JNK Confers5-fluorouracil Resistance In P53-deficient And Mutant P53-expressing Colon Cancer Cells By Inducing Survival Autophagy

Deficiency or mutation in the p53tumor suppressor gene occurs commonly in human cancer and can contribute to disease progression and chemotherapy resistance. Currently, although the controversy about the pro-survival or anticancer effect of autophagy is still heated, the data in vitro and in vivo seem like to more support the idea that autophagy facilitates the cancer cells’ resistance to chemotherapy treatment. Recent studies imply a role for mitogen-activated protein kinases (MAPKs) in regulating chemoresistance and autophagy.Purpose:Investigate the autophagic expression in p53-deficient HCT116cancer cells (HCT116p53-/-) and p53-mutagenic HT-29cancer cells under the treatment of5-Fluorouracil (5-FU) and analyze the relationship between autophagy and5-FU resistance and the possible molecular mechanism.Methods:Examine the autophagic expression in HCT116p53+/+, RKO, HCT116p53-/-and HT-29cells after5-FU treatment by western blotting. Study cell viability and autophagic expression in HCT116P53-/-and HT-29cells after5-FU treatment by MTT, flow cytometry, western blotting and immunofluorescent. The mechanism of5-FU resistance was clarified by specific pharmacological inhibitionand small interference RNA technology.Results:We reported that5-Fluorouracil (5-FU) treatment caused aberrant autophagosome accumulation in HCT116p53-/-and HT-29cancer cells but not in HCT116p53+/+and RKO cells. Specific inhibition of autophagy can potentiate the re-sensitization of these resistant cancer cells to5-FU and significantly enhance5-FU-induced apoptosis. In further analysis, we show that the c-Jun NH2-terminal kinase (JNK) activation and phosphorylation of Bcl-2are key determinants in5-FU-induced autophagy. Inhibition of JNK by SP600125compound or by siRNA interference-specific knockdown suppressed autophagy and phosphorylation of c-Jun and Bcl-2, but increased5-FU-induced apoptosis in both HCT116p53-/-and HT29cells.Conclusions:Our results suggest that JNK activation confers5-FU resistance in HCT116p53-/-and HT29cells by promoting autophagy as a pro-survival effect likely via inducing Bcl-2phosphorylation, which provides a promising strategy to improve efficacy of5-FU-based chemotherapy for colorectal cancer patients harboring p53gene mutation.