EXPRESSION AND LOCALIZATION OF AMINOPEPTIDASE-A, AMINOPEPTIDASE-N, AND DIPEPTIDYL PEPTIDASE-IV IN BENIGN AND MALIGNANT HUMAN PROSTATE TISSUE

BACKGROUND. Cell-surface peptidases are ectoenzymes which regulate the access of bioactive peptides to their receptors on cell membranes. Ab normalities in their expression and function result in altered peptide activity which contribute to neoplastic transformation and/or progres sion. METHODS. Expression of aminopeptidase A (APA), aminopeptidase N (APN, CD13), and dipeptidyl peptidase IV (DPP IV, CD26) was immunohist ochemically examined in 20 benign and 33 malignant prostate tissues (1 9 primaries and 14 metastases). RESULTS. Benign prostatic stroma exhib ited no APA, APN, or DPP IV immunoreactivity. Stromal cells surroundin g prostatic carcinoma cells demonstrated increased APA expression in 2 4/33 (73%) of tumors. Benign prostatic epithelial cells strongly expre ssed APN and DPP IV but not APA. In contrast, APN was expressed in >80 % of tumor cells in 5/33 (15%) of specimens, heterogeneously expressed (20-80% of cells positive) in 4/33 (12%) of specimens, and minimally expressed or absent in 24/33 (73%) of tumor specimens, with a similar pattern of expression in primary and metastatic tumors. DPP IV was exp ressed by >80% of tumor cells in 18/19 (95%) of primary prostate cance r specimens, but in only 7/14 (50%) of metastases. CONCLUSIONS. These data show that cell-surface peptidases are differentially expressed by normal prostatic stromal and epithelial cells, with increased express ion of APA in the stroma surrounding prostate cancer cells, absent APN expression in most tumor cells, and a decreased frequency of DPP IV e xpression in metastatic tumors. Further studies will elucidate the bio logical effects of the presence or loss of cell-surface peptidases in the benign and malignant prostate. (C) 1997 Wiley-Liss, Inc.