CTSB and cancer: CSTB, also known as stefin B, belongs to the cystatins superfamily which has primarily been explored with respect to its capacity to inhibit intracellular cysteine proteases leaking from lysosomes (10) and has been implicated in several types of cancers, such as breast, lung and colorectal cancers, glioblastoma, squamous cell carcinoma of the head and neck, laryngeal, esophageal and hepatocellular carcinomas, and prostatic adenocarcinoma (11–20).