 2 x 90 mg/kg CsA injected s.c. Serum cortisol levels were determined by radioimmunoassay adjusted for expected values. The whole blood CsA levels were determined by a commercially available fluorescence polarization immunoassay. Serum cortisol levels, both baseline and ACTH stimulated, significantly increased after both low and high dose CsA treatment. The increase was dose dependent. The mean baseline cortisol levels increased from 5.7 (SD = 6.3) to 15.0 nmol/l (SD = 7.2) in the low dose group and from 7.7 (SD = 4.9) to 44.9 nmol/l (SD = 13.8) in the high dose group. The mean cortisol levels 8 h after ACTH stimulation increased from 53.3 (SD = 34.5) to 106.0 nmol/l (SD = 33.0) in the low dose group and from 47.7 (SD = 12.2) to 153.0 nmol/l (SD = 55.1) in the high dose group.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1995RN32200018

    View details for PubMedID 7579569

  • INHIBITION OF LYSOSOMAL ACID SPHINGOMYELINASE BY AGENTS WHICH REVERSE MULTIDRUG-RESISTANCE BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH Jaffrezou, J. P., Chen, G., Duran, G. E., Muller, C., Bordier, C., Laurent, G., Sikic, B. I., Levade, T. 1995; 1266 (1): 1-8

    Abstract

    An increasing body of evidence appears to implicate the lipid bilayer of multidrug resistant (MDR) cells with P-glycoprotein activity. Several cationic amphiphilic drugs (CADs) have been extensively described as modulators of MDR. These same agents are also known to (1) inhibit lysosomal acid sphingomyelinase (ASmase), a phospholipid degrading enzyme, and/or (2) induce phospholipidosis in animal tissues or cultured cell lines. In this report, we randomly selected 17 CADs and evaluated their potency in modulating MDR in the murine MDR P388/ADR leukemia cell line. We compared these results with their ability to inhibit ASmase and observed a significant dose-dependent linear relationship (95% central confidence interval), between ASmase inhibition and MDR reversal. This approach permitted us to identify three new modestly potent chemosensitizers: trimipramine, desipramine, and mianserine. Modulation of MDR was not cell line specific, since CADs at 10 microM increased doxorubicin (DOX) and vinblastine (VBL) (but not methotrexate, MTX) cytotoxicity in both P388/ADR and the human MDR cell lines MES-SA/Dx5 and K562/R7, but not in the parental drug-sensitive cells. Although all chemosensitizing CADs at 10 microM significantly increased Rhodamine-123 (Rho-123) accumulation in the human leukemia MDR cell line K562/R7 and most presented significant displacement of the photoaffinity labelling probe iodoarylazidoprazosin, no correlation between these observations and the ability of CADs to sensitize MDR cells to DOX and VBL was found. In conclusion, our study strongly suggests that the chemosensitizing potency of agents such as CADs may be due to a dual mechanism of action: direct antagonism of P-gp activity and indirect modulation of P-gp activity through the disruption of cellular lipid metabolism.

    View details for Web of Science ID A1995QT13600001

    View details for PubMedID 7718613

  • Drug resistance in clinical oncology and hematology. Introduction. Hematology/oncology clinics of North America Fisher, G. A., Sikic, B. I. 1995; 9 (2): xi-xii

    View details for PubMedID 7642462

  • CLINICAL-STUDIES WITH MODULATORS OF MULTIDRUG-RESISTANCE HEMATOLOGY-ONCOLOGY CLINICS OF NORTH AMERICA Fisher, G. A., Sikic, B. I. 1995; 9 (2): 363-382

    Abstract

    Improved understanding of the mechanisms underlying chemotherapeutic failure has led to new strategies to circumvent drug resistance. Expression of the multidrug transporter, P-glycoprotein (P-gp), is likely to be a significant mechanism contributing to the clinical resistance of some cancers to chemotherapy. Phase I trials of currently available MDR modulators have yielded important pharmacologic principles pertaining to normal tissue P-gp function and its influence on the disposition of MDR-related anticancer drugs. Currently available P-glycoprotein inhibitors lack the potency to completely reverse the MDR phenotype at clinically achievable concentrations. Despite this, encouraging clinical results have been obtained in the hematolymphoid malignancies. As these more potent modulators become available, careful characterization of pharmacologic interactions with MDR-related cytotoxins will be critical to the rational design of Phase II and III studies that will ultimately test the efficacy of MDR modulation.

    View details for Web of Science ID A1995QT66400007

    View details for PubMedID 7642468

  • Novel mechanism of resistance to paclitaxel (Taxol(R)) in human K562 leukemia cells by combined selection with PSC 833 ONCOLOGY RESEARCH Jaffrezou, J. P., Dumontet, C., Derry, W. B., Duran, G., Chen, G., Tsuchiya, E., Wilson, L., Jordan, M. A., Sikic, B. I. 1995; 7 (10-11): 517-527

    Abstract

    A paclitaxel-resistant cell line, KPTA5, was established by co-selecting the parental erythroleukemic cell line K562 with stepwise increased concentrations of paclitaxel (Taxol) in the presence of the cyclosporin D analogue PSC 833 (2 microM), a potent modulator of the multidrug resistance phenotype. KPTA5 cells are 9-fold resistant to paclitaxel and taxotere, but do not exhibit significant resistance to Vinca alkaloids, etoposide, anthracyclines, antimetabolites, or alkylating agents. Doubling time and morphology were similar to the parental K562 cells. Reverse transcriptase-polymerase chain reaction (rt-PCR) analysis revealed no alterations in the expression of the mdr1 and MRP genes. Cellular paclitaxel accumulation was unchanged. Cell cycle analyses showed that at 20 nM there was a significantly higher proportion of K562 cells blocked in G2/M, in comparison with KPTA5 cells. In both cases, disruption of the mitotic spindles and the presence of multiple mitotic asters were comparable but occurred at lower paclitaxel concentrations in K562 cells than in KPTA5 cells. There was no difference in total tubulin content between K562 and KPTA5 cells as analyzed by immunoblotting with an anti-beta-tubulin monoclonal antibody. However, we found that KPTA5 cells presented a 2-fold increase both in 5 beta-tubulin mRNA expression and in the corresponding tubulin protein Class IV isotype content, as evaluated by rt-PCR and immunostaining. In conclusion, the KPTA5 cell line displays a novel mechanism of resistance to paclitaxel which does not involve altered cellular drug accumulation. The data presented suggest that alterations in expression of the 5 beta-tubulin gene may be involved in paclitaxel resistance.

    View details for Web of Science ID A1995TX48800005

    View details for PubMedID 8866664

  • EVIDENCE FOR TRANSCRIPTIONAL CONTROL OF HUMAN MDR1 GENE-EXPRESSION BY VERAPAMIL IN MULTIDRUG-RESISTANT LEUKEMIC-CELLS MOLECULAR PHARMACOLOGY Muller, C., Goubin, F., Ferrandis, E., CORNILSCHARWTZ, I., Bailly, J. D., Bordier, C., Benard, J., Sikic, B. I., Laurent, G. 1995; 47 (1): 51-56

    Abstract

    We investigated the mechanism of verapamil (VRP) effects on mdr1 gene expression in two leukemic multidrug-resistant (MDR) cell lines, K562/ADR and CEM VLB100. Exposure to VRP for 24 hr resulted in a decrease in mdr1 mRNA levels that was dose related at concentrations between 15 and 50 microM. The maximal decrease of mdr1 mRNA levels was found to be 6-fold in the K562/ADR cells and 3-fold in the CEM VLB100 cells. The effect of VRP on mdr1 mRNA levels was, however, biphasic. At 100 microM VRP, which strongly inhibited cell proliferation, a 2-fold increase of mdr1 mRNA levels was observed in the K562/ADR cells. To determine whether the decrease of mRNA levels resulted from post-transcriptional mechanisms, mRNA stability was studied after blocking of transcription with actinomycin D in VRP-treated cells and in control cells. This study revealed that mdr1 mRNA was stable in both cell lines and no increase in mdr1 mRNA degradation was observed in the 30 microM VRP-treated cells versus control cells (half-lives of 23 hr versus 14 hr for the K562/ADR cells and 15.5 hr versus 10.0 hr for the CEM VLB100 cells). The suggestion of a transcriptional mechanism was confirmed by nuclear run-on assays. A 4-fold decrease in the mdr1 gene transcription rate was observed in the 30 microM VRP-treated CEM VLB100 cells. The decreased transcription rate could be due to the decrease in mdr1 proximal promoter activity observed in CEM VLB100 cells transiently transfected with the mdr1 promoter fused to the chloramphenicol acetyltransferase gene. Indeed, after exposure to 30 microM VRP, chloramphenicol acetyltransferase activity was decreased by 2-fold. This study reports for the first time a down-regulation of mdr1 gene transcription by a pharmacological agent. These results provide further identification of the regulatory mechanisms involved in the overexpression of mdr1 in MDR cells and may help in the development of new strategies for MDR reversal.

    View details for Web of Science ID A1995QE16700006

    View details for PubMedID 7838133

  • ANALYSIS OF INTRACELLULAR RETENTION OF MORPHOLINYL ANTHRACYCLINES IN MULTIDRUG-RESISTANT CANCER-CELLS BY INTERACTIVE LASER CYTOMETRY INTERNATIONAL JOURNAL OF ONCOLOGY Lau, D. H., Duran, G. E., Sikic, B. I. 1994; 5 (6): 1273-1277

    Abstract

    Interactive laser cytometry was applied to measure intracellular fluorescence of doxorubicin (DOX) accumulation in a uterine sarcoma cell line, MES-SA and a series of multidrug resistant sublines, Dx0.3, Dx1 and Dx5. Exposure of each cell line to 10 mu M DOX for 2 h resulted in an intracellular fluorescent level directly correlated to its sensitivity to the drug but inversely related to its cellular P-glycoprotein (P-gp) level. The morpholinyl anthracyclines, methoxymorpholinyl DOX (MMDX) and morpholinyl DOX (MRA), were equally highly cytotoxic against the multidrug sensitive and resistant cancer cells. After exposure to 10 mu M of MMDX or MRA for 2 h, the multidrug resistant cells, Dx5, retained as much intracellular fluorescence as the multidrug sensitive cells, MES-SA. In the resistant cells, the intracellular fluorescence of MMDX or MRA was 8 fold higher than that of DOX. Interactive laser. cytometer is a useful fool for screening cancer cells with the MDR phenotype and for identifying new anthracyclines effective against drug resistant malignancies.

    View details for Web of Science ID A1994PT93300012

    View details for PubMedID 21559709

  • MULTIDRUG-RESISTANCE IN LYMPHOMAS JOURNAL OF CLINICAL ONCOLOGY Yuen, A. R., Sikic, B. I. 1994; 12 (11): 2453-2459

    Abstract

    To discuss the significance of multidrug resistance (MDR) in human lymphomas and to review recent and ongoing clinical trials using MDR modulators.A medical literature search was used to identify articles that reported results on the expression or modulation of MDR in human lymphomas. This review summarizes the various methods for detecting expression of the mdr1 gene in tumor specimens, the patterns of expression in lymphomas, and recent and upcoming clinical trials using modulating agents to reverse MDR.There is considerable variation in the assays used to evaluate the expression of mdr1 in lymphomas. Current methodology includes reverse transcriptase polymerase chain reaction (rt-PCR) for assay of mdr1 mRNA, and immunohistochemistry or flow cytometry for detection of the multidrug transporter, P-glycoprotein (P-gp). The preponderance of evidence suggests that mdr1 expression is relatively low in untreated patients (10% to 20% of lymphomas positive), but increases in patients with recurrent disease (50% to 70% positive). Some evidence suggests that mdr1 expression is a prognostic factor for response to chemotherapy, as well as for subsequent survival. Verapamil and cyclosporine (CsA) have been used as competitive inhibitors of the multidrug transporter P-gp in early clinical trials. Although these studies show some activity in modulating clinical MDR, both verapamil and CsA manifest considerable toxicities at doses below those required for complete inhibition of P-gp function.MDR due to the expression of the mdr1 gene is an important factor in the course of patients with lymphomas. Continued clinical trials with more potent and less toxic modulators are needed to define the ultimate benefit of modulating MDR in lymphomas.

    View details for Web of Science ID A1994PP88000033

    View details for PubMedID 7964963

  • VOLUME-ACTIVATED CHLORIDE CURRENT IS NOT RELATED TO P-GLYCOPROTEIN OVEREXPRESSION CANCER RESEARCH Dong, Y. J., Chen, G., Duran, G. E., Kouyama, K., Chao, A. C., Sikic, B. I., Gollapudi, S. V., Gupta, S., Gardner, P. 1994; 54 (19): 5029-5032

    Abstract

    It has been suggested that P-glycoprotein (P-gp), an ATP-dependent transporter responsible for classical multidrug resistance, is also a volume-regulated chloride channel. We reexamined this hypothesis by use of whole-cell patch clamp recordings of three matched pairs of cell lines, which were either drug-sensitive or drug-resistant due to P-gp overexpression. We demonstrate here that volume-regulated chloride-selective currents can be induced in cells with or without P-gp expression. Overexpression of either P-gp or cystic fibrosis transmembrane conductance regulator, the protein product of the CF gene and another member of the ATP-dependent transporters, is associated with a hypotonicity-induced, rapid onset, transient current prior to onset of the volume-sensitive chloride-selective current, an apparent nonspecific effect related to the overexpression of an integral membrane protein. These results suggest that there is no relationship between P-gp and the chloride channel activated by cell swelling.

    View details for Web of Science ID A1994PH77400001

    View details for PubMedID 7923110

  • METABOLIC CONVERSION OF METHOXYMORPHOLINYL DOXORUBICIN - FROM A DNA STRAND BREAKER TO A DNA CROSS-LINKER BRITISH JOURNAL OF CANCER Lau, D. H., Duran, G. E., Lewis, A. D., Sikic, B. I. 1994; 70 (1): 79-84

    Abstract

    Methoxymorpholinyl doxorubicin (MMDX) is a novel anti-cancer anthracycline that differs from doxorubicin in its mechanisms of action, pattern of resistance and metabolism. Whereas doxorubicin is primarily an inhibitor of topoisomerase II, MMDX inhibits both topoisomerases I and II, resulting in predominantly single-strand DNA cleavage and, to a lesser extent, double-strand DNA breakage. MMDX is equally cytotoxic in vitro against the doxorubicin-sensitive and -resistant uterine sarcoma cell lines, MES-SA and Dx5. Using fluorescent laser cytometry, MMDX was retained intracellularly to a similar extent in MES-SA and Dx5; the intracellular retention of MMDX was 7.5-fold higher than that of doxorubicin in Dx5. The cytotoxicity of MMDX on an ovarian carcinoma cell line, ES-2, was potentiated 50-fold by preincubating the drug with human liver microsomes and NADPH. This cytotoxic potentiation was associated with the appearance of DNA interstrand cross-links. The in vitro potentiation of MMDX was inhibited by cyclosporin A, which is a substrate for human cytochrome P450 IIIA.

    View details for Web of Science ID A1994NW11800014

    View details for PubMedID 8018545

  • MDR1 GENE-EXPRESSION IN CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIAS AND LYMPHOMAS - A CRITICAL-EVALUATION BY 4 TECHNIQUES LEUKEMIA BROPHY, N. A., Marie, J. P., ROJAS, V. A., Warnke, R. A., MCFALL, P. J., Smith, S. D., Sikic, B. I. 1994; 8 (2): 327-335

    Abstract

    Expression of the multidrug resistance gene mdr1 is reported to be an important determinant of responsiveness to therapy and survival in some cancers. Many different methods have been used to evaluate mdr1 expression in these studies. This paper compares four methods for determination of mdr1 expression. We studied the mdr1 gene expression in 36 freshly established cell lines from 28 children with acute lymphoblastic leukemia (16 T-ALL, six BCP-ALL, two B-ALL (L3), two biphenotypic leukemias, two Burkitt's lymphomas). Leukemic specimens were obtained at the time of diagnosis in 16 cases, and after chemotherapy in 20 cases. In all the samples, mdr1 mRNA was measured by slot blotting and reverse transcriptase polymerase chain reaction (rt-PCR), and the presence of the mdr1 product, P-glycoprotein, was detected by immunohistochemistry with the MRK-16 monoclonal antibody. In situ mdr1 RNA hybridization was performed in 30 cases. Complete agreement was noted between all the techniques in 14 cases (39%). Results differed on a single test result in another 39% of the cases. These 78% of cases were considered assessable, and the consensus result was presumed to be correct. By this consensus criterion, immunohistochemistry yields both false negative (11%), and false positive (11%) results. RNA slot blotting has a high (21%) false positive rate. In situ mRNA hybridization and rt-PCR have the highest concordance, 80%. The 28 patients from whom these cell lines were derived appear to represent a very poor prognosis group, since there are only two patients (with Burkitt's lymphoma) who are long-term survivors. Nonetheless, a complete clinical response to therapy was correlated with absence of mdr1 expression in assessable cases (p = 0.04). These four methods of determining mdr1 expression often yield discordant results. Therefore, the use of at least two methods for evaluating mdr1 expression is advisable. Rt-PCR is recommended because of its relative simplicity and specificity. This should be supplemented by a technique (immunohistochemistry or flow cytometry) able to detect heterogeneity of P-glycoprotein expression among cells.

