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 resista nce. To determine whether GST-pi is implicated in betel and tobacco re lated oral carcinogenesis and/or drug resistance, its expression was s tudied in oral untreated primary squamous cell carcinomas (SCCs), recu rrent tumours and matched normal oral tissues by immunohistochemical a nd 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 expressi on in the oral mucosa of consumers of betel and tobacco observed in th e matched normal tissues may support the physiological role of this de toxification enzyme in the metabolism of xenobiotics and elimination o f toxic constituents of tobacco. The hallmark of the study is the sign ificant increase in GST-pi expression in recurrent oral SCCs, compared to the matched normal tissues, as well as primary oral tumours, sugge sting its potential role as an indicator of prolonged exposure to carc inogens, or prognosis of the disease. (C) 1997 Elsevier Science Ltd.