gamma-Glutamyl transpeptidase in normal and neoplastic prostate glands

gamma-Glutamyl transpeptidase (GGT) is a cytoplasmic membrane-bound enzyme important in the metabolism of glutathione and other gamma-glutamyl compounds. It is present in highest levels in the kidney and is also expressed prominently in reproductive organs such as the prostate gland. Because GGT has never been examined in prostatic carcinoma, we used a new polyclonal antibody (GGT 129) for immunohistochemical localization of GGT in normal prostate gland and 72 prostatic carcinomas. The normal lining secretory cells of ducts and acini showed apical immunoreactivity for GGT, but the basal epithelial cells were negative. Most of the prostatic adenocarcinomas had GGT staining patterns and intensity similar to those of normal prostatic secretory cells, because the majority of neoplastic cells showed immunopositivity in more than 80% of the adenocarcinomas. In comparing the percentage of cells staining for GGT with clinicopathologic parameters, there was no correlation between the number of positive cells and the Gleason score, the percentage of intraglandular carcinoma, capsule penetration, or seminal vesicle invasion. Immunostaining for GGT lacks value as a prognostic factor and does not correlate with standard clinicopathologic parameters. GGT may be important, however, for growth and maintenance of both normal and neoplastic prostatic cells. Modulating GGT levels or administering drugs that can be activated by GGT may have therapeutic value.