CTSB and neoplasm: In addition to representing renal function, Cys-C is a cysteine protease inhibitor in all human tissues, which may attenuate the immune response to malignant cells.34,62 Furthermore, elevated Cys-C may correlate with inflammatory states in patients with cancer.63,64 Overall, increased serum Cys-C and decreased tumor tissue Cys-C appear to signal advanced stages of disease, although the role of Cys-C in RCC tumorigenesis and prognosis in this study is likely limited by sample size and warrants further study.