Hormonal regulation of zinc metabolism in a human prostatic carcinoma cell line (PC-3).

Cells from a human prostatic adenocarcinoma cell line (PC3) were maintained in M199 medium, with and without 5% Bobby calf serum, to examine aspects of cellular zinc metab olism. Cultures contained 0.5 to 1.0 x 106 cells/dish. En hanced 65Zn accumulation in response to dexamethasone was observed after 24 hr in culture. The rate of efflux of accumu lated 65Zn was not influenced by this hormone. Dihydrotestosterone had no effect on the accumulation of 65Zn by whole cells. Between 60 and 75% of the accumulated 65Zn was found in the cytosol (166,000 x g supernatant) fraction. Analysis of zinc distribution in cytosol by gel filtration chromatography revealed two major zinc-containing peaks, one comprised of high-molecular-weight zinc-containing proteins and a low-mo lecular-weight fraction that eluted identically to purified metallothionein (MT). Ion exchange chromatography of this lowmolecular-weight fraction resolved it into two components com parable to the major forms of MT purified from liver. Prior to differential 65Zn accumulation (12 hr), increased 65Zn was bound to the MT-like fraction in dexamethasone-treated cells and increased [35S]cystine was incorporated into this protein fraction. Other steroid hormones (dihydrotestosterone, hydrocortisone), as well as prostaglandin E2, resulted in an increased amount of bound 65Zn in the MT fraction, while estradiol and cortisone had no effect. Incubation of cells with actinomycin D or cycloheximide blocked the stimulatory effect of dexameth asone on the prostatic MT-like fraction. These experiments suggest that the MT genes are expressed in prostatic carci noma cells. Moreover, they show that various aspects of pros tatic zinc metabolism, particularly those related to MT, are influenced by certain steroid hormones, namely dexametha sone and dihydrotestosterone.