Description:
<jats:title>Abstract</jats:title>
<jats:p>Gemcitabine (2′, 2′-difluoro 2′-deoxycytidine, dFdC) is a cytotoxic pyrimidine antimetabolite used as first-line chemotherapeutic agent for the treatment of a wide range of solid tumors and hematologic malignancies. It is as a pro-drug that undergoes cellular uptake through transporters like human equilibrative nucleoside transporter (hENT1/SLC29A1) and human concentrative nucleoside transporters (hCNT1/SLC28A1 and hCNT3/SLC28A3) followed by extensive intracellular phosphorylation by kinases like deoxycytidine kinase (DCK) and cytidine monophosphate kinase (CMPK) to its active diphosphorylated (dFdCDP) and triphosphorylated (dFdCTP) forms. Gemcitabine is primarily inactivated via deamination to its less potent metabolite 2′, 2′-difluorodeoxyuridine (dFdU) by cytidine deaminase (CDA). High inter-patient variability in response to gemcitabine treatment has been a major concern in gemcitabine chemotherapy. However, association of pharmacogenomics with gemcitabine pharmacokinetics (PK) has not been extensively studied so far. In the present study, therefore, we investigated association between single nucleotide polymorphisms (SNPs) within genes involved in gemcitabine transport/metabolic pathway and pharmacokinetic parameter estimates for gemcitabine and metabolites in patients diagnosed with solid tumors. Pharmacokinetic blood sampling (n=40) was as follows: pre-infusion, 5, 15, 30, 45 min, and 1, 1.25, 1.5, 2, 6, 24, 48 and 72 hours after the end of gemcitabine infusion. Gemcitabine and dFdU concentrations in plasma and intracellular dFdCTP levels in PBMCs were measured using HPLC-UV and LC MS/MS. A total of 86 SNPs in 14 genes viz. CDA, CMPK, CTPS, DCK, DCTD, NME1, NME2, NME3, NME4, NT5C2, NT5C3, SLC28A1, SLC28A3, and SLC29A1 were genotyped using Sequenom-based assays. Pharmacogenomic association was evaluated using Wilcoxon rank-sum test and Kruskal-Wallis one-way analysis of variance by ranks (p≤0.05). SNPs in 5′ nucleotidase genes- rs1163075, rs1926029, rs11598702 and rs1712517 in NT5C2 and rs3750117 in NT5C3 were associated with gemcitabine elimination clearance. SNPs in CDA- rs1048977 and rs4655226 were associated with dFdU clearance. SNPs in CTPS- rs4430318, rs61780437 and rs1044457 were strongly associated with higher dFdCTP formation clearance. Additionally, CDA, DCTD, SLC28A1, SLC28A3 and SLC29A1 SNPs were also associated with dFdCTP formation clearance. The results from our study indicate pharmacogenomic association between gemcitabine pharmacokinetic pathway SNPs and PK parameters. Presence of these SNPs could impact outcomes for patients receiving gemcitabine therapy.</jats:p>
<jats:p>Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1882. doi:1538-7445.AM2012-1882</jats:p>