CTSL and cancer: Cathepsin L (CatL)is a lysosomal cysteine protease belonging to the papain superfamily,which has been related to some cancerous pathologies, such as theprogression of certain tumors1,2 or metastasis by degradingthe extracellular matrix.3,4 CatL has become a promisingtarget in cancer treatment as its expression is exclusively high inmalignant cells, in contrast to that of other cathepsins.5 Inhibition of CatL might delay progression tothe S phase6 or induce senescence7 or apoptosis.