Tea Polyphenol inhibits autophagy to sensitize Epirubicin-induced apoptosis in human bladder cancer cells.

Resistance to anticancer agents such as Epirubicin (EPI) becomes a great challenge for treating bladder cancer. However, the mechanism by which chemoresistance arised is still elusive. In the present study, we showed evidence that EPI induced cytoprotective autophagy in bladder cancer cell lines T24 and BIU87. In addition, EPI robustly activated JNK-mediated phosphorylation of Bcl-2 and disruption of Bcl-2/Beclin-1 complex. Furthermore, the green tea derivative tea polyphenol (TP) inhibited EPI-induced autophagy and promoted apoptosis induced by EPI in bladder cancer cells. These results revealed a pathway for EPI-induced autophagy that involved in JNK/Bcl-2/Beclin-1 in bladder cancer cells, and that TP synergistically promoted EPI-induced apoptosis at least partly through autophagy inhibition. Thus, TP could be utilized in combination with EPI to improve EPI-based bladder cancer therapy.