Clinical Focus

  • Fellow
  • Hematology

Academic Appointments

Professional Education

  • Medical Education:Stanford University (2008) CA
  • Fellowship:Stanford Hospital and ClinicsCA
  • Residency:Stanford Hospital and ClinicsCA
  • Internship:Stanford Hospital and ClinicsCA
  • Board Certification: Internal Medicine, American Board of Internal Medicine
  • Board Certification: Hematology, American Board of Internal Medicine


All Publications

  • Isocitrate dehydrogenase 1 and 2 mutations induce BCL-2 dependence in acute myeloid leukemia NATURE MEDICINE Chan, S. M., Thomas, D., Corces-Zimmerman, M. R., Xavy, S., Rastogi, S., Hong, W., Zhao, F., Medeiros, B. C., Tyvoll, D. A., Majeti, R. 2015; 21 (2): 90-96

    View details for DOI 10.1038/nm.3788

    View details for Web of Science ID 000348974800021

  • Isocitrate dehydrogenase 1 and 2 mutations induce BCL-2 dependence in acute myeloid leukemia. Nature medicine Chan, S. M., Thomas, D., Corces-Zimmerman, M. R., Xavy, S., Rastogi, S., Hong, W., Zhao, F., Medeiros, B. C., Tyvoll, D. A., Majeti, R. 2015; 21 (2): 178-184


    Mutant isocitrate dehydrogenase (IDH) 1 and 2 proteins alter the epigenetic landscape in acute myeloid leukemia (AML) cells through production of the oncometabolite (R)-2-hydroxyglutarate (2-HG). Here we performed a large-scale RNA interference (RNAi) screen to identify genes that are synthetic lethal to the IDH1(R132H) mutation in AML and identified the anti-apoptotic gene BCL-2. IDH1- and IDH2-mutant primary human AML cells were more sensitive than IDH1/2 wild-type cells to ABT-199, a highly specific BCL-2 inhibitor that is currently in clinical trials for hematologic malignancies, both ex vivo and in xenotransplant models. This sensitization effect was induced by (R)-2-HG-mediated inhibition of the activity of cytochrome c oxidase (COX) in the mitochondrial electron transport chain (ETC); suppression of COX activity lowered the mitochondrial threshold to trigger apoptosis upon BCL-2 inhibition. Our findings indicate that IDH1/2 mutation status may identify patients that are likely to respond to pharmacologic BCL-2 inhibition and form the rational basis for combining agents that disrupt ETC activity with ABT-199 in future clinical studies.

    View details for DOI 10.1038/nm.3788

    View details for PubMedID 25599133

  • Mutant WT1 is associated with DNA hypermethylation of PRC2 targets in AML and responds to EZH2 inhibition. Blood Sinha, S., Thomas, D., Yu, L., Gentles, A. J., Jung, N., Corces-Zimmerman, M. R., Chan, S. M., Reinisch, A., Feinberg, A. P., Dill, D. L., Majeti, R. 2015; 125 (2): 316-326


    Acute myeloid leukemia (AML) is associated with deregulation of DNA methylation; however, many cases do not bear mutations in known regulators of CpG methylation. We found that mutations in WT1, IDH2, and CEBPA were strongly linked to DNA hypermethylation in AML using a novel integrative analysis of TCGA data based on Boolean implications, if-then rules that identify all individual CpG sites that are hypermethylated in the presence of a mutation. Introduction of mutant WT1 (WT1mut) into wildtype AML cells induced DNA hypermethylation, confirming mutant WT1 to be causally associated with DNA hypermethylation. Methylated genes in WT1mut primary patient samples were highly enriched for polycomb repressor complex 2 (PRC2) targets, implicating PRC2 dysregulation in WT1mut leukemogenesis. We found that PRC2 target genes were aberrantly repressed in WT1mut AML, and that expression of mutant WT1 in CD34+ cord blood cells induced myeloid differentiation block. Treatment of WT1mut AML cells with shRNA or pharmacologic PRC2/EZH2 inhibitors promoted myeloid differentiation, suggesting EZH2 inhibitors may be active in this AML subtype. Our results highlight a strong association between mutant WT1 and DNA hypermethylation in AML, and demonstrate that Boolean implications can be used to decipher mutation-specific methylation patterns that may lead to therapeutic insights.

