GlutathioneS-transferase expression in malignant mesothelioma and non-neoplastic mesothelium: an immunohistochemical study

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Abstract
Expression of the glutathioneS-transferase (GST) subclasses α, μ and π was investigated immunohistochemically in 20 normal or hyperplastic mesothelium and in 57 malignant mesothelioma cases. These results were correlated with survival and also with P-170 glycoprotein expression. Nearly all the non-neoplastic mesothelium cases were positive for GSTα and π. About half of the non-neoplastic cases were positive for μ. Twenty-nine (51%) malignant mesotheliomas were positive for at least one of the GST species; 21 (37%) showed immunoreactivity for α, 18 (31.5%) for μ and 21 (37%) for π. A total of 54 mesothelioma cases displayed immunoreactivity for the P-170 glycoprotein. For GSTπ and GSTμ, a statistical significance between expression and increased survival was found (respectivelyP=0.012 and 0.024) while for GSTα no significance was found. The results of this study demonstrate that expression of GSTπ correlates positively with increased survival in malignant mesothelioma. It is also concluded that, in mesothelioma, GST and P-170 glycoprotein may contribute to the resistance to cytotoxic drugs frequently observed in these tumours. No correlation between GST and P-170 expression was demonstrated.