CTSB and neoplasm: In terms of pharmacology, arsenic is most commonly used for anti-tumor functions because it can inhibit the growth of solid tumor cells, promote cell apoptosis, resist tumor angiogenesis, promote partial differentiation, degrade certain specific fusion proteins, downregulate the expression of the Bcl-2 protein, downregulate mitochondrial transmembrane potential ∆Ψm, and activate cysteine protease caspases.