    View details for DOI 10.1182/blood-2014-03-566018

    View details for PubMedID 25398938

  • Interaction of TIF-90 and filamin A in the regulation of rRNA synthesis in leukemic cells. Blood Nguyen, L. X., Chan, S. M., Ngo, T. D., Raval, A., Kim, K. K., Majeti, R., Mitchell, B. S. 2014; 124 (4): 579-589


    The transcription initiation factor I (TIF-IA) is an important regulator of the synthesis of ribosomal RNA (rRNA) through its facilitation of the recruitment of RNA polymerase I (Pol I) to the ribosomal DNA promoter. Activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, which occurs commonly in acute myelogenous leukemia, enhances rRNA synthesis through TIF-IA stabilization and phosphorylation. We have discovered that TIF-IA coexists with a splicing isoform, TIF-90, which is expressed preferentially in the nucleolus and at higher levels in proliferating and transformed hematopoietic cells. TIF-90 interacts directly with Pol I to increase rRNA synthesis as a consequence of Akt activation. Furthermore, TIF-90 binds preferentially to a 90-kDa cleavage product of the actin binding protein filamin A (FLNA) that inhibits rRNA synthesis. Increased expression of TIF-90 overcomes the inhibitory effect of this cleavage product and stimulates rRNA synthesis. Because activated Akt also reduces FLNA cleavage, these results indicate that activated Akt and TIF-90 function in parallel to increase rRNA synthesis and, as a consequence, cell proliferation in leukemic cells. These results provide evidence that the direct targeting of Akt would be an effective therapy in acute leukemias in which Akt is activated.

    View details for DOI 10.1182/blood-2013-12-544726

    View details for PubMedID 24850755

  • Intensive serial biomarker profiling for the prediction of neutropenic Fever in patients with hematologic malignancies undergoing chemotherapy: a pilot study. Hematology reports Chan, S. M., Chadwick, J., Young, D. L., Holmes, E., Gotlib, J. 2014; 6 (2): 5466-?


    Neutropenic fever (NF) is a life-threatening complication of myelosuppressive chemotherapy in patients with hematologic malignancies and triggers the administration of broad-spectrum antimicrobials. The ability to accurately predict NF would permit initiation of antimicrobials earlier in the course of infection with the goal of decreasing morbid complications and progression to septic shock and death. Changes in the blood level of inflammatory biomarkers may precede the occurrence of NF. To identify potential biomarkers for the prediction of NF, we performed serial measurements of nine biomarkers [C-reactive protein (CRP), protein C, interleukin (IL)-6, IL-8, IL-10, IL-1β, tumor necrosis factor-α, monocyte chemotactic protein-1, and intercellular adhesion molecule-1] using a multiplex ELISA array platform every 6-8 hours in patients undergoing myelosuppressive chemotherapy for hematologic malignancies. We found that the blood levels of IL-6 and CRP increased significantly 24 to 48 hours prior to the onset of fever. In addition, we showed that frequent biomarker monitoring is feasible using a bedside micro sample test device. The results of this pilot study suggest that serial monitoring of IL-6 and CRP levels using a bedside device may be useful in the prediction of NF. Prospective studies involving a larger cohort of patients to validate this observation are warranted. This trial is registered at (NCT01144793).

    View details for DOI 10.4081/hr.2014.5466

    View details for PubMedID 25013718

  • Broad-Scale Phosphoprotein Profiling of Beta Adrenergic Receptor (beta-AR) Signaling Reveals Novel Phosphorylation and Dephosphorylation Events PLOS ONE Chruscinski, A. J., Singh, H., Chan, S. M., Utz, P. J. 2013; 8 (12)


