Immunohistochemical expression of π-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 π-class of glutathione S-transferase (GSTπ) on 74 archival sequential prostate specimens. The antibody used was derived from rabbits immunized against purified human GSTπ. Paraffin blocks containing both benign tissue and adenocarcinoma were studied. RESULTS. Heterogeneous expression of GSTπ in benign acini was found in 96% of cases, but GSTπ was not expressed in 95% of invasive adenocarcinomas of the prostate, nor was it expressed in any of the loci of high grade prostatic intraepithelial neoplasia. Basal cells of benign acini showed strong, diffuse staining for GSTπ, whereas the secretory luminal epithelium expressed GSTπ weakly and locally. CONCLUSIONS. This study confirms the down-regulation of GSTπ in adenocarcinoma of the prostate and shows that the loss of GSTπ expression is a phenotype associated with malignant transformation.