MicroRNA-145 Suppresses Osteosarcoma Metastasis via Targeting MMP16.

Background: Metastasis is a leading cause of mortality for osteosarcoma (OS) patients, and its molecular pathological mechanisms remain to be elucidated. Previous studies have suggested a significant role of microRNAs (miRNAs) in the control of cancel cell migration and invasion.

Methods: Real-time PCR was used to screen the differentially expressed miRNAs between OS with or without metastasis, and miR-145 underexpression was observed in metastatic OS. Luciferase assay was performed to validate the target gene.

Results: Further, we identified three genes, MMP16, ADAM17 and metadherin, as possible targets of miR-145. We identified MMP16 as a target gene of miR-145 and ruled out ADAM17 and metadherin as targets in OS using a dual luciferase reporter system. Subsequently, we determined and compared the expression level of MMP16 in human OS samples and showed that the mRNA and protein levels of MMP16 were significantly up-regulated in primary OS with metastasis compared with those without metastasis. We also altered miR-145 expression by transfecting OS cells with miR-145 mimics or inhibitors. MMP16 expression was similarly downregulated in the cells transfected with miR-145 mimics or MMP16-specific siRNA, and the invasive and migratory capability of those cells was significantly suppressed compared with negative controls. MMP16 expression was consistently significantly upregulated in the cells transfected with miR-145 inhibitors, and the invasive and migratory capability of those cells was significantly promoted compared with negative controls. Conclcusion: Our results suggest that miR-145 functions as a tumor metastasis suppressor gene by down-regulating MMP16 and may be a potential target in osteosarcoma treatment.