    View details for Web of Science ID A1994MZ59900021

    View details for PubMedID 7905944

  • CYCLOSPORINE A AND CYCLOSPORINE SDZ PSC 833 ENHANCE ANTI-CD5 RICIN A-CHAIN IMMUNOTOXINS IN HUMAN LEUKEMIC T-CELLS BLOOD Jaffrezou, J. P., Sikic, B. I., Laurent, G. 1994; 83 (2): 482-489

    Abstract

    Recent studies have shown that cyclosporin A (CsA) may affect ricin A-chain immunotoxin (RTA-IT) therapy. In this study, we evaluated the ability of CsA and its nonimmunosuppressive analog, SDZ PSC 833, to enhance anti-CD5 T101 RTA-ITs in vitro. Both 4 mumol/L CsA and 4 mumol/L SDZ PSC 833 significantly and specifically enhanced the cytotoxic activity of T101 RTA-IT on the human lymphoblastic T-cell line, CEM III (101-fold and 105-fold, respectively). Furthermore, these Cs also enhanced the cytotoxicity of the more potent T101 F(ab')2 RTA-IT (ninefold and eightfold, respectively). The effect of human plasma, originating from four patients enrolled in a phase I high-dose CsA regimen, was examined on T101 RTA-IT cytotoxicity on CEM III cells. In each case, with plasma CsA levels between 3,090 and 4,860 ng/mL (2.5 to 4 mumol/L), a significant increase in T101 RTA-IT-mediated cytotoxicity was observed ranging from 31% to 60%. Neither CsA nor SDZ PSC 833 affected the rate of RTA-IT binding, internalization, intracellular trafficking, or degradation. Analysis of internalized T101 RTA-IT molecules showed that these were essentially intact, which suggests that these enhancers may act only on a small population of RTA-ITs that escapes present investigational techniques. In conclusion, because the concentrations used are clinically achievable, Cs appear to be promising agents for in vivo enhancement of RTA-ITs.

    View details for Web of Science ID A1994MR98600024

    View details for PubMedID 7506953

  • Clinical reversal of multidrug resistance. Cancer treatment and research Sikic, B. I., Fisher, G. A., Lum, B. L., BROPHY, N. A., Yahanda, A. M., ADLER, K. M., Halsey, J. 1994; 73: 149-165

    View details for PubMedID 7710904

  • EFFECTS OF THE METHOXYMORPHOLINO DERIVATIVE OF DOXORUBICIN AND ITS BIOACTIVATED FORM VERSUS DOXORUBICIN ON HUMAN LEUKEMIA AND LYMPHOMA CELL-LINES AND NORMAL BONE-MARROW CANCER CHEMOTHERAPY AND PHARMACOLOGY Kuhl, J. S., Duran, G. E., Chao, N. J., Sikic, B. I. 1993; 33 (1): 10-16

    Abstract

    The methoxymorpholino derivative of doxorubicin (MMDX; FCE 23672) has recently entered clinical trials because of its broad spectrum of preclinical antitumor activity and non-cross-resistance in multidrug-resistant (MDR) tumor models. MMDX is activated in the liver to a > 10 times more potent metabolite that cross-links DNA. To assess the potential of this drug in hematologic malignancies, we studied the myelotoxicity in vitro and antitumor effect of MMDX as well as its bioactivated form (MMDX+) in a panel of 14 different human leukemia and lymphoma cell lines. The tumor specificity of MMDX in CEM and K562 cells was similar to that of doxorubicin (DOX), and that of MMDX+ was slightly superior. All of the 14 cell lines were found to be more sensitive to MMDX and MMDX+ than were granulocyte-macrophage progenitors. On a molar basis, MMDX was approximately 3-100 times more active than DOX, and MMDX+ was 10-1,000 times more potent than DOX. The cytotoxic effect of MMDX and MMDX+ in two P-glycoprotein-positive MDR sublines was greatly improved in comparison with that of DOX. Whereas the response to DOX in the different leukemia and lymphoma cell lines was highly heterogeneous, the response to MMDX and MMDX+ was rather homogeneous. The novel anthracycline MMDX and its bioactivated form MMDX+ are highly active against this panel of human leukemia and lymphoma cell lines and demonstrate potentially greater selectivity for tumor cells in vitro as compared with normal bone marrow precursors.

    View details for Web of Science ID A1993MC70700002

    View details for PubMedID 8269583

  • MOLECULAR TARGETS IN ONCOLOGY - IMPLICATIONS OF THE MULTIDRUG RESISTANCE GENE PHARMACOTHERAPY Lum, B. L., Gosland, M. P., Kaubisch, S., Sikic, B. I. 1993; 13 (2): 88-109

    Abstract

    The curative potential of chemotherapy for a number of tumor types has been obscured by the fact that many patients initially have striking remissions but later relapse and die. At the time of relapse many patients manifest resistance to a wide array of structurally unrelated antineoplastic agents, hence the term multidrug resistance (MDR). Other tumor types, such as those arising in the colon, kidneys, liver, and lungs, tend to exhibit poor response to available cytotoxic drugs. The MDR phenomenon includes cross-resistance among the anthracyclines (doxorubicin, daunorubicin), the epipodophyllotoxins (etoposide, teniposide), the vinca alkaloids (vinblastine, vincristine), taxol, and other compounds. In vitro studies in cell culture indicate that this form of resistance is associated with amplification or overexpression of the mdr1 gene. The mdr1 gene codes for the expression of a cell surface protein, P-glycoprotein (P-gp), which acts as an energy-dependent efflux pump that transports drugs associated with MDR out of the cell before cytotoxic effects occur. The protein is expressed in normal human tissues such as the gastrointestinal tract, liver, and kidneys, where it is thought to serve as an excretory pathway for xenobiotic drugs and toxins. Preliminary studies demonstrated the presence of P-gp in tumor samples from patients with acute leukemia, multiple myeloma, lymphomas, and a variety of solid tumors. A number of drugs are able to reverse MDR, including calcium-channel blockers, phenothiazines, quinidine, antimalarial agents, antiestrogenic and other steroids, and cyclosporine. Limited results from clinical trials with small numbers of patients suggest that the addition of verapamil, diltiazem, quinine, trifluoperazine, or cyclosporine to chemotherapeutic regimens has the potential to reverse MDR; however, toxicities limit their clinical usefulness. A number of trials are under way to identify more active and less toxic modulators of MDR.

    View details for Web of Science ID A1993KU15100003

    View details for PubMedID 8097038

  • CHARACTERIZATION OF COVALENT DNA-BINDING OF MORPHOLINO AND CYANOMORPHOLINO DERIVATIVES OF DOXORUBICIN JOURNAL OF THE NATIONAL CANCER INSTITUTE Lau, D. H., Duran, G. E., Sikic, B. I. 1992; 84 (20): 1587-1592

    Abstract

    The doxorubicin analogues cyanomorpholino doxorubicin (MRA-CN) and morpholino doxorubicin (MRA) were synthesized in an attempt to avoid the cardiotoxicity and drug resistance of doxorubicin therapy. MRA-CN forms interstrand DNA cross-links without requiring microsomal metabolic activation in the presence of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) to form a product that alkylates DNA, but MRA requires metabolic activation. Alkylation produces DNA cross-links, which are associated with potentiation of the cytotoxicity of some drugs.Our purpose was to study the DNA binding of MRA-CN and MRA with and without metabolic activation in order to better understand the mechanisms for cross-linking DNA.We used [3H]MRA and [3H]MRA-CN, with the 3H labeled at C-2 and C-6 of the morpholino ring. MRA (10 nM) was incubated with human liver microsomes with or without NADPH to measure DNA binding. In addition, a filter elution assay was used to determine the nature and extent of drug binding to DNA in the human ovarian carcinoma cell line ES-2. We studied the appearance of interstrand cross-links versus total DNA adducts in pBR322 plasmid DNA incubated with 100 nM MRA-CN in cell-free medium and then subjected to denaturation and agarose gel electrophoresis.Regardless of the extracellular concentration of the drug (1-100 nM), 85% of intracellular MRA-CN was covalently bound to DNA, and the total amount of drug bound to DNA was proportional to extracellular drug concentration. No covalent binding of MRA to DNA was found in cells exposed to 10 nM MRA alone for 2 hours. In contrast, 10% of the intracellular drug was bound to DNA if the cells were exposed to MRA preincubated with human liver microsomes and NADPH. The percentage of plasmids containing at least one interstrand cross-link rose from 35% at 15 minutes to 92% at 2 hours. We estimate that eight molecules of MRA-CN were adducted per molecule of pBR322 DNA (or one drug adduct per 545 base pairs), with a minimum of 12% of the adducts forming interstrand cross-links.These results suggest that the carbons at positions 2 and 6 of the morpholino ring of both MRA-CN and the activated metabolite of MRA are retained in the drug-DNA adduct. They also indicate that the formation of interstrand DNA cross-links by MRA-CN is preceded by formation of drug adducts to a single strand of DNA.

    View details for Web of Science ID A1992JV38100012

    View details for PubMedID 1404452

  • USE OF ETOPOSIDE IN COMBINATION WITH CYCLOSPORINE FOR PURGING MULTIDRUG-RESISTANT LEUKEMIC-CELLS FROM BONE-MARROW IN A MOUSE MODEL EXPERIMENTAL HEMATOLOGY Kuhl, J. S., Sikic, B. I., Blume, K. G., Chao, N. J. 1992; 20 (9): 1048-1054

    Abstract

    Cyclosporin (CsA) is a potent modulator of multidrug resistance (MDR) and has been combined with etoposide (VP-16) to purge MDR leukemic cells from human bone marrow (BM) in vitro. We studied the feasibility of this approach in an in vivo model for autologous BM transplantation using the murine leukemia cell line P388 and its MDR variant P388/ADR. Colony-forming assays with 2-h drug exposure revealed a tumor selectivity of VP-16 for P388 cells compared to normal murine marrow granulocyte-macrophage colony-forming units (CFU-GM), whereas P388/ADR cells were resistant to VP-16. Simultaneous incubation with CsA restored sensitivity in these cells. Almost 4 logs of cell kill were achieved by treating P388/ADR cells with 60 microM VP-16 plus 2.5 microM CsA (combination A) or 40 microM VP-16 plus 10 microM CsA (combination B), whereas there was a 2.5-log reduction of CFU-GM at these doses. Even though the myelotoxicity of VP-16 was increased by the addition of CsA, this effect was nonspecific as shown by a similar chemosensitization in sensitive P388 as well as in P388/VP 2.5 cells, an atypical MDR variant lacking P-glycoprotein. In vivo experiments addressed the ability of BM treated with VP-16 and CsA to rescue lethally irradiated mice and to purge leukemic cells. In total, 1/14 lethally irradiated mice died due to sepsis within 10 days after receiving 15 x 10(6) BM cells treated ex vivo with combination A in contrast to 1/4 for combination B. All 16 surviving animals demonstrated long-term engraftment. When simulated remission marrow contaminated with 0.1% P388/ADR was purged with VP-16 (60 microM) or CsA (2.5 microM) alone, all mice died from leukemia before day 16 after transplantation (median 14.3 and 12.2 days). In contrast, nine of ten animals receiving similar marrow purged with combination A survived > 60 days without any evidence of disease (p < 0.01). We conclude that combining VP-16 and CsA was effective in purging MDR leukemia cells from transplanted BM in this murine model.

    View details for Web of Science ID A1992JP95200003

    View details for PubMedID 1468539

  • ROLE OF CYTOCHROME-P-450 FROM THE HUMAN CYP3A GENE FAMILY IN THE POTENTIATION OF MORPHOLINO DOXORUBICIN BY HUMAN LIVER-MICROSOMES CANCER RESEARCH Lewis, A. D., Lau, D. H., Duran, G. E., Wolf, C. R., Sikic, B. I. 1992; 52 (16): 4379-4384

    Abstract

    The cytotoxicity of the morpholino derivative of doxorubicin (MRA) can be potentiated 50- to 100-fold by human liver microsomes and NADPH (J. Natl. Cancer Inst., 81: 1034, 1989). This metabolic potentiation is inhibited by carbon monoxide or hypoxia, indicating that it is cytochrome P-450-dependent. The potentiation is also inhibited by the cytochrome P-450 inhibitors, SKF-525A and cimetidine. The metabolism by the microsomes is substrate-specific, varying markedly with alterations of either the morpholino or anthracycline ring substituents. No potentiation occurred with doxorubicin itself, or the cyanomorpholinyl, methoxypiperidinyl, N-hydroxyethyl or the O-bridged cyanomorpholinyl analogues of doxorubicin. We utilized a panel of human liver microsomes and cytochrome P-450 type-specific antibodies to further identify the isoform(s) of cytochrome P-450 that potentiated the cytotoxicity of MRA. The potentiation correlates well with the benzyloxyresorufin assay (r2 = 0.98) and aflatoxin B1 metabolism (r2 = 0.98), both assays that are relatively specific for CYP3A proteins. Correlations were also observed for the expression of protein(s) cross-reacting with an antibody against rat cytochrome P-450 CYP3A1 (r2 = 0.97) and MRA metabolism. This antibody against the rat cytochrome P-450 CYP3A isoform(s) inhibited more than 90% of the potentiation of the cytotoxicity by human liver microsomes. Antibodies against the CYP1A2, CYP2C6, and CYP2B2 isoforms produced no inhibition, nor did their expression by Western blotting correlate with MRA potentiation. Complete inhibition of the potentiation of MRA by human liver microsomes was found when the CYP3A substrates cyclosporin A and erythromycin were used in the reaction system. These data indicate that the CYP3A isoform(s) of cytochrome P-450 play a major role in the metabolism of MRA in vitro to a more active species.

    View details for Web of Science ID A1992JJ83700012

    View details for PubMedID 1643634

  • EXPRESSION OF MULTIDRUG RESISTANCE GENE MDR1 MESSENGER-RNA IN A SUBSET OF NORMAL BONE-MARROW CELLS BRITISH JOURNAL OF HAEMATOLOGY Marie, J. P., BROPHY, N. A., EHSAN, M. N., Aihara, Y., Mohamed, N. A., CORNBLEET, J., Chao, N. J., Sikic, B. I. 1992; 81 (2): 145-152

    Abstract

    The multidrug resistance gene mdr1, encoding P-glycoprotein (P-gp), can be expressed at high levels in tumour cells derived from normal tissues with constitutive high expression of this gene. In myelogenous leukaemia, the incidence of increased expression of mdr1 gene contrasts with the low expression of this gene in normal bone marrow (b.m.). To detect cells expressing mdr1 gene in normal and post-chemotherapy b.m., we used in situ RNA hybridization and RNA phenotyping by the polymerase chain reaction for mdr1 mRNA detection. The presence of P-gp was evaluated by immunocytochemistry with MRK16. Fifteen b.m. (eight normal and seven post chemotherapy) were tested by in situ hybridization and either PCR (three b.m.) or immunocytochemistry (11 b.m.) or both (one b.m.). With in situ mRNA hybridization, a subset (7.7% +/- 3.1%) of b.m. cells expressed mdr1 mRNA in all cases tested, with no significant differences between normal b.m. and post chemotherapy b.m. 18% of myeloid recognizable cells and 7% of the cells with lymphoid morphology expressed mdr1 mRNA. By RNA phenotyping, the four samples tested for in situ hybridization and two additional post chemotherapy b.m. expressed mdr1. MRK16 was unable to detect a significant number of cells expressing P-gp either by immunocytochemistry in the 12 b.m. tested for in situ hybridization (0% in nine cases; 0.4%, 1% and 3% of positive cells in three cases), or by flow cytometry in six additional normal b.m. (0-1.4% positive cells).

