Also, they showed that CRC patients with high levels of CST3 exhibited a significantly higher risk of death25 and that the levels of CTSB and CST3 were significantly higher within the group of metastatic melanoma patients, suggesting that CST3 may be elevated in malignant sera to balance the increased values of CTSB.43 It is likely that the balance of CST3 and CTSB affects CRC tumorigenesis, although various cathepsins and cystatins would be regulated depending on the cellular circumstances. Here, CTSB is linked to metastatic melanoma.