Independent Studies (6)
- Directed Reading in Radiology
RAD 299 (Aut, Win, Spr, Sum)
- Early Clinical Experience in Radiology
RAD 280 (Aut, Win, Spr, Sum)
- Graduate Research
RAD 399 (Aut, Win, Spr, Sum)
- Medical Scholars Research
RAD 370 (Aut, Win, Spr, Sum)
- Readings in Radiology Research
RAD 101 (Aut, Win, Spr, Sum)
- Undergraduate Research
RAD 199 (Aut, Win, Spr, Sum)
- Directed Reading in Radiology
A titratable two-step transcriptional amplification strategy for targeted gene therapy based on ligand-induced intramolecular folding of a mutant human estrogen receptor.
Molecular imaging and biology
2014; 16 (2): 224-234
The efficacy and safety of cardiac gene therapy depend critically on the level and the distribution of therapeutic gene expression following vector administration. We aimed to develop a titratable two-step transcriptional amplification (tTSTA) vector strategy, which allows modulation of transcriptionally targeted gene expression in the myocardium.We constructed a tTSTA plasmid vector (pcTnT-tTSTA-fluc), which uses the cardiac troponin T (cTnT) promoter to drive the expression of the recombinant transcriptional activator GAL4-mER(LBD)-VP2, whose ability to transactivate the downstream firefly luciferase reporter gene (fluc) depends on the binding of its mutant estrogen receptor (ERG521T) ligand binding domain (LBD) to an ER ligand such as raloxifene. Mice underwent either intramyocardial or hydrodynamic tail vein (HTV) injection of pcTnT-tTSTA-fluc, followed by differential modulation of fluc expression with varying doses of intraperitoneal raloxifene prior to bioluminescence imaging to assess the kinetics of myocardial or hepatic fluc expression.Intramyocardial injection of pcTnT-tTSTA-fluc followed by titration with intraperitoneal raloxifene led to up to tenfold induction of myocardial fluc expression. HTV injection of pcTnT-tTSTA-fluc led to negligible long-term hepatic fluc expression, regardless of the raloxifene dose given.The tTSTA vector strategy can effectively modulate transgene expression in a tissue-specific manner. Further refinement of this strategy should help maximize the benefit-to-risk ratio of cardiac gene therapy.
View details for DOI 10.1007/s11307-013-0673-4
View details for PubMedID 23955099
Noninvasive imaging of hypoxia-inducible factor-1a gene therapy for myocardial ischemia.
Human gene therapy methods
2013; 24 (5): 279-288
Abstract Hypoxia-inducible factor-1 alpha (HIF-1α) gene therapy holds great promise for the treatment of myocardial ischemia. Both preclinical and clinical evaluations of this therapy are underway and can benefit from a vector strategy that allows noninvasive assessment of HIF-1α expression as an objective measure of gene delivery. We have developed a novel bidirectional plasmid vector (pcTnT-HIF-1α-VP2-TSTA-fluc), which employs the cardiac troponin T (cTnT) promoter in conjunction with a two-step transcriptional amplification (TSTA) system to drive the linked expression of a recombinant HIF-1α gene (HIF-1α-VP2) and the firefly luciferase gene (fluc). The firefly luciferase (FLuc) activity serves as a surrogate for HIF-1α-VP2 expression, and can be noninvasively assessed in mice using bioluminescence imaging after vector delivery. Transfection of cultured HL-1 cardiomyocytes with pcTnT-HIF-1α-VP2-TSTA-fluc led to a strong correlation between FLuc and HIF-1α-dependent vascular endothelial growth factor expression (r(2)=0.88). Intramyocardial delivery of pcTnT-HIF-1α-VP2-TSTA-fluc into infarcted mouse myocardium led to persistent HIF-1α-VP2 expression for 4 weeks, even though it improved neither CD31+ microvessel density nor echocardiographically determined left ventricular systolic function. These results lend support to recent findings of suboptimal efficacy associated with plasmid-mediated HIF-1α therapy. The imaging techniques developed herein should be useful for further optimizing HIF-1α-VP2 therapy in preclinical models of myocardial ischemia.
View details for DOI 10.1089/hgtb.2013.028
View details for PubMedID 23937265
A c-Myc Activation Sensor-Based High-Throughput Drug Screening Identifies an Antineoplastic Effect of Nitazoxanide.
Molecular cancer therapeutics
2013; 12 (9): 1896-1905
Deregulation of c-Myc plays a central role in the tumorigenesis of many human cancers. Yet, the development of drugs regulating c-Myc activity has been challenging. To facilitate the identification of c-Myc inhibitors, we developed a molecular imaging sensor based high throughput-screening (HTS) system. This system uses a cell-based assay to detect c-Myc activation in a HTS format, which is established from a pure clone of a stable breast cancer cell line that constitutively expresses a c-Myc activation sensor. Optimization of the assay performance in the HTS format resulted in uniform and robust signals at the baseline. Using this system, we performed a quantitative HTS against approximately 5,000 existing bioactive compounds from five different libraries. Thirty-nine potential hits were identified, including currently known c-Myc inhibitors. There are a few among the top potent hits that are not known for anti-c-Myc activity. One of these hits is nitazoxanide (NTZ), a thiazolide for treating human protozoal infections. Validation of NTZ in different cancer cell lines revealed a high potency for c-Myc inhibition with IC50 ranging between 10 - 500nM. Oral administration of NTZ in breast cancer xenograft mouse models significantly suppressed tumor growth by inhibition of c-Myc and induction of apoptosis. These findings suggest a potential of NTZ to be repurposed as a new anti-tumor agent for inhibition of c-Myc associated neoplasia. Our work also demonstrated the unique advantage of molecular imaging in accelerating discovery of drugs for c-Myc targeted cancer therapy.
View details for DOI 10.1158/1535-7163.MCT-12-1243
View details for PubMedID 23825064
Reporter protein complementation imaging assay to screen and study nrf2 activators in cells and living animals.
2013; 85 (15): 7542-7549
NF-E2-related factor-2 (Nrf2) activators promote cellular defense mechanism and facilitate disease prevention associated with oxidative stress. In the present study, Nrf2 activators were identified using cell-based luciferase enzyme fragment complementation (EFC) assay, and the mechanism of Nrf2 activation was studied by molecular imaging. Among the various Nrf2 activators tested, pterostilbene (PTS) showed effective Nrf2 activation, as seen by luminometric screening, and validation in a high throughput-intact cell-imaging platform. Further, PTS increased the expression of Nrf2 downstream target genes, which was confirmed using luciferase reporter driven by ARE-NQO1 and ARE-GST1 promoters. Daily administration of PTS disturbed Nrf2/Keap1 interaction and reduced complemented luciferase signals in HEK293TNKS mouse tumor xenografts. This study reveals the potentials of Nrf2 activators as chemosensitizing agents' for therapeutic intervention in cancer treatment. Hence, the validated assay can be used to evaluate the identified activators preclinically in small animal models by noninvasive molecular imaging approach.
View details for DOI 10.1021/ac401569j
View details for PubMedID 23826874
Dual-therapeutic reporter genes fusion for enhanced cancer gene therapy and imaging.
2013; 20 (5): 529-537
Two of the successful gene-directed enzyme prodrug therapies include herpes simplex virus-thymidine kinase (HSV1-TK) enzyme-ganciclovir prodrug and the Escherichia coli nitroreductase (NTR) enzyme-CB1954 prodrug strategies; these enzyme-prodrug combinations produce activated cytotoxic metabolites of the prodrugs capable of tumor cell death by inhibiting DNA synthesis and killing quiescent cells, respectively. Both these strategies also affect significant bystander cell killing of neighboring tumor cells that do not express these enzymes. We have developed a dual-combination gene strategy, where we identified HSV1-TK and NTR fused in a particular orientation can effectively kill tumor cells when the tumor cells are treated with a fusion HSV1-TK-NTR gene- along with a prodrug combination of GCV and CB1954. In order to determine whether the dual-system demonstrate superior therapeutic efficacy than either HSV1-TK or NTR systems alone, we conducted both in vitro and in vivo tumor xenograft studies using triple negative SUM159 breast cancer cells, by evaluating the efficacy of cell death by apoptosis and necrosis upon treatment with the dual HSV1-TK genes-GCV-CB1954 prodrugs system, and compared the efficiency to HSV1-TK-GCV and NTR-CB1954. Our cell-based studies, tumor regression studies in xenograft mice, histological analyses of treated tumors and bystander studies indicate that the dual HSV1-TK-NTR-prodrug system is two times more efficient even with half the doses of both prodrugs than the respective single gene-prodrug system, as evidenced by enhanced apoptosis and necrosis of tumor cells in vitro in culture and xenograft of tumor tissues in animals.
View details for DOI 10.1038/gt.2012.66
View details for PubMedID 22914496
The Impact of Oxidative Stress on Islet Transplantation and Monitoring the Graft Survival by Non-Invasive Imaging
CURRENT MEDICINAL CHEMISTRY
2013; 20 (9): 1127-1146
Islet transplantation is an attractive strategy to treat severe diabetic conditions in patients suffering from autoimmune derived diabetes, and it has currently been considered a forefront research arena in diabetes. Major aim of islet transplantation is to achieve successful insulin independent disease free survival. The key challenges in transplanted islets are the generation of reactive oxygen species (ROS) and associated oxidative stress, pro-inflammatory cytokine - (TNF?) mediated apoptotic induction, attack by immune cells, and achieving revascularization with minimal hypoxic microenvironment. Free radicals and their derivatives are constantly produced in living systems, but at relatively low level, and in a balanced state. Oxidative stress, which occurs as a result of an imbalance between the intracellular free radicals production and the cellular antioxidant defense mechanisms in the transplanted islets, can lead to cell death. The balance between oxidants and antioxidants in a cell can be easily disturbed by increase in ROS production or reduction in the level of cellular antioxidant defensive substances, which can cause many metabolic complications, including pancreatic ?-cell damage. Antioxidants function as blockers of radical processes by eliminating harmful ROS produced during normal cellular metabolism. A complex antioxidant defense mechanism has been developed by nature in cells to protect the cellular homeostasis. This system mainly includes antioxidant enzymes, vitamins and minerals. As transplanted islet survival is crucial for achieving successful therapy, most of these antioxidants can be used as a supplement to scavenge the local ROS thereby improving the survival of transplanted islets. Currently, very few techniques have been routinely used to qualitatively and quantitatively assess the survival and function of islet grafts, especially to confirm the success of treatment, which includes metabolic parameters such as blood glucose, insulin and C-peptide levels. These biochemical measurements provide markers at only the late stages of islet rejection. Use of molecular imaging techniques has the potential for real-time non-invasive monitoring of the functional status and viability of transplanted islet grafts in living animals. This review mainly focuses on the current status of islet transplantations, potential preventive strategies used to reduce oxidative stress-mediated toxicity in islet grafts, and use of molecular imaging as a tool to quantitatively evaluate the functional status of the transplanted islets in living animals.
View details for Web of Science ID 000316615700003
View details for PubMedID 23317098
A transgenic tri-modality reporter mouse.
2013; 8 (8)
Transgenic mouse with a stably integrated reporter gene(s) can be a valuable resource for obtaining uniformly labeled stem cells, tissues, and organs for various applications. We have generated a transgenic mouse model that ubiquitously expresses a tri-fusion reporter gene (fluc2-tdTomato-ttk) driven by a constitutive chicken β-actin promoter. This "Tri-Modality Reporter Mouse" system allows one to isolate most cells from this donor mouse and image them for bioluminescent (fluc2), fluorescent (tdTomato), and positron emission tomography (PET) (ttk) modalities. Transgenic colonies with different levels of tri-fusion reporter gene expression showed a linear correlation between all three-reporter proteins (R(2)=0.89 for TdTomato vs Fluc, R(2)=0.94 for Fluc vs TTK, R(2)=0.89 for TdTomato vs TTK) in vitro from tissue lysates and in vivo by optical and PET imaging. Mesenchymal stem cells (MSCs) isolated from this transgenics showed high level of reporter gene expression, which linearly correlated with the cell numbers (R(2)=0.99 for bioluminescence imaging (BLI)). Both BLI (R(2)=0.93) and micro-PET (R(2)=0.94) imaging of the subcutaneous implants of Tri-Modality Reporter Mouse derived MSCs in nude mice showed linear correlation with the cell numbers and across different imaging modalities (R(2)=0.97). Serial imaging of MSCs transplanted to mice with acute myocardial infarction (MI) by intramyocardial injection exhibited significantly higher signals in MI heart at days 2, 3, 4, and 7 (p<0.01). MSCs transplanted to the ischemic hindlimb of nude mice showed significantly higher BLI and PET signals in the first 2 weeks that dropped by 4(th) week due to poor cell survival. However, laser Doppler perfusion imaging revealed that blood circulation in the ischemic limb was significantly improved in the MSCs transplantation group compared with the control group. In summary, this mouse can be used as a source of donor cells and organs in various research areas such as stem cell research, tissue engineering research, and organ transplantation.
View details for DOI 10.1371/journal.pone.0073580
View details for PubMedID 23951359
- Noninvasive imaging of hypoxia-inducible factor-1? gene therapy for myocardial ischemia Hum Gene Ther Methods. 2013 Aug 12. [Epub ahead of print] 2013
Real time dynamic imaging and current targeted therapies in the war on cancer: a new paradigm.