    View details for Web of Science ID A1992HY85200002

    View details for PubMedID 1353683

  • Use of etoposide in combination with cyclosporine for purging multidrug resistant leukemic cells from bone marrow in a mouse model. Progress in clinical and biological research Kühl, J. S., Sikic, B. I., Blume, K. G., Chao, N. J. 1992; 377: 25-34

    View details for PubMedID 1438422

  • Purging multidrug resistant cells from bone marrow. Progress in clinical and biological research Chao, N. J., Aihara, M., Kühl, J. S., Sikic, B. I., Blume, K. G. 1992; 377: 13-23

    View details for PubMedID 1438409

  • MULTIFACTORIAL MECHANISMS ASSOCIATED WITH BROAD CROSS-RESISTANCE OF OVARIAN-CARCINOMA CELLS SELECTED BY CYANOMORPHOLINO DOXORUBICIN CANCER RESEARCH Lau, D. H., Lewis, A. D., EHSAN, M. N., Sikic, B. I. 1991; 51 (19): 5181-5187

    Abstract

    The cyanomorpholino derivative of doxorubicin (MRA-CN) is a DNA intercalator and alkylator that is a highly potent cytotoxin, non-cross-resistant in multidrug-resistant cells, and noncardiotoxic in comparison with doxorubicin. To further examine mechanisms of action and resistance to MRA-CN, a cell line resistant to MRA-CN, ES-2R, was established by growing a human ovarian carcinoma cell line, ES-2, in increasing concentrations of the drug. The resistant subline was 4-fold resistant to MRA-CN and cross-resistant to other DNA cross-linking agents, cisplatin (7-fold) and carmustine (3-fold), as well as to the DNA strand-breaking agents etoposide (6-fold), doxorubicin (2-fold), bleomycin (5-fold), and ionizing radiation (2-fold). In contrast, ES-2R cells were not cross-resistant to vinblastine. Several months of additional growth of ES-2R cells in MRA-CN did not yield higher, stable levels of drug resistance. A low level of P-glycoprotein was detectable in the ES-2R cells. However, the extent of intracellular accumulation of [3H]MRA-CN by this resistant cell line was identical to that of the sensitive line. The number of DNA cross-links formed by cisplatin in ES-2R was only 50% of that of the ES-2 cells and was associated with a 50% increase in the rate of repair of these cross-links in the resistant cells. Ionizing radiation induced similar amounts of single- and double-strand breaks in the ES-2 line as well as in the ES-2R cells. There was no apparent difference between the two cell lines in the rate and extent of repair of these DNA breaks. Thus, enhanced DNA repair cannot explain the phenomenon of cross-resistance to radiation. Comparisons of glutathione (GSH) content and the enzymes involved in GSH homeostasis showed significant differences. Resistant cells contained 1.5-fold more GSH, a 2.2-fold increase in gamma-glutamyltranspeptidase activity, and a 2.4-fold increase in GSH reductase compared with ES-2 cells (all P less than 0.05). Total glutathione-S-transferase (GST) activity was 2.6-fold higher (P less than 0.01) in the ES-2R line. The pi-class GST subunit by Western blotting and GST activity toward ethacrynic acid were increased 2-fold in the resistant cells. Depletion of GSH levels in ES-2R cells by buthionine sulfoximine restored the sensitivity of ES-2R to MRA-CN. These findings implicate a role for GSH metabolism in the resistance phenotype of ES-2R cells. We have previously reported that these cells have an increased generation time and decreased topoisomerase II content. Thus, the ES-2R cell line exhibits a complex phenotype of broad cross-resistance, which is likely to involve multiple mechanisms, and includes enhanced DNA repair and increased GSH content and GST activity.

    View details for Web of Science ID A1991GH25000017

    View details for PubMedID 1717140

  • LATE CONSOLIDATIVE RADIATION-THERAPY IN THE TREATMENT OF LIMITED-STAGE SMALL-CELL LUNG-CANCER CANCER Carlson, R. W., Sikic, B. I., Gandara, D. R., HENDRICKSON, C. G., WITTLINGER, P. S., Shields, J. A., Wong, P. P., WHITE, J. E., MEAKIN, C. J., MCWHIRTER, K. M., Lamborn, K. R., Phillips, T. L. 1991; 68 (5): 948-958

    Abstract

    Two hundred twenty-three patients were enrolled on this randomized Phase III trial testing the value of late consolidative involved-field radiation therapy in the treatment of limited-stage small cell lung cancer (SCLC). Patients were treated with induction chemotherapy consisting of alternating cycles of procarbazine, vincristine, lomustine, and cyclophosphamide (POCC) and etoposide, doxorubicin, and methotrexate (VAM) for 6 to 9 months. Responding patients were then randomized at 6 or 9 months to chemotherapy alone or to involved-field radiation therapy. All partial and complete responders received prophylactic cranial irradiation. Of the 180 eligible and evaluable patients, 80 (44%) achieved a complete response and 39 (22%) achieved a partial response (overall rate of response, 66%). Actuarial median survival time was 11.6 months, with 16% of patients surviving 2 years and 11% surviving 5 years. Forty-eight patients were randomized to chemotherapy alone (24 patients) versus chemotherapy plus involved-field radiation therapy (24 patients). There were no significant differences in time to progression or survival between those patients receiving or not receiving involved-field radiation therapy. The thorax was the site of first relapse in 58% of patients randomized to chemotherapy alone versus 29% in patients randomized to chemotherapy plus involved-field radiation therapy (P equals 0.042). The major acute toxicity was reversible myelosuppression, and the major late toxicity was chronic central nervous system dysfunction. The authors conclude that the addition of late consolidative radiation therapy to induction chemotherapy in the treatment of limited-stage SCLC is well tolerated and improves local control, but does not improve time to progression or rates of survival.

    View details for Web of Science ID A1991GD02500006

    View details for PubMedID 1655219

  • ANTICANCER DRUG DISCOVERY JOURNAL OF THE NATIONAL CANCER INSTITUTE Sikic, B. I. 1991; 83 (11): 738-740

    View details for Web of Science ID A1991FN23400001

    View details for PubMedID 2041045

  • A COMBINED APPROACH FOR PURGING MULTIDRUG-RESISTANT LEUKEMIC-CELL LINES IN BONE-MARROW USING A MONOCLONAL-ANTIBODY AND CHEMOTHERAPY BLOOD Aihara, M., Aihara, Y., SCHMIDTWOLF, G., SCHMIDTWOLF, I., Sikic, B. I., Blume, K. G., Chao, N. J. 1991; 77 (9): 2079-2084

    Abstract

    Selective removal of malignant cells (purging) from bone marrow (BM) is a concern in autologous BM transplantation (ABMT). Use of vincristine, etoposide, or doxorubicin for purging could be rendered ineffective by the presence of multidrug-resistant (MDR) tumor cells. To circumvent this particular problem, we investigated whether 17F9, a monoclonal IgG2b antibody directed against the cell surface product of the MDR gene, P-glycoprotein, is effective in selective removal of MDR cells from BM when used with rabbit complement (C'). Using two different cell lines we have demonstrated that 17F9 + C' selectively lyses MDR-positive cells. Three rounds of antibody + C' resulted in 96.4% +/- 3.6% kill of K562/DOX and 100% +/- 0% of CEM/VLB cells. Mixtures of malignant cells and normal BM resulted in 99.85% removal of K562/DOX and 99.91% removal of CEM/VLB clonogenic cells. This treatment did not affect normal committed precursors compared with C' alone. The addition of the cytotoxic agent etoposide (VP-16) following antibody purging results in a 4.6 log reduction of malignant cells. Furthermore, this antibody was effective when used against patients' leukemic blasts. These results suggest the use of 17F9 + C' is effective and selective for removal of MDR cells from BM before ABMT and the addition of VP-16 enhances the purging efficacy.

    View details for Web of Science ID A1991FJ95700034

    View details for PubMedID 1673356

  • THE USE OF PROBENECID AS A CHEMOPROTECTOR AGAINST CISPLATIN NEPHROTOXICITY CANCER Jacobs, C., Kaubisch, S., Halsey, J., Lum, B. L., GOSLAND, M., Coleman, C. N., Sikic, B. I. 1991; 67 (6): 1518-1524

    Abstract

    Probenecid inhibits cisplatin (CP) secretion in humans and protects against CP-induced nephrotoxicity in rats. The authors conducted a Phase I trial of escalating doses of CP using probenecid as a chemoprotector. Fifty-four courses of CP at doses ranging from 100 to 160 mg/m2 were given by 24-hour infusion to 36 patients. There was no renal impairment at any dose. Ototoxicity, however, became the dose-limiting toxicity; 14 patients experienced a 20 or greater decibel (dB) loss. Seven percent of courses were associated with a leukocyte count of less than 1.5 x 10/microliters, and 19% with a platelet count of less than 50 x 10(3)/microliters. Only three patients developed neurotoxicity. Correlating pharmacokinetic data and toxicity, the authors found that high cumulative dose, area under the curve (AUC) for unbound platinum, and cumulative AUC were associated with ototoxicity and peripheral neuropathy. It was concluded that probenecid may protect against CP nephrotoxicity and warrants further investigation. Its unique mechanism of action and lack of toxicity make it ideal to combine with other chemoprotectors.

    View details for Web of Science ID A1991FC04000009

    View details for PubMedID 1848154

  • MODULATION OF ETOPOSIDE (VP-16) CYTOTOXICITY BY VERAPAMIL OR CYCLOSPORINE IN MULTIDRUG-RESISTANT HUMAN LEUKEMIC-CELL LINES AND NORMAL BONE-MARROW EXPERIMENTAL HEMATOLOGY Chao, N. J., Aihara, M., Blume, K. G., Sikic, B. I. 1990; 18 (11): 1193-1198

    Abstract

    We studied the effects of two modulators of multidrug resistance (MDR), cyclosporine and verapamil, on the cytotoxicity of etoposide (VP-16) in normal human bone marrow; two human leukemia cell lines, K562 and CEM; their MDR variants, K562/DOX and CEM/VLB; and mixtures of normal marrow and leukemic cells. VP-16 was selectivity toxic to the parental leukemic cells, with IC-50 values of 2 microM for CEM cells, 1.5 microM for K562 cells, and 12 microM for normal marrow CFU-GM. This selectivity was lost in the MDR variant leukemia cells, with IC-50s of 20 microM in K562/DOX and 8 microMs in CEM/VLB. Cyclosporine, 6 microMs, and verapamil, 20 microM, alone were nontoxic to bone marrow CFU-GM, and did not significantly increase the toxicity of VP-16 to normal marrow cells or to the two drug-sensitive leukemic cell lines. However, cyclosporine specifically enhanced the cytotoxicity of VP-16 in the MDR leukemia cells, reducing the IC-50 to the same level as the parental sensitive cells. Verapamil was considerably less effective. In a mixing experiment that included K562/DOX cells and normal bone marrow, cyclosporine increased the toxicity of VP-16 to the resistant leukemic cells by nearly 20-fold. Because the cytotoxic effect of cyclosporine is additive for resistant tumor cells, its combination with VP-16 may be useful in the purging of contaminating tumor cells prior to autologous bone marrow transplantation.

    View details for Web of Science ID A1990EK13700009

    View details for PubMedID 2226679

  • SUCCESSFUL TREATMENT OF METASTATIC THYMIC CARCINOMA WITH CISPLATIN, VINBLASTINE, BLEOMYCIN, AND ETOPOSIDE CHEMOTHERAPY CANCER Carlson, R. W., Dorfman, R. F., Sikic, B. I. 1990; 66 (10): 2092-2094

    Abstract

    Thymic carcinomas are rare malignant neoplasms of the thymic epithelium that are distinguished from the malignant thymomas by the presence of cytologic atypia. Thymic carcinomas may metastasize outside of the thorax and are associated with a very poor prognosis. Complete responses of thymic carcinoma to chemotherapy alone have not been reported. A 21-year-old man with metastatic undifferentiated carcinoma of probable thymic origin is presented who achieved a pathologic complete response with cisplatin, vinblastine, and bleomycin chemotherapy. Additional consolidative chemotherapy with cisplatin and etoposide was administered. The patient remains disease-free 5 years after diagnosis. Cisplatin, vinblastine, and bleomycin chemotherapy appears to have significant activity against thymic carcinoma.

    View details for Web of Science ID A1990EH74500007

    View details for PubMedID 1699650

  • ASSESSMENT OF PURGING WITH MULTIDRUG RESISTANCE (MDR) MODULATORS AND VP-16 - RESULTS OF LONG-TERM MARROW CULTURE EXPERIMENTAL HEMATOLOGY Aihara, M., Sikic, B. I., Blume, K. G., Chao, N. J. 1990; 18 (8): 940-944

    Abstract

    We studied the effects of two modulators of multidrug resistance (MDR), cyclosporine and verapamil, on the cytotoxicity of etoposide (VP-16) in normal bone marrow cells. VP-16 was toxic to normal bone marrow at concentrations greater than 50 microM, resulting in no granulocyte-macrophage colony-forming units (CFU-GM) in short-term methylcellulose cultures. However, in long-term marrow cultures (LTMC) treatment with VP-16 without the addition of MDR modulators resulted in only a twofold decrease in total cell number at a VP-16 concentration of 50 microM, compared to media alone in the adherent cell layer, and approximately 20% recovery of CFU-GM. The addition of MDR modulators did not result in excessive cytotoxicity, reducing the total CFU-GM by two- to threefold even at the higher VP-16 concentration. Therefore, these modulators in conjunction with VP-16 can be safely used on normal bone marrow cells and may provide an effective method to purge MDR-tumor cells.

    View details for Web of Science ID A1990DV80300016

    View details for PubMedID 2387345

  • MODIFICATION OF CISPLATIN TOXICITY WITH DIETHYLDITHIOCARBAMATE JOURNAL OF CLINICAL ONCOLOGY Berry, J. M., Jacobs, C., Sikic, B., Halsey, J., Borch, R. F. 1990; 8 (9): 1585-1590

    Abstract

    Diethyldithiocarbamate (DDTC), a heavy metal-chelating agent, has been shown to decrease cisplatin (CP) toxicity in preclinical studies. This phase I dose-escalation study was undertaken to investigate DDTC as a chemoprotector in patients with advanced cancer. Thirty-five courses of CP in doses ranging from 120 to 160 mg/m2 were given intravenous (IV) bolus to 19 patients. DDTC at 4 g/m2 was infused over 1 hour, starting 45 minutes after CP. There was minimal nephrotoxicity with a mean creatine clearance of 99 mL/min +/- 4 pretreatment and 86 mL/min +/- 4 on day 21. Two courses were associated with a WBC count less than 2,000/mm3 and one course with a platelet count of 15,000/mm3. Two patients had grade 2 neurotoxicity. Hearing loss occurred in 11 patients: five greater than or equal to 20 dB, five greater than or equal to 40 dB, and one greater than or equal to 60 dB. All patients who received cranial irradiation had ototoxicity compared with 43% of those without radiation (P less than .05). All patients experienced toxicity during the DDTC infusion, including hypertension, flushing, diaphoresis, agitation, and local burning. We conclude that DDTC can protect against CP nephrotoxicity at doses up to 160 mg/m2. Ototoxicity became the dose-limiting factor.

    View details for Web of Science ID A1990DX47500017

    View details for PubMedID 2167955

  • PARADOXICAL INCREASE IN DNA CROSS-LINKING IN A HUMAN OVARIAN-CARCINOMA CELL-LINE RESISTANT TO CYANOMORPHOLINO DOXORUBICIN CANCER RESEARCH Lau, D. H., Ross, K. L., Sikic, B. I. 1990; 50 (13): 4056-4060

    Abstract

    The cyanomorpholino analog of doxorubicin (MRA-CN) is a potent cytotoxic agent which is known to cross-link DNA. A human ovarian carcinoma cell line, ES-2, was grown in increasing concentrations of MRA-CN from 0.1 to 0.5 nM. The resultant resistant subline, ES-2R, was 4-fold resistant to MRA-CN. DNA damage and repair in response to MRA-CN were compared in the parental and resistant cell lines using alkaline elution. DNA cross-links were detectable after 3-h incubation of the cells at 37 degrees C in MRA-CN at concentrations greater than or equal to 1.0 nM. Paradoxically, 2-fold more cross-links were detected in the ES-2R cells as compared with the ES-2 cells. This paradoxical difference in cross-links between the 2 cell lines was observed to increase with time of exposure to 2.5 nM of MRA-CN. Non-protein-associated DNA strand breaks were also detected in the 2 cell lines after exposure to 2.5 nM of the drug. The ES-2 cells consistently showed twice as many breaks as the ES-2R cells, which could explain the paradoxical higher apparent DNA cross-linking observed with the ES-2R cells after exposure to MRA-CN. Studies of the time course of cross-link repair after exposure to MRA-CN revealed that 75% of the DNA cross-links disappeared in the ES-2R cells by the end of 8 h in drug-free medium. In contrast, cross-links in the ES-2 cells were undetectable after 4 h, which coincided with a progressive increase in DNA strand breaks. The topoisomerase II level in the ES-2 cells was 2- to 4-fold higher than that in the ES-2R cells. However, proteinase K treatment of the lysed cells did not increase the number of apparent strand breaks produced by MRA-CN, suggesting that topoisomerase II may not be involved. These findings indicate that, in addition to DNA cross-linking, MRA-CN causes DNA strand breakage. Resistance to MRA-CN in the ES-2R cells is associated with more apparent DNA cross-linking and less DNA strand breakage, which may be a consequence of differences in DNA repair and/or nonspecific DNA degradation between the resistant and the sensitive cell lines.

    View details for Web of Science ID A1990DK78300043

    View details for PubMedID 2162251

  • DELIVERY OF A NORMAL INFANT FOLLOWING CISPLATIN, VINBLASTINE, AND BLEOMYCIN (PVB) CHEMOTHERAPY FOR MALIGNANT TERATOMA OF THE OVARY DURING PREGNANCY GYNECOLOGIC ONCOLOGY CHRISTMAN, J. E., Teng, N. N., LEBOVIC, G. S., Sikic, B. I. 1990; 37 (2): 292-295

    Abstract

    Pregnancy complicated by an immature teratoma is rare, with a reported incidence of 0.07%. A case report of a grade 3 immature teratoma measuring 18 x 20 cm, with operative intraabdominal rupture (FIGO stage IC), is reported. The poor prognosis of malignant germ cell tumors treated by surgery alone seems to indicate a need for adjunctive chemotherapy. One course of multiagent chemotherapy consisting of cisplatin, vinblastine, and bleomycin (PVB) was initiated during the midtrimester. After an uncomplicated vaginal delivery at term of a normal infant, the planned regimen of chemotherapy was resumed. Subsequent "second-look" laparotomy was negative for malignant disease. The actual risk of PVB chemotherapy in pregnancy cannot be assessed by a single case report. The delivery of a normal infant is encouraging.

