MicroRNA-33b Inhibits the Proliferation and Migration of Osteosarcoma Cells via Targeting Hypoxia-Inducible Factor-1α

Recently, microRNA (miR)-33b has been demonstrated to act as a tumor suppressor in osteosarcoma. However, the regulatory mechanism of miR-33b in osteosarcoma cell proliferation and migration remains largely unknown. In this study, real-time PCR showed that miR-33b was significantly downregulated in osteosarcoma tissues compared to their matched adjacent nontumor tissues. Its expression was also decreased in several common osteosarcoma cell lines, including Saos-2, MG63, U2OS, and SW1353, when compared to normal osteoblast cell line hFOB. Overexpression of miR-33b suppressed U2OS cell proliferation and migration. HIF-1 alpha was further identified as a target of miR-33b, and its protein levels were reduced after overexpression of miR33b in U2OS cells. Moreover, overexpression of HIF-1 alpha significantly reversed the suppressive effect of miR33b on U2OS cell proliferation and migration. In addition, HIF-1 alpha was found to be significantly upregulated in osteosarcoma tissues compared to adjacent nontumor tissues, and their expression levels were inversely correlated to the miR-33b levels in osteosarcoma tissues. According to these findings, miR-33b plays a suppressive role in the regulation of osteosarcoma cell proliferation and migration via directly targeting HIF-1 alpha. Therefore, we suggest that the miR-33b/HIF-1 alpha axis may become a promising therapeutic target for osteosarcoma.