Cathepsins and cystatins in extracellular fluids - useful biological markers in cancer

Proteases of all four classes have been shown to participate in processes of tumor growth, vascularisation, invasion and metastasis. Their levels in tumor tissue extracts can provide useful clinical information to predict disease free and overall survival in various types of cancer. Recently we found that cysteine proteinases cathepsins B and H and their endogenous protein inhibitors stefins A, B and cystatin C can also predict prognosis when measured extracellularly. In melanoma and colorectal cancer patients high serum levels of cathepsins as well as high levels of stefins A and B and cystatin C correlated with shorter survival. On the other hand, cathepsin B/cystatin C complex was found to be less abundant in sera of patients with malignant tumors than in those with benign diseases or in healthy controls.