Onset of androgen action in MCF-7 human breast cancer cells is not accompanied by receptor depletion.

Quantitative and qualitative changes in estrogen receptor follow addition of estradiol to estrogen responsive MCF-7 human breast cancer cells. We asked whether similar changes would accompany treatment of these cells with physiologically relevant concentrations of androgens. Androgen receptor sites were quantified by competitive protein binding assays on whole cells or extracts at various times following hormone addition. Both direct and exchange assays were employed. The androgen receptor in all of these experiments remained in a form which is completely exchangeable and approx 85% salt extractable. Quantity of receptor was unchanged (30,000 sites/cell, Kd 0.1 nM). Responsiveness to hormone treatment was demonstrated by antagonizing the estrogen dependent augmentation of cytoplasmic progesterone receptor in the MCF-7 cells with androgens. Thus, the androgen receptor was shown to be biologically active, but no time dependent quantitative or qualitative changes were observed during the first 6 h following androgen treatment.