Human prostate-specific transglutaminase: A new prostatic marker with a unique distribution pattern

Human prostate-specific transglutaminase (hTG(p)) is a cross-linking enzyme , the physiologic function of which has not been established unequivocally yet. To gain insight into its distribution, we raised antisera against hTG( p). By using Western blotting analysis, we found that these antisera specif ically recognize a 77-kDa protein in prostatic fluids, seminal plasmas, and prostatic tissues. The concentrations of hTG(p) in these fluids and tissue s were found to be highly variable among individuals. Immunohistochemical e xamination of several formalin-fixed paraffin-embedded human tissues reveal ed an exclusive expression in the prostate. The histologic localization and distribution of hTG(p) within the prostate was assessed by studying multip le sections from tumor-containing prostatectomy specimens and needle biopsi es. hTG(p) expression was entirely restricted to luminal epithelial cells. No basal epithelial cells or stromal cells were stained. Within the prostat e, large areas without any hTG(p)-positive cells were seen. Immunopositive cells were present either in a scattered pattern or concentrated in single or multiple glands in which all luminal epithelial cells expressed hTG(p). The latter staining pattern occurred frequently, but not exclusively, in th e peripheral zone, whereas scattered expression was most often observed in the transitional zone. Expression of the hTG(p) protein could occasionally be observed in high-grade prostatic intraepithelial neoplasia, but was not detected in prostate carcinoma cells. The expression pattern as observed fo r hTG(p) has not been found thus far for any other prostate-specific marker .