2013; 3 (6): 437-447
In biology, as every science student is made to learn, ontology recapitulates phylogeny. In medicine, however, oncology recapitulates polemology, the science of warfare: The medical establishment is transitioning from highly toxic poisons that kill rapidly dividing normal and malignant cells with little specificity to tailored therapies that target the tumors with the lethality of the therapeutic warhead. From the advent of the information age with the incorporation of high-tech intelligence, reconnaissance, and surveillance has resulted in "data fusion" where a wide range of information collected in near real-time can be used to redesign most of the treatment strategies currently used in the clinic. The medical community has begun to transition from the 'black box' of tumor therapy based solely on the clinical response to the 'glass box' of dynamic imaging designed to bring transparency to the clinical battlefield during treatment, thereby informing the therapeutic decision to 'retreat or repeat'. The tumor microenvironment is dynamic, constantly changing in response to therapeutic intervention, and therefore the therapeutic assessment must map to this variable and ever-changing landscape with dynamic and non-static imaging capabilities. The path to personalized medicine will require incorporation and integration of dynamic imaging at the bedside into clinical practice for real-time, interactive assessment of response to targeted therapies. The application of advanced real time imaging techniques along with current molecularly targeted anticancer therapies which alter cellular homeostasis and microenvironment can enhance therapeutic interventions in cancer patients and further improve the current status in clinical management of patients with advanced cancers.
View details for DOI 10.7150/thno.5658
View details for PubMedID 23781290
Therapeutic evaluation of microRNAs by molecular imaging.
2013; 3 (12): 964-985
MicroRNAs (miRNAs) function as regulatory molecules of gene expression with multifaceted activities that exhibit direct or indirect oncogenic properties, which promote cell proliferation, differentiation, and the development of different types of cancers. Because of their extensive functional involvement in many cellular processes, under both normal and pathological conditions such as various cancers, this class of molecules holds particular interest for cancer research. MiRNAs possess the ability to act as tumor suppressors or oncogenes by regulating the expression of different apoptotic proteins, kinases, oncogenes, and other molecular mechanisms that can cause the onset of tumor development. In contrast to current cancer medicines, miRNA-based therapies function by subtle repression of gene expression on a large number of oncogenic factors, and therefore are anticipated to be highly efficacious. Given their unique mechanism of action, miRNAs are likely to yield a new class of targeted therapeutics for a variety of cancers. More than thousand miRNAs have been identified to date, and their molecular mechanisms and functions are well studied. Furthermore, they are established as compelling therapeutic targets in a variety of cellular complications. However, the notion of using them as therapeutic tool was proposed only recently, given that modern imaging methods are just beginning to be deployed for miRNA research. In this review, we present a summary of various molecular imaging methods, which are instrumental in revealing the therapeutic potential of miRNAs, especially in various cancers. Imaging methods have recently been developed for monitoring the expression levels of miRNAs and their target genes by fluorescence-, bioluminescence- and chemiluminescence-based imaging techniques. Mature miRNAs bind to the untranslated regions (UTRs) of the target mRNAs and regulate target genes expressions. This concept has been used for the development of fluorescent reporter-based imaging strategies to monitor the functional status of endogenous miRNAs, or the respective miRNAs transiently co-expressed in cells. Bioluminescence-based imaging strategies have been used to investigate various stages of miRNA processing and its involvement in different cellular processes. Similarly, chemiluminsecence methods were developed for in vitro miRNA imaging such as monitoring their therapeutic roles in various cancer cell lines.
View details for DOI 10.7150/thno.4928
View details for PubMedID 24396507
- Therapeutic Evaluation of microRNAs by Molecular Imaging THERANOSTICS 2013; 3 (12): 953-974
Discovery and validation of small-molecule heat-shock protein 90 inhibitors through multimodality molecular imaging in living subjects
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (37): E2476-E2485
Up-regulation of the folding machinery of the heat-shock protein 90 (Hsp90) chaperone protein is crucial for cancer progression. The two Hsp90 isoforms (? and ?) play different roles in response to chemotherapy. To identify isoform-selective inhibitors of Hsp90(?/?)/cochaperone p23 interactions, we developed a dual-luciferase (Renilla and Firefly) reporter system for high-throughput screening (HTS) and monitoring the efficacy of Hsp90 inhibitors in cell culture and live mice. HTS of a 30,176 small-molecule chemical library in cell culture identified a compound, N-(5-methylisoxazol-3-yl)-2-[4-(thiophen-2-yl)-6-(trifluoromethyl)pyrimidin-2-ylthio]acetamide (CP9), that binds to Hsp90(?/?) and displays characteristics of Hsp90 inhibitors, i.e., degradation of Hsp90 client proteins and inhibition of cell proliferation, glucose metabolism, and thymidine kinase activity, in multiple cancer cell lines. The efficacy of CP9 in disrupting Hsp90(?/?)/p23 interactions and cell proliferation in tumor xenografts was evaluated by non-invasive, repetitive Renilla luciferase and Firefly luciferase imaging, respectively. At 38 h posttreatment (80 mg/kg × 3, i.p.), CP9 led to selective disruption of Hsp90?/p23 as compared with Hsp90?/p23 interactions. Small-animal PET/CT in the same cohort of mice showed that CP9 treatment (43 h) led to a 40% decrease in (18)F-fluorodeoxyglucose uptake in tumors relative to carrier control-treated mice. However, CP9 did not lead to significant degradation of Hsp90 client proteins in tumors. We performed a structural activity relationship study with 62 analogs of CP9 and identified A17 as the lead compound that outperformed CP9 in inhibiting Hsp90(?/?)/p23 interactions in cell culture. Our efforts demonstrated the power of coupling of HTS with multimodality molecular imaging and led to identification of Hsp90 inhibitors.
View details for DOI 10.1073/pnas.1205459109
View details for Web of Science ID 000309208000012
View details for PubMedID 22895790
Cationic versus Neutral Microbubbles for Ultrasound-mediated Gene Delivery in Cancer
2012; 264 (3): 721-732
To test whether plasmid-binding cationic microbubbles (MBs) enhance ultrasound-mediated gene delivery efficiency relative to control neutral MBs in cell culture and in vivo tumors in mice.Animal studies were approved by the institutional animal care committee. Cationic and neutral MBs were characterized in terms of size, charge, circulation time, and DNA binding. Click beetle luciferase (CBLuc) reporter plasmids were mixed with cationic or neutral MBs. The ability of cationic MBs to protect bound plasmids from nuclease degradation was tested by means of a deoxyribonuclease (DNase) protection assay. Relative efficiencies of ultrasound-mediated transfection (ultrasound parameters: 1 MHz, 1 W/cm(2), 20% duty cycle, 1 minute) of CBLuc to endothelial cells by using cationic, neutral, or no MBs were compared in cell culture. Ultrasound-mediated gene delivery to mouse hind limb tumors was performed in vivo (n = 24) with insonation (1 MHz, 2 W/cm(2), 50% duty cycle, 5 minutes) after intravenous administration of CBLuc with cationic, neutral, or no MBs. Tumor luciferase activity was assessed by means of serial in vivo bioluminescence imaging and ex vivo analysis. Results were compared by using analysis of variance.Cationic MBs (+15.8 mV; DNA binding capacity, 0.03 pg per MB) partially protected bound DNA from DNase degradation. Mean CBLuc expression of treated endothelial cells in culture was 20-fold higher with cationic than with neutral MBs (219.0 relative light units [RLUs]/µg protein ± 92.5 [standard deviation] vs 10.9 RLUs/µg protein ± 2.7, P = .001) and was significantly higher (P < .001) than that in the no MB and no ultrasound control groups. Serial in vivo bioluminescence of mouse tumors was significantly higher with cationic than with neutral MBs ([5.9 ± 2.2] to [9.3 ± 5.2] vs [2.4 ± 0.8] to [2.9 ± 1.1] × 10(4) photons/sec/cm(2)/steradian, P < .0001) and versus no MB and no ultrasound controls (P < .0001). Results of ex vivo analysis confirmed these results (? = 0.88, P < .0001).Plasmid-binding cationic MBs enhance ultrasound-mediated gene delivery efficiency relative to neutral MBs in both cell culture and mouse hind limb tumors.
View details for DOI 10.1148/radiol.12112368
View details for Web of Science ID 000308645500013
View details for PubMedID 22723497
Oxidative stress-mediated cytotoxicity and apoptosis induction by TiO2 nanofibers in HeLa cells
EUROPEAN JOURNAL OF PHARMACEUTICS AND BIOPHARMACEUTICS
2012; 81 (2): 324-333
Titanium dioxide nanoparticles are increasingly being used in pharmaceutical and cosmetic products. The high aspect ratio of fibrous nanomaterials, such as carbon nanotubes and TiO(2) nanofibers (TiO(2)NFs), similar to the one used in this study makes them an attractive structural material and has attracted a lot of attention due to their possible negative health effects as suggested by their morphological similarities with asbestos. In the present study, therefore, toxicity of TiO(2)NFs was evaluated in human cervical adenocarcinoma HeLa cells. The TEM and XRD analyses showed that TiO(2)NFs used in this study are pure with uniform diameter of around 200 nm, and their length to width aspect ratio ranged between 5 and 15. Exposure of HeLa cells to TiO(2)NFs induced significant cytotoxicity even at doses as low as 2 ?g/ml. The intracellular uptake of TiO(2)NFs in cells was shown by Alizarin Red S (ARS) labeled nanofibers. The mechanism of toxicity is mainly due to the induction of cellular oxidative stress, as revealed by elevated ROS levels, reduced antioxidant levels, and increased lipid peroxidation leading to apoptosis. The cell cycle analysis indicated G(2)/M cell cycle arrest in the cells exposed to TiO(2)NF. TiO(2)NFs treatment to HeLa cells resulted in increased expression of proapoptotic proteins Bax with an increase in cytosolic Cytochrome-C and inhibition of anti-apoptotic protein Bcl-2. Our results revealed the potential mechanism of cellular effects of TiO(2)NFs.
View details for DOI 10.1016/j.ejpb.2012.02.013
View details for Web of Science ID 000305591700011
View details for PubMedID 22446064
Intratumoral versus Intravenous Gene Therapy Using a Transcriptionally Targeted Viral Vector in an Orthotopic Hepatocellular Carcinoma Rat Model
JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY
2012; 23 (5): 704-711
To evaluate the feasibility of intratumoral delivery of adenoviral vector carrying a bidirectional two-step transcriptional amplification (TSTA) system to amplify transcriptional strength of cancer-specific Survivin promoter in a hepatocellular carcinoma model.MCA-RH7777 cells were implanted in rat liver, and tumor formation was confirmed with [(18)F]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET). The adenoviral vector studied had Survivin promoter driving a therapeutic gene (tumor necrosis factor-?-related apoptosis-inducing ligand [TRAIL]) and a reporter gene (firefly luciferase [FL]; Ad-pSurvivin-TSTA-TRAIL-FL). Tumor-bearing rats were administered Ad-pSurvivin-TSTA-TRAIL-FL intravenously (n = 7) or intratumorally (n = 8). For control groups, adenovirus FL under cytomegalovirus (CMV) promoter (Ad-pCMV-FL) was administered intravenously (n = 3) or intratumorally (n = 3). One day after delivery, bioluminescence imaging was performed to evaluate transduction. At 4 and 7 days after delivery, 18F-FDG-PET was performed to evaluate therapeutic efficacy.With intravenous delivery, Ad-pSurvivin-TSTA-TRAIL-FL showed no measurable liver tumor FL signal on day 1 after delivery, but showed better therapeutic efficacy than Ad-pCMV-FL on day 7 (PET tumor/liver ratio, 3.5 ± 0.58 vs 6.0 ± 0.71; P = .02). With intratumoral delivery, Ad-pSurvivin-TSTA-TRAIL-FL showed positive FL signal from all tumors and better therapeutic efficacy than Ad-pCMV-FL on day 7 (2.4 ± 0.50 vs 5.4 ± 0.78; P = .01). In addition, intratumoral delivery of Ad-pSurvivin-TSTA-TRAIL-FL demonstrated significant decrease in tumoral viability compared with intravenous delivery (2.4 ± 0.50 vs 3.5 ± 0.58; P = .03).Intratumoral delivery of a transcriptionally targeted therapeutic vector for amplifying tumor-specific effect demonstrated better transduction efficiency and therapeutic efficacy for liver cancer than systemic delivery, and may lead to improved therapeutic outcome for future clinical practice.
View details for DOI 10.1016/j.jvir.2012.01.053
View details for Web of Science ID 000303557000020
View details for PubMedID 22387029
Noninvasive optical imaging of nitroreductase gene-directed enzyme prodrug therapy system in living animals
2012; 19 (3): 295-302
Gene-directed enzyme prodrug therapy (GDEPT) is a promising and emerging strategy that attempts to limit the systemic toxicity inherent to cancer chemotherapy by means of tumor-targeted delivery and expression of an exogenous gene whose product converts nontoxic prodrug(s) into activated cytotoxic agent(s). The bacterial nitroreductase (NTR) enzyme, coupled with its substrate prodrug 5-(azaridin-1-yl)-2,4-dinitrobenzamide (CB1954), is a promising GDEPT strategy that has reached clinical trials. However, no strategy exists to visually monitor and quantitatively evaluate the therapeutic efficacy of NTR/CB1954 prodrug therapy in cells and imaging in living animals. As the success of any GDEPT is dependent upon the efficiency of transgene expression in vivo, we developed a safe, sensitive and reproducible noninvasive imaging method to monitor NTR transgene expression that would allow quantitative assessment of both therapeutic efficacy and diagnostic outcome of NTR/CB1954 prodrug therapy in the future. Here, we investigate the use of a novel fluorescent imaging dye CytoCy5S (a Cy5-labeled quenched substrate of NTR enzyme) on various cancer cell lines in vitro and in NTR-transfected tumor-bearing animals in vivo. CytoCy5S-labeled cells become fluorescent at 'red-shifted' wavelengths (638?nm) when reduced by cellular NTR enzyme and remains trapped within the cells for extended periods of time. The conversion and entrapment was dynamically recorded using a time-lapsed microscopy. Systemic and intratumoral delivery of CytoCy5S to NTR-expressing tumors in animals indicated steady and reproducible signals even 16?h after delivery (P<0.001). This is the first study to address visual monitoring and quantitative evaluation of NTR activity in small animals using CytoCy5S, and establishes the capability of NTR to function as an imageable reporter gene.
