MiR-154-5p Inhibits Prostate Cancer Bone Metastasis by Inactivating PI3K/AKT Signaling

Abstract Background: Generally, both strands of a single pre-miRNA have been demonstrated to play a similar role in the same tumor type. However, there are no available literatures yet so far clarifying the opposite roles of both strands froma single miRNAin one tumor type. The purpose of this study is to investigate the functional role of both strands of miR-154 in bone metastasis of prostate cancer (PCa). Methods: miR-154-5p expression was examinedin 285 clinicalPCa tissuesby in situ hybridization. The clinical correlation ofmiR-154-5p expression with clinicopathological features,and overall and bone metastasis-free survival inPCa patients was evaluated by Kaplan-Meier survival and statisticalanalysis. The biological roles of miR-154-3p and miR-154-5p in the bone metastasis of PCa were investigated both in vitroand in vivo.Bioinformatics analysis, western blot and luciferase reporter analysis were used to determinethe potential targets of miR-154-5p.Luciferase assay and Western blotting were performed to clarify the underlying pathway implicated in the role of miR-154-5p in bone metastasis of PCa.Results: Contrary to the well established pro-bone metastatic role of miR-154-3p in PCa, we found that miR-154-5p expression was reduced in PCa tissues with bone metastasis andbone metastatic PCa cell lines. Downexpression of miR-154-5p was positively associated with bone metastasis status, and predicted poorer bone metastasis-free survival in PCa patients. Gain of function experiments showed that upregulating miR-154-5p repressed, while silencing miR-154-5p promoted invasion, migration and proliferation capacities of PCa cells in vitro. Conversely, miR-154-3p yielded an opposite effect oninvasion and migration capacities of PCa cells. Importantly, administration of agomir-154-5p effectivelyinhibited bone metastasis of PCa cellsin vivo. Mechanistic dissection further demonstrated miR-154-5p inhibited invasion, migration and proliferation by targeting EGFR and FGFR1, leading to inactivation of PI3K/AKT signaling. However, the autocrine levels of corresponding ligands in the supernantant of PCa cells were not affected by the changed expression of miR-154-5p.Conclusion: Our results for the first time reveal the different role of both strands froma single miRNA in bone metastasis of PCa, which will facilitate the development of anti-bone metastatic therapeutic strategy in PCa.