Cat B is a lysosomal cysteine protease whose upregulated activity is associated with the progression of breast cancer, ovarian, colorectal, lung, pancreatic adenocarcinoma and others [30,31,32] Cat B secreted by exocytosis may facilitate cancer progression and metastasis development by degradation of the extracellular matrix (ECM) and by activation, processing and degradation of growth factors, cytokines and chemokines. The gene discussed is CTSB; the disease is cancer.