View details for DOI 10.1038/gt.2011.101
View details for Web of Science ID 000301355800008
View details for PubMedID 21753794
- Biodegradable polymer nanocarriers for therapeutic antisense microRNA delivery in living animals. Proceedings of SPIE 2012; 8232 (1) (Jan 21)
- Therapeutic Evaluation of microRNAs by Molecular Imaging. Theranostics 2012: (in press)
- Syntheses and Discovery of a Novel Class of Cinnamic Hydroxamates as Histone Deacetylase (HDAC) Inhibitors by Multimodality Molecular Imaging of Heat Shock Protein 90 (Hsp90) Chaperone Interactions in Living Subjects. JNCI 2012: (Under Review)
Ultrasound-Mediated Gene Delivery with Cationic Versus Neutral Microbubbles: Effect of DNA and Microbubble Dose on In Vivo Transfection Efficiency
2012; 2 (11): 1078-1091
To assess the effect of varying microbubble (MB) and DNA doses on the overall and comparative efficiencies of ultrasound (US)-mediated gene delivery (UMGD) to murine hindlimb skeletal muscle using cationic versus neutral MBs.Cationic and control neutral MBs were characterized for size, charge, plasmid DNA binding, and ability to protect DNA against endonuclease degradation. UMGD of a codon optimized firefly luciferase (Fluc) reporter plasmid to endothelial cells (1 MHz, 1 W/cm², 20% duty cycle, 1 min) was performed in cell culture using cationic, neutral, or no MBs. In vivo UMGD to mouse hindlimb muscle was performed by insonation (1 MHz, 2 W/cm², 50% duty cycle, 5 min) after intravenous administration of Fluc combined with cationic, neutral, or no MBs. Gene delivery efficiency was assessed by serial in vivo bioluminescence imaging. Efficiency of in vivo UMGD with cationic versus neutral MBs was systematically evaluated by varying plasmid DNA dose (10, 17.5, 25, 37.5, and 50 µg) while maintaining a constant MB dose of 1x10(8) MBs and by changing MB dose (1x10(7), 5x10(7), 1x10(8), or 5x10(8) MBs) while keeping a constant DNA dose of 50 µg.Cationic and size-matched control neutral MBs differed significantly in zeta potential with cationic MBs being able to bind plasmid DNA (binding capacity of 0.03 pg/MB) and partially protect DNA from nuclease degradation while neutral MBs could not. Cationic MBs enhanced UMGD compared to neutral MBs as well as no MB and no US controls both in cell culture (P < 0.001) and in vivo (P < 0.05). Regardless of MB type, in vivo UMGD efficiency increased dose-dependently with DNA dose and showed overall maximum transfection with 50 µg DNA. However, there was an inverse correlation (? = -0.90; P = 0.02) between DNA dose and the degree of enhanced UMGD efficiency observed with using cationic MBs instead of neutral MBs. The delivery efficiency advantage associated with cationic MBs was most prominent at the lowest investigated DNA dose (7.5-fold increase with cationic versus neutral MBs at a DNA dose of 10 µg; P = 0.02) compared to only a 1.4-fold increase at a DNA dose of 50 µg (P < 0.01). With increasing MB dose, overall in vivo UMGD efficiency increased dose-dependently with a maximum reached at a dose of 1x10(8) MBs with no further significant increase with 5x10(8) MBs (P = 0.97). However, compared to neutral MBs, cationic MBs enhanced UMGD efficiency the most at low MB doses. Relative enhancement of UMGD efficiency using cationic over neutral MBs decreased from a factor of 27 for 1x10(7) MBs (P = 0.02) to a factor of 1.4 for 1x10(8) MBs (P < 0.01) and no significant difference for 5x10(8) MBs.Cationic MBs enhance UMGD to mouse skeletal muscle relative to neutral MBs but this is dependent on MB and DNA dose. The enhancement effect of cationic MBs on UMGD efficiency is more evident when lower doses of MBs or DNA are used, whereas the advantage of cationic MBs over neutral MBs is substantially reduced in the presence of excess MBs or DNA.
View details for DOI 10.7150/thno.4240
View details for Web of Science ID 000312955800005
View details for PubMedID 23227124
Non-invasive Bioluminescence Imaging of Myoblast-Mediated Hypoxia-Inducible Factor-1 Alpha Gene Transfer
MOLECULAR IMAGING AND BIOLOGY
2011; 13 (6): 1124-1132
We tested a novel imaging strategy, in which both the survival of transplanted myoblasts and their therapeutic transgene expression, a recombinant hypoxia-inducible factor-1? (HIF-1?-VP2), can be monitored using firefly luciferase (fluc) and Renilla luciferase (hrl) bioluminescence reporter genes, respectively.The plasmid pUbi-hrl-pUbi-HIF-1?-VP2, which expresses both hrl and HIF-1?-VP2 using two ubiquitin promoters, was characterized in vitro. C2c12 myoblasts stably expressing fluc and transiently transfected with pUbi-hrl-pUbi-HIF-1?-VP2 were injected into the mouse hindlimb. Both hrl and fluc expression were monitored using bioluminescence imaging (BLI).Strong correlations existed between the expression of hRL and each of HIF-1?-VP2, VEGF, and PlGF (r(2) > 0.83, r(2) > 0.82, and r(2) > 0.97, respectively). In vivo, both transplanted cells and HIF-1?-VP2 transgene expression were successfully imaged using BLI.An objective evaluation of myoblast-mediated gene transfer in living mice can be performed by monitoring both the survival and the transgene expression of transplanted myoblasts using the techniques developed herein.
View details for DOI 10.1007/s11307-011-0471-9
View details for Web of Science ID 000296794400009
View details for PubMedID 21267661
In Vitro and in Vivo Molecular Imaging of Estrogen Receptor alpha and beta Homo- and Heterodimerization: Exploration of New Modes of Receptor Regulation
2011; 25 (12): 2029-2040
Estrogen receptor (ER) biology reflects the actions of estrogens through the two receptors, ER? and ER?, although little is known regarding the preference for formation of ER homo- vs. heterodimers, and how this is affected by the level of ligand occupancy and preferential ligand affinity for one of the ER subtypes. In this report, we use a split optical reporter-protein complementation system to demonstrate the physical interaction between ER? and ER? in response to different ER ligands in cells and, for the first time, by in vivo imaging in living animals. The genetically encoded reporter vectors constructed with the ligand-binding domains of ER? and ER?, fused to split firefly or Renilla luciferase (Fluc or hRluc) fragments, were used for this study. This molecular proteomic technique was used to detect ER?/ER? or ER?/ER? homodimerization, or ER?/ER? heterodimerization induced by ER subtype-selective and nonselective ligands, and selective ER modulators (SERM), as well as in dimers in which one mutant monomer was unable to bind estradiol. The SERM-bound ER? and ER? form the strongest dimers, and subtype-preferential homodimerization was seen with ER?-selective ligands (methyl piperidino pyrazole/propyl pyrazole triol) and the ER?-selective ligands (diarylpropionitrile/tetrahydrochrysene/genistein). We also demonstrated that a single ligand-bound monomer can form homo- or heterodimers with an apo-monomer. Xenografts of human embryonic kidney 293T cells imaged in living mice by bioluminescence showed real-time ligand induction of ER?/ER? heterodimerization and reversal of dimerization upon ligand withdrawal. The results from this study demonstrate the value of the split luciferase-based complementation system for studying ER-subtype interactions in cells and for evaluating them in living animals by noninvasive imaging. They also probe what combinations of ER? and ER? dimers might be the mediators of the effects of different types of ER ligands given at different doses.
View details for DOI 10.1210/me.2011-1145
View details for Web of Science ID 000298055800005
View details for PubMedID 22052998
Potent, tumor-specific gene expression in an orthotopic hepatoma rat model using a Survivin-targeted, amplifiable adenoviral vector
2011; 18 (6): 606-612
Ideal cancer gene therapies should have high tumor specificity and efficacy, and allow systemic administration to target metastases. We recently developed a bi-directional, two-step transcriptional amplification (TSTA) system driven by the tumor-specific Survivin promoter (pSurv) to amplify the correlated expression of both the reporter gene firefly luciferase (FL) and therapeutic gene tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Here, we compare the specificity and potency of an adenovirus carrying this system (Ad-pSurv-TSTA-TRAIL-FL) to a nonspecific vector (Ad-pCMV-FL) in an orthotopic hepatocellular carcinoma (HCC) rat model after systemic administration. At 24?h after injection of Ad-pCMV-FL, bioluminescence imaging revealed a trend (P=0.30) towards greater FL expression in liver versus tumor. In striking contrast, Ad-pSurv-TSTA-TRAIL-FL showed increased FL activity within the tumor compared with the liver (P<0.01), a strong trend towards reduced liver expression compared with Ad-pCMV-FL (P=0.07), and importantly, similar FL levels within tumor compared with Ad-pCMV-FL (P=0.32). Hence, this vector shows potent, tumor-specific transgene expression even after extensive liver transduction and may be of significant value in avoiding hepatotoxicity in HCC patients. Future studies will explore the benefits of tumor-specific TRAIL expression in this model, the potential to target metastases and the extension of this vector for the treatment of other Survivin-positive tumors is warranted.
View details for DOI 10.1038/gt.2011.5
View details for Web of Science ID 000291438900010
View details for PubMedID 21307888
The Fate and Toxicity of Raman-Active Silica-Gold Nanoparticles in Mice
SCIENCE TRANSLATIONAL MEDICINE
2011; 3 (79)
Raman spectroscopy is an optical imaging method that is based on the Raman effect, the inelastic scattering of a photon when energy is absorbed from light by a surface. Although Raman spectroscopy is widely used for chemical and molecular analysis, its clinical application has been hindered by the inherently weak nature of the Raman effect. Raman-silica-gold-nanoparticles (R-Si-Au-NPs) overcome this limitation by producing larger Raman signals through surface-enhanced Raman scattering. Because we are developing these particles for use as targeted molecular imaging agents, we examined the acute toxicity and biodistribution of core polyethylene glycol (PEG)-ylated R-Si-Au-NPs after different routes of administration in mice. After intravenous administration, PEG-R-Si-Au-NPs were removed from the circulation by macrophages in the liver and spleen (that is, the reticuloendothelial system). At 24 hours, PEG-R-Si-Au-NPs elicited a mild inflammatory response and an increase in oxidative stress in the liver, which subsided by 2 weeks after administration. No evidence of significant toxicity was observed by measuring clinical, histological, biochemical, or cardiovascular parameters for 2 weeks. Because we are designing targeted PEG-R-Si-Au-NPs (for example, PEG-R-Si-Au-NPs labeled with an affibody that binds specifically to the epidermal growth factor receptor) to detect colorectal cancer after administration into the bowel lumen, we tested the toxicity of the core nanoparticle after administration per rectum. We observed no significant bowel or systemic toxicity, and no PEG-R-Si-Au-NPs were detected systemically. Although additional studies are required to investigate the long-term effects of PEG-R-Si-Au-NPs and their toxicity when carrying the targeting moiety, the results presented here support the idea that PEG-R-Si-Au-NPs can be safely used in living subjects, especially when administered rectally.
View details for DOI 10.1126/scitranslmed.3001963
View details for Web of Science ID 000292976700004
View details for PubMedID 21508310
Imaging Cellular Receptors in Breast Cancers: An Overview
CURRENT PHARMACEUTICAL BIOTECHNOLOGY
2011; 12 (4): 508-527
Breast cancer, a leading cause of cancer death in women, is strongly correlated with the up- and down-regulation of hormone and growth factor receptors. Therefore, improving our understanding of such receptor status in different stages of breast cancer will help in the development of novel diagnostic and therapeutic solutions. In particular, molecular imaging technology in association with advanced molecular and cell biology techniques could reveal in detail dynamic molecular events in cells, allowing the study of crucial molecular pathological changes occurring in cancer and other diseases. Molecular imaging techniques such as PET, SPECT, MRI, and the combinatorial techniques have made tremendous strides in elucidating the role of cellular receptors, helping to monitor the course of breast cancer development and the therapeutic efficacy of novel drugs. Optical imaging of cellular receptors is emerging as a powerful tool given the advancement of fluorescent and bioluminescent proteins. Estrogen receptor, progesterone receptor, and HER2/neu have been adopted clinically to detect different types of breast cancer and to test novel treatment strategies; however, other cellular receptors may also be involved in breast cancer subtyping and could emerge as treatment prospects. This review will focus on the recent developments of imaging various cellular receptors pertaining to the growth and development of breast cancer.