    β-adrenergic receptors (β-ARs) are model G-protein coupled receptors that mediate signal transduction in the sympathetic nervous system. Despite the widespread clinical use of agents that target β-ARs, the signaling pathways that operate downstream of β-AR stimulation have not yet been completely elucidated. Here, we utilized a lysate microarray approach to obtain a broad-scale perspective of phosphoprotein signaling downstream of β-AR. We monitored the time course of phosphorylation states of 54 proteins after β-AR activation mouse embryonic fibroblast (MEF) cells. In response to stimulation with the non-selective β-AR agonist isoproterenol, we observed previously described phosphorylation events such as ERK1/2(T202/Y204) and CREB(S133), but also novel phosphorylation events such as Cdc2(Y15) and Pyk2(Y402). All of these events were mediated through cAMP and PKA as they were reproduced by stimulation with the adenylyl cyclase activator forskolin and were blocked by treatment with H89, a PKA inhibitor. In addition, we also observed a number of novel isoproterenol-induced protein dephosphorylation events in target substrates of the PI3K/AKT pathway: GSK3β(S9), 4E-BP1(S65), and p70s6k(T389). These dephosphorylations were dependent on cAMP, but were independent of PKA and correlated with reduced PI3K/AKT activity. Isoproterenol stimulation also led to a cAMP-dependent dephosphorylation of PP1α(T320), a modification known to correlate with enhanced activity of this phosphatase. Dephosphorylation of PP1α coincided with the secondary decline in phosphorylation of some PKA-phosphorylated substrates, suggesting that PP1α may act in a feedback loop to return these phosphorylations to baseline. In summary, lysate microarrays are a powerful tool to profile phosphoprotein signaling and have provided a broad-scale perspective of how β-AR signaling can regulate key pathways involved in cell growth and metabolism.

    View details for DOI 10.1371/journal.pone.0082164

    View details for Web of Science ID 000328566100089

    View details for PubMedID 24340001

  • Role of DNMT3A, TET2, and IDH1/2 mutations in pre-leukemic stem cells in acute myeloid leukemia INTERNATIONAL JOURNAL OF HEMATOLOGY Chan, S. M., Majeti, R. 2013; 98 (6): 648-657


    Aberrant changes in the epigenome are now recognized to be important in driving the development of multiple human cancers including acute myeloid leukemia. Recent advances in sequencing technologies have led to the identification of recurrent mutations in genes that regulate DNA methylation including DNA methyltransferase 3A (DNMT3A), ten-eleven translocation 2 (TET2), and isocitrate dehydrogenase 1 (IDH1) and IDH2. These mutations have been shown to promote self-renewal and block differentiation of hematopoietic stem/progenitor cells. Acquisition of these mutations in hematopoietic stem cells can lead to their clonal expansion resulting in a pre-leukemic stem cell (pre-LSC) population. Pre-LSCs retain the ability to differentiate into the full spectrum of mature daughter cells but can become fully transformed with the acquisition of additional driver mutations. Here, we review the effects of mutations in DNMT3A, TET2, and IDH1/2 on mouse and human hematopoiesis, the current understanding of their role in pre-LSCs, and therapeutic strategies to eliminate this population which may serve as a cellular reservoir for relapse.

    View details for DOI 10.1007/s12185-013-1407-8

    View details for Web of Science ID 000328481700005

    View details for PubMedID 23949914

  • Role of cysteine 288 in nucleophosmin cytoplasmic mutations: sensitization to toxicity induced by arsenic trioxide and bortezomib LEUKEMIA Huang, M., Thomas, D., Li, M. X., Feng, W., Chan, S. M., Majeti, R., Mitchell, B. S. 2013; 27 (10): 1970-1980


    Mutations in exon 12 of the NPM1 gene (NPMc+) define a distinct subset of acute myelogenous leukemias (AML) in which the NPMc+ protein localizes aberrantly to the leukemic cell cytoplasm. We have found that introduction of the most common NPMc+ variant into K562 and 32D cells sensitizes these cells to apoptosis induced by drugs such as bortezomib and arsenic trioxide that induce reactive oxygen species (ROS) formation and that cytotoxicity is prevented in the presence of N-acetyl-1-cysteine, a ROS scavenger. The substitution of tryptophan288 by cysteine occurs in the great majority of NPM1c+ mutations. Mutagenesis of C288 to alanine re-localizes NPMc+ from the cytoplasm to the nucleolus and attenuates the sensitivity of cells expressing this mutation to bortezomib and arsenic trioxide. Primary AML leukemic cells expressing NPMc+ are also significantly more sensitive than other AML cells to apoptosis induced by both drugs at pharmacologically achievable doses. We conclude that the presence of a cysteine moiety at position 288 results in the cytoplasmic localization of NPM1c+ and the increased sensitivity to bortezomib and arsenic trioxide. These data suggest that bortezomib and arsenic trioxide may have increased therapeutic efficacy in NPM1c+ leukemias.Leukemia accepted article preview online, 23 July 2013. doi:10.1038/leu.2013.222.

