Overcoming cisplatin resistance in osteosarcoma through the miR-199a-modulated inhibition of HIF-1α.

Dysregulation of miRNAs has been shown to contribute to multiple tumorigenic processes, as well as to correlate with tumour progression and prognosis. miR-199a has been shown to be dysregulated in multiple tumour types. However, the association between miR-199a and the chemoresistance features of osteosarcoma are not well understood, the target genes for miR-199a and the regulatory mechanisms are also unknown. In the present study, we demonstrated that miR-199a is expressed at low levels in osteosarcoma cells and patient samples. By the selection and establishment of cisplatin resistant osteosarcoma cell line, we observed a correlation between miR-199a and cisplatin resistance in osteosarcoma cells: resistant cells exhibit attenuated miR-199a expressions and exogenous overexpression of miR-199a sensitizes osteosarcoma cells to cisplatin. Moreover, we identified HIF-1α as a direct target for miR-199a. Intriguingly, cisplatin resistant osteosarcoma cells display significantly elevated HIF-1α expression under hypoxia. We report here overexpression of miR-199a resensitizes cisplatin resistant cells to cisplatin through inhibition of HIF-1α in vitro and in vivo. Finally, by analysing the clinical osteosarcoma patient samples, we demonstrate a reverse correlation between miR-199a and HIF-1α mRNAs. Our study will provide mechanisms for the miRNA-mediated anticancer therapy and miR-199a may be considered a promising therapeutic agent for osteosarcoma patients who fail to respond to conventional chemotherapy.