    View details for Web of Science ID A1990DE81300025

    View details for PubMedID 1693127

  • PRELIMINARY-RESULTS OF CONCURRENT RADIOTHERAPY AND CHEMOTHERAPY IN ADVANCED CERVICAL-CARCINOMA - A PHASE I-II PROSPECTIVE INTERGROUP NCOG-RTOG STUDY GYNECOLOGIC ONCOLOGY John, M., Flam, M., Sikic, B., Rotman, M., Cooper, J., Malec, M., Hannigan, J., Phillips, T. 1990; 37 (1): 1-5

    Abstract

    Thirty-eight patients with advanced carcinoma of the cervix were prospectively treated with a concurrent combination of radiotherapy (RT) and chemotherapy (CT) using the drugs 5-fluorouracil (5FU), mitomycin C and cis-platinum as part of a Northern California Oncology Group (NCOG) and Radiation Therapy Oncology Group (RTOG) intergroup study. RT consisted of 36.00 Gy to the pelvis in 4 weeks followed by a 9.00-Gy parametrial boost. This was followed by two intracavitary applications for a total of 4000 mg hr of radium equivalent when possible. 5FU (1000 mg/m2/24 hr for 96 hr by iv infusion) and mitomycin C (10 mg/m2/iv bolus) were given during the second week of external RT. 5FU (dose as above) and cis-platinum (75 mg/m2/iv over 6 hr) were given during the first intracavitary application. Of 36 patients evaluable for toxicity, 11% had grade 3 nonhematological toxicity and 11% had reversible grade 4 hematological toxicity. There were no toxic deaths. A complete response rate of 62.5% was obtained overall (median survival not reached). This study suggests that this particular combination of RT and CT in advanced cervical carcinoma is effective and well tolerated.

    View details for Web of Science ID A1990DA10500001

    View details for PubMedID 2108909

  • REVERSAL BY CEFOPERAZONE OF RESISTANCE TO ETOPOSIDE, DOXORUBICIN, AND VINBLASTINE IN MULTIDRUG RESISTANT HUMAN SARCOMA-CELLS CANCER RESEARCH Gosland, M. P., Lum, B. L., Sikic, B. I. 1989; 49 (24): 6901-6905

    Abstract

    The cephalosporins are a family of semisynthetic antibiotics, some of which have structural features associated with substrates for the multidrug transporter, P-glycoprotein. The activity of a series of six cephalosporins in reversing multidrug resistance (MDR) was examined in MDR variants (Dx5 cells) of the human sarcoma line MES-SA. Dx5 cells express high levels of the mdr1 gene product P-glycoprotein and are 25- to 30-fold resistant to doxorubicin (DOX), etoposide (VP-16), and vinblastine (VBL). Cytotoxicity was measured by the MTT assay. Cefoperazone (1.0 mM) was the most effective modulator of MDR, lowering the IC50 for VP-16 by 29-fold (29x), for VBL by 16x, and for DOX by 14x. Ceftriaxone at 1.0 mM produced 10x modulation of VP-16 cytotoxicity, 8x for DOX, and 2x for VBL. The reversal of resistance was concentration dependent, decreasing to 4x and 5x, respectively, for DOX with 0.25 mM cefoperazone and ceftriaxone. No modulation of cytotoxicity was observed in the parental MES-SA cells, which do not express mdr1. Cefazolin, cefotetan, cephradine, and ceftazidime were ineffective, producing less than 5x modulation of DOX at 1.0 mM. Among these cephalosporins, cefoperazone and ceftriaxone were the most highly protein bound in the media (30 and 52%), and the most lipid soluble, with octanol/water partitioning coefficients of -0.49 and -0.60. Varying the serum concentration in medium from 5 to 50% had less than a two-fold effect on the modulation of MDR by ceftriaxone. The ability to reverse MDR among these agents is associated with lipid solubility, high protein binding, a polycyclic planar geometry, and the presence of the piperazine group in cefoperazone. These data and the potential for achieving high tissue concentrations indicate that cefoperazone merits further study as a modulator of MDR.

    View details for Web of Science ID A1989CC88900005

    View details for PubMedID 2582432

  • Antitumor antibiotics. Current opinion in oncology Sikic, B. I. 1989; 1 (2): 198-202

    View details for PubMedID 2489960

  • DETECTION OF CELL-AFFECTING AGENTS WITH A SILICON BIOSENSOR SCIENCE Parce, J. W., Owicki, J. C., KERCSO, K. M., Sigal, G. B., Wada, H. G., MUIR, V. C., BOUSSE, L. J., Ross, K. L., Sikic, B. I., McConnell, H. M. 1989; 246 (4927): 243-247

    Abstract

    Cellular metabolism is affected by many factors in a cell's environment. Given a sufficiently sensitive method for measuring cellular metabolic rates, it should be possible to detect a wide variety of chemical and physical stimuli. A biosensor has been constructed in which living cells are confined to a flow chamber in which a potentiometric sensor continually measures the rate of production of acidic metabolites. Exploratory studies demonstrate several applications of the device in basic science and technology.

    View details for Web of Science ID A1989AU63600035

    View details for PubMedID 2799384

  • ASSOCIATION OF DNA CROSS-LINKING WITH POTENTIATION OF THE MORPHOLINO DERIVATIVE OF DOXORUBICIN BY HUMAN-LIVER MICROSOMES JOURNAL OF THE NATIONAL CANCER INSTITUTE Lau, D. H., Lewis, A. D., Sikic, B. I. 1989; 81 (13): 1034-1038

    Abstract

    The morpholino analog of doxorubicin (DOX), 3'-deamino-3'-(4"-morpholinyl)-doxorubicin (MRA), is 0.5- to 10-fold more potent than DOX in vitro but 100- to 200-fold more potent in vivo, which indicated that biotransformation in vivo may generate a highly potent metabolite(s). A likely mechanism for such biotransformation is hepatic mixed-function oxidation. At a concentration of 5 microM, MRA was incubated for 30 minutes at 37 degrees C with 1 mg of human liver microsomes/mL and 0.45 mM of NADPH. The cytotoxicity of the microsome- and NADPH-treated MRA was 44-fold higher than that of the untreated MRA in the human ovarian carcinoma cell line ES-2. This potentiation did not occur for MRA treated with boiled microsomes and NADPH, active microsomes in the absence of NADPH, or Tris buffer plus NADPH. No potentiation was observed with DOX or the highly potent cyanomorpholino derivative of DOX, MRA-CN, under any of the above conditions. After 2 hours of exposure of the ES-2 cells to microsome- and NADPH-treated MRA, dose-dependent DNA cross-links were observed with 5 nM or more of MRA, whereas only DNA strand breaks were detected in cells exposed to 500 nM of untreated MRA or MRA incubated under other conditions. These data indicate that MRA is biotransformed by the hepatic mixed-function oxidases to a potent DNA-alkylating metabolite(s), which may be important in the determination of the pharmacologic and toxicologic profile of MRA. The active metabolite(s) of MRA may be analogous to MRA-CN, which cross-links DNA without requiring bioactivation.

    View details for Web of Science ID A1989AC88500011

    View details for PubMedID 2733045

  • DNA CROSS-LINKING AND CYTO-TOXICITY OF THE ALKYLATING CYANOMORPHOLINO DERIVATIVE OF DOXORUBICIN IN MULTIDRUG-RESISTANT CELLS JOURNAL OF THE NATIONAL CANCER INSTITUTE Scudder, S. A., Brown, J. M., Sikic, B. I. 1988; 80 (16): 1294-1298

    Abstract

    The cyanomorpholino derivative of doxorubicin (MRA-CN) is an anthracycline that is extremely potent and non-cross-resistant with doxorubicin (DOX) in multidrug-resistant cells. MRA-CN binds to and cross-links DNA and thus has been proposed to act as a targeted alkylating agent. In our study, the number of DNA interstrand and DNA-protein cross-links produced by MRA-CN was identical in multidrug-resistant Dx5 and parental MES-SA cells, as shown by alkaline elution analysis. The amount of cross-linking was directly proportional to drug concentration at concentrations from 10(-11) to 10(-7) M MRA-CN. Extensive DNA cross-linking was evident within 30 minutes of drug exposure. After 1 hour of drug exposure, the number of DNA cross-links increased for 90 minutes, reached a plateau, and then began to decrease after 120 minutes. Loss of cell viability was also observed as early as 3 hours after exposure to MRA-CN. The finding of the same number of DNA cross-links in MES-SA and Dx5 cells indicates that similar amounts of MRA-CN are likely to enter the nuclei of multidrug-resistant and sensitive cells. Other anthracyclines have major differences in nuclear distribution in sensitive and resistant cells. Several factors may contribute to the non-cross-resistance of MRA-CN in multidrug-resistant cells. (a) The lipophilicity of MRA-CN facilitates cell entry. (b) The substitution and loss of basicity at the amino nitrogen may reduce the affinity of the drug for the P-glycoprotein efflux pump, compared with that of DOX. (c) The detoxification function of P-glycoprotein may be less effective for drugs that produce rapid and irreversible cell damage, such as the DNA-targeted alkylation caused by MRA-CN.

    View details for Web of Science ID A1988Q509800004

    View details for PubMedID 3172256

  • CHARACTERIZATION AND IMMUNOASSAY OF HUMAN TUMOR-ASSOCIATED GALACTOSYLTRANSFERASE ISOENZYME-II CANCER RESEARCH Uemura, M., Winant, R. C., Sikic, B. I., Brandt, A. E. 1988; 48 (18): 5325-5334

    Abstract

    Galactosyltransferase (GT) (EC 2.4.1.38) was purified to homogeneity from human ovarian tumor effusion fluid and normal human serum by chromatography on alpha-lactalbumin and anti-human immunoglobulin affinity (to selectively absorb contaminating IgG) columns. Both preparations showed a single, broad band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis centered at a molecular weight of 48,000, but nondenaturing polyacrylamide gel electrophoresis of GT isolated from tumor effusion fluid revealed the presence of a series of oligomeric proteins possessing GT activity, which were barely detectable in normal human serum. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of N-glycanase- and O-glycanase-treated GT revealed that each endoglycanase removed carbohydrate with an approximate molecular weight of 3,000, revealing the presence of both N-linked and O-linked oligosaccharide substitutions on GT. Purified GT (containing a mixture of GT isoenzymes) was used to immunize BALB/c mice for monoclonal antibody (MAb) preparation. Four of the MAb isolated reacted with GT. MAb 3872 (patent pending; an IgG1) was determined to be specific for a cancer-associated GT isoenzyme (GT-II) by immunostaining of Western blots and nondenaturing polyacrylamide gel electrophoresis of GT specifically eluted from a MAb 3872 affinity column. Two 125I-labeled cyanogen bromide peptides (Mr 8,400 and 7,400) prepared from 125I-GT were specifically bound and eluted from a MAb 3872 affinity column, demonstrating that the MAb 3872 GT-II-specific antigenic epitope resides on these peptides. MAb 3872 was immobilized on 1,1'-carbonyldiimidazole-activated trisacryl GF-2000 and used to specifically assay serum GT-II levels in 29 individual normal human serum samples and 77 serum samples from 38 patients with advanced ovarian tumors. The normal serum GT-II level was found to be 85.3 +/- 30.9 milliunits/ml, with a range of 17 to 160 milliunits/ml. Of the 38 tumor patients, 33 showed GT-II values in excess of 200 milliunits/ml, with a range of 216 to 8,469 milliunits/ml. Serial samples obtained from the ovarian tumor patients suggested that the serum GT-II level reflected the tumor burden of the patient.

    View details for Web of Science ID A1988P987300043

    View details for PubMedID 3136919

  • ADVANCED EPITHELIAL OVARIAN-CANCER - SALVAGE WHOLE ABDOMINAL IRRADIATION FOR PATIENTS WITH RECURRENT OR PERSISTENT DISEASE AFTER COMBINATION CHEMOTHERAPY JOURNAL OF CLINICAL ONCOLOGY SCHRAY, M. F., Martinez, A., HOWES, A. E., Podratz, K. C., Ballon, S. C., Malkasian, G. D., Sikic, B. I. 1988; 6 (9): 1433-1439

    Abstract

    Between 1979 and 1984, 53 patients received whole abdominal irradiation in a curative salvage effort for residual (32 patients) or recurrent (21 patients) epithelial ovarian cancer after combination chemotherapy (cisplatin-based in 48 patients). Residual cancer less than or equal to 2 cm in diameter was confirmed at operation in all patients before irradiation consisting of 2,550 to 3,000 rad to the whole abdomen with partial liver/kidney shielding and boosting of the dose to the diaphragmatic/paraaortic nodal regions and pelvis to approximately 4,000 and 5,000 rad, respectively. Twelve patients (23%) did not complete therapy as a result of hematologic intolerance. Actuarial overall and disease-free survival at 3 years are 35% and 30%, respectively, with follow-up for disease-free patients ranging from 30 to 79 months (median, 43 months). Twenty-seven of 36 relapses (75%) occurred within the irradiated abdomen alone. At 3 years, 70% of patients with well- or moderately-differentiated tumors were disease-free v 10% of those with poorly differentiated tumors (P less than .001). Among prognostic factors evaluated, including grade, initial residual disease before chemotherapy, residual disease at time of irradiation, age, chemotherapy response v progression, and completion of irradiation, only grade and initial residual disease before chemotherapy were statistically significant in multivariate analysis (both P less than .01). Patients with the combination of high-grade tumor, initial residual disease greater than 2 cm before chemotherapy, and macroscopic disease after "second-look" laparotomy do not benefit from irradiation. Eleven patients (21%) developed an apparent treatment-related bowel obstruction after completion of irradiation. Selected subsets of patients do well; however, the role of irradiation in this setting can be confirmed only with randomized clinical study.

    View details for Web of Science ID A1988Q160500011

    View details for PubMedID 3418375

  • ENHANCEMENT OF THE CLINICAL ACTIVITY OF MELPHALAN BY THE HYPOXIC CELL SENSITIZER MISONIDAZOLE CANCER RESEARCH Coleman, C. N., Carlson, R. W., Halsey, J., Kohler, M., Gribble, M., Sikic, B. I., Jacobs, C. 1988; 48 (12): 3528-3532

    Abstract

    One hundred patients with non-small cell lung cancer were entered by members of the Northern California Oncology Group into a randomized Phase II trial of i.v. melphalan versus i.v. melphalan with concomitant oral misonidazole. The patients had not received prior chemotherapy. Eighty-five patients were evaluable for assessment of response and 89 were evaluable for toxicity analysis. The melphalan/misonidazole group had a superior response rate (two complete and four partial responses among 42 patients or 14%) compared to the melphalan group in which there were no responses among 43 patients (p = 0.024, two-sided Fisher exact test). Since hematological toxicity was equivalent in the two groups, there was an improvement in therapeutic index. Data from 12 patients undergoing pharmacological studies demonstrated that the plasma concentration of melphalan was 25% higher in the misonidazole group, a difference that is not statistically significant. Although the mechanism of interaction has not been fully established, this randomized trial demonstrates that a chemosensitizer can enhance the clinical antitumor activity of an alkylating agent and suggests that chemosensitizers in combination with alkylating agents should be investigated in further clinical trials.

    View details for Web of Science ID A1988N713400041

    View details for PubMedID 2836059

  • DOXORUBICIN AND THE ALKYLATING ANTHRACYCLINE 3'-DEAMINO-3'-(3-CYANO-4-MORPHOLINYL) DOXORUBICIN - COMPARATIVE INVITRO POTENCY AGAINST LEUKEMIA AND BONE-MARROW CELLS JOURNAL OF THE NATIONAL CANCER INSTITUTE Beckman, R. A., MCFALL, P. J., Sikic, B. I., Smith, S. D. 1988; 80 (5): 361-365

    Abstract

    The new anthracycline analogue 3'-deamino-3'-(3-cyano-4-morpholinyl) doxorubicin (MRA-CN) is an intensely potent compound that has been shown to be 100-1,000 times more potent than doxorubicin (DOX) in vivo and in vitro. In addition, MRA-CN has been non-cross-resistant with DOX in DOX-selected models of multidrug resistance. We now report the effect of MRA-CN (and DOX) on leukemia cell lines established from patients with common, T-cell, and B-cell acute lymphoblastic leukemia, as well as with monoblastic leukemia. The effect of MRA-CN on the leukemia cells was compared to its toxicity on normal myeloid progenitors (therapeutic ratio) and to the effect of DOX on the leukemia and normal cells. MRA-CN was found to be 100 times more potent than DOX against normal myeloid progenitors--colony-forming units, granulocyte-macrophage (CFU-GM)--and 40-240 times more potent than DOX against leukemia cell lines. In addition, the therapeutic ratio was uniformly greater than 1, indicating that each leukemia cell line tested was more sensitive than CFU-GM to MRA-CN in vitro. There was a lack of correlation between MRA-CN and DOX at a drug concentration at which the colony formation is inhibited by 50% in the leukemia cell lines (correlation coefficient = 0.38), which supported the previous reports of non-cross-resistance between these two agents. The favorable therapeutic ratio, the non-cross-resistance with DOX, and the previously described lack of cardiac toxicity all make MRA-CN an attractive candidate for clinical trials in patients with acute leukemia.