    View details for DOI 10.1038/leu.2013.222

    View details for Web of Science ID 000325642600003

  • Complete remission of primary plasma cell leukemia with bortezomib, doxorubicin, and dexamethasone: a case report. Cases journal Chan, S. M., George, T., Cherry, A. M., Medeiros, B. C. 2009; 2 (1): 121-?


    Plasma cell leukemia (PCL) is a rare lymphoproliferative disorder considered to be a variant of multiple myeloma. It is an aggressive disease with a poor clinical response to standard chemotherapeutic agents.A novel regimen consisting of bortezomib, doxorubicin, and dexamethasone is currently under active evaluation for the treatment of multiple myeloma. We employed this combination as front-line chemoinduction therapy for a case of primary PCL.Complete remission was achieved with rapid normalization of hematologic parameters. The combination of bortezomib, doxorubicin and dexamethasone demonstrates promise in the treatment of PCL.

    View details for DOI 10.1186/1757-1626-2-121

    View details for PubMedID 19192311

  • Notch signals positively regulate activity of the mTOR pathway in T-cell acute lymphoblastic leukemia BLOOD Chan, S. M., Weng, A. P., Tibshirani, R., Aster, J. C., Utz, P. J. 2007; 110 (1): 278-286


    Constitutive Notch activation is required for the proliferation of a subgroup of T-cell acute lymphoblastic leukemia (T-ALL). Downstream pathways that transmit pro-oncogenic signals are not well characterized. To identify these pathways, protein microarrays were used to profile the phosphorylation state of 108 epitopes on 82 distinct signaling proteins in a panel of 13 T-cell leukemia cell lines treated with a gamma-secretase inhibitor (GSI) to inhibit Notch signals. The microarray screen detected GSI-induced hypophosphorylation of multiple signaling proteins in the mTOR pathway. This effect was rescued by expression of the intracellular domain of Notch and mimicked by dominant negative MAML1, confirming Notch specificity. Withdrawal of Notch signals prevented stimulation of the mTOR pathway by mitogenic factors. These findings collectively suggest that the mTOR pathway is positively regulated by Notch in T-ALL cells. The effect of GSI on the mTOR pathway was independent of changes in phosphatidylinositol-3 kinase and Akt activity, but was rescued by expression of c-Myc, a direct transcriptional target of Notch, implicating c-Myc as an intermediary between Notch and mTOR. T-ALL cell growth was suppressed in a highly synergistic manner by simultaneous treatment with the mTOR inhibitor rapamycin and GSI, which represents a rational drug combination for treating this aggressive human malignancy.

    View details for DOI 10.1182/blood-2006-08-039883

    View details for Web of Science ID 000247611000041

    View details for PubMedID 17363738

  • Proteome-wide analysis in Saccharomyces cerevisiae identifies several PHD fingers as novel direct and selective binding modules of histone H3 methylated at either lysine 4 or lysine 36 JOURNAL OF BIOLOGICAL CHEMISTRY Shi, X., Kachirskaia, I., Walter, K. L., Kuo, J. A., Lake, A., Davrazou, F., Chan, S. M., Martin, D. G., Fingerman, I. M., Briggs, S. D., Howe, L., Utz, P. J., Kutateladze, T. G., Lugovskoy, A. A., Bedford, M. T., Gozani, O. 2007; 282 (4): 2450-2455


    The PHD finger motif is a signature chromatin-associated motif that is found throughout eukaryotic proteomes. Here we have determined the histone methyl-lysine binding activity of the PHD fingers present within the Saccharomyces cerevisiae proteome. We provide evidence on the genomic scale that PHD fingers constitute a general class of effector modules for histone H3 trimethylated at lysine 4 (H3K4me3) and histone H3 trimethylated at lysine 36 (H3K36me3). Structural modeling of PHD fingers demonstrates a conserved mechanism for recognizing the trimethyl moiety and provides insight into the molecular basis of affinity for the different methyl-histone ligands. Together, our study suggests that a common function for PHD fingers is to transduce methyl-lysine events and sheds light on how a single histone modification can be linked to multiple biological outcomes.

