Steroid hormone regulation of prostate-specific antigen gene expression in breast cancer

We have recently reported that about 30-40% of female breast tumours produce prostate-specific antigen (PSA) and that PSA production is associated with the presence of oestrogen (ER) and progesterone (PR) receptors. We have now developed a tissue culture system to study the regulation of the PSA gene in breast cancer. The breast carcinoma cell line T-47D produces PSA when stimulated by androgens, progestins and glucocorticoids/mineralocorticoids but not oestrogens. PSA mRNA appears approximately 2 h after stimulation; PSA protein appears after 4-8 h. Among 38 compounds tested, only androgens and progestins were able to stimulate PSA production at concentrations below 10(-9) M. Evidence that the progesterone and androgen receptors can regulate the PSA gene independently was provided as follows: (a) the progestin norgestimate, which does not bind to the androgen receptor, up-regulates the PSA gene at concentrations as low as 10(-10) M; (b) triamicinolone acetonide, which does not bind to the androgen receptor (AR) but binds to the PR, acts similarly to norgestimate; (c) the antiandrogen cyproterone acetate, which blocks the androgen receptor but has progestational activity, up-regulates the PSA gene at concentrations as low as 10(-10) M; (d) the antiprogestine mifepristone completely blocks the stimulation of the specific progestin norgestimate. Our tissue culture system identified androgen-progestin agonist activities of 17 alpha-ethinyloestradiol, the antioestrogen RU56, 187 and the antiprogestin mifepristone. Our data suggest that the expression of the PSA gene in the female breast is under the control of androgens and progestins. Our tissue culture system is a highly sensitive in vitro method for evaluating the biological activity of candidate compounds having agonist and antagonist steroid hormone activity.