Regulation of Prostatic Acid Phosphatase Expression and Secretion by Androgen in LNCaP Human Prostate Carcinoma Cells

Abstract

The expression and the secretion of human prostatic acid phosphatase (PAcP), a differentiation antigen which is the major acid phosphatase in prostate epithelial cells, are thought to be regulated by an androgen. We investigated this regulatory mechanism at the post-transcriptional level in LNCaP human prostate carcinoma cells using a cDNA clone for the secretory form of PAcP. 5α-Dihydrotestosterone (DHT, an active form of endogenous androgen) stimulated the secretion of PAcP from cells grown in a steroid-reduced medium and in a defined serum-free medium, respectively. The secreted PAcP activity was increased following a DHT dose in a dose-dependent fashion at concentrations of up to 1 μM. Further, the stimulation of PAcP secretion occurred following the period of exposure to DHT. During a 5-day treatment period, with 10 nM of DHT in the steroid-reduced medium, the secretion of PAcP was stimulated approximately 150% over that from control cells. Nevertheless, PAcP was secreted from cells grown in the absence of added DHT. First, the androgen dependency of PAcP expression was examined. The expression and the secretion of PAcP were observed in cells that were grown in a defined serum-free medium and grown in a steroid-reduced medium, in the absence of DHT. The increased secretion by DHT was further demonstrated to be in part due to an increase in PAcP mRNA level, as evidenced by Northern blot analysis. PAcP mRNA levels were elevated approximately 2-fold and corresponded to an increase of approximately 2.5-fold in the secreted level of newly synthesized 35S-PAcP. Then, the effect of DHT on the secretory process was investigated. Results of pulse-chase labeling experiments indicated that the secretory rate of PAcP was stimulated by about 50% on average by DHT. In conclusion, our data demonstrated that, in LNCaP cells, the expression and the secretion of PAcP regulated by androgen are apparently hormone-responsive processes. Further, DHT stimulation of PAcP secretion operates within at least two levels: increased PAcP mRNA and stimulation of the secretory pathway.