View details for Web of Science ID 000289770000006
View details for PubMedID 21342102
Non-Invasive Imaging of Ferucarbotran Labeled INS-1E Cells and Rodent Islets in Vitro and in Transplanted Diabetic Rats
CURRENT PHARMACEUTICAL BIOTECHNOLOGY
2011; 12 (4): 488-496
Transplantation of pancreatic islets is a promising strategy for restoring insulin secretion in diabetes mellitus. To monitor transplanted islets, a method to evaluate the distribution in a non-invasive manner in vivo is needed. INS-1E, a stable differentiated insulin secreting cell line, and rodent islets were used to monitor cell transplantation by MRI. For labeling INS-1E cells in vitro, increasing concentrations of Resovist in culture medium were tested. For MR imaging in a clinical 3T scanner, we placed a layer of labeled INS-1E cells between two layers of 4% gelatin. Viability assay was performed. Cell function was evaluated by static incubation assay to assess insulin secretion. For in vivo imaging, iron labeled rodent islets were transplanted into the liver of streptozotocin induced diabetic rats and visualized by MRI. Blood sugar values were controlled and liver tissue was removed for histological analysis. SPIO labeled INS-1E cells did not show altered viability or reduced glucose stimulated insulin secretion in vitro. Double staining of labeled and unlabeled INS-1E cells showed no difference in the staining pattern. Labeling of rodent islets with SPIOs does not reduce their secretory activity or alter their viability. We visualized SPIO-labeled INS-1E cells and rat islets in vitro using a clinical 3T scanner. Diabetic rats transplanted with SPIO-labeled islets became normoglycemic. MR imaging successfully verified the distribution of labeled transplanted cells in vivo. Labeling INS-1E cells and rat islets with SPIOs does not alter their viability, while enabling MR imaging of labeled cells in vitro and within the living organism.
View details for Web of Science ID 000289770000004
View details for PubMedID 21342106
- Molecular Imaging in Current Pharmaceuticals CURRENT PHARMACEUTICAL BIOTECHNOLOGY 2011; 12 (4): 458-458
Oxidative Stress Mediates the Effects of Raman-Active Gold Nanoparticles in Human Cells
2011; 7 (1): 126-136
Polyethylene glycol (PEG)ylated Raman-active gold nanoparticles (PEG-R-AuNPs) consist of an interchangeable Raman organic molecule layer held onto a gold nanocore by a silica shell. PEG-R-AuNPs have been shown preclinically to increase the sensitivity and specificity of Raman spectroscopy, with picomolar sensitivity and multiplexing capabilities. Although clinical trials are being designed to use functionalized PEG-R-AuNPs in various applications (e.g., to target dysplastic bowel lesions during colonoscopy), the effects of these nanoparticles on human cells remain unknown. The occurrence and mechanisms underlying any potential cytotoxicity induced by these nanoparticles (0-1000 PEG-R-AuNPs/cell) are investigated in immortalized human HeLa and HepG2 cell lines at several time points (0-48 h) after exposure. Using fluorometric assays, cell viability (MTT), reactive oxygen species (ROS) generation (dichlorofluorescein diacetate), protein oxidation (protein carbonyl content), and total cellular antioxidant concentrations the concentrations (metmyoblobin-induced oxidation of ABTS) are assessed. Analysis of lipid oxidation using an enzyme immunoassay (8-isoprostane concentrations), gene expression of antioxidant enzymes using quantitative reverse transcription polymerase chain reactions, and the intracellular location of PEG-R-AuNPs using transmission electron microscopy is also undertaken. PEG-R-AuNPs cause no cytotoxicity in either HeLa or HepG2 cells in the acute setting as ROS generation is balanced by antioxidant enzyme upregulation. Following prolonged exposures (48 h) at relatively high concentrations (1000 PEG-R-AuNPs/cell), nanoparticles are found within vesicles inside cells. Under these conditions, a minimal amount of cytotoxicity is seen in both cell lines owing to increases in cellular oxidative stress, most likely due to ROS overwhelming the antioxidant defenses. Evidence of oxidative stress-induced damage includes increased lipid and protein oxidation. Although further in vivo toxicity studies are necessary, these initial encouraging results show that PEG-R-AuNPs cause minimal toxicity in human cells in the acute setting, which bodes well for potential future applications of these nanoparticles in living subjects.
View details for DOI 10.1002/smll.201001466
View details for Web of Science ID 000285794100015
View details for PubMedID 21104804
Noninvasive molecular imaging of c-Myc activation in living mice
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2010; 107 (36): 15892-15897
The cytoplasmic Myc protein (c-Myc) regulates various human genes and is dysregulated in many human cancers. Phosphorylation mediates the protein activation of c-Myc and is essential for the function of this transcription factor in normal cell behavior and tumor growth. To date, however, the targeting of Myc as a therapeutic approach for cancer treatment has been achieved primarily at the nonprotein level. We have developed a molecular imaging sensor for noninvasive imaging of c-Myc activity in living subjects using a split Firefly luciferase (FL) complementation strategy to detect and quantify the phosphorylation-mediated interaction between glycogen synthase kinase 3beta (GSK3beta) and c-Myc. This sensor system consists of two fusion proteins, GSK 35-433-CFL and NFL-c-Myc, in which specific fragments of GSK3beta and c-Myc are fused with C-terminal and N-terminal fragments of the split FL, respectively. The sensor detects phosphorylation-specific GSK3beta-c-Myc interaction, the imaging signal of which correlates with the steady-state and temporal regulation of c-Myc phosphorylation in cell culture. The sensor also detects inhibition of c-Myc activity via differential pathways, allowing noninvasive monitoring of c-Myc-targeted drug efficacy in intact cells and living mice. Notably, this drug inhibition is detected before changes in tumor size are apparent in mouse xenograft and liver tumor models. This reporter system not only provides an innovative way to investigate the role of functional c-Myc in normal and cancer-related biological processes, but also facilitates c-Myc-targeted drug development by providing a rapid quantitative approach to assessing cancer response to therapy in living subjects.
View details for DOI 10.1073/pnas.1007443107
View details for Web of Science ID 000281637800049
View details for PubMedID 20713710
A molecularly engineered split reporter for imaging protein-protein interactions with positron emission tomography
2010; 16 (8): 921-U123
Improved techniques to noninvasively image protein-protein interactions (PPIs) are essential. We molecularly engineered a positron emission tomography (PET)-based split reporter (herpes simplex virus type 1 thymidine kinase), cleaved between Thr265 and Ala266, and used this in a protein-fragment complementation assay (PCA) to quantify PPIs in mammalian cells and to microPET image them in living mice. An introduced point mutation (V119C) markedly enhanced thymidine kinase complementation in PCAs, on the basis of rapamycin modulation of FKBP12-rapamycin-binding domain (FRB) and FKBP12 (FK506 binding protein), the interaction of hypoxia-inducible factor-1alpha with the von Hippel-Lindau tumor suppressor, and in an estrogen receptor intramolecular protein folding assay. Applications of this unique split thymidine kinase are potentially far reaching, including, for example, considerably more accurate monitoring of immune and stem cell therapies, allowing for fully quantitative and tomographic PET localization of PPIs in preclinical small- and large-animal models of disease.
View details for DOI 10.1038/nm.2185
View details for Web of Science ID 000280649200033
View details for PubMedID 20639890
Indirect imaging of cardiac-specific transgene expression using a bidirectional two-step transcriptional amplification strategy
2010; 17 (7): 827-838
Transcriptional targeting for cardiac gene therapy is limited by the relatively weak activity of most cardiac-specific promoters. We have developed a bidirectional plasmid vector, which uses a two-step transcriptional amplification (TSTA) strategy to enhance the expression of two optical reporter genes, firefly luciferase (fluc) and Renilla luciferase (hrluc), driven by the cardiac troponin T (cTnT) promoter. The vector was characterized in vitro and in living mice using luminometry and bioluminescence imaging to assess its ability to mediate strong, correlated reporter gene expression in a cardiac cell line and the myocardium, while minimizing expression in non-cardiac cell lines and the liver. In vitro, the TSTA system significantly enhanced cTnT-mediated reporter gene expression with moderate preservation of cardiac specificity. After intramyocardial and hydrodynamic tail vein delivery of an hrluc-enhanced variant of the vector, long-term fluc expression was observed in the heart, but not in the liver. In both the cardiac cell line and the myocardium, fluc expression correlated well with hrluc expression. These results show the vector's ability to effectively amplify and couple transgene expression in a cardiac-specific manner. Further replacement of either reporter gene with a therapeutic gene should allow non-invasive imaging of targeted gene therapy in living subjects.
View details for DOI 10.1038/gt.2010.30
View details for Web of Science ID 000279614600002
View details for PubMedID 20237511
Antioxidants Improve Early Survival of Cardiomyoblasts After Transplantation to the Myocardium
MOLECULAR IMAGING AND BIOLOGY
2010; 12 (3): 325-334
We tested the hypothesis that modulation of the microenvironment (using antioxidants) will increase stem cell survival in hypoxia and after transplantation to the myocardium.Rat cardiomyoblasts were stably transfected with a reporter gene (firefly luciferase) for bioluminescence imaging (BLI). First, we examined the role of oxidative stress in cells under hypoxic conditions. Subsequently, stem cells were transplanted to the myocardium of rats using high-resolution ultrasound, and their survival was monitored daily using BLI.Under hypoxia, oxidative stress was increased together with decreased cell survival compared to control cells, both of which were preserved by antioxidants. In living subjects, oxidative stress blockade increased early cell survival after transplantation to the myocardium, compared to untreated cells/animals.Modulation of the local microenvironment (with antioxidants) improves stem cell survival. Increased understanding of the interaction between stem cells and their microenvironment will be critical to advance the field of regenerative medicine.
View details for DOI 10.1007/s11307-009-0274-4
View details for Web of Science ID 000277375300011
View details for PubMedID 20013064
A Novel Estrogen Receptor Intramolecular Folding-based Titratable Transgene Expression System
2009; 17 (10): 1703-1711
The use of regulated gene expression systems is important for successful gene therapy applications. In this study, ligand-induced structural change in the estrogen receptor (ER) was used to develop a novel ER intramolecular folding-based transcriptional activation system. The system was studied using ER-variants of different lengths, flanked on either side by the GAL4-DNA-binding domain and the VP16-transactivation domain (GAL4(DBD)-ER-VP16). The ER ligands of different types showed efficient ligand-regulated transactivation. We also characterized a bidirectional transactivation system based on the ER and demonstrated its utility in titrating both reporter and therapeutic gene expression. The ligand-regulated transactivation system developed by using a mutant form of the ER (G521T, lacking affinity for the endogenous ligand 17beta-estradiol, whereas maintaining affinity for other ligands) showed efficient activation by the ligand raloxifene in living mice without significant interference from the circulating endogenous ligand. The ligand-regulated transactivation system was used to test the therapeutic efficiency of the tumor suppressor protein p53 in HepG2 (p53(+/+)) and SKBr3 (p53(-/-)/mutant-p53(+/+)) cells in culture and tumor xenografts in living mice. The multifunctional capabilities of this system should be useful for gene therapy applications, to study ER biology, to evaluate gene regulation, ER ligand screening, and ER ligand biocharacterization in cells and living animals.
View details for DOI 10.1038/mt.2009.171
View details for Web of Science ID 000270851900008
View details for PubMedID 19654568
Imaging Gene Expression in Human Mesenchymal Stem Cells: From Small to Large Animals
2009; 252 (1): 117-127
To evaluate the feasibility of reporter gene imaging in implanted human mesenchymal stem cells (MSCs) in porcine myocardium by using clinical positron emission tomography (PET)-computed tomography (CT) scanning.Animal protocols were approved by the Institutional Administrative Panel on Laboratory Animal Care. Transduction of human MSCs by using different doses of adenovirus that contained a cytomegalovirus (CMV) promoter driving the mutant herpes simplex virus type 1 thymidine kinase reporter gene (Ad-CMV-HSV1-sr39tk) was characterized in a cell culture. A total of 2.25 x 10(6) transduced (n = 5) and control nontransduced (n = 5) human MSCs were injected into the myocardium of 10 rats, and reporter gene expression in human MSCs was visualized with micro-PET by using the radiotracer 9-(4-[fluorine 18]-fluoro-3-hydroxymethylbutyl)-guanine (FHBG). Different numbers of transduced human MSCs suspended in either phosphate-buffered saline (PBS) (n = 4) or matrigel (n = 5) were injected into the myocardium of nine swine, and gene expression was visualized with a clinical PET-CT. For analysis of cell culture experiments, linear regression analyses combined with a t test were performed. To test differences in radiotracer uptake between injected and remote myocardium in both rats and swine, one-sided paired Wilcoxon tests were performed. In swine experiments, a linear regression of radiotracer uptake ratio on the number of injected transduced human MSCs was performed.In cell culture, there was a viral dose-dependent increase of gene expression and FHBG accumulation in human MSCs. Human MSC viability was 96.7% (multiplicity of infection, 250). Cardiac FHBG uptake in rats was significantly elevated (P < .0001) after human MSC injection (0.0054% injected dose [ID]/g +/- 0.0007 [standard deviation]) compared with that in the remote myocardium (0.0003% ID/g +/- 0.0001). In swine, myocardial radiotracer uptake was not elevated after injection of up to 100 x 10(6) human MSCs (PBS group). In the matrigel group, signal-to-background ratio increased to 1.87 after injection of 100 x 10(6) human MSCs and positively correlated (R(2) = 0.97, P < .001) with the number of administered human MSCs.Reporter gene imaging in human MSCs can be translated to large animals. The study highlights the importance of co-administering a "scaffold" for increasing intramyocardial retention of human MSCs.
