Evaluation of EZH2 SNPs in cholangiocarcinoma patients.

Abstract

10611 Background: Cholangiocarcinoma (CCA) is an aggressive tumor arising from biliary tract epithelium.CCA is the second most common primary hepatic malignancy, with a progressive increasing incidence in western countries. Polycomb group protein Enhancer of Zeste homolog 2 (EZH2) is overexpressed in several human carcinomas, including CCA, where EZH2 overexpression is associated with tumor progression. The aim of this study is to evaluate the correlation between candidate EZH2 Single Nucleotide Polymorphisms (SNPs) with clinical outcome in CCA patients. Methods: Genomic DNA was extracted from blood samples of 75 patients [44 male and 31 female, with average age of 62.3 (range, 26-80 years)] affected by hystologically confirmed advanced CCA, treated with the epirubicin-cisplatin-xeloda (ECX) regimen. We performed an in silico characterization to select EZH2 SNPs (rs2302427 C/G, rs6464926 C/T, rs17171119 T/G and rs887569 C/T) from 26 EZH2 SNPs described previously. Genotyping was performed through Taqman PCR. Prognostic value of selected EZH2 SNPs was assesses by correlation with time to progression (TTP) and overall survival (OS). OS and TTP curves were obtained through Kaplan-Meier method, and comparison with survival distribution was evaluated with logrank test. Results: Through specific software (PROMO 3.0, MicroSNiper and Gene Card) we performed an in silico analysis based on functional characterization criteria (transcription factor binding-TFB, miRNA binding and missense mutations). We selected 4 EZH2 SNP alleles showing specific relevance in CCA because of their differential TFB affinity (PPARα/RXRα, E2F-1, Pax-5 and p53). The rs887569 C/T SNP was significantly associated with clinical outcome. The TT genotype predicted a significantly longer OS in CCA patients (TT vs CT-CC p=0.026). Moreover, the TT genotype showed a trend-like association with reduced risk of death (HR=0.59, 95%CI=0.33-1.05, p=0.075), at multivariate analysis. Conclusions: These results suggest the role of rs887569 EZH2 SNP as a possible predictive marker of OS in advanced CCA patients treated with ECX regimen, and offer a potential new tool for treatment optimization.