Background. Cancer of the head and neck represents a diverse group of malignant diseases; so far, no factor in a wide spectrum of biochemical and histological candidate-markers has yet been identified to predict reliably the natural course of the disease or its response to the therapy to be used in routine clinical practice. Among the factors that promote tumor growth and invasion, several protease systems, implemented in proteolytic degradation of extracellular matrix components, were studied, including papain-like lysosomal cysteine proteases (e.g. cathepsins B and L) and their physiological inhibitors cystatins (e.g. stefins A and B, cystatin C). The aim of the present report is to review the published studies on clinical applicability of cysteine cathepsins and their endogenous inhibitors stefins in squamous cell carcinoma of the head and neck and to present recent research results from this area conducted jointly by the Institute of Oncology Ljubljana and ENT Department of the University Medical Center Ljubljana, Slovenia.
Conclusions. According to our experience, immunohistochemical staining of cysteine cathepsins and stefins seems to be of limited value for predicting either treatment response or patients' survival. However, the results of studies on stefin A in tumor tissue cytosols should be considered hypothesis-generating and deserves further evaluation in the frame of prospective controlled multicentric clinical study.