View details for DOI 10.1148/radiol.2513081616
View details for Web of Science ID 000268362900015
View details for PubMedID 19366903
Comparison of Optical Bioluminescence Reporter Gene and Superparamagnetic Iron Oxide MR Contrast Agent as Cell Markers for Noninvasive Imaging of Cardiac Cell Transplantation
MOLECULAR IMAGING AND BIOLOGY
2009; 11 (3): 178-187
In this study, we compared firefly luciferase (Fluc) reporter gene and superparamagnetic iron oxide (Feridex) as cell markers for longitudinal monitoring of cardiomyoblast graft survival using optical bioluminescence imaging (BLI) and magnetic resonance imaging (MRI), respectively.Rats (n = 31) underwent an intramyocardial injection of cardiomyoblasts (2 x 10(6)) labeled with Fluc, Feridex, or no marker (control) or an injection of Feridex alone (75 microg). Afterward, rats were serially imaged with BLI or MRI and killed at different time points for histological analysis.BLI revealed a drastically different cell survival kinetics (half-life = 2.65 days over 6 days) than that revealed by MRI (half-life = 16.8 days over 80 days). Injection of Feridex alone led to prolonged tissue retention of Feridex (> or =16 days) and persistent MR signal (> or =42 days).Fluc BLI reporter gene imaging is a more accurate gauge of transplanted cell survival as compared to MRI of Feridex-labeled cells.
View details for DOI 10.1007/s11307-008-0182-z
View details for Web of Science ID 000265686900005
View details for PubMedID 19034584
Molecular Imaging of Phosphorylation Events for Drug Development
MOLECULAR IMAGING AND BIOLOGY
2009; 11 (3): 144-158
Protein phosphorylation mediated by protein kinases controls numerous cellular processes. A genetically encoded, generalizable split firefly luciferase (FL)-assisted complementation system was developed for noninvasive monitoring phosphorylation events and efficacies of kinase inhibitors in cell culture and in small living subjects by optical bioluminescence imaging.An Akt sensor (AST) was constructed to monitor Akt phosphorylation and the effect of different PI-3K and Akt inhibitors. Specificity of AST was determined using a non-phosphorylable mutant sensor containing an alanine substitution (ASA).The PI-3K inhibitor LY294002 and Akt kinase inhibitor perifosine led to temporal- and dose-dependent increases in complemented FL activities in 293T human kidney cancer cells stably expressing AST (293T/AST) but not in 293T/ASA cells. Inhibition of endogenous Akt phosphorylation and kinase activities by perifosine also correlated with increase in complemented FL activities in 293T/AST cells but not in 293T/ASA cells. Treatment of nude mice bearing 293T/AST xenografts with perifosine led to a 2-fold increase in complemented FL activities compared to that of 293T/ASA xenografts. Our system was used to screen a small chemical library for novel modulators of Akt kinase activity.This generalizable approach for noninvasive monitoring of phosphorylation events will accelerate the discovery and validation of novel kinase inhibitors and modulators of phosphorylation events.
View details for DOI 10.1007/s11307-008-0187-7
View details for Web of Science ID 000265686900002
View details for PubMedID 19048345
Uptake kinetics and biodistribution of C-14-D-luciferin-a radiolabeled substrate for the firefly luciferase catalyzed bioluminescence reaction: impact on bioluminescence based reporter gene imaging
EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
2008; 35 (12): 2275-2285
Firefly luciferase catalyzes the oxidative decarboxylation of D: -luciferin to oxyluciferin in the presence of cofactors, producing bioluminescence. This reaction is used in optical bioluminescence-based molecular imaging approaches to detect the expression of the firefly luciferase reporter gene. Biokinetics and distribution of the substrate most likely have a significant impact on levels of light signal and therefore need to be investigated.Benzene ring (14)C(U)-labeled D-luciferin was utilized. Cell uptake and efflux assays, murine biodistribution, autoradiography and CCD-camera based optical bioluminescence imaging were carried out to examine the in vitro and in vivo characteristics of the tracer in cell culture and in living mice respectively.Radiolabeled and unlabeled D-luciferin revealed comparable levels of light emission when incubated with equivalent amounts of the firefly luciferase enzyme. Cell uptake assays in pCMV-luciferase-transfected cells showed slow trapping of the tracer and relatively low uptake values (up to 22.9-fold higher in firefly luciferase gene-transfected vs. nontransfected cells, p = 0.0002). Biodistribution studies in living mice after tail-vein injection of (14)C-D-luciferin demonstrated inhomogeneous tracer distribution with early predominant high radioactivity levels in kidneys (10.6% injected dose [ID]/g) and liver (11.9% ID/g), followed at later time points by the bladder (up to 81.3% ID/g) and small intestine (6.5% ID/g), reflecting the elimination routes of the tracer. Kinetics and uptake levels profoundly differed when using alternate injection routes (intravenous versus intraperitoneal). No clear trapping of (14)C-D-luciferin in firefly luciferase-expressing tissues could be observed in vivo.The data obtained with (14)C-D-luciferin provide insights into the dynamics of D: -luciferin cell uptake, intracellular accumulation, and efflux. Results of the biodistribution and autoradiographic studies should be useful for optimizing and adapting optical imaging protocols to specific experimental settings when utilizing the firefly luciferase and D: -luciferin system.
View details for DOI 10.1007/s00259-008-0870-6
View details for Web of Science ID 000261654000015
View details for PubMedID 18661130
Noninvasive Imaging of Therapeutic Gene Expression Using a Bidirectional Transcriptional Amplification Strategy
2008; 16 (11): 1848-1856
Promoters that limit transgene expression to tumors play a vital role in cancer gene therapy. Although tumor specific, the human Survivin promoter (pSurv) elicits low levels of transcription. A bidirectional two-step transcriptional amplification (TSTA) system was designed to enhance expression of the therapeutic gene (TG) tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL or TR) and the reporter gene firefly luciferase (FL) from pSurv. An adenoviral vector carrying the enhanced targeting apparatus (Ad-pSurv-TR-G8-FL) was tested for efficiency and specificity of gene expression in cells and in living animals. Compared to the one-step systems (Ad-pSurv-FL or Ad-pSurv-TR), the bidirectional TSTA system showed tenfold higher expression of both the therapeutic and the reporter gene and their expression correlated in cells (R(2) = 0.99) and in animals (R(2) = 0.67). Noninvasive quantitative monitoring of magnitude and time variation of TRAIL gene expression was feasible by bioluminescence imaging of the transcriptionally linked FL gene in xenograft tumors following intratumoral adenoviral injection. Moreover, the TSTA adenovirus maintained promoter specificity in nontarget tissues following tail vein administration. These studies demonstrate the potential of the bidirectional TSTA system to achieve high levels of gene expression from a weak promoter, while preserving specificity and the ability to image expression of the TG noninvasively.
View details for DOI 10.1038/mt.2008.180
View details for Web of Science ID 000260472600015
View details for PubMedID 18766175
Dual-targeted contrast agent for US assessment of tumor angiogenesis in vivo
2008; 248 (3): 936-944
To develop and validate a dual-targeted ultrasonographic (US) imaging agent with microbubbles (MBs) that attaches to both vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) and alpha(v)beta(3) integrin and to compare the US imaging signal obtained from dual-targeted MBs (MB(D)) with that from single-targeted MBs (MB(S)) in a murine model of tumor angiogenesis.Animal protocols were approved by the institutional Administrative Panel on Laboratory Animal Care. Single- and dual-targeted US imaging agents were prepared by attaching anti-VEGFR2, anti-alpha(v)beta(3) integrin, or both antibodies to the shell of perfluorocarbon-filled MBs. Binding specificities of targeted MBs compared with isotype-matched immunoglobulin G-labeled control MBs (MB(C)) and nontargeted nonlabeled MBs (MB(N)) were tested with VEGFR2-positive and alpha(v)beta(3) integrin-positive cells (mouse SVR cells) and control cells (mouse 4T1 cells). In vivo imaging signals of contrast material-enhanced US by using anti-VEGFR2-targeted MBs (MB(V)), anti-alpha(v)beta(3) integrin-targeted MBs (MB(I)), MB(D), and MB(C) were quantified in 49 mice bearing SK-OV-3 tumors (human ovarian cancer). Tumor tissue was stained for VEGFR2, alpha(v)beta(3) integrin, and CD31.Attachment of MB(D) to SVR cells (mean, 0.74 MBs per cell +/- 0.05 [standard deviation]) was significantly higher than attachment to 4T1 cells (mean, 0.04 +/- 0.03), and attachment to SVR cells was higher for MB(D) than for MB(V) (mean, 0.58 +/- 0.09), MB(I) (mean, 0.42 +/- 0.21), MB(C) (mean, 0.11 +/- 0.13), and MB(N) (mean, 0.01 +/- 0.01) (P < .05). Imaging signal in the murine tumor angiogenesis model was significantly higher (P < .001) for MB(D) (mean, 16.7 +/- 7.2) than for MB(V) (mean, 11.3 +/- 5.7), MB(I) (mean, 7.8 +/- 5.3), MB(C) (mean, 2.8 +/- 0.9), and MB(N) (mean, 1.1 +/- 0.4). Immunofluorescence confirmed expression of VEGFR2 and alpha(v)beta(3) integrin on tumor vasculature.Dual-targeted contrast-enhanced US directed at both VEGFR2 and alpha(v)beta(3) integrin improves in vivo visualization of tumor angiogenesis in a human ovarian cancer xenograft tumor model in mice.http://radiology.rsnajnls.org/cgi/content/full/248/3/936/DC1.
View details for DOI 10.1148/radiol.2483072231
View details for Web of Science ID 000258541500031
View details for PubMedID 18710985
The death domain-containing kinase RIP1 regulates p27(Kip1) levels through the PI3K-Akt-forkhead pathway
2008; 9 (8): 766-773
Elucidating the cross-talk between inflammatory and cell proliferation pathways might provide important insights into the pathogenesis of inflammation-induced cancer. Here, we show that the receptor-interacting protein 1 (RIP1)-an essential mediator of inflammation-induced nuclear factor-kappaB (NF-kappaB) activation-regulates p27(Kip1) levels and cell-cycle progression. RIP1 regulates p27(Kip1) levels by an NF-kappaB-independent signal that involves activation of the phosphatidylinositol 3-kinase (PI3K)-Akt-forkhead pathway. Mouse embryonic fibroblasts (MEFs) from RIP1-knockout mice express high levels of p27(Kip1). Reconstitution of MEFs with RIP1 downregulates p27(Kip1) levels in a PI3K-dependent manner. RIP1 regulates p27(Kip1) at the messenger RNA level by regulating the p27(Kip1) promoter through the forkhead transcription factors. RIP1 expression blocks accumulation of cells in G(1) in response to serum starvation and favours cell-cycle progression. Finally, we show that overexpression of p27(Kip1) blocks the effects of RIP1 on the cell cycle. Thus, our study provides a new insight into how components of inflammatory and immune signalling pathways regulate cell-cycle progression.
View details for DOI 10.1038/embor.2008.102
View details for Web of Science ID 000258146000015
View details for PubMedID 18566599
A human estrogen receptor (ER)alpha mutation with differential responsiveness to nonsteroidal ligands: Novel approaches for studying mechanism of ER action
2008; 22 (7): 1552-1564
Estrogens, acting through the estrogen receptors (ERs), play crucial roles in regulating the function of reproductive and other systems under physiological and pathological conditions. ER activity in regulating target genes is modulated by the binding of both steroidal and synthetic nonsteroidal ligands, with ligand binding inducing ERs to adopt various conformations that control their interactions with transcriptional coregulators. Previously, we developed an intramolecular folding sensor with a mutant form of ERalpha (ER(G521T)) that proved to be essentially unresponsive to the endogenous ligand 17beta-estradiol, yet responded very well to certain synthetic ligands. In this study, we have characterized this G521T-ER mutation in terms of the potency and efficacy of receptor response toward several steroidal and nonsteroidal ligands in two different ways: directly, by ligand effects on mutant ER conformation (by the split-luciferase complementation system), and indirectly, by ligand effects on mutant ER transactivation. Full-length G521T-ER shows no affinity for estradiol and does not activate an estrogen-responsive reporter gene. The synthetic pyrazole agonist ligand propyl-pyrazole-triol is approximately 100-fold more potent than estradiol in inducing intramolecular folding and reporter gene transactivation with the mutant ER, whereas both ligands have high potency on wild-type ER. This estradiol-unresponsive mutant ER can also specifically highlight the agonistic property of the selective ER modulator, 4-hydroxytamoxifen, by reporter gene transactivation, even in the presence of estradiol, and it can exert a dominant-negative effect on estrogen-stimulated wild-type ER. This system provides a model for ER-mutants that show differential ligand responsiveness to gene activation to gain insight into the phenomenon of hormone resistance observed in endocrine therapies of ER-positive breast cancers.
View details for DOI 10.1210/me.2007-0570
View details for Web of Science ID 000257144500004
View details for PubMedID 18451095
Molecular Imaging of Hypoxia-Inducible Factor 1 alpha and von Hippel-Lindau Interaction in Mice
2008; 7 (3): 139-146
Tumor hypoxia plays a crucial role in tumorigenesis. Under hypoxia, hypoxia-inducible factor 1 alpha (HIF-1 alpha) regulates activation of genes promoting malignant progression. Under normoxia, HIF-1 alpha is hydroxylated on prolines 402 and 564 and is targeted for ubiquitin-mediated degradation by interacting with the von Hippel-Lindau protein complex (pVHL). We have developed a novel method of studying the interaction between HIF-1 alpha and pVHL using the split firefly luciferase complementation-based bioluminescence system in which HIF-1 alpha and pVHL are fused to amino-terminal and carboxy-terminal fragments of the luciferase, respectively. We demonstrate that hydroxylation-dependent interaction between the HIF-1 alpha and pVHL leads to complementation of the two luciferase fragments, resulting in bioluminescence in vitro and in vivo. Complementation-based bioluminescence is diminished when mutant pVHLs with decreased affinity for binding HIF-1 alpha are used. This method represents a new approach for studying interaction of proteins involved in the regulation of protein degradation.
