MicroRNA-603 functions as an oncogene by suppressing BRCC2 protein translation in osteosarcoma

The present study was conducted to investigate the expression of miR-603 in osteosarcoma cells, and the effect of miR-603 on the biological behavior and expression of breast cancer cell 2 (BRCC2) in osteosarcoma cells. In the present study, qRT-PCR was used to measure the levels of miRNA and mRNA. The results showed that miR-603 was significantly upregulated in human osteosarcoma tissues and cell lines. MTT and colony formation assays were employed to evaluate the role of miR-603 in the regulation of osteosarcoma cell proliferation. The results showed that overexpression of miR-603 promoted the proliferation of MG-63 and U2OS cells. Furthermore, a nude mouse subcutaneous tumor model indicated that miR-603 promoted osteosarcoma growth in vivo. Moreover, miR-603 expression levels were increased in patients with distant metastasis in comparison with levels in patients without distant metastasis. We discovered that BRCC2 may be a target of miR-603. Our results demonstrated that overexpression of miR-603 suppressed BRCC2 protein expression, and an miR-603 inhibitor enhanced BRCC2 protein expression as determined by western blot assay and immunohistochemical analysis. Luciferase reporter assays confirmed that BRCC2 is a direct target of miR-603 in osteosarcoma cells, and the results suggest that miR-603 downregulates BRCC2 expression in osteosarcoma via translational inhibition. Finally, we found that the reduction in BRCC2 expression induced by miR-603 was responsible for the enhanced colony formation and proliferative ability noted in the MG-63 and U2OS cells. In conclusion, miR-603 enhanced osteosarcoma growth by downregulation of BRCC2 expression via translational inhibition.