miR-188-5p inhibits tumour growth and metastasis in prostate cancer by repressing LAPTM4B expression

Abstract

Elucidation of the molecular targets and pathways regulated by the tumoursuppressive miRNAs can shed light on the oncogenic and metastatic processes in prostate cancer (PCa). Using miRNA profiling analysis, we find that miR-188-5p was significantly down-regulated in metastatic PCa. Down-regulation of miR-188-5p is an independent prognostic factor for poor overall and biochemical recurrencefree survival. Restoration of miR-188-5p in PCa cells (PC-3 and LNCaP) significantly suppresses proliferation, migration and invasion in vitro and inhibits tumour growth and metastasis in vivo. We also find overexpression of miR-188-5p in PC-3 cells can significantly enhance the cells' chemosensitivity to adriamycin. LAPTM4B is subsequently identified as a direct target of miR-188-5p in PCa, and is found to be significantly over-expressed in PCa. Knockdown of LAPTM4B phenotypically copies miR-188-5p-induced phenotypes, whereas ectopic expression of LAPTM4B reverses the effects of miR-188-5p. We also find that restoration of miR-188-5p can inhibit the PI3K/AKT signaling pathway via the suppression of LAPTM4B. Taken together, this is the first report unveils that miR-188-5p acts as a tumour suppressor in PCa and may therefore serve as a useful therapeutic target for the development of new anticancer therapy.