GLUTATHIONE-S-TRANSFERASE EXPRESSION IN MALIGNANT MESOTHELIOMA AND NONNEOPLASTIC MESOTHELIUM - AN IMMUNOHISTOCHEMICAL STUDY

Expression of the glutathione S-transferase (GST) subclasses alpha, mu and pi was investigated immunohistochemically in 20 normal or hyperpl astic mesothelium and in 57 malignant mesothelioma cases. These result s were correlated with survival and also with P-170 glycoprotein expre ssion. Nearly all the nonneoplastic mesothelium cases were positive fo r GST alpha and pi. About half of the non-neoplastic cases were positi ve for mu. Twenty-nine (51%) malignant mesotheliomas were positive for at least one of the GST species; 21 (37%) showed immunoreactivity for alpha, 18 (31.5%) for mu and 21 (37%) for pi. A total of 54 mesotheli oma cases displayed immunoreactivity for the P-170 glycoprotein. For G ST pi and GST mu, a statistical significance between expression and in creased survival was found (respectively P = 0.012 and 0.024) while fo r GST alpha no significance was found. The results of this study demon strate that expression of GST pi correlates positively with increased survival in malignant mesothelioma. It is also concluded that, in meso thelioma, GST and P-170 glycoprotein may contribute to the resistance to cytotoxic drugs frequently observed in these tumours. No correlatio n between GST and P-170 expression was demonstrated.