Targeting cathepsin S induces tumor cell autophagy via the EGFR–ERK signaling pathway

Cathepsin S is a cellular cysteine protease, which is frequently over-expressed in human cancer cells and plays important role in tumor metastasis. However, the role of cathepsin S in regulating cancer cell survival and death remains undefined. The aim of this study was to determine whether targeting cathepsin S could induce autophagy/apoptosis in cancer cells. In this study, we demonstrated that targeting cathepsin S by either specific small molecular inhibitors or cathepsin S siRNA induced autophagy and subsequent apoptosis in human cancer cells, and the induction of autophagy was dependent on the phosphorylation of EGFR and activation of the EGFR-related ERK/MAPK-signaling pathway. In conclusion, the current study reveals that cathepsin S plays an important role in the regulation of cell autophagy through interference with the EGFR–ERK/MAPK-signaling pathway.