    View details for DOI 10.1074/jbc.C600286200

    View details for Web of Science ID 000243593200036

    View details for PubMedID 17142463

  • Selective tyrosine kinase inhibition by imatinib mesylate for the treatment of autoimmune arthritis JOURNAL OF CLINICAL INVESTIGATION Paniagua, R. T., Sharpe, O., Ho, P. P., Chan, S. M., Chang, A., Higgins, J. P., Tomooka, B. H., Thomas, F. M., Song, J. J., Goodman, S. B., Lee, D. M., Genovese, M. C., Utz, P. J., Steinman, L., Robinson, W. H. 2006; 116 (10): 2633-2642


    Tyrosine kinases play a central role in the activation of signal transduction pathways and cellular responses that mediate the pathogenesis of rheumatoid arthritis. Imatinib mesylate (imatinib) is a tyrosine kinase inhibitor developed to treat Bcr/Abl-expressing leukemias and subsequently found to treat c-Kit-expressing gastrointestinal stromal tumors. We demonstrate that imatinib potently prevents and treats murine collagen-induced arthritis (CIA). We further show that micromolar concentrations of imatinib abrogate multiple signal transduction pathways implicated in RA pathogenesis, including mast cell c-Kit signaling and TNF-alpha release, macrophage c-Fms activation and cytokine production, and fibroblast PDGFR signaling and proliferation. In our studies, imatinib attenuated PDGFR signaling in fibroblast-like synoviocytes (FLSs) and TNF-alpha production in synovial fluid mononuclear cells (SFMCs) derived from human RA patients. Imatinib-mediated inhibition of a spectrum of signal transduction pathways and the downstream pathogenic cellular responses may provide a powerful approach to treat RA and other inflammatory diseases.

    View details for DOI 10.1172/JCI28546

    View details for Web of Science ID 000240965700013

    View details for PubMedID 16981009

  • Single-cell analysis of siRNA-mediated gene silencing using multiparameter flow cytometry. Cytometry. Part A : the journal of the International Society for Analytical Cytology Chan, S. M., Olson, J. A., Utz, P. J. 2006; 69 (2): 59-65


    Use of synthetic short interfering RNAs (siRNAs) to study gene function has been limited by an inability to selectively analyze subsets of cells in complex populations, low and variable transfection efficiencies, and semiquantitative assays for measuring protein down-regulation. Intracellular flow cytometry can overcome these limitations by analyzing populations at the single-cell level in a high-throughput and quantitative fashion. Individual cells displaying a knockdown phenotype can be selectively interrogated for functional responses using multiparameter analysis.Lck-specific siRNA was delivered into Jurkat T cells or peripheral blood mononuclear cells (PBMCs) to suppress endogenous Lck expression. Transfected cells were fluorescently stained for intracellular Lck and analyzed using multiparameter flow cytometry. The Lck(lo) Jurkat subpopulation was selectively analyzed for CD69 up-regulation and phospho-states of signaling proteins following T-cell receptor (TCR) stimulation. Surface expression levels of CD4 and CD8 on transfected CD3+ gated PBMCs were correlated with intracellular Lck levels.A subpopulation of Jurkat cells with reduced levels of Lck was clearly resolved from cells with wildtype levels of Lck. Both CD69 up-regulation and ZAP70 phosphorylation were suppressed in Lck(lo) cells when compared with those in Lck(hi) cells upon TCR stimulation. Knockdown of intracellular Lck in primary T lymphocytes reduced surface expression of CD4 in a dose-dependent manner.Multiparameter flow cytometry is a powerful technique for the quantitative analysis of siRNA-mediated protein knockdown in complex hard-to-transfect cell populations.

    View details for PubMedID 16419066

  • Multiplexed protein array platforms for analysis of autoimmune diseases ANNUAL REVIEW OF IMMUNOLOGY Balboni, I., Chan, S. M., Kattah, M., Tenenbaum, J. D., Butte, A. J., Utz, P. J. 2006; 24: 391-418


    Several proteomics platforms have emerged in the past decade that show great promise for filling in the many gaps that remain from earlier studies of the genome and from the sequencing of the human genome itself. This review describes applications of proteomics technologies to the study of autoimmune diseases. We focus largely on biased technology platforms that are capable of analyzing a large panel of known analytes, as opposed to techniques such as two-dimensional gel electrophoresis (2DIGE) or mass spectroscopy that represent unbiased approaches (as reviewed in 1). At present, the main analytes that can be systematically studied in autoimmunity include autoantibodies, cytokines and chemokines, components of signaling pathways, and cell-surface receptors. We review the most commonly used platforms for such studies, citing important discoveries and limitations that exist. We conclude by reviewing advances in biomedical informatics that will eventually allow the human proteome to be deciphered.

