INHIBITION OF PROSTATIC EPITHELIAL-CELL PROLIFERATION BY A FACTOR SECRETED SPECIFICALLY BY PROSTATIC STROMAL CELLS

Stromal cells from the prostate were recently shown to inhibit clonal growth of the prostatic carcinoma cell lines PC-3 (hormone-independent ) and LNCaP (hormone-sensitive) in coculture. Our study revealed that stromal cell-conditioned medium strongly inhibited proliferation of PC -3 and LNCaP cells when grown in monolayer culture. Antiproliferative activity was found to be reversible, and was produced specifically by prostatic stromal cells and not by stromal cells derived from skin, fo reskin, uterus, kidney, and Wilms' tumor. Inhibition was not species-s pecific, since the cell lines AT-2.1 and MATLyLu, derived from the Dun ning rat prostate tumor, were also sensitive. No inhibition, however, occurred on breast and renal carcinoma cell lines, suggesting a prosta te-specific action. The putative inhibiting factor(s) could be concent rated and partially purified by ammonium sulfate precipitation. The po ssible role in stromal control of epithelial eel proliferation is disc ussed. (C) 1995 Wiley-Liss, Inc.