The cellular level of prostatic acid phosphatase and the growth of human prostate carcinoma cells

Prostatic acid phosphatase (PAcP) is a prostate epithelium-specific differentiation antigen. It has been demonstrated that human PAcP exhibits 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 PAcP, to study changes in cellular PAcP activity during cell growth. Our results demonstrated that PAcP activity increased when the cells reached confluence. Stimulation of cell growth by fresh culture medium or 5α-dihydrotestosterone (DHT), a classical stimulator of prostate epithelial growth, resulted in a decline in PAcP activity. Moreover, transfection 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 cell growth rate, suggesting that PAcP may be involved in regulating the growth of human prostate carcinoma cells.