Down‐regulated RBM5 inhibits bladder cancer cell apoptosis by initiating an miR‐432‐5p/β‐catenin feedback loop

RNA-binding motif protein 5 (RBM5) acts as a tumor suppressor in various human cancers and presents with several important characteristics, such as the potentiation of apoptosis, inhibition of the cell cycle, and alternative splicing of Fas and caspase-2 precursor mRNA. However, its role in bladder urothelial carcinoma (BUC) remains unknown. In this study, we found that RBM5 expression was significantly down-regulated in BUC tissues when compared with the adjacent nontumor tissues. The down-regulation of RBM5 activates ²-catenin, which binds to the T-cell factor/lymphocyte enhancer factor element of the miR-432-5p promoter and elevates the expression of miR-432-5p in bladder cancer cells. The up-regulated miR-432-5p directly targets 3′-UTR and depresses RBM5 expression. Thus, RBM5–miR-432-5p–²-catenin forms a feedback loop in regulating bladder cancer cell apoptosis. Our findings provide evidence that the regulatory feedback loop among RBM5, miR-432-5p, and Wnt–²-catenin is responsible for the progress of bladder cancer cells.—Zhang, Y.-P., Liu, K.-L., Wang, Y.-X., Yang, Z., Han, Z.-W., Lu, B.-S., Qi, J.-C, Yin, Y.-W., Teng, Z.-H., Chang, X.-L., Li, J.-D., Xin, H., Li, W. Down-regulated RBM5 inhibits bladder cancer cell apoptosis by initiating an miR-432-5p/²-catenin feedback loop. FASEB J. 33, 10973–10985 (2019). www.fasebj.org