The expression of ABC transporter in colorectal cancer : A study about ABCC5 and ABCC11 gene expression in colorectal cancer

Abstract: Introduction. Stage III colorectal cancer is treated with adjuvant chemotherapy based on 5-fluorouracil and leucovorin. Drug resistance to anticancer treatment might be due to adenosine triphosphate binding cassette transporter family members.Aim. The aim of study was to analyze the expression of two ABC transporters, known as ABCC5 and ABCC11, in tumor tissue obtained from stage III colorectal cancer patients and to correlate the results to clinical data including disease-free survival. Patients and Methods. The expression of ABCC5 and ABCC11 was analyzed in 488 patients out of which 225 were treated with 5-fluorouracil in combination with leucovorin whereas 263 did not receive any chemotherapy. Gene expression was determined using real time qPCR and related to clinical variables. Results. ABCC5 expression was associated with age (r =0.34, P =0.0001) and tumor location (P = 0.0001). ABCC5 expression was not associated with disease-free survival in both groups of treated (P=0.22) and untreated patients (P=0.83). ABCC11 was not associated with disease-free survival in the group of treated patients(P=0.35). Low expression of ABCC11 was significantly associated with a longer disease-free survival of untreated patients (P=0.01). Since the P-value was significant, a further analysis called cox regression multivariate analysis was performed in search of an interaction between the expression of ABCC11 and other covariates. Cox regression multivariate analysis showed that the expression of ABCC11 was an independent marker for disease-free survival in untreated patients [HR 0.67 (range 0.49-0.93), P=0.015]. Conclusions. None of the two analyzed genes predicted disease-free survival of patients treated with 5-fluorouracil.