Immunohistochemical expression of pi-class glutathione S-transferase is down-regulated in adenocarcinoma of the prostate

BACKGROUND. Glutathione S-transferase is often up-regulated in neoplastic tissues. A single previous study found a loss of expression associated with carcinogenesis of the prostate. METHODS. To extend these results, the authors performed immunohistochemical staining for the pi-class of glutathione S-transferase (GST pi) on 74 archival sequential prostate specimens. The antibody used was derived from rabbits immunized against purified human GST pi. Paraffin blocks containing both benign tissue and adenocarcinoma were studied. RESULTS. Heterogeneous expression of GST pi in benign acini was found in 96% of cases, but GST pi was not expressed in 95% of invasive adenocarcinomas of the prostate, nor was it expressed in any of the foci of high grade prostatic intraepithelial neoplasia. Basal cells of benign acini showed strong, diffuse staining for GST pi, whereas the secretory luminal epithelium expressed GST pi weakly and focally. CONCLUSIONS. This study confirms the down-regulation of GST pi in adenocarcinoma of the prostate and shows that the loss of GST pi expression is a phenotype associated with malignant transformation. (C) 1997 American Cancer Society.