They play a fundamental role in maintainingtissue homeostasis and are involved in the immune response, as wellas cell development, differentiation, and apoptosis.237 Alteration in expression levels of these enzymes is correlatedwith several pathological disorders, including cancer, and poor prognoses.238,239 Cathepsin B is especially important in terms of promoting proteolysisin the extracellular matrix (ECM), thereby promoting tumor angiogenesis,invasion, and metastasis.240 Special effortshave therefore been made to develop cathepsin B-responsive diagnosticand therapeutic platforms. The gene discussed is CTSB; the disease is cancer.