    View details for Web of Science ID A1988N138200011

    View details for PubMedID 3357201

  • ANTIBODY-DIRECTED TARGETING OF LIPOSOMES TO HUMAN CELL-LINES - ROLE OF BINDING AND INTERNALIZATION ON GROWTH-INHIBITION CANCER RESEARCH Berinstein, N., Matthay, K. K., Papahadjopoulos, D., Levy, R., Sikic, B. I. 1987; 47 (22): 5954-5959

    Abstract

    Small unilamellar liposomes containing methotrexate or methotrexate-gamma-aspartate were conjugated to Staphylococcus aureus protein A and were thus able to bind cell-specific immunoglobulins for targeting to malignant human B- and T-cell lines. We were able to demonstrate enhanced protein A liposome uptake and growth inhibition by targeting with an anti-major histocompatibility complex class II antibody recognizing two different B-cell lines. The enhanced growth inhibition was specific for the targeting antibody and amounted to a 2- to 3-fold lowering of the concentration of drug required to inhibit cell growth by 50% as compared to nontargeted liposomes or liposomes targeted with an antibody not recognizing a cell surface antigen. A strong association between enhanced growth inhibition and liposome internalization as assessed by fluorescent-activated cell sorter analysis of carboxyfluorescein containing protein A liposomes was seen. By contrast, specific enhancement of growth inhibition was not seen with several anti-idiotype antibodies or antibodies to T-cell differentiation antigens. Liposome internalization did not occur with these antibodies. Failure of growth inhibition and PA liposome internalization could not be explained by differences in cell binding of the antibody PA liposomes or the degree of protein A binding of the targeting antibody. Although the ability of the targeting antibody to bind to the cell and to protein A are important, these factors alone are not sufficient to guarantee internalization and growth inhibition. Variations in rates of internalization of various cell surface antigen-antibody complexes may account for different protein A liposome mediated cytotoxicities.

    View details for Web of Science ID A1987K885800026

    View details for PubMedID 3664498

  • A THERAPY PLANNING ARCHITECTURE THAT COMBINES DECISION-THEORY AND ARTIFICIAL-INTELLIGENCE TECHNIQUES COMPUTERS AND BIOMEDICAL RESEARCH Langlotz, C. P., Fagan, L. M., Tu, S. W., Sikic, B. I., Shortliffe, E. H. 1987; 20 (3): 279-303

    Abstract

    Through our experience with the ONCOCIN cancer therapy consultation system, we have identified a set of medical planning problems to which no single existing computer-based reasoning technique readily applies. In response to the need for automated assistance with this class of problems, we have devised a computer program called ONYX that combines decision-theoretic and artificial intelligence approaches to planning. We discuss our rationale for devising a new planning architecture and describe in detail how that architecture is implemented. The program's planning process consists of three steps: (i) the use of rules derived from therapy planning strategies to generate a small set of plausible plans, (ii) the use of knowledge about the structure and behavior of the human body to create simulations that predict possible consequences of each plan for the patient, and (iii) the use of decision theory to rank the plans according to how well the results of each simulation meet the treatment goals. This architecture explicitly manages the uncertainty inherent in many planning tasks, introduces a possible mechanism for the dissemination of decision-theoretic therapy advice, and potentially increases the number of problem solving domains in which expert system techniques can be effectively applied.

    View details for Web of Science ID A1987H761400006

    View details for PubMedID 3301187

  • DIFFERENTIAL PROTECTIVE EFFECTS OF VARYING DEGREES OF HYPOXIA ON THE CYTOTOXICITIES OF ETOPOSIDE AND BLEOMYCIN CANCER CHEMOTHERAPY AND PHARMACOLOGY Yamauchi, T., Raffin, T. A., Yang, P., Sikic, B. I. 1987; 19 (4): 282-286

    Abstract

    Oxygen is thought to be involved both directly and indirectly in the mechanisms of action of several anti-cancer agents. We studied the effects of various oxygen concentrations on the cytotoxicities of the following drugs: bleomycin (BLM), etoposide (VP-16), doxorubicin (DOX), and mitomycin C (MMC). Human sarcoma cells, MESSA, were exposed to drug for 1 h at one of several oxygen concentrations: less than 1%, 2.5%, 5%, 21%, and 95%. Cytotoxicity was assessed by cellular incorporation of 3H-thymidine into DNA 5 days after drug exposure. Control experiments varying oxygen concentration without drugs demonstrated toxicity only at the highest concentration (95%). Three different responses of drug sensitivity to varying oxygen tensions were observed. BLM, which has been shown to utilize oxygen as a substrate in generating free radicals and producing DNA scission, demonstrated a progressive increase in cytotoxicity over the entire range of increasing oxygen concentrations. This is consistent with the model of a BLM-cation-oxygen complex and catalytic reduction of oxygen. VP-16, which also produces DNA strand breakage but by interaction with topoisomerase II, exhibited a threshold response. VP-16 toxicity was ameliorated by anoxic conditions (less than 1% O2), but not by oxygen concentrations of 2.5%-95%. The reason for this protective effect of anoxia with VP-16 is not clear. In contrast, acute anoxia had no effect on the cytotoxicities of DOX and MMC. We conclude that acute hypoxia protects cells from both BLM and VP-16 but that the nature of that protection is different. VP-16 toxicity is blunted only by severe anoxia, whereas BLM exhibits a dose response effect over the entire range of oxygen concentrations.

    View details for Web of Science ID A1987J198800003

    View details for PubMedID 2439223

  • HIGH-DOSE MEGESTROL-ACETATE THERAPY OF OVARIAN-CARCINOMA - A PHASE-II STUDY BY THE NORTHERN CALIFORNIA ONCOLOGY GROUP SEMINARS IN ONCOLOGY Sikic, B. I., Scudder, S. A., Ballon, S. C., SORIERO, O. M., CHRISTMAN, J. E., SUEY, L., EHSAN, M. N., Brandt, A. E., Evans, T. L. 1986; 13 (4): 26-32

    Abstract

    The activity of high-dose megestrol acetate was studied in 47 patients with epithelial ovarian cancers after failure of initial chemotherapy. The dose of megestrol acetate was 800 mg/d orally (PO) for 4 weeks and then 400 mg/d until tumor progression. Patients generally had far-advanced disease. Prior therapy included cisplatin, doxorubicin, and cyclophosphamide (PAC) or other cisplatin-containing regimens in 37, other combinations in eight, and single agents in only two patients. Seventeen patients (36%) developed intestinal obstructions within the first 2 months on study. Tumor histology was serous in 37, endometrioid in six, and clear-cell in two. Two thirds of the tumors were histologic grade 3, and the others were grade 2. Complete remission was obtained in one patient, with time to progression of 4 months. There were three partial remissions, with times to progression of 4, 5, and 18 months. The overall response rate (complete and partial) was 8%. Three additional patients had minor remissions (3, 5, and 8 months), and five had stable disease, for 3, 4, 5, 6, and 9 months. There was no correlation of response with grade, histologic type, or site of disease, but responding patients had a longer survival from diagnosis to protocol entry and from protocol failure to death than did nonresponding patients. The major side effect of megestrol acetate was increased appetite, which caused one patient to withdraw from the study, and resulted in a 10- to 20-kg weight gain in five patients. Plasma levels of megestrol acetate averaged 600 ng/mL in the first month of therapy and decreased to approximately 400 ng/mL at 8 and 12 weeks, after the drug dosage had been reduced. Serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were markedly lower during megestrol therapy compared with pretreatment values. Megestrol acetate at 1 microgram/mL in vitro inhibited soft agar colony formation from one of 17 specimens of ovarian carcinomas. We conclude that megestrol acetate in high doses has modest, but definite, palliative effects in some patients with advanced ovarian carcinoma in whom chemotherapy has failed. A controlled trial of megestrol plus combination chemotherapy as first-line treatment of advanced ovarian carcinoma should be considered.

    View details for Web of Science ID A1986F742200006

    View details for PubMedID 3099393

  • ADVANCED EPITHELIAL OVARIAN-CANCER - TOXICITY OF WHOLE ABDOMINAL IRRADIATION AFTER OPERATION, COMBINATION CHEMOTHERAPY, AND REOPERATION GYNECOLOGIC ONCOLOGY SCHRAY, M. F., Martinez, A., HOWES, A. E., Ballon, S. C., Podratz, K. C., Sikic, B. I., Malkasian, G. D. 1986; 24 (1): 68-80

    Abstract

    Thirty-five patients with advanced ovarian cancer have received, as salvage therapy, irradiation consisting of 30 Gy to the entire abdominal contents with partial liver/kidney shielding and boosts to 42 and 51 Gy for the paraaortic/diaphragmatic and pelvic regions, respectively. These patients had received 6 to 25 cycles (median, 11 cycles) of prior combination chemotherapy (included cisplatin in 30), with "second-look" laparotomy performed in 33; 24 (68%) had three or more laparotomies. Acute gastrointestinal toxicity was generally mild. Significant hematologic toxicity (leukocytes less than 2000/mm3; or platelets less than 100,000/mm3) was seen in 19 (54%); platelet suppression occurred in 18 of these 19. Nine patients failed to complete the prescribed course of therapy; in seven, this was secondary to hematologic toxicity. Amount of prior chemotherapy and advanced age correlated with degree of hematologic toxicity. Five patients without evidence of disease (laparotomy confirmed) have developed treatment-related bowel obstruction. No other chronic toxicity of clinical significance has been observed. Seven patients have developed bowel obstruction associated with progressive neoplasm. Irradiation was well tolerated symptomatically, but hematologic toxicity associated with prior chemotherapy prevented its completion in 20% of patients. Clinical manifestations of radiation bowel toxicity have been moderate to date and should be interpreted in the context of the aggressive combined modality program.

    View details for Web of Science ID A1986C116100009

    View details for PubMedID 3699578

  • VERAPAMIL-MEDIATED SENSITIZATION OF DOXORUBICIN-SELECTED PLEIOTROPIC RESISTANCE IN HUMAN SARCOMA-CELLS - SELECTIVITY FOR DRUGS WHICH PRODUCE DNA SCISSION CANCER RESEARCH Harker, W. G., Bauer, D., ETIZ, B. B., Newman, R. A., Sikic, B. I. 1986; 46 (5): 2369-2373

    Abstract

    The effects of verapamil on the cytotoxicity and accumulation of multiple drugs were studied in a model of pleiotropic resistance generated by doxorubicin (DOX) selection of the human sarcoma cell line MES-SA. The in vitro sensitivity of the DOX-resistant variant (named Dx5), which is 50- to 100-fold resistant to DOX compared to MES-SA, was enhanced approximately 7-fold by verapamil (3 micrograms/ml). In addition, the cytotoxicity of several agents to which the Dx5 line displays cross-resistance, i.e., daunorubicin, dactinomycin, mitoxantrone, and etoposide, was also enhanced 2- to 14-fold by verapamil. These agents share the properties of DNA intercalation and/or interaction with topoisomerase II. In contrast, verapamil did not alter the sensitivity of Dx5 to several other agents to which cross-resistance had been demonstrated, i.e., vincristine, vinblastine, colchicine, mitomycin C, and melphalan; nor did verapamil enhance the cytotoxicity of DOX or other agents against the DOX-sensitive parent, MES-SA. The sensitizing effect of verapamil did not correlate well with its effects on intracellular drug accumulation. [14C]DPX accumulation was increased by 30-40% in Dx5 but not in MES-SA cells in the presence of verapamil. [3H]Vinblastine accumulation was increased by 24-72% in both MES-SA and Dx5 cells in the presence of verapamil, although cytotoxicity of the Vinca alkaloids was not affected. In this human sarcoma model of DOX-selected pleiotropic resistance, verapamil partially reversed the resistance to DOX, as well as four of the nine drugs for which cross-resistance had been demonstrated in Dx5. The potentiation by verapamil of the cytotoxicity of some but not all of these antitumor agents suggests that factors other than altered drug transport may be responsible. The pattern of sensitization, restricted to agents which produce DNA strand scission by interaction with topoisomerase II, suggests that verapamil may be acting to promote the formation or inhibit the repair of such DNA strand breaks.

    View details for Web of Science ID A1986C056500034

    View details for PubMedID 3754487

  • INVITRO SELECTION AND CHARACTERIZATION OF A BLEOMYCIN-RESISTANT SUBLINE OF B-16 MELANOMA CANCER RESEARCH ZUCKERMAN, J. E., Raffin, T. A., Brown, J. M., Newman, R. A., ETIZ, B. B., Sikic, B. I. 1986; 46 (4): 1748-1753

    Abstract

    A subline of B16 melanoma cells which is 10-fold resistant to bleomycin (BLM) was developed by exposure of the parental cell line to sequential increases in BLM concentration. This resistance to BLM is stable for over 30 passages in drug-free medium. Neither double minute chromosomes nor homogeneously staining regions were evident in karyotypes of the resistant cells. The subline, B16/BLM-R1, was slightly radioresistant, with a D0 ratio of 1.4 compared to the parental cells. No cross-resistance was observed to a number of cytotoxic drugs, including doxorubicin, melphalan, cisplatin, carmustine, dactinomycin, mitomycin C, and vinblastine. However, slight cross-resistance (2-fold) was noted with etoposide. Marked resistance to BLM also was demonstrated in vivo in mice bearing B16/BLM-R1 implanted s.c. Possible mechanisms of BLM resistance in these cells were explored through examination of the degree of drug inactivation by BLM hydrolase and measurement of single- and double-strand DNA scission, as well as repair of single strand breaks by the alkaline elution technique. The specific activity of BLM hydrolase was 70% higher in the resistant subline, commensurate with a 50% increase in protein content in these cells. Because this is insufficient to account for the 10-fold resistance, BLM hydrolase activity does not appear to be a major determinant of resistance in B16/BLM-R1. The overall number of single and double strand breaks in DNA produced by bleomycin treatment did not differ in the sensitive and resistant cells. The cross-resistance with ionizing radiation and etoposide suggests an enhanced capability of B16/BLM-R1 cells to withstand or repair single strand breaks in DNA. However, this was not evident by measuring repair of single strand scission by alkaline elution.

    View details for Web of Science ID A1986A645600035

    View details for PubMedID 2418953

  • NEUROLOGIC DYSFUNCTION IN PATIENTS TREATED FOR SMALL CELL-CARCINOMA OF THE LUNG - A CLINICAL AND RADIOLOGICAL STUDY INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS CHAK, L. Y., ZATZ, L. M., Wasserstein, P., Cox, R. S., KUSHLAN, P. D., PORZIG, K. J., Sikic, B. I. 1986; 12 (3): 385-389

    Abstract

    The neurologic dysfunction in 7 patients treated for small cell carcinoma (SCC) of the lung by combination chemotherapy and prophylactic brain irradiation was evaluated. The disease appeared to be a diffuse encephalopathy frequently affecting the higher cortical functions. Five out of seven patients had progressive dysfunction leading to death in 1 to 26 months; one patient had stabilization of symptoms followed by death in 21 months, probably from the neurologic disease as well as SCC; one patient's symptoms improved. The clinical course of the neurologic disorder seemed different from the known reactions to brain irradiation and from the other neurologic syndromes associated with lung cancer. The relative contributions of cranial irradiation and treatment with chemotherapeutic agents in producing the neurotoxicity are not known. Computed tomographic (CT) brain scans done after the onset of symptoms did not show any focal signs or necrosis. However, there was a suggestion of progressive increase in intracranial fluid volume on the scans. The incidence of the disorder, 10.2% among a group of 49 patients, suggests the need for prospective studies to evaluate the problem.

    View details for Web of Science ID A1986A965100014

    View details for PubMedID 3007408

  • BIOCHEMICAL AND CELLULAR DETERMINANTS OF BLEOMYCIN CYTOTOXICITY CANCER SURVEYS Sikic, B. I. 1986; 5 (1): 81-91

    Abstract

    Bleomycin is a mixture of cytotoxic glycopeptides which function as mininucleases, binding to DNA and producing single and double strand breaks by the formation of an activated oxygen complex. Bleomycin is an effective agent against a few human cancers, notably lymphomas, testicular and ovarian germ cell cancers and certain squamous carcinomas. Most human cancers are resistant to bleomycin a priori, however, and those which are initially sensitive frequently develop resistance to the drug during therapy. Several potential modes of resistance to bleomycin have been identified in cell culture and animal tumour models, although their relative importance in determining the responsiveness of human cancers to the drug is not well understood. Bleomycin is selectively toxic to cells in the M and G2 phases of the cell cycle, and generally more effective against actively dividing rather than resting cells. Thus, the cytokinetic state of the tumour cell population is an important determinant of drug activity. Oxygen is an essential substrate for bleomycin's action, with the degree of cytotoxicity directly related to ambient oxygen. Both acutely and chronically hypoxic cells form a substantial fraction of the cell population of many tumours, and may serve as a reservoir of cells resistant to bleomycin on this epigenetic basis. Metabolic inactivation of bleomycin is a mechanism of resistance to the drug in some cells and may influence toxicity in normal tissues. Bleomycin hydrolase activity is low in lungs and skin, the two major sites of normal tissue toxicities, and levels of this enzyme have been elevated in some but not all tumour cell lines selected for resistance to bleomycin. The capacity to repair or withstand single and double strand DNA breaks may also be an important determinant of resistance to the drug. Most yeast and mammalian cell mutants, which are hypersensitive to ionizing radiation because of defects in DNA repair, are also more sensitive to bleomycin than wild-type cells. A number of agents which interact with membranes or inhibit DNA repair, such as ethanol, lidocaine, verapamil and caffeine, have been reported to sensitize cells to bleomycin in vitro.

