Abstract: Objective To assess the effects of down-regulating a human translesion DNA synthesis (TLS) gene REV3L on sensitizing drug-resistant tumor cells for chemotherapy. Methods The study experimentally suppressed the REV3L expression in human Oxaliplatin resistant colon cancer cells (THC8307/L-OHP) by the interference RNA technology (RNAi).Real-time qPCR and Immunocytochemistry can be used for judging the transfection efficiency by RNAi. The level of drug sensitivity was measured by MTT（Thiazolyl blue tetrazolium bromide ). The resistance index (RI) and relative reversion of drug resistance are calculated by statistical methods. The cell apoptosis of was determined by flow cytometry and cytomorphology. Results THC8370/L-OHP cells transfected with mU6pro-siREV3 significantly reduced the cellular REV3L mRNA and protein levels (P<0.05), as judged by qRT-PCR and immunocytochemistry respectively. The IC50 (Inhibitory Concentration 50) by Oxaliplatin and the RI were markedly decreased (P<0.05). Depletion of cellular REV3L also enhanced apoptosis (P<0.05). Conclusions Depletion of REV3L from Oxaliplatin-resistant human colon cancer cells enhances the drug-sensitivity and induces apoptosis. Hence, REV3L is a potential target for tumor gene therapy.

Key words: Key words: REV3L, RNA interference, human colon cancer cell, drug resistance, apoptosis.