Glutathione S-transferase pi expression in matched human normal and malignant oral mucosa

Over-expression of glutathione S-transferase pi (GST-pi) class isozyme is often associated with malignant transformation and/or drug resistance. To determine whether GST-pi is implicated in betel and tobacco related oral carcinogenesis and/or drug resistance, its expression was studied in oral untreated primary squamous cell carcinomas (SCCs), recurrent tumours and matched normal oral tissues by immunohistochemical and immunoblotting techniques. The GST-pi expression in primary tumours predominantly varied from mild to moderate levels and no significant difference in its expression was observed in the matched normal tissue surrounding these lesions. Mild to moderate levels of GST-pi expression in the oral mucosa of consumers of betel and tobacco observed in the matched normal tissues may support the physiological role of this detoxification enzyme in the metabolism of xenobiotics and elimination of toxic constituents of tobacco. The hallmark of the study is the significant increase in GST-pi expression in recurrent oral SCCs, compared to the matched normal tissues, as well as primary oral tumours, suggesting its potential role as an indicator of prolonged exposure to carcinogens, or prognosis of the disease.