Androgen and oestrogen responsiveness of stromal cells derived from the human hyperplastic prostate: Oestrogen regulation of the androgen receptor

Stromal cells derived from collagenase-digested benign hyperplastic adult prostates were isolated and grown in culture. Androgen and oestrogen receptor status were determined and growth in response to mibolerone (a synthetic androgen) and oestradiol-17β was measured. In addition, the ability of oestrogens to regulate the androgen receptor in stromal cells was investigated. [³H]Thymidine incorporation into DNA was stimulated by mibolerone in primary and secondary cultures, but sensitivity was lost with subsequent passages. Androgen stimulation of [³H]thymidine incorporation was consistently inhibited by the anti-androgen cyproterone acetate. Oestradiol-l7β also stimulated [³H]thymidine incorporation into DNA, and this effect was inhibited by the anti-oestrogen tamoxifen. Sensitivity to oestradiol was lost with subsequent passages. A combination of mibolerone and oestradiol was not synergistic in increasing [³H]thymidine incorporation into DNA, but maximal stimulation occurred at 100-fold lower concentrations of mibolerone and oestradiol when the two hormones were applied in combination. Specific high-affinity [³H]mibolerone- and [³H]oestradiol-binding sites were demonstrated by radioligand binding in intact cells. The affinity for oestradiol binding to its receptor exceeded that quantified for mibolerone binding to the androgen receptor, whilst the number of oestradiol-binding sites was approximately tenfold less than that quantified for mibolerone. Treatment with oestradiol down-regulated the number of [³H]mibolerone binding sites 1.7-fold (P<0.005) as early as day 2 after oestradiol treatment. In conclusion, we successfully cultured stromal cells derived from hyperplastic prostates which retained sensitivity to androgen and oestrogen. These results suggest that mibolerone and oestradiol exert their biological effects independently of each other, but there is a close relationship in which one steroid increases the sensitivity of the other in the stromal cells of the hyperplastic prostate.