THE CELLULAR-LEVEL OF PROSTATIC ACID-PHOSPHATASE AND THE GROWTH OF HUMAN PROSTATE CARCINOMA-CELLS

Prostatic acid phosphatase (PAcP) is a prostate epithelium-specific di fferentiation antigen. It has been demonstrated that human PAcP exhibi ts endogenous protein tyrosine phosphatase (PYP) activity, and that it represents the major PYP activity in normal prostate cells. Thus, it has been postulated that cellular PAcP may play a role in the tyrosine phosphorylation-mediated signal transduction. In this paper, we used LNCaP human prostate carcinoma cells, which express the endogenous PAc P, to study changes in cellular PAcP activity during cell growth. Our results demonstrated that PAcP activity increased when the cells reach ed confluence. Stimulation of cell growth by fresh culture medium or S a-dihydrotestosterone (DHT), a classical stimulator of prostate epithe lial growth, resulted in a decline in PAcP activity. Moreover, transfe ction of PC-3 cells, which do not express PAcP, with a PAcP-expressing vector led to diminished cellular growth rate. These data established an inverse relationship between the cellular level of PAcP and the ce ll growth rate, suggesting that PAcP may be involved in regulating the growth of hu man prostate carcinoma cells.