MicroRNA-218 increases cellular sensitivity to Rapamycin via targeting Rictor in cervical cancer

We previously reported that microRNA-218 was frequently lost in cervical cancer and restoration of microRNA-218 increased cellular radio-sensitivity via inhibiting. Herein, we aim to investigate the effects of microRNA-218 on cellular response to mTOR inhibition. The expression of microRNA-218 and Rictor were measured by Taqman PCR and real time PCR in a panel of 15 cervical cancer tissues. MicroRNA-218 was stably overexpressed in four cervical cancer cell lines and a series of in vitro and in vivo experiments were performed to investigate cellular sensitivity to Rapamycin. In primary cultured cervical cancer cells, the expression of microRNA-218 was negatively correlated with the mRNA level of Rictor, which predicted cellular sensitivity to Rapamycin (p = 0.002, R(2)  = 0.6810). In vitro, overexpression of microRNA-218 significantly reduced the level of Rictor and enhanced the growth-inhibition, cell cycle arrest, and apoptosis induced by Rapamycin. In vivo, overexpression of microRNA-218 further enhanced the suppressive effects of Rapamycin on tumor growth. In conclusion, we demonstrated that microRNA-218 could re-sensitize cervical cancer to Rapamycin through targeting Rictor. Moreover, patients with loss of microRNA-218 presented notable resistance to Rapamycin, indicating that microRNA-218 might be a valid marker for patients-stratification in future clinical trials.