EXPRESSION OF ACID CYSTEINE PROTEINASE-INHIBITOR (ACPI) IN THE NORMALHUMAN PROSTATE, BENIGN PROSTATIC HYPERPLASIA AND ADENOCARCINOMA

Acid cysteine proteinase inhibitor (ACPI or cystatin A) is a protein ( 12 kDa) which inhibits the action of several cysteine proteinases, e.g . cathepsins Bi H, L and S. In this study the cellular location of ACP I has been immunohistochemically investigated in the normal human pros tate, in benign prostatic hyperplasia (BPH) and in adenocarcinoma. ACP I was found in the basal epithelial cells of the normal prostate. The secretory epithelial cells did not express ACPI. In the hyperplastic p rostate, the expression of ACPI was decreased and it was also expresse d more focally in the basal cells. Hyperplastic basal cells also expre ssed ACPI. In prostatic adenocarcinoma, no ACPI expression was found. The absence of ACPI expression was obvious and if the sections contain ed both benign and malignant cells, only the benign glandular structur es always expressed ACPI. The results suggest that expression of ACPI might be related to prostatic epithelial cell proliferation and differ entiation. Possibly the detection of ACPI in tissue sections might be helpful in identifying prostatic adenocarcinoma, especially in cases w ith small carcinomatous foci. (C) 1995 Wiley-Liss, Inc.