    View details for DOI 10.1146/annurev.immunol.24.021605.090709

    View details for Web of Science ID 000237583300013

    View details for PubMedID 16551254

  • An array of possibilities for the study of autoimmunity NATURE Fathman, C. G., Soares, L., Chan, S. M., Utz, P. J. 2005; 435 (7042): 605-611


    Since the completion of the sequencing of the human genome, scientific focus has shifted from studying genes to analysing the much larger number of proteins encoded by them. Several proteins can be generated from a single gene depending on how the genetic information is read (transcribed) and how the resultant protein is modified following translation (post-translational modification). Genomic and proteomic technologies are already providing useful information about autoimmune disease, and they are likely to lead to important discoveries within the next decade.

    View details for DOI 10.1038/nature03726

    View details for Web of Science ID 000229476200038

    View details for PubMedID 15931213

  • The challenge of analyzing the proteome in humans with autoimmune diseases HUMAN IMMUNOLOGY: PATIENT-BASED RESEARCH Chan, S. M., Utz, P. J. 2005; 1062: 61-68


    Analysis of blood samples from patients suffering from autoimmune diseases remains a mainstay in the clinic for initial diagnosis, prognostication, and clinical decision making. In particular, testing for the presence of serum autoantibodies has proved to be one of the most useful confirmatory assays for many different diseases. Recent genomic and transcript profiling studies have implicated certain cytokines, surface receptors, signaling pathways, and cell types in the pathogenesis of inflammatory diseases. The next obvious step is to delve into the much more complex level that follows the genome and transcriptome-the expressed proteome. This review focuses on several proteomics technologies being applied and/or developed by our laboratory for the study of autoimmunity, cancer, and cardiovascular disease, all of which are known to be associated with defects in immunity and inflammation. The findings of other participants in the recent Human Immunology Conference hosted by the Dana Foundation and the New York Academy of Sciences (May 17 & 18, 2005) are included. In particular, major pitfalls in the study of the human proteome are pointed out, and important areas for immediate investigation to move the field forward as rapidly as possible are proposed.

    View details for DOI 10.1196/annals.1358.009

    View details for Web of Science ID 000236473100007

    View details for PubMedID 16461789

  • Suppression of Lck sensitizes acute lymphoblastic T cells to the antiproliferative action of interferon alpha Clinical Immunology Steven M. Chan, Paul J. Utz 2005; 115 (S183)
  • Protein microarrays for multiplex analysis of signal transduction pathways NATURE MEDICINE Chan, S. M., Ermann, J., Su, L., Fathman, C. G., Utz, P. J. 2004; 10 (12): 1390-1396


    We have developed a multiplexed reverse phase protein (RPP) microarray platform for simultaneous monitoring of site-specific phosphorylation of numerous signaling proteins using nanogram amounts of lysates derived from stimulated living cells. We first show the application of RPP microarrays to the study of signaling kinetics and pathway delineation in Jurkat T lymphocytes. RPP microarrays were used to profile the phosphorylation state of 62 signaling components in Jurkat T cells stimulated through their membrane CD3 and CD28 receptors, identifying a previously unrecognized link between CD3 crosslinking and dephosphorylation of Raf-1 at Ser259. Finally, the potential of this technology to analyze rare primary cell populations is shown in a study of differential STAT protein phosphorylation in interleukin (IL)-2-stimulated CD4(+)CD25(+) regulatory T cells. RPP microarrays, prepared using simple procedures and standard microarray equipment, represent a powerful new tool for the study of signal transduction in both health and disease.

