[Glutathione-S-transferase expression in oral squamous cell carcinoma]

A large number of oral cancer patients shows poor or partial response to chemotherapy and the mechanisms are poorly understood. Glutathione-S-transferase (GST) is one of the molecules involved in resistance to natural product-based chemotherapeutics. It is an enzyme able to conjugate several substances (metabolites, drugs) to reduct glutathione. Today several isoenzymes of GST are known: GST-alpha, GST-mu, GST-pi, GST-theta. Over-expression of glutathione S-transferase-pi class isozyme is often associated with malignant transformation. Several studies reported that GST-pi staining patterns and their distribution may be helpful in identifying high-risk oral lesions. However, GST is surely involved in resistance to alchilant agents.To verify the possibility of implication of GST in oral cancerogenesis and in natural chemioresistance, the authors examined the protein expression patterns by immunohistochemistry in paraffin-embedded specimens of primary untreated oral cancers (OSCC).GST-a and GST-pi expression in 17 cases of OSCC at different degree of cellular differentiation have been evaluated by immunohistochemistry.The GST-pi expression in primary tumours predominantly varied from mild to moderate levels. The GST-a expression was often quite similar to GST-pi expression with a few exceptions.Expression of GST enzymes is an important signal for multidrug resistance: positive staining for both GST-pi and GST-a could constitute a hallmark of chemoresistant groups of OSSC.