miR-20a-directed regulation of BID is associated with the TRAIL sensitivity in colorectal cancer

MicroRNAs (miRNAs) are small, non-coding RNAs that play important roles in cancer processes. Although miR-20a has been reported to be altered in a range of cancers, the role of miR-20a in colorectal cancer is not fully characterized, and the relationship between miR-20a dysregulation and the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sensitivity is not defined. In the present study, we demonstrated significant upregulation of miR-20a in the serum of colorectal cancer patients, tumor tissues and cell lines by quantitative RT-PCR analysis. Furthermore, we found that the TRAIL-induced apoptosis was associated with the expression level of miR-20a in colorectal cancer. The knockdown of miR-20a by inhibitors increased the antitumor effect of TRAIL via caspase-8 dependent pathway. BID, which is a pro-apoptotic member of the Bcl-2 family, was found to be directly regulated by miR-20a in SW480 cells. The knockdown of miR-20a inhibited the translocation of tBID to the mitochondria, which induced the mitochondrial pathway of apoptosis. Notably, we found that the knockdown of miR-20a also reversed the resistance of TRAIL in established TRAIL-resistant SW480 cells by tBID-mitochondria pathway. Therefore, our results suggest that miR-20a acts as a tumor promoter in colorectal cancer, and the understanding of the miR-20a might be a potential therapeutic target for colorectal cancer.