miR-1307-5p suppresses proliferation and tumorigenesis of bladder cancer via targeting MDM4 and the Hippo signaling pathway.

Background: Emerging evidence has shown that miR-1307-5p is involved in tumorigenesis of various types of cancer. This study aims to assess the role and mechanism of miR-1307-5p in bladder cancer.

Methods: Bioinformatics analyses were carried out with clinical datasets in the public domains. To investigate the cellular functions of miR-1307-5p, assays of cell proliferation, cell cycle and cell apoptosis were conducted in bladder cancer cell lines and xenografts. The molecular mechanisms of miR-1307-5p were studied using luciferase reporter, RT-qPCR, and western blotting analyses.

Results: We found that miR-1307-5p expression was significantly decreased in bladder cancer tissues, and its lower level was associated with poor prognosis. Cellular assays indicated the tumor-suppressor roles of miR-1307-5p were linked to cell proliferation, cell cycle inhibition, and cell apoptosis promotion. Conversely, anti-miR-1307-5p facilitated cell proliferation and cell cycle and antagonized cell apoptosis. In the in vivo setting, tumor growth was suppressed by miR-1307-5p overexpression. We found by bioinformatic and luciferase reporter assays that miR-1307-5p targets the 3'-UTR of MDM4, a well-known Inhibitor of TP53-mediated transactivation, cell cycle arrest and apoptosis. Specifically, miR-1307-5p markedly reduced MDM4 proteins expression, decreased the expression of Ki-67 and PCNA, and increased the expression of cleaved-caspase 3 and caspase 9. While in parallel assays, anti-miR-1307-5p had opposite effects. In addition, we found that miR-1307-5p overexpression would suppress bladder cancer cell growth by inhibiting MDM4 and its downstream Hippo pathway.

Conclusion: In bladder cancer, miR-1307-5p functions as a tumor suppressor and has the potentials as biomarker and therapeutical agent.