miR-133a enhances the sensitivity of Hep-2 cells and vincristine-resistant Hep-2v cells to cisplatin by downregulating ATP7B expression

The expression levels of the copper transporter P-type adenosine triphosphatase (ATP7B) are known correlate with tumor cell sensitivity to cisplatin. However, the mechanisms underlying cisplatin resistance remained poorly understood. Therefore, in the present study, we treated Hep-2 cells and in-house-developed vincristine-resistant Hep-2v cells with 50, 100, or 200 mu M cisplatin and assessed cell viability after 24 or 48 h. Hep-2v cells were shown to be resistant to 50-200 mu M cisplatin. Furthermore, using immunofluorescence staining and western blot analysis, we noted that ATP7B, but not copper-transporting ATPase 1 (ATP7A), expression was significantly increased in Hep-2v cells, and this increase was maintained at a higher level compared with Hep-2 cells. As ATP7B is a target of microRNA 133a (miR-133a), the ability of miR-133a to influence cisplatin sensitivity in Hep-2v cells was then assessed by CCK-8 assay. We noted that miR-133a expression was lower in both Hep-2 and Hep-2v cells compared with epithelial NP69 cells. Following treatment with 50 mu M cisplatin, in Hep-2v cells expressing exogenous miR-133a we noted reduced ATP7B expression, and these cells had a significantly lower survival rate compared with the control. The present study demonstrates that miR-133a enhances the sensitivity of multidrug-resistant Hep-2v cells to cisplatin by downregulating ATP7B expression.