View details for DOI 10.2310/7290.2008.00017
View details for Web of Science ID 000260954700004
View details for PubMedID 19123984
Monitoring of the biological response to murine Hindlimb ischemia with Cu-64-labeled vascular endothelial growth factor-121 positron emission tomography
2008; 117 (7): 915-922
Vascular endothelial growth factor-121 (VEGF121), an angiogenic protein secreted in response to hypoxic stress, binds to VEGF receptors (VEGFRs) overexpressed on vessels of ischemic tissue. The purpose of this study was to evaluate 64Cu-VEGF121 positron emission tomography for noninvasive spatial, temporal, and quantitative monitoring of VEGFR2 expression in a murine model of hindlimb ischemia with and without treadmill exercise training.64Cu-labeled VEGF121 and a VEGF mutant were tested for VEGFR2 binding specificity in cell culture. Mice (n=58) underwent unilateral ligation of the femoral artery, and postoperative tissue ischemia was assessed with laser Doppler imaging. Longitudinal VEGFR2 expression in exercised and nonexercised mice was quantified with 64Cu-VEGF121 positron emission tomography at postoperative day 8, 15, 22, and 29 and correlated with postmortem gamma-counting. Hindlimbs were excised for immunohistochemistry, Western blotting, and microvessel density measurements. Compared with the VEGF mutant, VEGF121 showed specific binding to VEGFR2. Perfusion in ischemic hindlimbs fell to 9% of contralateral hindlimb on postoperative day 1 and recovered to 82% on day 29. 64Cu-VEGF121 uptake in ischemic hindlimbs increased significantly (P < 0.001) from a control level of 0.61+/-0.17% ID/g (percentage of injected dose per gram) to 1.62+/-0.35% ID/g at postoperative day 8, gradually decreased over the following 3 weeks (0.59+/-0.14% ID/g at day 29), and correlated with gamma-counting (R2 = 0.99). Compared with nonexercised mice, 64Cu-VEGF121 uptake was increased significantly (P < or = 0.0001) in exercised mice (at day 15, 22, and 29) and correlated with VEGFR2 levels as obtained by Western blotting (R2 = 0.76). Ischemic hindlimb tissue stained positively for VEGFR2. In exercised mice, microvessel density was increased significantly (P<0.001) compared with nonexercised mice.64Cu-VEGF121 positron emission tomography allows longitudinal spatial and quantitative monitoring of VEGFR2 expression in murine hindlimb ischemia and indirectly visualizes enhanced angiogenesis stimulated by treadmill exercise training.
View details for DOI 10.1161/CIRCULATIONAHA.107.733220
View details for Web of Science ID 000253428100008
View details for PubMedID 18250264
RIP1 links inflammatory and growth factor signaling pathways by regulating expression of the EGFR
CELL DEATH AND DIFFERENTIATION
2008; 15 (2): 344-353
There is considerable interest in understanding how inflammatory responses influence cell proliferation and cancer. In this study, we show that the receptor-interacting protein (RIP1), a critical mediator of inflammation and stress-induced NF-kappaB activation, regulates the expression of the epidermal growth factor receptor (EGFR). Mouse embryo fibroblasts (MEFs) derived from RIP1 knockout mice express very high levels of the EGFR. Reconstitution of RIP1(-/-) MEFs with RIP1 results in a lowering of EGFR levels. RIP1 influences EGFR at the mRNA level by regulating the EGFR promoter. Expression of RIP1 inhibits the EGFR promoter. RIP1 downregulates EGFR expression by interfering with the function of Sp1, which is a key activator of EGFR transcription. RIP1 suppresses Sp1 activity and overexpression of Sp1 reverses RIP1-mediated repression of the EGFR promoter. RIP1 is present both in the cytoplasm and in the nucleus. RIP1 coimmunoprecipitates with Sp1 in vivo and binds directly to Sp1 in vitro. A RIP1 mutant lacking the death domain fails to suppress Sp1 activity and the EGFR promoter, suggesting a critical role for the RIP1 death domain in EGFR regulation. Thus, our study identifies a new link between inflammatory and growth factor signaling pathways mediated by RIP1 and provides insight into the mechanism used by RIP1 to regulate EGFR levels.
View details for DOI 10.1038/sj.cdd.4402268
View details for Web of Science ID 000252387900014
View details for PubMedID 18007664
US imaging of tumor angiogenesis with microbubbles targeted to vascular endothelial growth factor receptor type 2 in mice
2008; 246 (2): 508-518
To prospectively evaluate contrast material-enhanced ultrasonography (US) with microbubbles targeted to vascular endothelial growth factor receptor type 2 (VEGFR2) for imaging tumor angiogenesis in two murine tumor models.Animal protocols were approved by the Institutional Administrative Panel on Laboratory Animal Care. A US contrast agent, consisting of encapsulated gaseous microbubbles, was developed specifically to bind to VEGFR2 (by using anti-VEGFR2 antibodies and biotin-streptavidin interaction) which is up-regulated on endothelial cells of tumor blood vessels. VEGFR2-targeted microbubbles (MB(V)), control microbubbles (MB(C)), and nonlabeled microbubbles (MB(N)) were tested for binding specificity on cells expressing VEGFR2 (mouse angiosarcoma SVR cells) and control cells (mouse skeletal myoblast C2C12 cells). Expression of mouse VEGFR2 in culture cells was tested with immunocytochemical and Western blot analysis. Contrast-enhanced US imaging with MB(V) and MB(C) was performed in 28 tumor-bearing nude mice (mouse angiosarcoma, n = 18; rat malignant glioma, n = 10). Differences were calculated by using analysis of variance.In cell culture, adherence of MB(V) on SVR cells (2.1 microbubbles per SVR cell) was significantly higher than adherence of control microbubbles (0.01-0.10 microbubble per SVR cell; P < .001) and significantly more MB(V) attached to SVR cells than to C2C12 cells (0.15 microbubble per C2C12 cell; P < .001). In vivo, contrast-enhanced US imaging showed significantly higher average video intensity when using MB(V) compared with MB(C) for angiosarcoma and malignant glioma tumors (P < .001). Results of immunohistochemical analysis confirmed VEGFR2 expression on vascular endothelial cells of both tumor types.US imaging with contrast microbubbles targeted to VEGFR2 allows noninvasive visualization of VEGFR2 expression in tumor vessels in mice.
View details for DOI 10.1148/radio1.2462070536
View details for Web of Science ID 000252796300021
View details for PubMedID 18180339
Molecular imaging of the efficacy of heat shock protein 90 inhibitors in living subjects
2008; 68 (1): 216-226
Heat shock protein 90 alpha (Hsp90 alpha)/p23 and Hsp90 beta/p23 interactions are crucial for proper folding of proteins involved in cancer and neurodegenerative diseases. Small molecule Hsp90 inhibitors block Hsp90 alpha/p23 and Hsp90 beta/p23 interactions in part by preventing ATP binding to Hsp90. The importance of isoform-selective Hsp90 alpha/p23 and Hsp90 beta/p23 interactions in determining the sensitivity to Hsp90 was examined using 293T human kidney cancer cells stably expressing split Renilla luciferase (RL) reporters. Interactions between Hsp90 alpha/p23 and Hsp90 beta/p23 in the split RL reporters led to complementation of RL activity, which was determined by bioluminescence imaging of intact cells in cell culture and living mice using a cooled charge-coupled device camera. The three geldanamycin-based and seven purine-scaffold Hsp90 inhibitors led to different levels of inhibition of complemented RL activities (10-70%). However, there was no isoform selectivity to both classes of Hsp90 inhibitors in cell culture conditions. The most potent Hsp90 inhibitor, PU-H71, however, led to a 60% and 30% decrease in RL activity (14 hr) in 293T xenografts expressing Hsp90 alpha/p23 and Hsp90 beta/p23 split reporters respectively, relative to carrier control-treated mice. Molecular imaging of isoform-specific Hsp90 alpha/p23 and Hsp90 beta/p23 interactions and efficacy of different classes of Hsp90 inhibitors in living subjects have been achieved with a novel genetically encoded reporter gene strategy that should help in accelerating development of potent and isoform-selective Hsp90 inhibitors.
View details for DOI 10.1158/0008-5472.CAN-07-2268
View details for Web of Science ID 000252072100029
View details for PubMedID 18172314
Combinatorial library screening for developing an improved split-firefly luciferase fragment-assisted complementation system for studying protein-protein interactions
2007; 79 (6): 2346-2353
Split reporter-based bioluminescence imaging is a useful strategy for studying protein-protein as well as other intracellular interactions. We have used a combinatorial strategy to identify a novel split site for firefly luciferase with improved characteristics over previously published split sites. A combination of fragments with greater absolute signal with near-zero background signals was achieved by screening 115 different combinations. The identified fragments were further characterized by using five different interacting protein partners and an intramolecular folding strategy. Cell culture studies and imaging in living mice was performed to validate the new split sites. In addition, the signal generated by the newly identified combination of fragments (Nfluc 398/ Cfluc 394) was compared with different split luciferase fragments currently in use for studying protein-protein interactions and was shown to be markedly superior with a lower self-complementation signal and equal or higher postinteraction absolute signal. This study also identified many different combinations of nonoverlapping and overlapping firefly luciferase fragments that can be used for studying different cellular events such as subcellular localization of proteins, cell-cell fusion, and evaluating cell delivery vehicles, in addition to protein-protein interactions, both in cells and small living animals.
View details for DOI 10.1021/ac062053q
View details for Web of Science ID 000244867100020
View details for PubMedID 17295448
Reporter gene imaging of protein-protein interactions in living subjects
CURRENT OPINION IN BIOTECHNOLOGY
2007; 18 (1): 31-37
In the past few years there has been a veritable explosion in the field of reporter gene imaging, with the aim of determining the location, duration and extent of gene expression within living subjects. An important application of this approach is the molecular imaging of interacting protein partners, which could pave the way to functional proteomics in living animals and might provide a tool for the whole-body evaluation of new pharmaceuticals targeted to modulate protein-protein interactions. Three general methods are currently available for imaging protein-protein interactions in living subjects using reporter genes: a modified mammalian two-hybrid system, a bioluminescence resonance energy transfer (BRET) system, and split reporter protein complementation and reconstitution strategies. In the future, these innovative approaches are likely to enhance our appreciation of entire biological pathway systems and their pharmacological regulation.
View details for DOI 10.1016/j.copbio.2007.01.007
View details for Web of Science ID 000244593000006
View details for PubMedID 17254764
- Antibacterial activity of subterranean termites used in South Indian folk medicine. Indian Journal of Traditional Knowledge 2007; 6(4) (Oct): 559-562
An intramolecular folding sensor for imaging estrogen receptor-ligand interactions
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2006; 103 (43): 15883-15888
Strategies for high-throughput analysis of interactions between various hormones and drugs with the estrogen receptor (ER) are crucial for accelerating the understanding of ER biology and pharmacology. Through careful analyses of the crystal structures of the human ER (hER) ligand-binding domain (hER-LBD) in complex with different ligands, we hypothesized that the hER-LBD intramolecular folding pattern could be used to distinguish ER agonists from selective ER modulators and pure antiestrogens. We therefore constructed and validated intramolecular folding sensors encoding various hER-LBD fusion proteins that could lead to split Renilla/firefly luciferase reporter complementation in the presence of the appropriate ligands. A mutant hER-LBD with low affinity for circulating estradiol was also identified for imaging in living subjects. Cells stably expressing the intramolecular folding sensors expressing wild-type and mutant hER-LBD were used for imaging ligand-induced intramolecular folding in living mice. This is the first hER-LBD intramolecular folding sensor suited for high-throughput quantitative analysis of interactions between hER with hormones and drugs using cell lysates, intact cells, and molecular imaging of small living subjects. The strategies developed can also be extended to study and image other important protein intramolecular folding systems.
View details for DOI 10.1073/pnas.0607385103
View details for Web of Science ID 000241568500029
View details for PubMedID 17043219
Visualization of telomerase reverse transcriptase (hTERT) promoter activity using a trimodality fusion reporter construct
JOURNAL OF NUCLEAR MEDICINE
2006; 47 (2): 270-277
Our goal was to noninvasively measure chemotherapy-induced changes in the expression of critical tumor growth genes. To achieve this goal, we used radionuclide and optical methods to measure changes in human telomerase reverse transcriptase (hTERT) gene expression in tumor cells before and after 5-fluorouracil treatment.A fusion reporter construct, containing humanized Renilla luciferase (hrl, for bioluminescent imaging), monomeric red fluorescence protein 1 (mrfp1, for fluorescent imaging), and a truncated thymidine kinase (ttk, for imaging of radiolabeled acycloguanosines), was placed under the control of hTERT promoter fragments. These constructs were introduced into tumor cell lines with and without hTERT expression. Transfected cells were treated with 5-fluorouracil, a chemotherapeutic that decreases hTERT gene expression, and treatment-induced changes in hTERT promoter activity were imaged.When the fusion construct is introduced into cell lines that express hTERT, all 3 reporter systems are highly expressed and hTERT promoter activity can be visualized. Cell lines lacking hTERT transcription show no significant reporter expression. Decreases in hTERT gene expression caused by 5-fluorouracil treatment could be visualized in living 293T cells by both fluorescent microscopy and bioluminescent imaging.hTERT promoter activity can be monitored by 1 radionuclide and 2 optical reporter systems using a single reporter construct. This in vitro study provides evidence that our multimodality reporter construct can be used to study the expression of a critical tumor growth gene in living subjects.
View details for Web of Science ID 000235283500027
View details for PubMedID 16455633
- Split luciferase complementation assay for studying interaction of proteins x and y in living mice. CSH Protoc 2006; Nov1(6) (10.1101/): pdb.prot4596
- Effect of the subterranean termite used in the South Indian folk medicine. Indian Journal of Traditional Knowledge 2006; 5(3) (Jul): 376-9
- Split luciferase complementation assay for studying interaction of proteins x and y in cells. CSH Protoc 2006; Nov1;(6) (10.1101/): pdb.prot4596
Effects of epigenetic modulation on reporter gene expression: implications for stem cell imaging.
