Chemo-resistance remains a considerable obstacle encountered in osteosarcoma (OS) therapy. Evidence has implied that a reduction in the expression of microRNAs (miRs/miRNAs) leads to exacerbated chemo-resistance. Hence, to better understand the role of miR-192 in the pathogenesis of OS during methotrexate (MTX) treatment, we restore miR-192 in the MG-63 cells and investigate the mechanisms, which are associated with MTX-resistance in OS. Exogenetic overexpression of miR-192 was established by transfecting miR-192 mimics into MG-63 cells using Lipofectamine. Trypan blue dye exclusion test was performed to evaluate the proliferation of the MG-63 cells. Chemo-resistance to MTX was determined using the MTT method after 48 h. ELISA cell death assay was performed to evaluate the apoptosis rate. The quantitative RT-PCR (RT-qPCR) was applied to determine the mRNA expression levels before and after the transfection. Our results illustrated that miR-192 is down-regulated in OS tumor cells. Transfection of miR-192 noticeably alleviated the mRNA expression levels of MMP9, c-Myc, K-Ras, CXCR-4, and ADAMTS compared with the control groups (P-values< 0.05). MTX Combination treatment with miR-192 noticeably elevated the cytotoxic effect of MTX and alleviated its IC50 (P < 0.05). Moreover, miR-192 significantly increased the apoptotic effect of MTX. These results implied that miR-192 enhances the sensitivity of MG-63 cells to MTX. Collectively, our results elucidated that miR-192 contributes to chemo-sensitizing MG-63 cells to MTX, and could be considered as a promising agent to overcome MTX-resistance in OS.
