Cathepsins: Novel opportunities for antibody therapeutics in cancer.

Cathepsins, the most abundant lysosomal proteases, have key functions in cell maintenance and homeostasis. They are overexpressed and hypersecreted in cancer and associated with poor prognosis. Secreted cathepsins display pro-tumour activities in the tumour microenvironment and thus represent interesting molecular targets in oncology. Recently, several antibody-based cancer therapies have targeted the pro-tumour activity of the extracellular cathepsin pool, altering several cancer hallmarks, but not the intracellular cathepsin levels that are often crucial for cell homeostasis. In this mini-review, we describe advances in antibodies against extracellular cathepsins in cancer, and their effect on the proteolytic cascade, matrix remodelling, proliferation, and modulation of the anti-cancer immune response. We also discuss the add-on value of combination strategies (anti-cathepsin antibodies with chemotherapy and/or biologics) that make anti-cathepsin antibodies a new opportunity for disease management.