Impact of ABCB1 and ABCG2 Transporter in Outcome of Gallbladder Cancer

Abstract

BackgroundGallbladder cancer (GBC) is a biologically aggressive malignancy requiring appropriate biomarkers to improve its outcome. Role of ABC transporters (ABCB1 and ABCG2) has been linked to cancer aggressiveness, tumorigenesis and multidrug resistance. Herein, we studied the prognostic implication of ABCB1 and ABCG2 in GBC. MethodsFresh tissue (tumour & normal) samples collected from 54 patients who underwent R0 resection, were analysed for mRNA and protein expression of ABCB1 and ABCG2 by quantitative Real-Time PCR and western blotting respectively in this prospective study. The molecular findings were correlated with clinical-pathological parameters using χ2 and fisher exact test. The molecular changes in ABCB1 and ABCG2 was analysed for predicting overall survival (OS), disease free survival (DFS) and response to chemotherapy using Kaplan Meier log rank test and Cox regression multivariate analysis. ResultsThe mean age of the cohort was 50 ±13.2 with 26 (48.1%) patients had early stage gallbladder cancer (GBC). Overexpression of ABCB1 and ABCG2 was noted in 32/54(59%) and 40/54 (74%) cases respectively. The protein expression of ABCB1(P-glycoprotein) and ABCG2 (BCRP) was higher in 27/54 (50%) and 37/54 (59%) cases respectively. The mean OS and DFS was 20.7 ±11.5 and 19.3 ± 12.2 months at median follow up 24 months. The TNM stage, lymph node metastasis, and presence of gallstone were significant factors for predicting OS and DFS on multivariate analysis. Both ABCB1 and ABCG2 did not show any significant correlation with OS and DFS with similar incidence of late death and recurrence among over-expression and down-expression. Sub- group comparison suggests that change in expression pattern of ABCB1 and ABCG2 may not affect response to chemotherapy in GBC. ConclusionAltered expression of ABCB1 and ABCG2 may not be a useful prognostic marker for survival or response to chemotherapy in GBC. Presently, histo-pathological characteristics and associated gallstones are the important predictors for survival and recurrence in GBC.