Downregulation of miR-505-3p predicts poor bone metastasis-free survival in prostate cancer

The principal issue deriving from prostate cancer (PCa) is its propensity to metastasize to bone. To date, bone metastasis remains incurable, and therapeutic strategies are limited. Therefore, it is of paramount importance to explore predictive markers for bone metastasis of PCa. In the present study, we reported that miR-505-3p was significantly downregulated in bone metastatic PCa tissues compared with that in non-bone metastatic PCa tissues, but there was no significant difference in miR-505-3p expression between PCa and adjacent normal tissues. miR-505-3p expression was inversely associated with serum PSA levels, Gleason grade, N and M classification, and short bone metastasis-free survival in PCa patients, but had no effect on overall survival in PCa patients. Furthermore, upregulation of miR-505-3p suppressed the activity of TGF-β signaling by directly targeting downstream effectors of TGF-β signaling, SMAD2 and SMAD3, further inhibiting the invasion and migration abilities of PCa cells. Therefore, our findings unraveled a novel mechanism by which miR-505-3p inhibits bone metastasis of PCa, supporting the notion that miR-505-3p may serve as a predictive marker for bone metastasis of PCa.