Cathepsin O (CTSO)

Cathepsin O (CTSO) is a cysteine protease encoded by the CTSO gene, classified in the papain-like cathepsin family of enzymes. It is primarily involved in cellular protein degradation and turnover, influencing cell regulation and homeostasis. CTSO plays critical roles in cancer biology, notably by reducing protein levels of key regulatory proteins such as BRCA1 and ZNF423, thereby affecting tamoxifen response and serving as a prognostic marker in hormone receptor–positive breast cancer. Additionally, rare genetic variants in CTSO are linked to congenital developmental syndromes, and its expression is implicated in immune response and cellular defense. Pharmacologically, broad-spectrum cysteine protease inhibitors abolish CTSO activity, but no approved drugs selectively target CTSO. Potential therapeutic targeting is challenged by its fundamental role in normal cell processes and the risk of disrupting cellular homeostasis

Other names

Cathepsin OCTSOCTSO1CATO_HUMAN

Inhibition of cysteine protease activity. Reduction of protein degradation or turnover. Indirect modulation of signaling pathways critical to tumor progression.