This analysis encompassed a total of nine cathepsins include cathepsin B, cathepsin E, cathepsin F, cathepsin G, cathepsin H, cathepsin L2, cathepsin O, cathepsin S, and cathepsin Z, and six digestive system tumors (HCC, PCa, BTC, CRC, GC, and EC). The gene discussed is CTSO; the disease is colorectal carcinoma.