2006; 20 (1): 106-108
Tracking stem cell localization, survival, differentiation, and proliferation after transplantation in living subjects is essential for understanding stem cell biology and physiology. In this study, we investigated the long-term stability of reporter gene expression in an embryonic rat cardiomyoblast cell line and the role of epigenetic modulation on reversing reporter gene silencing. Cells were stably transfected with plasmids carrying cytomegalovirus promoter driving firefly luciferase reporter gene (CMV-Fluc) and passaged repeatedly for 3-8 months. Within the highest expressor clone, the firefly luciferase activity decreased progressively from passage 1 (843+/-28) to passage 20 (250+/-10) to passage 40 (44+/-3) to passage 60 (3+/-1 RLU/microg; P<0.05 vs. passage 1). Firefly luciferase activity was maximally rescued by treatment with 5-azacytidine (DNA methyltransferase inhibitor) compared with trichostatin A (histone deacetylase inhibitor) and retinoic acid (transcriptional activator; P<0.05). Increasing dosages of 5-azacytidine treatment led to higher levels of firefly luciferase mRNA (RT-PCR) and protein (Western blots) and inversely lower levels of methylation in the CMV promoter (DNA nucleotide sequence). These in vitro results were extended to in vivo bioluminescence imaging (BLI) of cell transplant in living animals. Cells treated with 5-azacytidine were monitored for 2 wk compared with 1 wk for untreated cells (P<0.05). These findings should have important implications for reporter gene-based imaging of stem cell transplantation.
View details for PubMedID 16246867
Split luciferase complementation assay for studying interaction of proteins x and y in cells.
2006; 2006 (6)
This protocol describes a split luciferase complementation assay used to study the interaction of proteins in cells. In the "split protein" strategy, a single reporter protein/enzyme (in this case, firefly luciferase [Fluc]) is cleaved into amino-terminal and carboxy-terminal halves; each half is fused to one of two interacting proteins, X and Y. Physical interactions between the two proteins, X and Y, reconstitute the functional reporter protein, leading to enzymatic activities that can be measured by in vitro or in vivo assays. It is important to perform the assay initially in cell culture before proceeding with animal imaging, not only to conserve animals, but also to establish the sensitivity of the assay.
View details for DOI 10.1101/pdb.prot4596
View details for PubMedID 22485983
Split luciferase complementation assay for studying interaction of proteins x and y in living mice.
2006; 2006 (6)
This protocol describes a split luciferase complementation assay that can be used to repetitively and noninvasively study the interaction of proteins in small living animals. After the expression of the appropriate vectors has been checked in cell culture in vivo, studies can be performed either by implanting transiently transfected cells for short-term analysis (maximum of 7 days), as described below, or with tumor models grown from tumor cells stably expressing the complete reporter system. For optical imaging, the number of cells implanted can be relatively low (~1-5 × 10(6)), and imaging can begin even before the tumors are palpable. When using a regulated reporter gene, it may be necessary to perform a dose-dependent pilot experiment with the inducer or repressor before performing the primary experiments. Animal models other than mice can be used, including rats and, in theory, transgenic animals in which the reporter constructs have been stably integrated into the genome. Animals larger than the rat would be difficult to image due to poor penetration of light. For these larger-animal models, the use of other imaging technologies such as microPET should be considered.
View details for DOI 10.1101/pdb.prot4595
View details for PubMedID 22485982
Novel fusion protein approach for efficient high-throughput screening of small molecule-mediating protein-protein interactions in cells and living animals
2005; 65 (16): 7413-7420
Networks of protein interactions execute many different intracellular pathways. Small molecules either synthesized within the cell or obtained from the external environment mediate many of these protein-protein interactions. The study of these small molecule-mediated protein-protein interactions is important in understanding abnormal signal transduction pathways in a variety of disorders, as well as in optimizing the process of drug development and validation. In this study, we evaluated the rapamycin-mediated interaction of the human proteins FK506-binding protein (FKBP12) rapamycin-binding domain (FRB) and FKBP12 by constructing a fusion of these proteins with a split-Renilla luciferase or a split enhanced green fluorescent protein (split-EGFP) such that complementation of the reporter fragments occurs in the presence of rapamycin. Different linker peptides in the fusion protein were evaluated for the efficient maintenance of complemented reporter activity. This system was studied in both cell culture and xenografts in living animals. We found that peptide linkers with two or four EAAAR repeat showed higher protein-protein interaction-mediated signal with lower background signal compared with having no linker or linkers with amino acid sequences GGGGSGGGGS, ACGSLSCGSF, and ACGSLSCGSFACGSLSCGSF. A 9 +/- 2-fold increase in signal intensity both in cell culture and in living mice was seen compared with a system that expresses both reporter fragments and the interacting proteins separately. In this fusion system, rapamycin induced heterodimerization of the FRB and FKBP12 moieties occurred rapidly even at very lower concentrations (0.00001 nmol/L) of rapamycin. For a similar fusion system employing split-EGFP, flow cytometry analysis showed significant level of rapamycin-induced complementation.
View details for DOI 10.1158/0008-5472.CAN-05-0588
View details for Web of Science ID 000231188600049
View details for PubMedID 16103094
Imaging protein-protein interactions in living subjects
TRAC-TRENDS IN ANALYTICAL CHEMISTRY
2005; 24 (5): 446-458
View details for Web of Science ID 000234203000028
Firefly luciferase enzyme fragment complementation for imaging in cells and living animals
2005; 77 (5): 1295-1302
We identified different fragments of the firefly luciferase gene based on the crystal structure of firefly luciferase. These split reporter genes which encode for protein fragments, unlike the fragments currently used for studying protein-protein interactions, can self-complement and provide luciferase enzyme activity in different cell lines in culture and in living mice. The comparison of the fragment complementation associated recovery of firefly luciferase enzyme activity with intact firefly luciferase was estimated for different fragment combinations and ranged from 0.01 to 4% of the full firefly luciferase activity. Using a cooled optical charge-coupled device camera, the analysis of firefly luciferase fragment complementation in transiently transfected subcutaneous 293T cell implants in living mice showed significant detectable enzyme activity upon injecting d-luciferin, especially from the combinations of fragments identified (Nfluc and Cfluc are the N and C fragments of the firefly luciferase gene, respectively): Nfluc (1-475)/Cfluc (245-550), Nfluc (1-475)/Cfluc (265-550), and Nfluc (1-475)/Cfluc (300-550). The Cfluc (265-550) fragment, upon expression with the nuclear localization signal (NLS) peptide of SV40, shows reduced enzyme activity when the cells are cotransfected with the Nfluc (1-475) fragment expressed without NLS. We also proved in this study that the complementing fragments could be efficiently used for screening macromolecule delivery vehicles by delivering TAT-Cfluc (265-550) to cells stably expressing Nfluc (1-475) and recovering signal. These complementing fragments should be useful for many reporter-based assays including intracellular localization of proteins, studying cellular macromolecule delivery vehicles, studying cell-cell fusions, and also developing intracellular phosphorylation sensors based on fragment complementation.
View details for DOI 10.1021/ac0484777
View details for Web of Science ID 000227409800021
View details for PubMedID 15732910
- Imaging protein-protein interactions in living subjects. TRAC: Trends in Analytical Chemistry 2005; 24(5): 446-458
Novel bidirectional vector strategy for amplification of therapeutic and reporter gene expression
HUMAN GENE THERAPY
2004; 15 (7): 681-690
Molecular imaging methods have previously been employed to image tissue-specific reporter gene expression by a two-step transcriptional amplification (TSTA) strategy. We have now developed a new bidirectional vector system, based on the TSTA strategy, that can simultaneously amplify expression for both a target gene and a reporter gene, using a relatively weak promoter. We used the synthetic Renilla luciferase (hrl) and firefly luciferase (fl) reporter genes to validate the system in cell cultures and in living mice. When mammalian cells were transiently cotransfected with the GAL4-responsive bidirectional reporter vector and various doses of the activator plasmid encoding the GAL4-VP16 fusion protein, pSV40-GAL4-VP16, a high correlation (r(2) = 0.95) was observed between the expression levels of both reporter genes. Good correlations (r(2) = 0.82 and 0.66, respectively) were also observed in vivo when the transiently transfected cells were implanted subcutaneously in mice or when the two plasmids were delivered by hydrodynamic injection and imaged. This work establishes a novel bidirectional vector approach utilizing the TSTA strategy for both target and reporter gene amplification. This validated approach should prove useful for the development of novel gene therapy vectors, as well as for transgenic models, allowing noninvasive imaging for indirect monitoring and amplification of target gene expression.
View details for Web of Science ID 000222786900006
View details for PubMedID 15242528
Molecular imaging of homodimeric protein-protein interactions in living subjects.
2004; 18 (10): 1105-1107
Homodimeric protein interactions are potent regulators of cellular functions, but are particularly challenging to study in vivo. We used a split synthetic renilla luciferase (hRLUC) complementation-based bioluminescence assay to study homodimerization of herpes simplex virus type 1 thymidine kinase (TK) in mammalian cells and in living mice. We quantified and imaged homodimerization of TK chimeras containing N-terminal (N-hRLUC) or C-terminal (C-hRLUC) fragments of hRLUC in the upstream and downstream positions, respectively (tail-to-head homodimer). This was monitored using luminometry (68-fold increase, and was significantly [P<0.01] above background light emission) and by CCD camera imaging of living mice implanted with ex vivo transfected 293T cells (2.7-fold increase, and is significantly [P<0.01] above background light emission). We also made a mutant-TK to generate N-hRLUC mutant TK and mutant TK-C-hRLUC by changing a single amino acid at position 318 from arginine to cysteine, a key site that has previously been reported to be essential for TK homo-dimerization, to support the specificity of the hRLUC complementation signal from TK homodimerization. Ex vivo substrate (8-3H Penciclovir) accumulation assays in 293T cells expressing the TK protein chimeras showed active TK enzyme. We also devised an experimental strategy by constructing variant TK chimeras (possessing extra N-hRLUC or C-hRLUC 'spacers') to monitor incremental lack of association of the tail-to-head TK homodimer. Application of this potentially generalizable assay to screen for molecules that promote or disrupt ubiquitous homodimeric protein-protein interactions could serve not only as an invaluable tool to understand biological networks but could also be applied to drug discovery and validation in living subjects.
View details for PubMedID 15132989
- Molecular imaging of homodimeric protein-protein interactions in living subjects FASEB JOURNAL 2004; 18 (7): 1105-?
MicroPET imaging of Cre-loxP-mediated conditional activation of a herpes simplex virus type 1 thymidine kinase reporter gene
2004; 11 (7): 609-618
Site-specific recombination tools such as the Cre-loxP system are used to create animal models where conditional gene deletion/activation studies are required. In the current proof of principle study, we have demonstrated that a PET reporter gene (PRG), the herpes simplex virus type 1 thymidine kinase (HSV1-tk), can be made to remain silent and can be activated by Cre-loxP-mediated recombination in cell culture and in living mice. An adenovirus carrying a silent HSV1-tk was tail-vein injected (1 x 10(9) PFU) in six transgenic mice that express Cre recombinase in their liver (Cre+) and in four control mice (Cre-). The liver-specific expression of the PRG in Cre+ mice was detected in the microPET following injection of the reporter probe, 9-[4-fluoro-3-(hydroxymethyl)butyl]guanine ([(18)F]-FHBG). The [(18)F]-FHBG accumulation in the liver in terms of percent-injected dose per gram of tissue was 7.72+/-1.13 for the Cre+ mice and 0.10+/-0.02 for the Cre- mice (P<0.05) 48 h after adenoviral injection. These results were further validated by quantitative RT-PCR, western blotting and by in vitro assays for herpes simplex virus type 1 thymidine kinase enzyme activity. Thus by using the Cre-loxP system it is possible to modulate a PRG and noninvasively monitor the extent of Cre-loxP-mediated gene activation by imaging in a microPET scanner.
View details for DOI 10.1038/sj.gt.3302194
View details for Web of Science ID 000220281300006
View details for PubMedID 14724687
Molecular imaging of drug-modulated protein-protein interactions in living subjects
2004; 64 (6): 2113-2119
Networks of protein interactions mediate cellular responses to environmental stimuli and direct the execution of many different cellular functional pathways. Small molecules synthesized within cells or recruited from the external environment mediate many protein interactions. The study of small molecule-mediated interactions of proteins is important to understand abnormal signal transduction pathways in cancer and in drug development and validation. In this study, we used split synthetic renilla luciferase (hRLUC) protein fragment-assisted complementation to evaluate heterodimerization of the human proteins FRB and FKBP12 mediated by the small molecule rapamycin. The concentration of rapamycin required for efficient dimerization and that of its competitive binder ascomycin required for dimerization inhibition were studied in cell lines. The system was dually modulated in cell culture at the transcription level, by controlling nuclear factor kappaB promoter/enhancer elements using tumor necrosis factor alpha, and at the interaction level, by controlling the concentration of the dimerizer rapamycin. The rapamycin-mediated dimerization of FRB and FKBP12 also was studied in living mice by locating, quantifying, and timing the hRLUC complementation-based bioluminescence imaging signal using a cooled charged coupled device camera. This split reporter system can be used to efficiently screen small molecule drugs that modulate protein-protein interactions and also to assess drugs in living animals. Both are essential steps in the preclinical evaluation of candidate pharmaceutical agents targeting protein-protein interactions, including signaling pathways in cancer cells.