    View details for Web of Science ID A1986E492300004

    View details for PubMedID 2439200

  • PRELIMINARY-OBSERVATIONS OF INTRAPERITONEAL CARBOPLATIN PHARMACOKINETICS DURING A PHASE-I STUDY OF THE NORTHERN-CALIFORNIA-ONCOLOGY-GROUP CANCER CHEMOTHERAPY AND PHARMACOLOGY DeGregorio, M. W., Lum, B. L., Holleran, W. M., WILBUR, B. J., Sikic, B. I. 1986; 18 (3): 235-238

    Abstract

    The pharmacokinetic behavior of carboplatin administered by the i.p. route at a dose of 200 mg/m2 was studied during five courses of therapy in four patients with ovarian cancer. A regional pharmacologic advantage was noted with carboplatin administered by this route, with peak peritoneal fluid concentrations 18-fold those in plasma, and area under the curve (AUC) for the peritoneum showing a 18-fold and 6-fold increase over plasma AUC at 4 and 24 h, respectively. The mean residence time of total platinum in the peritoneum was 4.7 h. Approximately 10% and 40% of plasma platinum was protein bound at 4 and 24 h after treatment, respectively, whereas peritoneal fluid platinum showed minimal protein binding. Peak plasma platinum levels were comparable to those recorded in previous studies with i.v. doses of carboplatin. Peritoneal clearance of carboplatin in these four patients appeared to be less than that previously reported for cisplatin. Further studies are in progress with higher doses of i.p. carboplatin.

    View details for Web of Science ID A1986F914200010

    View details for PubMedID 3542268

  • CISPLATIN, DOXORUBICIN, AND CYCLOPHOSPHAMIDE CHEMOTHERAPY FOR ADVANCED ENDOMETRIAL CARCINOMA CANCER TREATMENT REPORTS Turbow, M. M., Ballon, S. C., Sikic, B. I., KORETZ, M. M. 1985; 69 (5): 465-467

    Abstract

    Nine of 19 patients (47%) with widespread or recurrent endometrial carcinoma responded to chemotherapy with cisplatin, doxorubicin, and cyclophosphamide. Two complete clinical responses and seven partial responses were achieved. A "second-look" laparotomy documented the complete response in one patient. The addition of cisplatin to doxorubicin and cyclophosphamide increased toxicity without increasing the antitumor activity previously reported for the two-drug combination. Performance status had a marked influence on response, while sites of metastases, amount of residual disease, and histologic grade did not affect the response rate. A schema for the treatment of patients with endometrial carcinoma with progestins and/or cytotoxic chemotherapy is suggested.

    View details for Web of Science ID A1985AKJ9300001

    View details for PubMedID 4039978

  • CENTRAL NERVOUS-SYSTEM TOXICITY AND CEREBROSPINAL-FLUID PHARMACOKINETICS OF INTRAVENTRICULARLY ADMINISTERED BLEOMYCIN IN BEAGLES CANCER RESEARCH Levin, V. A., Byrd, D., Sikic, B. I., ETIZ, B. B., Campbell, J., BORCICH, J. K., Davis, R. L. 1985; 45 (8): 3810-3815

    Abstract

    The neurotoxic effects and cerebrospinal fluid (CSF) pharmacokinetics of bleomycin were evaluated in beagles after chronic intraventricular administration twice a week for 8 consecutive weeks. Bleomycin was reasonably well tolerated at doses of 0.067 to 0.3 mg/week. Doses higher than 0.3 mg/week produced marked elevation of CSF protein levels and a necrotizing vasculitis within the central nervous system. Pharmacokinetic studies were performed approximately 1 month after the completion of the toxicity studies. [3H]inulin was used as a reference compound. Both [3H]inulin and bleomycin were cleared from the CSF more slowly than in previous studies and more slowly than in normal dogs, which suggests that bulk CSF absorption was reduced by the drug, probably secondary to protein-induced blockage of the arachnoid granulations through which CSF is normally absorbed. Because a "minimally toxic" dose of bleomycin (approximately 0.1 mg/week) produces a CSF C X t of only 1.9 mg/min/ml, we believe that a Phase I clinical trial would be too dangerous given the limited therapeutic potential that a dose of 0.1 mg/week could achieve.

    View details for Web of Science ID A1985AMU5400061

    View details for PubMedID 2410102

  • GASTRIN RELEASING PEPTIDE IS A SELECTIVE MITOGEN FOR SMALL CELL LUNG-CARCINOMA INVITRO JOURNAL OF CLINICAL INVESTIGATION Weber, S., ZUCKERMAN, J. E., Bostwick, D. G., Bensch, K. G., Sikic, B. I., Raffin, T. A. 1985; 75 (1): 306-309

    Abstract

    Human small cell lung carcinoma (SCLC) cells have been shown to contain significant levels of a bombesin-immunoreactive peptide. The 27-amino acid peptide, gastrin releasing peptide (GRP), has recently been shown to be responsible for the bombesin-like immunoreactivity found in SCLC cells. Among four lung cancer cell lines examined in vitro, GRP exhibited mitogenic activity for two SCLC subtypes, but not for a squamous carcinoma or adenocarcinoma lung cell line. The mitogenicity of the GRP molecule has been isolated to the carboxyterminal fragment, designated GRP 14-27, which is in part homologous to bombesin. The aminoterminal fragment, GRP 1-16, is no homologous to bombesin and exhibits no mitogenic activity. Thus, GRP may be an important growth regulating or autocrine factor in human SCLC.

    View details for Web of Science ID A1985AAG6500043

    View details for PubMedID 2981251

  • BLEOMYCIN, MITOMYCIN, AND CISPLATIN THERAPY FOR ADVANCED SQUAMOUS CARCINOMA OF THE UTERINE CERVIX - A PHASE-II STUDY OF THE NORTHERN-CALIFORNIA-ONCOLOGY-GROUP CANCER TREATMENT REPORTS Picozzi, V. J., Sikic, B. I., Carlson, R. W., Koretz, M., Ballon, S. C. 1985; 69 (7-8): 903-905

    Abstract

    Twenty-eight patients with advanced squamous carcinoma of the uterine cervix received cisplatin, bleomycin, and mitomycin after failure of surgery and/or irradiation to control disease. Six patients (21%) achieved responses (two complete; four partial), ranging from 3 to 7+ months. Toxicity was acceptable for most patients; however, dose reduction because of myelosuppression was frequently required. Bleomycin was delivered by continuous iv infusion, and no significant pulmonary toxicity was observed. Although this combination of drugs has activity in advanced squamous carcinoma of the uterine cervix, the addition of cisplatin to bleomycin and mitomycin did not significantly increase the clinical response rate.

    View details for Web of Science ID A1985APC8900032

    View details for PubMedID 2410123

  • CHEMOTHERAPY OF SMALL-CELL CARCINOMA OF LUNG - A RANDOMIZED COMPARISON OF ALTERNATING AND SEQUENTIAL COMBINATION CHEMOTHERAPY PROGRAMS JOURNAL OF CLINICAL ONCOLOGY Daniels, J. R., CHAK, L. Y., Sikic, B. I., Lockbaum, P., Kohler, M., Carter, S. K., Reynolds, R., Bohnen, R., Gandara, D., Yu, J. 1984; 2 (11): 1192-1199

    Abstract

    One hundred forty-seven eligible patients with small-cell carcinoma of the lung (SCCL) have been randomized to receive alternating (A) or sequential (S) combination chemotherapy. Initial treatment was with three cycles of VAM (A) or two cycles of POCC (S). VAM consists of VP16-213 200 mg/m2 intravenously (IV) day 1, Adriamycin (Adria Laboratories, Columbus, Ohio) 50 mg/m2 IV day 1, and methotrexate 30 mg/m2 IV day 1 repeated at 21-day intervals. POCC consists of cyclophosphamide 600 mg/m2 IV days 1 and 8, vincristine 1.5 mg/m2 (maximum, 2 mg) IV days 1 and 8, CCNU 60 mg/m2 po day 1, and procarbazine 100 mg/m2 po days 2 through 15. After initial treatment, all patients received whole brain radiation therapy (3,000 rad/10 fractions/2 wk). Patients with limited disease in addition received irradiation encompassing the tumor, hilar, mediastinal, and supraclavicular regions (5,000 rad/25 fractions/5 wk). After radiation, patients on arm A received POCC alternating with VAM; patients on arm S received POCC until progression when they were to be treated with VAM. The alternating arm was superior with respect to rate of complete remission (CR), median disease-free survival (MDFS), and median survival (MS). The advantage of alternating therapy was not as clearly demonstrated in the limited disease groups when interposition of involved field radiation delayed the initiation of the alternating schedule. In limited disease alone, comparing arm A with arm S, no statistically significant differences were noted. The CR rate was 42% v 54%, MDFS was 14 v 10 months, and MS was 16 v 10 months. In extensive disease, the CR rate was 44% v 20% (P = .03), MDFS was 6 v 4 months (P = .003), and MS was 10 v 7 months (P = .001). Improved treatment outcome in SCCL is achieved when combination chemotherapy regimens of similar effectiveness are administered in an alternating rather than sequential schedule.

    View details for Web of Science ID A1984TR09800002

    View details for PubMedID 6092554

  • INCREASED INCIDENCE OF ACUTE NONLYMPHOCYTIC LEUKEMIA FOLLOWING THERAPY IN PATIENTS WITH SMALL CELL-CARCINOMA OF THE LUNG JOURNAL OF CLINICAL ONCOLOGY CHAK, L. Y., Sikic, B. I., TUCKER, M. A., Horns, R. C., Cox, R. S. 1984; 2 (5): 385-390

    Abstract

    A group of 158 patients with small cell carcinoma of the lung were followed for 174.5 person-years of observation to determine the risk of acute leukemia. Three cases of acute nonlymphocytic leukemia were observed at 2.3, 2.7, and 3.0 years. The relative risk of developing leukemia was 316 (95% confidence limit, 76-818) and the actuarial risk was 25% +/- 13% at 3.1 years. The relative risk for leukemia was significantly increased in these patients (p less than 0.0001).

    View details for Web of Science ID A1984SS13800006

    View details for PubMedID 6327924

  • 2ND-LOOK LAPAROTOMY IN EPITHELIAL OVARIAN-CARCINOMA - PRECISE DEFINITION, SENSITIVITY, AND SPECIFICITY OF THE OPERATIVE PROCEDURE GYNECOLOGIC ONCOLOGY Ballon, S. C., PORTNUFF, J. C., Sikic, B. I., Turbow, M. M., Teng, N. N., SORIERO, O. M. 1984; 17 (2): 154-160

    Abstract

    Twenty-five women treated with chemotherapy for epithelial ovarian carcinoma underwent "second-look" laparotomy after thorough clinical and radiographic examinations failed to detect residual tumor. Chest roentgenogram, barium enema, upper gastrointestinal series with small-bowel follow through, and abdominopelvic CAT scan were obtained in all patients prior to operation. Inspection, palpation, and multiple biopsies were performed in accordance with precise and detailed protocol requirements. Eight patients (32%) had gross tumor found at laparotomy, while 6 (24%) had no suspicion of residual disease at operation but had cytologic or microscopic evidence of tumor found on review of submitted specimens. Eleven patients (44%) had no gross or microscopic evidence of residual ovarian carcinoma. After follow-up of from 4 to 25 months, 1 of these 11 patients (9%) has suffered a recurrence. The maximum sensitivity of "second-look" laparotomy is 85.7%, and the maximum specificity is 90.9% in this series. Any additional recurrences observed over time will decrease both the sensitivity and specificity of the operation. The sites of microscopic disease support rigid adherence to a precise operative procedure which should minimize the false negative rate.

    View details for Web of Science ID A1984SE71100003

    View details for PubMedID 6706223

  • CONTINUOUS INFUSION OR BOLUS INJECTION IN CANCER-CHEMOTHERAPY ANNALS OF INTERNAL MEDICINE Carlson, R. W., Sikic, B. I. 1983; 99 (6): 823-833

    Abstract

    Continuous intravenous infusion of anticancer drugs is being incorporated into more experimental chemotherapy protocols. The rationale for use of continuous infusions generally includes the restriction of cytotoxic mechanisms of a drug to a specific phase of the cell cycle and the short half-life of some drugs. Two such agents are cytarabine and bleomycin; continuous exposure to these drugs greatly increases their antitumor effects in cell cultures and animal models. Toxicity to normal tissues may also be reduced by continuous infusion, notably the pulmonary toxicity of bleomycin, the cardiac toxicity of doxorubicin, and the myelosuppression of fluorouracil. Recent advances in infusion pump technology have made continuous intravenous infusion therapy more practical. Unfortunately, most clinical studies of the continuous infusion of anticancer drugs have been uncontrolled. Further randomized, controlled clinical trials comparing schedules of drug administration are necessary before definitive recommendations can be made.

    View details for Web of Science ID A1983RU40300016

    View details for PubMedID 6197002

  • COMBINATION CISPLATIN, VINBLASTINE, AND BLEOMYCIN CHEMOTHERAPY (PVB) FOR MALIGNANT GERM-CELL TUMORS OF THE OVARY JOURNAL OF CLINICAL ONCOLOGY Carlson, R. W., Sikic, B. I., Turbow, M. M., Ballon, S. C. 1983; 1 (10): 645-651

    Abstract

    Nine women with germ-cell tumors of the ovary (three endodermal sinus tumors, four immature teratomas, and two mixed germ-cell tumors) were treated with cisplatin, vinblastine, and bleomycin (PVB) chemotherapy after cytoreductive operations. Five patients were stage I, three were stage III, and one patient had recurrent disease. All nine women are alive and without evidence of disease with a median follow-up of 31 months from diagnosis and 27 months since completion of PVB. Treatment toxicity although occasionally severe was rapidly reversible.

    View details for Web of Science ID A1983RM39600009

    View details for PubMedID 6199468

  • PULMONARY TOXICITY OF ANTITUMOR AGENTS CANCER TREATMENT REVIEWS Muggia, F. M., Louie, A. C., Sikic, B. I. 1983; 10 (4): 221-243

    View details for Web of Science ID A1983RZ20000002

    View details for PubMedID 6198083

  • DIAGNOSTIC ACCURACIES OF CLINICAL-STUDIES IN PATIENTS WITH SMALL CELL-CARCINOMA OF THE LUNG JOURNAL OF CLINICAL ONCOLOGY CHAK, L. Y., PARYANI, S. B., Sikic, B. I., Lockbaum, P., Torti, F. M., Carter, S. K. 1983; 1 (5): 290-294

    Abstract

    The diagnostic accuracy of clinical studies done in 38 patients with small cell carcinoma of the lung was analyzed by comparing the test results to autopsy findings. The chest radiograph was accurate in 31 of 38 patients (82%). The accuracy of the chest radiograph was higher in evaluating the lung parenchyma and mediastinum than in evaluating the hilum and pleura. Computerized tomographic brain scan was accurate in 11 of 12 patients. However, all the diagnostic studies used for assessing the liver, including physical examination, serum liver enzyme and bilirubin measurements, and radionuclide liver scan, were only moderately accurate. More accurate studies for detecting liver metastasis in patients with small cell carcinoma are needed.

    View details for Web of Science ID A1983QW73600002

    View details for PubMedID 6321683

  • ABSORPTION OF ANTI-NEOPLASTIC DRUGS FOLLOWING LARGE-VOLUME LP ADMINISTRATION TO RATS CANCER TREATMENT REPORTS LITTERST, C. L., Torres, I. J., Arnold, S., McGunagle, D., FURNER, R., Sikic, B. I., Guarino, A. M. 1982; 66 (1): 147-155

    View details for Web of Science ID A1982MW08500024

    View details for PubMedID 7053249

  • PATTERNS OF FAILURE IN SMALL CELL-CARCINOMA OF THE LUNG CANCER CHAK, L. Y., Daniels, J. R., Sikic, B. I., Torti, F. M., Lockbaum, P., Carter, S. K. 1982; 50 (9): 1857-1863

    Abstract

    The initial sites and frequencies of disease progression in 97 patients with small cell carcinoma of the lung treated in a Northern California Oncology protocol were analyzed. Among the extensive disease complete responders (25 patients), the chest was the most frequent initial relapse site (18 patients), followed by the liver (nine patients) and bone (six patients). For those patients who had a partial or no response to treatment, the chest was the most frequent site of persistent disease and the majority progressed in the chest initially. The addition of chest irradiation (5000 rad/5 weeks) to patients with limited disease significantly reduced the incidence of relapse (25%) and prolonged the disease-free interval in the chest in the complete responders, but did not affect the failure pattern in partial and nonresponders. All patients received prophylactic cranial irradiation and three limited disease patients (10%) and three extensive disease patients (4%) progressed in the brain.

