Low-expression of miR-7 promotes cell proliferation and exhibits prognostic value in osteosarcoma patients.

AIM: MicroRNAs (miRNAs) play important roles in occurrence and development of osteosarcoma. Previous studies had verified the role of microRNA-7 (miR-7) in various diseases, especially in cancers. Our purpose in this study was to investigate the values of miR-7 in development and prognosis of osteosarcoma. METHODS: QRT-PCR was used to measure the expression of miR-7 in osteosarcoma tissues, adjacent tissues and healthy tissues as well as in osteosarcoma cell lines MG63, U2OS and normal osteoblastic cell line hFOB1.19. CCK-8 and siRNA assays were performed to estimate the effect of miR-7 in the process of cell proliferation. The Kaplan-Meier and Cox regression analysis were performed to detect the prognostic values of the miR-7 in osteosarcoma patients. RESULTS: The results demonstrated that miR-7 expression decreased in osteosarcoma tissues and cell lines compared with the controls. Proliferation assay declared that the cell proliferation was accelerated by down-regulation of miR-7. Kaplan-Meier exhibited that the overall survival time of low-miR-7 expression was shorter than those with high-miR-7 expression (P=0.001). Cox regression analysis revealed that Enneking, distant metastasis and recurrence were all prognostic factors just like low-miR-7. CONCLUSION: The expression of miR-7 was lower in osteosarcoma tissues and cell lines and miR-7 acted as a tumor suppressor. The low-expression of miR-7 was associated with clinicopathologic characteristics (age, tumor site, Enneking, therapies). Moreover, miR-7 might be an independent prognostic marker and promote cell proliferation in osteosarcoma.