Most cancer-associated proteases are extracellular enzymes and some of them are also known to be secreted by normal cells.[3b, 4] Lysosomal cysteine proteases (i.e. cysteine cathepsins), however, are localized in the endolysosomal vesicles of healthy cells, and they translocate to the cell surface and/or are secreted into the extracellular tumor milieu during cancer progression. The gene discussed is CTSB; the disease is cancer.