    View details for Web of Science ID A1982PL42900032

    View details for PubMedID 6288227

  • PULMONARY-DISEASE AS A COMPLICATION OF CHLOROZOTOCIN CHEMOTHERAPY CANCER TREATMENT REPORTS Ahlgren, J. D., Smith, F. P., KERWIN, D. M., Sikic, B. I., Weiner, J. H., SCHEIN, P. S. 1981; 65 (3-4): 223-229

    Abstract

    Two of 200 patients treated with chlorozotocin have evidenced interstitial pulmonary disease. The cumulative doses of chlorozotocin were 480 and 670 mg/m2 when symptoms developed. Pulmonary function tests in both patients showed impaired diffusion, and an alveolar-arterial gradient which worsened with exercise. Open-lung biopsy in one patient showed typical interstitial inflammation and early fibrosis, and excluded lymphangitic spread of tumor. Discontinuation of chlorozotocin resulted in either improvement or stabilization of the pulmonary disease.

    View details for Web of Science ID A1981LV60300007

    View details for PubMedID 6453644

  • HUMAN-TUMOR CLONOGENIC ASSAYS - AN OVERVIEW CANCER CHEMOTHERAPY AND PHARMACOLOGY Sikic, B. I., Taber, R. L. 1981; 6 (3): 201-203

    View details for Web of Science ID A1981MV09400001

    View details for PubMedID 7318143

  • METHODOLOGIC PROBLEMS IN CLONOGENIC ASSAYS OF SPONTANEOUS HUMAN-TUMORS CANCER CHEMOTHERAPY AND PHARMACOLOGY MacKintosh, F. R., Evans, T. L., Sikic, B. I. 1981; 6 (3): 205-210

    Abstract

    Colony formation in soft agar was used to investigate growth properties and drug sensitivity in 102 tumor specimens from 91 patients. Sufficient colony growth for sensitivity testing with various drugs was obtained in 36 of 67 specimens (54%) with adequate cell yield and pathologically documented malignancy. Room temperature (20-24 degrees C) is superior to both 4 degrees C and 37 degrees C for 12-36 h storage and transport of malignant effusions. By contrast, fine mincing in sterile saline or balanced salt solution, and refrigerated storage (4 degrees C) appear optimal in experiments with three solid tumors. The use of buffered NH4Cl to lyse red blood cells markedly reduced plating efficiencies, and also reduced the percentage of tumors in which drug sensitivities could be tested from 64% to 38%. Several combinations of potential growth factors and culture media have been tested. Insulin enhanced plating efficiency (PE) in all six adenocarcinomas tested. Drug sensitivity of tumors was not affected by varying plating efficiency up to five-fold in two tumors. In eleven cases tumor cells were exposed to combinations of two or more drugs, and results assessed for evidence of drug interactions. In almost all cases, these two-drug combinations produced additive cell killing than either antagonistic or greater-than-additive effects.U

    View details for Web of Science ID A1981MV09400002

    View details for PubMedID 7032738

  • RELATIVE PULMONARY TOXICITY AND ANTI-TUMOR EFFECTS OF 2 NEW BLEOMYCIN ANALOGS, PEPLEOMYCIN AND TALLYSOMYCIN-A CANCER TREATMENT REPORTS Sikic, B. I., SIDDIK, Z. H., Gram, T. E. 1980; 64 (4-5): 659-667

    Abstract

    The relative therapeutic and toxic effects of two new analogs were compared with bleomycin over a range of doses. Therapeutic effects were determined in mice bearing Lewis lung carcinoma and B16 melanoma. On a milligram-per-kilogram basis, tallysomycin A was two to three times as potent as bleomycin in inhibiting the growth of these two experimental solid tumors in vivo. However, tallysomycin A was also two to three times as potent as bleomycin in producing pulmonary toxic effects. Lethality and skin toxicity were similarly increased. Pepleomycin, on the other hand, was approximately equivalent to bleomycin in antitumor potency but exhibited significantly less pulmonary toxicity. Despite this decreased lung toxicity, pepleomycin was more lethal, with 50% and 100% mortality at doses which produced 0 and 19% mortality, respectively, in mice treated with bleomycin. Pepleomycin also had a peculiar central nervous system toxicity characterized by hyperirritability and persistent gyrating movements of the animals. Thus, there are distinct quantitative as well as qualitative differences in the therapeutic and toxic properties of these two analogs compared to bleomycin.

    View details for Web of Science ID A1980KT23500018

    View details for PubMedID 6159079

  • HEPATIC CYTOCHROME P-450-DEPENDENT METABOLISM AND ENZYMATIC CONJUGATION OF FOREIGN COMPOUNDS IN VITAMIN-A-DEFICIENT RATS PHARMACOLOGY SIDDIK, Z. H., Drew, R., LITTERST, C. L., Mimnaugh, E. G., Sikic, B. I., Gram, T. E. 1980; 21 (6): 383-390

    Abstract

    The temporal effects of vitamin A deficiency on hepatic cytochrome P-450-dependent and conjugation reactions were studied in the rat. Cytochrome P-450 levels and N-methyl-p-chloroaniline N-demethylase activity were significantly reduced in the deficient animals. No other changes in parameters dependent on cytochrome P-450 were observed in vitro. Decreases in hepatic cytochrome P-450 were accompanied by a prolongation in hexobarbital sleeping times in deficient animals. The p-aminobenzoic acid N-acetyltransferase activity was higher in the deficient animals at 8 weeks, but by 10 weeks the activity in fact was significantly lower as compared to controls. Activities of 'native' and UDP N-acetylglucosamine 'activated' UDP-glucuronyltransferase were reduced in vitamin A deficiency. In contrast to this general pattern of impaired drug metabolism in vitamin A deficiency, glutathione S-aryltransferase activity was markedly enhanced at all time points from 4 to 10 weeks. Activities of this enzyme were twice controls at 6 weeks, a time at which no other enzyme changes were observed.

    View details for Web of Science ID A1980KX52600003

    View details for PubMedID 7220590

  • PHARMACOKINETICS AND PROTEIN-BINDING OF CIS-DICHLORODIAMMINE PLATINUM (II) ADMINISTERED AS A ONE-HOUR OR AS A 20-HOUR INFUSION CANCER CHEMOTHERAPY AND PHARMACOLOGY GULLO, J. J., LITTERST, C. L., Maguire, P. J., Sikic, B. I., Hoth, D. F., Woolley, P. V. 1980; 5 (1): 21-26

    Abstract

    The pharmacokinetics of cis-dichlorodiam-minoplatinum (II) (cisplatin) have been studied in seven patients, of whom four received the drug as a one hour infusion and three received it as a 20 h infusion. The patients receiving the drug over one hour exhibited biphasic clearance of total platinum with a rapid initial phase (8.7-22.5 min) and a prolonged second phase (30.5-106 h). Free (ultrafilterable) cisplatin was readily detectable in this group and was rapidly cleared (half-life about 22 min). The volume of distribution of the drug was 50.3-65.6 liters and it was 26.6-50% excreted in the urine in 48 h. In the patients receiving the 20 h infusion, a more complex plasma elimination curve was seen, with the appearance of a secondary peak. Free drug was not detectable in these patients and they showed less urinary excretion (21.4-25.9% at 48 h) than the one hour group. Cisplatin was bound to several plasma proteins, including albumin, transferrin, and gamma-globulin. The data indicate that cisplatin is retained in the body more extensively after a 20 h infusion than after a one hour infusion.

    View details for Web of Science ID A1980KV35500004

    View details for PubMedID 6161715

  • LIPOSOMAL PROTECTION OF ADRIAMYCIN-INDUCED CARDIOTOXICITY IN MICE CANCER RESEARCH Rahman, A., KESSLER, A., More, N., Sikic, B., Rowden, G., Woolley, P., SCHEIN, P. S. 1980; 40 (5): 1532-1537

    View details for Web of Science ID A1980JR28800029

    View details for PubMedID 7370991

  • LACK OF CORRELATION BETWEEN CORTISOL-INDUCED PRECOCIOUS MATURATION OF THE FETAL RABBIT LUNG AND DRUG-METABOLISM BIOCHEMICAL PHARMACOLOGY SIDDIK, Z. H., Sikic, B. I., Drew, R., Mimnaugh, E. G., LITTERST, C. L., Gram, T. E. 1979; 28 (5): 683-685

    View details for Web of Science ID A1979GR21400021

    View details for PubMedID 444254

  • EFFECTS OF ALPHA-TOCOPHEROL ON THE TOXICITY, DISPOSITION, AND METABOLISM OF ADRIAMYCIN IN MICE TOXICOLOGY AND APPLIED PHARMACOLOGY Mimnaugh, E. G., SIDDIK, Z. H., Drew, R., Sikic, B. I., Gram, T. E. 1979; 49 (1): 119-126

    View details for Web of Science ID A1979HB21600016

    View details for PubMedID 473197

  • ENHANCEMENT OF BLEOMYCIN ACTIVITY AGAINST LEWIS LUNG-TUMORS IN MICE BY LOCAL HYPERTHERMIA CANCER RESEARCH Magin, R. L., Sikic, B. I., Cysyk, R. L. 1979; 39 (9): 3792-3795

    Abstract

    The cytotoxicity of the drug bleomycin in vitro has previously been shown to be enhanced by hyperthermia. This report demonstrates in vivo a more than additive interaction between local tumor hyperthermia (43 degrees, 60 min) and bleomycin (15 mg/kg s.c.) against s.c.-implanted Lewis lung carcinomas in mice. Local hyperthermia was produced by the application of 2450-MHz microwaves to the region of the tumor without induction of significant whole-body hyperthermia. The combined drug and heat treatments were applied to tumors on Days 4, 7, and 10 following implantation. The response of the tumors to simultaneous treatment was a 17-day growth delay compared with controls, whereas the local hyperthermia and bleomycin individually resulted in only 3- and 4-day growth delays, respectively. If the two treatments were given either 4 or 24 hr apart only an additive effect on growth delay was observed.

    View details for Web of Science ID A1979HK21200082

    View details for PubMedID 89905

  • DISTRIBUTION OF IMIPRAMINE-C-14 IN MICE BEARING LEWIS LUNG-CARCINOMA LIFE SCIENCES Drew, R., Sikic, B. I., Mimnaugh, E. G., LITTERST, C. L., Gram, T. E. 1979; 25 (21): 1813-1820

    View details for Web of Science ID A1979HZ55400005

    View details for PubMedID 529988

  • INVITRO DRUG-METABOLISM IN MALE AND FEMALE ATHYMIC, NUDE-MICE LIFE SCIENCES LITTERST, C. L., Sikic, B. I., Mimnaugh, E. G., Guarino, A. M., Gram, T. E. 1978; 22 (19): 1723-1730

    View details for Web of Science ID A1978FB08700007

    View details for PubMedID 672423

  • EFFECT OF WHOLE-BODY HYPERTHERMIA ON DISPOSITION AND METABOLISM OF ADRIAMYCIN IN RABBITS CANCER RESEARCH Mimnaugh, E. G., WARING, R. W., Sikic, B. I., Magin, R. L., Drew, R., LITTERST, C. L., Gram, T. E., Guarino, A. M. 1978; 38 (5): 1420-1425

    View details for Web of Science ID A1978EX66300039

    View details for PubMedID 639069

  • EFFECTS OF ASCORBIC-ACID DEFICIENCY AND REPLETION ON PULMONARY, RENAL, AND HEPATIC DRUG-METABOLISM IN GUINEA-PIG ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS Sikic, B. I., Mimnaugh, E. G., LITTERST, C. L., Gram, T. E. 1977; 179 (2): 663-671

    View details for Web of Science ID A1977CZ82900033

    View details for PubMedID 403863

  • EFFECTS OF DIETARY ASCORBIC-ACID SUPPLEMENTATION ON HEPATIC DRUG-METABOLIZING-ENZYMES IN GUINEA-PIG BIOCHEMICAL PHARMACOLOGY Sikic, B. I., Mimnaugh, E. G., Gram, T. E. 1977; 26 (21): 2037-2041

    View details for Web of Science ID A1977DW51300013

    View details for PubMedID 411495

  • INTERACTION OF FLURAZEPAM WITH DIPHENYLHYDANTOIN IN RAT DRUG METABOLISM AND DISPOSITION Sikic, B. I., BAUMEL, I. P. 1976; 4 (6): 584-586

    View details for Web of Science ID A1976CN27200011

    View details for PubMedID 11981

  • REPEAT ADMINISTRATION OF MARIHUANA SMOKE TO HUMANS ARCHIVES OF GENERAL PSYCHIATRY RENAULT, P. F., Schuster, C. R., FREEDMAN, D. X., Sikic, B., NEBELDEM, D., Halaris, A. 1974; 31 (1): 95-102

    View details for Web of Science ID A1974T529800012

    View details for PubMedID 4835990

  • EVALUATION OF A PROGRAM FOR TREATMENT OF ALCOHOLISM IN CROATIA INTERNATIONAL JOURNAL OF SOCIAL PSYCHIATRY Sikic, B. I., Walker, R. D., PETERSON, D. R. 1972; 18 (3): 171-182

    View details for Web of Science ID A1972Z068100002

    View details for PubMedID 4670080

Conference Proceedings


  • Predictors for success in a phase III trial - an analysis of 315 phase II chemotherapy trials for advanced cancers Ueda, S. M., Kapp, D. S., Sugiyama, V. E., Stave, C., Shin, J. Y., Monk, B. J., Sikic, B. I., Osann, K., Chan, J. K. ACADEMIC PRESS INC ELSEVIER SCIENCE. 2007: 362-363
  • Gene expression profiling predicts outcome in de novo acute myeloid leukemia (AML) with normal karyotype: Results of children's oncology group (COG) study POG #9421. Lacayo, N. J., O'Brien, M., Jain, S., Meshinchi, S., Yu, R., Juric, D., Chang, M. N., Tebshirani, R., Ravindranath, Y., Weinstein, H. J., Sikic, B. I., Van Houten Dahl, G. AMER SOC HEMATOLOGY. 2006: 542A-542A
  • Differential gene expression patterns and interaction networks in BCR/ABL positive and negative adult acute lymphoblastic leukemias. Juric, D., Lacayo, N. J., Ramsey, M. C., Racevskis, J., Wiernik, P. H., Rowe, J. M., Goldstone, A. H., O'Dwyer, P. J., Paietta, E., Sikic, B. I. AMER SOC HEMATOLOGY. 2006: 520A-520A
  • Gene expression profiling and FLT3 status correlate with outcome in de novo acute myeloid leukemia (AML) with normal karyotype: Results of children's oncology group (COG) study POG #9421. Lacayo, N., Meshinchi, S., Raimondi, S., Saraiya, C., O'Brien, M., Yu, R., Juric, D., Chang, M., Willman, C., Tibshirani, R., Ravindranath, Y., Sikic, B., Weinstein, H., Dahl, G. V. AMER SOC HEMATOLOGY. 2005: 667A-667A
  • A phase I trial of oblimersen and gemcitabine in refractory and advanced malignancies Fisher, G., Advani, R., Wakelee, H., Jacobs, C., Gladysheva, K., Fitzgerald, A. M., Sikic, B. AMER SOC CLINICAL ONCOLOGY. 2005: 234S-234S
  • A phase II study of gefitinib in combination with FOLFOX-4 (IFOX) in patients with metastatic colorectal cancer. Cho, C. D., Fisher, G. A., Halsey, J., Jambalos, C. N., Schwartz, E. J., Rouse, R. V., Advani, R. H., Wakelee, H. A., Lum, B. L., Sikic, B. I. AMER ASSOC CANCER RESEARCH. 2003: 6103S-6103S
  • Protein expression study of ovarian surface epithelial neoplasms using tissue microarray analysis: Emergence of a clear cell signature profile Balzer, B., Schaner, M., Ross, D., Montgomery, K., Teng, N., Sikic, B., Longacre, T. NATURE PUBLISHING GROUP. 2003: 181A-181A
  • Protein expression study of ovarian surface epithelial neoplasms using tissue microarray analysis: Emergence of a clear cell signature profile Balzer, B., Schaner, M., Ross, D., Montgomery, K., Teng, N., Sikic, B., Longacre, T. NATURE PUBLISHING GROUP. 2003: 181A-181A
  • A phase I study of ZD 1839 (Iressa) in combination with oxaliplatin, 5-fluorouracil (5-FU) and leucovorin (LV) in advanced solid malignancies Fisher, G. A., Cho, C. D., Halsey, J. Z., Advani, R. H., Yuen, A. R., Lum, B. L., Sikic, B. I. ELSEVIER SCI LTD. 2002: S63-S63
  • The effect of oral valspodar (psc 833), a modulator of multidrug resistance, on the pharmacokinetics of liposomal doxorubicin. Lum, B. L., Chin, D. L., Cho, C. D., Advani, R., Fisher, G. A., Halsey, J., Sikic, B. I. NATURE PUBLISHING GROUP. 2002: P48-P48
  • A phase I trial of doxorubicin, paclitaxel, and valspodar (PSC 833), a modulator of multidrug resistance Advani, R., Fisher, G. A., Lum, B. L., Hausdorff, J., Halsey, J., Litchman, M., Sikic, B. I. AMER ASSOC CANCER RESEARCH. 2001: 1221-1229

    Abstract

    P-glycoprotein is an efflux pump for many drugs including doxorubicin and paclitaxel. This study evaluated the coadministration of these drugs with the P-glycoprotein inhibitor valspodar (PSC 833) with the aim of determining: (a) maximum tolerated doses (MTDs) of doxorubicin followed by paclitaxel (DP); (b) the MTD of DP combined with PSC 833 (DPV), without and with filgrastim (G-CSF); and (c) the pharmacokinetic interactions of PSC 833 with doxorubicin and paclitaxel.For the first cycle, patients received doxorubicin as a 15-min infusion followed by paclitaxel as a 1-h infusion. For the second cycle, patients received reduced doses of DP with PSC 833 at 5 mg/kg p.o., four times a day for 12 doses.Thirty-three patients with various refractory malignancies were enrolled and assessable. The MTD of DP without PSC 833 was 35 mg/m(2) doxorubicin and 150 mg/m(2) paclitaxel. The MTD of DPV without G-CSF was 12.5 mg/m(2) doxorubicin and 70 mg/m(2) paclitaxel. The dose-limiting toxicity for both DP and DPV was neutropenia without thrombocytopenia. With G-CSF, the MTD for DPV was 20 mg/m(2) doxorubicin and 90 mg/m(2) paclitaxel. No grade 4 nonhematological toxicities were observed. Five partial and two minor tumor remissions were observed. Paired pharmacokinetics with and without PSC 833 revealed substantial drug interactions with both doxorubicin and paclitaxel.PSC 833 can be administered safely with doxorubicin and paclitaxel. The pharmacokinetic profiles of these drugs are significantly affected by PSC 833, requiring approximately 60% dose reductions for equivalent degrees of myelosuppression.