View details for Web of Science ID 000220249100033
View details for PubMedID 15026351
- Impact of physico- chemical parameters on the microbial population and its nature in a major retting zone of Kerala, S. India. International Journal of Environmental Studies, UK 2004; 61(5): 595-597
- Traditional therapeutic uses of animals among tribal population of Tamil Nadu. Indian Journal of Traditional Knowledge 2004; 3(2) (Apr): 198-205
Loss of expression, and mutations of Smad 2 and Smad 4 in human cervical cancer
2003; 22 (31): 4889-4897
Mutations in Smads, intermediates of transforming growth factor-beta signaling, are known to contribute to the loss of sensitivity to transforming growth factor-beta, a common feature of many neoplastic cells. However, not much information is available on Smad alterations in cervical cancer and so we probed, for the first time, for alterations in Smad 2 and Smad 4 genes using human cervical cancer cell lines and human cervical tissue samples. Using PCR/reverse transcription-PCR, single-stranded conformation polymorphism analysis and DNA sequencing, we observed a deletion of 'G' in the L3 loop (crucial in Smad-receptor interaction) in C-33A cells, and an insertion of 'A' in codon 122 (loss of MH2 domain) from a cervical tumor sample, both of which caused frame shift and pretermination in Smad 2. In addition, a G/A transition at 31 bp upstream-nontranslated regions of exon 8 of Smad 4 was found in Bu 25TK cells. Smad 2 expression was less in some of the cervical tumor samples than that of nonmalignant samples and six cancer samples showed C-terminal deletions that abolish Smad 2 phosphorylation sites. The loss of expression of Smad 4 found in some cervical tumor samples was due to transcription loss rather than deletion of the gene. Our results highlight an important role for Smad 2 and Smad 4 in human cervical tumors.
View details for DOI 10.1038/sj.onc.1206806
View details for Web of Science ID 000184344600013
View details for PubMedID 12894231
Monitoring protein-protein interactions using split synthetic renilla luciferase protein-fragment-assisted complementation
2003; 75 (7): 1584-1589
In this study we developed an inducible synthetic renilla luciferase protein-fragment-assisted complementation-based bioluminescence assay to quantitatively measure real time protein-protein interactions in mammalian cells. We identified suitable sites to generate fragments of N and C portions of the protein that yield significant recovered activity through complementation. We validate complementation-based activation of split synthetic renilla luciferase protein driven by the interaction of two strongly interacting proteins, MyoD and Id, in five different cell lines utilizing transient transfection studies. The expression level of the system was also modulated by tumor necrosis factor alpha through NFkappaB-promoter/enhancer elements used to drive expression of the N portion of synthetic renilla luciferase reporter gene. This new system should help in studying protein-protein interactions and when used with other split reporters (e.g., split firefly luciferase) should help to monitor different components of an intracellular network.
View details for DOI 10.1021/ac020731c
View details for Web of Science ID 000181993600013
View details for PubMedID 12705589
Noninvasive imaging of protein-protein interactions in living subjects by using reporter protein complementation and reconstitution strategies
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2002; 99 (24): 15608-15613
In this study we have developed bioluminescence-imaging strategies to noninvasively and quantitatively image protein-protein interactions in living mice by using a cooled charge-coupled device camera and split reporter technology. We validate both complementation and intein-mediated reconstitution of split firefly luciferase proteins driven by the interaction of two strongly interacting proteins, MyoD and Id. We use transient transfection of cells and image MyoD-Id interaction after induction of gene expression in cell culture and in cells implanted into living mice. Techniques to study protein-protein interactions in living subjects will allow the study of cellular networks, including signal transduction pathways, as well as development and optimization of pharmaceuticals for modulating protein-protein interactions.
View details for DOI 10.1073/pnas.242594299
View details for Web of Science ID 000179530000065
View details for PubMedID 12438689
Noninvasive quantitative imaging of protein-protein interactions in living subjects
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2002; 99 (5): 3105-3110
We are developing methods to image molecular and cellular events in living subjects. In this study, we validate imaging of protein-protein interactions in living mice by using bioluminescent optical imaging. We use the well studied yeast two-hybrid system adapted for mammalian cells and modify it to be inducible. We employ the NF-kappaB promoter to drive expression of two fusion proteins (VP16-MyoD and GAL4-ID). We modulate the NF-kappaB promoter through tumor necrosis factor alpha. Firefly luciferase reporter gene expression is driven by the interaction of MyoD and ID through a transcriptional activation strategy. We demonstrate the ability to detect this induced protein-protein interaction in cell culture and image this induced interaction in living mice by using transiently transfected cells. The current approach will be a valuable and potentially generalizable tool to noninvasively and quantitatively image protein-protein interactions in living subjects. The approaches validated should have important implications for the study of protein-protein interactions in cells maintained in their natural in vivo environment as well as for the in vivo evaluation of new pharmaceuticals targeted to modulate protein-protein interactions.
View details for DOI 10.1073/pnas.052710999
View details for Web of Science ID 000174284600092
View details for PubMedID 11854471
Simple radioactive assay for the estimation of DNA breaks
JOURNAL OF APPLIED TOXICOLOGY
2002; 22 (1): 19-23
The intactness of DNA is an important part of the normal cellular structure. Any change to the DNA in the form of breaks leads to a change in the integrity, which in turn leads to abnormality in the cellular activity. Many discrepancies have been reported among the various methods of detecting DNA damage. Here, a simple, sensitive and reproducible method has been developed for the detection of DNA breaks by radioactive labelling of 5' broken ends. The method was evaluated by studying chemically induced DNA damage by using both organochloride (2,4-dichlorophenoxyacetic acid and lindane) and organophosphorus (sevin and phosphamidon) compounds at different concentrations. Phosphamidon, one of the organophosphorus compounds studied, showed complete degradation of the DNA after treatment. Radioactive analysis of phosphamidon showed higher counts at the lowest concentration (20 microg) of the chemical when compared with the control (2752 scintillation counts per minute, scm). Studies on the chemically induced DNA breaks by radiolabelling revealed that the cumulative effect of the organophosphorus and organochloride compounds showed maximum counts in all the samples (the highest being 2904 scm) when compared with the organophosphorus and organochloride compounds studied separately (the highest being 1881 and 2260 scm, respectively). Radiolabelling studies on the blood samples of 23 pesticide workers by the newly developed assay showed a significant positive correlation (0.893) between the number of years of exposure and the scintillation counts. A maximum of 11,702 scm (for 18 years of exposure) and a minimum of 1682 scm (for 4 years of exposure) were recorded compared with 1253 scm for the negative control. This method can be used effectively for estimation of the DNA breaks, irrespective of its nature.
View details for DOI 10.1002/jat.807
View details for Web of Science ID 000173603300003
View details for PubMedID 11807925
- Distribution of HCH residues in the Kuttanad wetland ecosystem of Kerala. Inter. J. Ecology and Environmental Science 2001; 7(1): 105-109
- Studies on the water quality of Kuttanad wetland ecosystem of Kerala. Pollution Research 2001; 20(1) (62): 138-148
Duplex RT-PCR for simultaneous detection of hepatitis A and hepatitis E virus isolated from drinking water samples
JOURNAL OF ENVIRONMENTAL MONITORING
2000; 2 (6): 587-590
A duplex reverse transcription polymerase chain reaction (RT-PCR) protocol for simultaneous detection of hepatitis A virus (HAV) and hepatitis E virus (HEV) in water samples has been developed and demonstrated. Both HAV and HEV were concentrated from drinking water samples through a one-step concentration protocol. Different cDNA could be produced in the RT step carried out with a random primer in a single reaction tube. Two different sets of primers specific for HAV-cDNA and HEV-cDNA were used for PCR amplification. Amplified DNA products representing HAV and HEV were identified by gel electrophoresis at 247 and 327 bp (base pair) sequences, respectively. Specific sets of primers amplified a single type of virus and no cross-reactivity of the primers was noticed in duplex RT-PCR. The protocol was used for direct isolation and detection of HAV and HEV from 23 water samples in urban areas of Chennai city. Out of these, nine water samples were positive for HAV, and three for HEV. All three samples positive for HEV were also positive for HAV. The test provides a rapid and economical means of water quality surveillance to specifically detect HAV and HEV.
View details for Web of Science ID 000165993200013
View details for PubMedID 11296746
- Pollution and infectious diseases. Science, India 2000; 3: 39-42
- Drinking water quality status of Kottarakara area, Kollam District, Kerala. Indian J. Environ. & Ecoplanning 2000; 3(1): 143-145
- Spatio temporal distribution and ecology of benthos in the Kuttanad wetland ecosystem. Pollution Research 1999; 18(3): 235-243
- A study on the distribution and ecology of phytoplankton in the Kuttanad wetland ecosystem, Kerala. Pollution Research 1999; 18(3): 261-269
- Distribution of heavy metals in Kuttanad wetland ecosystem of Kerala, India. Inter. J. Ecology and Environmental Science 1999; 25: 91-95
Membrane-impregnated probe for simultaneous PCR amplification and detection
WORLD JOURNAL OF MICROBIOLOGY & BIOTECHNOLOGY
1998; 14 (6): 933-934
View details for Web of Science ID 000078562600024
- Analysis of human immune response to potential hepatitis C viral epitopes. Acta Virologica 1998; 42: 141-145
- Membrane impregnated probe for simultaneous PCR amplification and detection. World Journal of Microbiology and Biotechnology 1998; 14: 933-934
A SIMPLE DEVICE FOR THE CONCENTRATION AND DETECTION OF ENTEROVIRUS, HEPATITIS-E VIRUS AND ROTAVIRUS FROM WATER SAMPLES BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION
JOURNAL OF VIROLOGICAL METHODS
1995; 55 (3): 401-415
A simultaneous concentration of enteroviruses, hepatitis E virus, and rotavirus from drinking water samples through a filtration column filled with granular activated carbon (GAC) was achieved. Urea-arginine phosphate buffer (UAPB) as an eluent at pH 9.0 was used for effective desorption and elution of viruses from GAC. Further concentration of viruses with magnesium chloride enabled nucleic acid extraction, cDNA synthesis, amplification with a specific set of primers for enterovirus, hepatitis E virus and rotavirus. Polymerase chain reaction (PCR) products were then confirmed by Southern transfer and hybridization with the relevant probes. The efficacy of the protocol was established with 100 1 of water samples seeded with poliovirus-1, providing 74% recovery in granular activated carbon based UAPB-RT-PCR. The GAC-based method for concentration of viruses from water samples was preferred, despite its somewhat lower efficacy compared to 80% in membrane filter based UAPB-RT-PCR protocol, due to the specific requirements of short-time and savings in cost of analyses. The protocol was used for the detection of waterborne viruses from 24 drinking water sources in urban areas of New Delhi. Direct isolation of viruses from water samples revealed that the 4 samples were positive for enteroviruses, two for hepatitis E virus, and 10 samples for rotavirus. One sample was positive for both hepatitis E virus and rotavirus, and another for all the 3 types of viruses.
View details for Web of Science ID A1995TH30800012
View details for PubMedID 8609205
- Concentration and detection of rota virus in water samples using polymerase chain reaction during a gasteroenteries epidemic outbreak in Madras city. International Journal of Environmental Studies 1994; 46: 323-327
DETECTION OF HEPATITIS-E VIRUS IN RAW AND TREATED WASTE-WATER WITH THE POLYMERASE CHAIN-REACTION
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
1993; 59 (8): 2558-2562
The main objective of this study was to determine the applicability of the polymerase chain reaction (PCR) to detection of hepatitis E virus (HEV) in sewage treatment plants and establishment of the prevalence of hepatitis viral diseases in a population. Epidemics of HEV infection because of inadequate public sanitation have been reported in several developing countries. A procedure for concentration of HEV in sewage samples through adsorption to membrane filters, elution with urea-arginine phosphate buffer, and subsequent reconcentration with magnesium chloride enabled us to concentrate HEV to volumes in the microliter range. HEV-specific cDNA was prepared by reverse transcription of the total RNA extracted from samples. Specific DNA amplification by PCR in combination with slot blot hybridization was used to demonstrate the presence of HEV in sewage samples from the inlets and outlets of three sewage treatment plants. The assay was specific for HEV, and a 240-bp amplified product was visualized by ethidium bromide fluorescence. Sewage samples adjusted to pH 5.0 for adsorption of viruses to membrane filters were PCR positive, while samples adjusted to pH 3.5 were PCR negative.
View details for Web of Science ID A1993LP83500032
View details for PubMedID 8368844
- Rapid detection of waterborne viruses using the polymerase chain reaction and a gene probe. Intervirology 1991; 34: 184-191
FEASIBILITY OF AN INTRAMOLECULAR COMPLEMENTATION STRATEGY FOR SPLIT-REPORTER GENE IMAGING OF DRUGGABLE PROTEIN MISFOLDING IN BRAIN CANCER
OXFORD UNIV PRESS INC. 2012: 11-11
View details for Web of Science ID 000310971300048
Noninvasive monitoring of ligand-dependent VEGF receptor-2 dimerization with split firefly luciferase
ELSEVIER SCIENCE INC. 2007: S96-S97
View details for Web of Science ID 000249950200173
Molecular imaging of HIF-1 alpha and pVHL interaction in living subjects using firefly luciferase complementation - Improvement over the Renilla luciferase system
ELSEVIER SCIENCE INC. 2006: S48-S49
View details for Web of Science ID 000241221600083
Molecular imaging of HIF-1 alpha and pVHL interaction in vivo: The study of structure/function relationship guiding HIF-1 alpha and pVHL
ELSEVIER SCIENCE INC. 2005: S133-S134
View details for Web of Science ID 000232083300224