Cathepsin-B is a cysteine protease that is abundant in various tumor cells such as colorectal cancer, malignant glioma, breast cancer, prostate cancer, and melanoma.69,70 Their caged MCR showed cathepsin-B selectivity when tested against cathepsin D, E, L, and caspase-3. The gene discussed is CTSB; the disease is malignant glioma.