MicroRNA-940 Targets INPP4A or GSK3β and Activates the Wnt/β-Catenin Pathway to Regulate the Malignant Behavior of Bladder Cancer Cells

In this report, we aimed to explore the role and regulatory mechanism of microRNA-940 (miR-940) in bladder cancer development. The expressions of miR-940 in bladder cancer tissues and cells were measured. miR-940 mimics, miR-940 inhibitor small interference RNA against INPP4A (si-INPP4A), and GSK3 beta (si-GSK3 beta) and their corresponding controls were then transfected into cells. We investigated the effects of miR-940, INPP4A, or GSK3 beta on cell proliferation, migration, invasion, and apoptosis. Additionally, target prediction and luciferase reporter assays were performed to investigate the targets of miR-940. The regulatory relationship between miR-940 and the Wnt/beta-catenin pathway was also investigated. miR-940 was upregulated in bladder cancer tissues and cells. Overexpression of miR-940 significantly increased bladder cancer cell proliferation, promoted migration and invasion, and inhibited cell apoptosis. INPP4A and GSK3 beta were the direct targets of miR-940, and knockdown of INPP4A or GSK3 beta significantly increased cancer cell proliferation, migration, and invasion and inhibited cell apoptosis. After miR-940 overexpression, the protein expression levels of c-Myc, cyclin D1, and beta-catenin were significantly increased, and the expression levels of p27 and p-beta-catenin were markedly decreased. The opposite effects were obtained after suppression of miR-940. XAV939, a tankyrase 1 inhibitor that could inhibit Wnt/beta-catenin signaling, significantly reversed the effects of miR-940 overexpression on cell migration and invasion. Our results indicate that overexpression of miR-940 may promote bladder cancer cell proliferation, migration, and invasion and inhibit cell apoptosis via targeting INPP4A or GSK3 beta and activating the Wnt/beta-catenin pathway. Our findings imply the key roles of suppressing miRNA-940 in the therapy of bladder cancer.