CTSB and breast cancer: Abnormal elevation of CTSB level can be used as a biomarker to anticipate the autophagy in breast cancer cells.31 In addition, SAHA can initiate the apoptosis of breast cancer cells through TRAIL DR5.32 Because apoptosis and autophagy are two closely related biological processes within cells and because there is not much evidence to indicate whether SAHA induces autophagy through TRAIL DR5-CTSB, we used specific siRNA to block the function of TRAIL DR5 and explored the roles of TRAIL DR5 in SAHA-induced autophagy.