The proposal seeks the opportunity for the Principal Investigator (PI) to gain knowledge and skills in molecular biology and clinical pharmacology under the direct supervision of two highly qualified sponsors to enhance his potential to develop into a successful independent investigator. The scope of this proposal will incorporate the necessary coursework, seminars, and hands-on experience in new techniques to enable the PI to complete an intensive research proposal over the full five years of the proposal. The overall scientific goal of this proposal is to establish the associations between functional polymorphisms in MRP2, BSEP, and BCRP drug efflux transporters and modulation of chemotherapeutic disposition. Because transporter proteins are critical determinants of the drug disposition process, functional studies in model cell systems will be utilized to evaluate transport activity and perform pharmacokinetic analyses. The hypothesis that transporter variants have significant functional consequences to protein activity and important implications for chemotherapy disposition and toxicity will be evaluated by 2 specific aims: First, MRP2, BCRP, and BSEP variants will be functionally characterized utilizing in vitro recombinant vaccinia-mediated transfection assays in HeLa cells and immunoblot and confocal immunofluoresecent analyses to evaluate total and cell surface protein expression. Second, functionally relevant variants identified in specific aim 1 will be studied in model cell systems utilizing precise functional assays, including inducible gene expression polarized stable cell lines and inside-out membrane vesicles, to provide a comprehensive evaluation of altered mechanisms of function, kinetic analysis, substrate specificity, and chemotherapy-mediated inhibition. Interindividual variation in drug disposition and response is a major concern for commonly prescribed drugs, but has particular relevance with regards to chemotherapeutic agents because efficacy is limited by narrow therapeutic indices. Significant interpatient differences are common with many chemotherapy regimens and it is apparent that genetic factors play vital roles in determining an individual's response to drug therapy. Defining drug transporter genotypes associated with altered disposition of anticancer agents may have significant therapeutic consequences for the use of chemotherapeutic agents in oncology patients by optimizing therapeutic indices and reducing mortality and morbidity associated with adverse effects.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Clinical Investigator Award (CIA) (K08)
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Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
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Okita, Richard T
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Vanderbilt University Medical Center
Schools of Medicine
United States
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DeGorter, Marianne K; Ho, Richard H; Leake, Brenda F et al. (2012) Interaction of three regiospecific amino acid residues is required for OATP1B1 gain of OATP1B3 substrate specificity. Mol Pharm 9:986-95
Ho, Richard H; Leake, Brenda F; Urquhart, Brad L et al. (2011) Functional characterization of genetic variants in the apical sodium-dependent bile acid transporter (ASBT; SLC10A2). J Gastroenterol Hepatol 26:1740-8
Schwarz, Ute I; Meyer zu Schwabedissen, Henriette E; Tirona, Rommel G et al. (2011) Identification of novel functional organic anion-transporting polypeptide 1B3 polymorphisms and assessment of substrate specificity. Pharmacogenet Genomics 21:103-14
Ho, Richard H; Leake, Brenda F; Kilkenny, Dawn M et al. (2010) Polymorphic variants in the human bile salt export pump (BSEP; ABCB11): functional characterization and interindividual variability. Pharmacogenet Genomics 20:45-57