Autophagy inhibition enhances sensitivity of endometrial carcinoma cells to paclitaxel.

Autophagy has been shown to be involved in cancer cell resistance to chemotherapy. Paclitaxel, a widely used chemotherapeutic drug, was demonstrated to induce autophagy in various cancer cells. Therefore, we sought to evaluate the role of autophagy on the paclitaxel-induced cell death in endometrial carcinoma. In this study, we found that paclitaxel induced autophagy in paclitaxel-insensitive HEC-1A and JEC cells, exhibiting an increased microtubule associated protein 1 light chain 3 (LC3)-II/LC3-I ratio, a decrease in p62/SQSTM1 abundance, the upregulation of Beclin 1 expression and punctate dots of yellow fluorescent protein (YFP)-LC3 in the cytosol. Paclitaxel-mediated cell death was further potentiated by pretreatment with autophagy inhibitor chloroquine (CQ) or shRNA against the autophagic gene beclin 1. Moreover, paclitaxel stimulated reactive oxygen species (ROS) generation, and inhibition of the ROS by antioxidant N-acetyl-cysteine (NAC) blocked paclitaxel-induced autophagy, indicating that paclitaxel-induced autophagy in endometrial carcinoma cells is mediated by ROS. These findings suggest that paclitaxel-elicited autophagic response plays a protective role that impedes the eventual death of endometrial carcinoma cell, and that autophagy-inhibitor therapy could be an effective and potent strategy to improve paclitaxel treatment outcomes in the treatment of endometrial carcinoma.