    View details for Web of Science ID 000168768500018

    View details for PubMedID 11350887

  • Treatment of refractory/relapsed AML with PSC833 plus mitoxantrone, etoposide, cytarabine (PSC-MEC) vs MEC: Randomized phase III trial (E2995). Greenberg, P., Advani, R., Tallman, M., Letendre, L., Saba, H., Dugan, K., Lee, S. J., Lum, B., Sikic, B. I., Paietta, E., Bennett, J., Rowe, J. M. AMER SOC HEMATOLOGY. 1999: 383A-383A
  • Mitoxantrone, etoposide, and cytarabine plus cyclosporine for patients with relapsed or refractory acute myeloid leukemia - An Eastern Cooperative Oncology Group Pilot Study Tallman, M. S., Lee, S., Sikic, B. I., Paietta, E., Wiernik, P. H., Bennett, J. M., Rowe, J. M. JOHN WILEY & SONS INC. 1999: 358-367

    Abstract

    One potential mechanism of drug resistance to chemotherapy is the overexpression of multidrug resistance (MDR) genes coding for P-glycoprotein (P-gp), which leads to reduced intracellular retention of chemotherapy. This study tested the efficacy and toxicity of mitoxantrone, etoposide, and intermediate dose cytarabine (MEC) with cyclosporine (CSP) as an MDR modulator in patients with recurrent and refractory acute myeloid leukemia, and also correlated P-gp expression in leukemia cells with response.Thirty-eight eligible patients who were in first recurrence after < 6 months of complete remission (CR) (11 patients), refractory to initial induction therapy or to one attempt at reinduction after recurrence (18 patients), in second recurrence (4 patients), or in recurrence after either allogeneic or autologous bone marrow transplantation (5 patients) received either MEC alone (13 patients) or MEC-CSP (25 patients). CSP was given as a loading dose of 6 mg/kg for 2 hours intravenously (i.v.) starting 2 hours before the first dose of etoposide, followed by a continuous i.v. infusion of 18 mg/kg/day for 98 hours.Three of the 13 patients (23%) who received MEC achieved CR, as did 6 of the 25 patients (24%) who received MEC-CSP. The median remission duration for all patients who achieved CR was 149 days (range, 26-466 days), 91 days (range, 81-172 days) for the 3 patients who received MEC, and 189.5 days (range, 26-466 days) for the patients treated with MEC-CSP. The median survival for the patients treated with MEC and MEC-CSP was 104 and 72 days, respectively.No significant association was found between P-gp expression and response. No apparent benefit in the CR rate, remission duration, or survival was observed with the addition of CSP to MEC.

    View details for Web of Science ID 000078208400013

    View details for PubMedID 10023703

  • Treatment of poor prognosis AML patients using PSC833 (valspodar) plus mitoxantrone, etoposide, and cytarabine (PSC-MEC) Advani, R., Visani, G., Milligan, D., Saba, H., Tallman, M., Rowe, J. M., Wiernik, P. H., Ramek, J., Dugan, K., Lum, B., Villena, J., Davis, E., Paietta, E., Litchman, M., Covelli, A., Sikic, B., Greenberg, P. KLUWER ACADEMIC/PLENUM PUBL. 1999: 47-56

    Abstract

    The failure of convenional chemotherapy in relapsed or refractory and other poor risk AML patients has been linked to expression of the multidrug resistance gene (mdr 1) product P-glycoprotein (P-gp). PSC 833 is a non-competitive inhibitor of P-gp and has been shown in vitro and in vivo to restore sensitivity of resistant tumor cells to anticancer drugs (ACDs). Induction chemotherapy consisting of cytarabine (C) in combination with PSC 833 and escalating doses of mitoxantrone (M) and etoposide (E) over 5 or 6 days were tested in two phase I/II studies in poor prognosis AML. Overall, 59 patients were evaluated: their age ranged between 18 and 70 years. Fourteen patients had primary refractory disease, 25 had relapsed within 9 months from first complete remission (CR), 5 were in second relapse, 10 had secondary AML, and 4 had relapsed post-bone marrow transplantation. PSC 833 was given as a constant i.v. infusion at a rate of 10 mg/kg/24 h for 5 or 6 days, depending on the duration of chemotherapy. In both studies a loading dose of 2 mg/kg of PSC 833 was given on day 1. In the 5-day regimen, the final study doses of the cytotoxic agents were C 1 g/m2/d, M 4.0 mg/m2/d, and E 40 mg/m2/d. In the 6-day regimen, the final study doses of the cytotoxic agents were C 1 g/m2/d, M 4.5 mg/m2/d and E 30 mg/m2/d. The combined efficacy results of both studies indicate that PSC-MEC is active in all treatment indications, complete remission being achieved in 2/5 (40%) second relapses, 8/25 (32%) early relapses, 3/10 (30%) secondary AML, 3/15 (20%) refractory patients and 1/4 (25%) post-BMT relapses. Based on historical controls, this observed overall CR rate (29%) is higher than expected in this high risk patient population. Our data indicate that, in refractory/relapsed AML patients, PSC-MEC regimens had encouraging antileukemic effects, is well tolerated, and has led to Phase III trials in this setting.

    View details for Web of Science ID 000082878700006

    View details for PubMedID 10500779

  • New approaches in cancer treatment Sikic, B. I. OXFORD UNIV PRESS. 1999: 149-153

    Abstract

    Major advances in cellular biology, genetics, pharmacology and immunology in the past decade are beginning to be translated into progress in cancer treatment. This progress is manifested by new cytotoxic drugs which have recently entered clinical practice (taxanes, topoisomerase I inhibitors, gemcitabine, vinorelbine, new purines), as well as the efficacy of monoclonal antibody therapies against the CD-20 antigen of B-cell lymphomas and the Her2/neu oncogene in breast cancer. Several new drugs in development are targeted at reversal or prevention of the multidrug resistance mechanism caused by expression of the MDR1 gene (P-glycoprotein). Tumour angiogenesis as a target is being studied in several early clinical trials. As with many other biological therapies, the evaluation of these compounds and their integration with standard therapies presents a major challenge to clinical investigators. The emerging field of genomics and gene expression micro-arrays will provide enormous information about the biology of cancers. This technology offers great opportunities for the discovery of new therapeutic targets, which should provide a basis for the design and evaluation of many new agents in the coming decade.

    View details for Web of Science ID 000085241700023

    View details for PubMedID 10676567

  • Neural network (NN) and linear regression limited sampling models (LSM) for etoposide (E) AUC determinations. Lum, B. L., Synold, T. W., Lane, K., Charnick, S. B., Sikic, B. I. NATURE PUBLISHING GROUP. 1996: OIA2-OIA2
  • REVERSAL OF MULTIDRUG-RESISTANCE TO CANCER-CHEMOTHERAPY LEYLANDJONES, B., Dalton, W., Fisher, G. A., Sikic, B. I. WILEY-LISS. 1993: 3484-3488

    Abstract

    In the past few years, the role of membrane-bound transport genes in human disease has been increasingly recognized and understood. Of these genes, the p170 membrane glycoprotein may function as an outward transport pump for many cancer chemotherapeutic drugs associated with the multidrug resistance phenotype. This article reviews the different classes of the current major modulators of multidrug resistance.

    View details for Web of Science ID A1993ML14300013

    View details for PubMedID 8242580

  • CLINICAL-TRIALS OF MODULATION OF MULTIDRUG-RESISTANCE - PHARMACOKINETIC AND PHARMACODYNAMIC CONSIDERATIONS Lum, B. L., Fisher, G. A., BROPHY, N. A., Yahanda, A. M., ADLER, K. M., Kaubisch, S., Halsey, J., Sikic, B. I. WILEY-LISS. 1993: 3502-3514

    Abstract

    A growing body of evidence indicates that expression of the mdr1 gene, which encodes the multidrug transporter, P-glycoprotein, contributes to chemotherapeutic resistance of human cancers. Expression of this protein in normal tissues such as the biliary tract, intestines, and renal tubules suggests a role in the excretion of toxins. Modulation of P-glycoprotein function in normal tissues may lead to decreased excretion of drugs and enhanced toxicities. A clinical trial of etoposide with escalating doses of cyclosporine (CsA) as a modulator of multidrug resistance was performed. CsA was delivered as a 2-hour loading dose followed by a 60-hour intravenous infusion, together with etoposide administered as a short infusion daily for 3 days. Patients received one or more courses of etoposide alone before the combined therapy to establish their clinical resistance to etoposide and to study etoposide pharmacokinetics without and then with CsA. Plasma and urinary etoposide was measured by high-performance liquid chromatography and plasma CsA by a nonspecific immunoassay. Conclusions from the initial phase I trial with the use of CsA as a modulator of etoposide are: (1) Serum CsA steady-state levels of up to 4800 ng/ml (4 microM) could be achieved with acceptable toxicity. (2) Toxicities caused by the combined treatment included increased nausea and vomiting, increased myelosuppression, and hyperbilirubinemia, consistent with modulation of P-glycoprotein function in the blood-brain barrier, hematopoietic stem cell, and biliary tract. Renal toxicity was uncommon, but severe in two patients with steady-state plasma CsA levels above 6000 ng/ml. (3) CsA administration had a marked effect on the pharmacokinetics of etoposide, with a doubling of the area under the concentration-time curve as a result of both decreased renal and nonrenal clearance, necessitating a 50% dose reduction in patients with normal renal function and hepatic function. (4) The recommended dose of CsA is a 6-7 mg/kg loading dose administered as a 2-hour intravenous infusion followed by a continuous infusion of 18-21 mg/kg/day for 60 hours with adjustments in the infusion rate to maintain steady-state serum levels of 3000-4800 ng/ml (2.5-4.0 M). We are performing additional phase I trials combining CsA with single-agent doxorubicin and taxol, and the CsA analog PSC-833 with various multidrug-resistant-related cytotoxins.

    View details for Web of Science ID A1993ML14300016

    View details for PubMedID 7902206

  • THE MODULATION OF MULTIDRUG-RESISTANCE - CLINICAL-STUDIES AT STANFORD Fisher, G. A., BROPHY, N. A., Yahanda, A. M., Adler, K. A., Lum, B. L., Bartlett, N. L., Halsey, J., Sikic, B. I. ELSEVIER SCIENCE PUBL B V. 1993: 255-266
  • COMBINED CHEMOTHERAPY AND RADIOTHERAPY FOR ADVANCED-STAGE CARCINOMAS OF THE CERVIX Sikic, B. I. KARGER. 1992: 153-162

    View details for Web of Science ID A1992BW35T00013

    View details for PubMedID 1511916

  • SENSITIZATION OF DRUG-RESISTANT HUMAN OVARIAN-CANCER CELLS TO CYANOMORPHOLINO DOXORUBICIN (MRA-CN) BY MODULATION OF GLUTATHIONE METABOLISM Lewis, A. D., Duran, G. E., Lau, D. H., Sikic, B. I. ELSEVIER SCIENCE INC. 1992: 821-824

    Abstract

    MRA-CN, the alkylating cyanomorpholino derivative of doxorubicin (DOX), is extremely potent (100 to 1000 fold increase in cytotoxicity in vitro and in vivo), more lipophilic, non-cardiotoxic, and non-cross-resistant in multidrug resistant cells compared to DOX. We have developed an ovarian carcinoma cell line ES-2R that is 4-fold resistant to MRA-CN, compared to the parental ES-2 cells. This resistant cell line exhibits cross-resistance to alkylators and ionizing radiation. Glutathione (GSH) and GSH-dependent enzymes were found to be altered in the resistant cells with 1.5-fold increase in GSH, and 2- to 3-fold increase in the pi-class glutathione-s-transferase (GST) protein. Both D,L buthionine-S,R-sulfoximine (BSO) and ethacrynic acid (EA), inhibitors of GSH biosynthesis and pi-class GST activity, respectively, could sensitize the ES-2R cells to MRA-CN. These findings implicate a role for GSH metabolism in resistance of ES-2R cells to MRA-CN. The data also indicates the potential utility of EA to modulate GST activity and sensitize tumor cells toward alkylators.

    View details for Web of Science ID A1992HJ37700041

    View details for PubMedID 1544857

  • CHARACTERIZATION AND IMMUNOASSAY OF HUMAN TUMOR-ASSOCIATED GALACTOSYLTRANSFERASE ISOENZYME-II Brandt, A. E., Winant, R. C., Uemura, M., Sikic, B. I. AMER ASSOC CANCER RESEARCH. 1987: 181-181
  • RESISTANCE AND CROSS-RESISTANCE STUDIES OF CYANOMORPHOLINO DOXORUBICIN (MRA-CN) Scudder, S. A., EHSAN, M. N., Tan, Y. O., Sikic, B. I. AMER ASSOC CANCER RESEARCH. 1987: 295-295
  • CHARACTERIZATION AND IMMUNOASSAY OF HUMAN TUMOR-ASSOCIATED GALACTOSYLTRANSFERASE ISOENZYME-II Brandt, A. E., Winant, R. C., Uemura, M., Sikic, B. I. WILEY-LISS. 1987: 158-158
  • ADVANCED EPITHELIAL OVARIAN-CANCER - WHOLE ABDOMINAL IRRADIATION FOR PATIENTS WITH RECURRENT OR PERSISTENT DISEASE FOLLOWING CHEMOTHERAPY Schray, M., Martinez, A., Howes, A., PODRATZ, K., Ballon, S., Sikic, B., MALKASIAN, G. LIPPINCOTT-RAVEN PUBL. 1985: 12-13
  • DIFFERENTIAL PROTECTIVE EFFECTS OF VARYING DEGREES OF HYPOXIA ON THE CYTOTOXICITIES OF ETOPOSIDE AND BLEOMYCIN Yamauchi, T., Raffin, T. A., Weber, S., ZUCKERMAN, J. E., Yang, P., Sikic, B. I. AMER COLL CHEST PHYSICIANS. 1984: 311-311
  • STRUCTURE-ACTIVITY OF ANTHRACYCLINES - 250-FOLD TO 1500-FOLD INCREASED POTENCY IN HUMAN-TUMORS, NON-CROSS-RESISTANCE, AND ABSENCE OF CARDIOTOXICITY IN THE CYANO-MORPHOLINO DERIVATIVE OF DOXORUBICIN Sikic, B. I., ACTON, E. M., EHSAN, M. N., Harker, W. G., Fagan, M. A., Newman, R. A., FRIEND, N. F., Brown, B. W. AMER ASSOC CANCER RESEARCH. 1984: 306-306
  • GASTRIN RELEASING PEPTIDE IS A SELECTIVE MITOGEN FOR SMALL CELL LUNG-CARCINOMA INVITRO Weber, S., ZUCKERMAN, J. E., Bostwick, D. G., Bensch, K. G., Sikic, B. I., Raffin, T. A. AMER COLL CHEST PHYSICIANS. 1984: 306-306

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