    View details for DOI 10.1038/nm1139

    View details for Web of Science ID 000225500900035

    View details for PubMedID 15558056

  • Murine CD4(+) CD25(+) regulatory T cells fail to undergo chromatin remodeling across the proximal promoter region of the IL-2 gene JOURNAL OF IMMUNOLOGY Su, L., Creusot, R. J., Gallo, E. M., Chan, S. M., Utz, P. J., Fathman, C. G., Ermann, J. 2004; 173 (8): 4994-5001


    CD4+CD25+ regulatory T cells (Treg) acquire unique immunosuppressive properties while maintaining an anergy phenotype when activated in vitro under conditions that induce IL-2 production and proliferation in conventional CD4+ T cells. We investigated the mechanism underlying one component of this naturally anergic phenotype, the inability of the Treg cells to produce IL-2 following activation. Analysis of freshly isolated murine CD4+CD25+ Treg and conventional CD4+CD25- T cells following PMA/ionomycin stimulation demonstrated no differences in inducible AP-1 formation, an important transcriptional complex in regulating IL-2 gene expression. Although p38 MAPK and ERK1/2 protein kinases were phosphorylated with similar kinetics, we observed diminished activation of JNK in the CD4+CD25+ Treg cells. However, lentiviral-mediated reconstitution of the JNK pathway using a constitutively active construct did not overcome the block in IL-2 synthesis. Using a PCR-based chromatin accessibility assay we found that the minimal IL-2 promoter region of CD4+CD25+ Treg cells, unlike conventional CD4 T cells, did not undergo chromatin remodeling following stimulation, suggesting that the inability of CD4+CD25+ Treg cells to secrete IL-2 following activation is controlled at the chromatin level.

    View details for Web of Science ID 000224392200028

    View details for PubMedID 15470042

  • Autoantibody profiling and lymphocyte characterization using autoantigen and lysate arrays. From Animal Models to Human Genetics: Research on the Induction and Pathogenicity of Autoantibodies. Utz PJ, Chan SM 2004; 4: 473-483
  • Role of antigen-presenting cells in mediating tolerance and autoimmunity JOURNAL OF EXPERIMENTAL MEDICINE Garza, K. M., Chan, S. M., Suri, R., Nguyen, L. T., Odermatt, B., Schoenberger, S. P., Ohashi, P. S. 2000; 191 (11): 2021-2027


    The mechanisms that determine whether receptor stimulation leads to lymphocyte tolerance versus activation remain poorly understood. We have used rat insulin promoter (RIP)-gp/P14 double-transgenic mice expressing the lymphocytic choriomeningitis virus (LCMV) glycoprotein (gp) on pancreatic beta-islet cells together with T cells expressing an LCMV-gp-specific T cell receptor to assess the requirements for the induction of autoimmunity. Our studies have shown that administration of the gp peptide gp33 leads to the activation of P14-transgenic T cells, as measured by the upregulation of activation markers and the induction of effector cytotoxic activity. This treatment also leads to expansion and deletion of P14 T cells. Despite the induction of cytotoxic T lymphocyte activity, peptide administration is not sufficient to induce diabetes. However, the administration of gp peptide together with an activating anti-CD40 antibody rapidly induces diabetes. These findings suggest that the induction of tolerance versus autoimmunity is determined by resting versus activated antigen-presenting cells.

    View details for Web of Science ID 000087527300019

    View details for PubMedID 10839816

  • Covalent linkage to beta(2)-microglobulin enhances the MHC stability and antigenicity of suboptimal CTL epitopes JOURNAL OF IMMUNOLOGY Uger, R. A., Chan, S. M., Barber, B. H. 1999; 162 (10): 6024-6028


    Many CTL epitopes of clinical importance, particularly those derived from tumor Ags, display relatively poor MHC binding affinity and stability. Because in vivo immunogenicity, and thus the efficacy of peptide-based vaccines, is thought to be determined by MHC/peptide complex stability, there is a need to develop a simple strategy for enhancing the binding of suboptimal epitopes. Toward this goal, the ability to enhance suboptimal peptides through covalent linkage to beta2-microglobulin (beta2m) was explored. Two suboptimal variants of a high-affinity Db-restricted influenza nucleoprotein peptide were covalently linked, via a polypeptide spacer, to the amino terminus of human beta2m and the recombinant fusion proteins expressed in Escherichia coli. When compared with their uncoupled counterparts, the beta2m-linked epitopes display enhanced MHC stabilization and antigenicity. Thus, tethering epitopes to beta2m provides a simple method for augmenting the biological activity of suboptimal peptides and could be useful in the design of peptide-based vaccines or immunotherapeutics.

    View details for Web of Science ID 000080240200049

    View details for PubMedID 10229842

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