An Antiestrogenic Action of Androgens in Human Breast Cancer Cells*

This study was designed to assess the multiple steroid receptor mediated activities of a series of synthetic 'progestins' on breast cancer cell growth, using the human ZR-75-1 cell line which possesses functional estrogen (ER), androgen (AR), and glucocorticoid (GR) receptors as well as progesterone (PgR) receptors. Four 17-hydroxyprogesterone derivatives (chlormadinone acetate, CMA; cyproterone acetate, CPA; medroxyprogesterone acetate, MPA; and megestrol acetate, MGA) and two 19-nortestosterone derivatives (norethindrone, NRE, and norgestrel, NRG) were thus investigated. Based on the requirement of estrogens for PgR-mediated antiproliferative effects and the reversal of PgR-mediated action by insulin, it was found that although all 'progestins' could inhibit ZR-75-1 cell growth through the PgR at low concentrations, the relative contribution of this receptor in cell growth control is highly variable between compounds. The quantitative importance of PgR-mediated inhibition of cell proliferation was inversely related to the amplitude of the androgenic effects induced by the compounds, the AR-mediated effects increasing in the order CPA less than MGA less than CMA less than NRE less than NRG less than MPA. The specificity of these androgenic effects is further supported by their reversal upon addition of the antiandrogen hydroxyflutamide. In addition, the 17-hydroxyprogesterone derivatives, but not the 19-nortestosterone derivatives, had glucocorticoid activities at high (micromolar) concentrations, as shown by reversal of growth inhibition by the antagonist RU486 in the presence of saturating concentrations of 5 alpha-dihydro-testosterone. All 'progestins' tested, except MPA and NRE, also had some antiglucocorticoid activity, NRG being the most potent in this respect. Finally, NRE and NRG exerted a marked mitogenic effect in estrogen-free medium which was clearly mediated through the ER as shown by the competitive reversal of their action by the steroidal antiestrogen EM-139. The present results show that growth measurements of the human breast cancer cells ZR-75-1 permit, with the appropriate steroid additions, the assay of progestin, androgen, estrogen, and glucocorticoid agonistic as well as antagonistic activities of test compounds. The present study shows, somewhat surprisingly, that while the AR is almost completely responsible for the action of MPA at low concentrations, the majority of the action of NRE, NRG, and MGA is also exerted through AR, while the androgenic action of CPA plays a lower role in the growth inhibition induced by this compound.(ABSTRACT TRUNCATED AT 400 WORDS)

Section: Discussionmentioning

confidence: 99%

Multiple actions of synthetic ‘progestins’ on the growth of ZR-75-1 human breast cancer cells: Anin vitro model for the simultaneous assay of androgen, progestin, estrogen, and glucocorticoid agonistic and antagonistic activities of steroids

Poulin

Baker

Poirier

et al. 1991

“…This effect of 5a-DHT has been shown to be mediated by the low-affinity binding of high concentrations of androgens to the estrogen receptor [15,16]. On the other hand, physiological (0.1-10 nM) concentrations of androgens can counteract induction of the progesterone receptor by 17~-estradiol (E2) in MCF-7 cells through an androgen receptor-mediated mechanism [17,18]. Moreover, in the T47-D human breast cancer cell line, 5a-DHT specifically induces the secretion of several proteins, an effect which is reversed by the antiandrogen flutamide [19,20].…”

Section: Introductionmentioning

confidence: 99%

Androgens inhibit basal and estrogen-induced cell proliferation in the ZR-75-1 human breast cancer cell line

Poulin

Baker

Labrie

1988

159

103

This study describes the inhibitory effect of 5 alpha-dihydrotestosterone (5 alpha-DHT) and its precursors testosterone (T) and androst-4-ene-3,17-dione (delta 4-DIONE) on the growth of the estrogen-sensitive human breast cancer cell line ZR-75-1. In the absence of estrogens, cell proliferation measured after a 12-day incubation period was 50-60% inhibited by maximal concentrations of 5 alpha-DHT, T, or delta 4-DIONE with half-maximal effects (IC50 values) observed at 0.10, 0.15 and 15 nM, respectively. This growth inhibition by androgens was due to an increase in generation time and a lowering of the saturation density of cell cultures. The antiestrogen LY156758 (300 nM) induced 25-30% inhibition of basal cell growth, its effect being additive to that of 5 alpha-DHT. The mitogenic effect of 1 nM estradiol (E2) was completely inhibited by increasing concentrations of 5 alpha-DHT with a potency (IC50 = 0.10 nM) similar to that measured when the androgen was used alone. E2 had a more rapid effect on cell proliferation than 5 alpha-DHT, the latter requiring at least 5 to 6 days to exert significant growth inhibition. As found in the absence of estrogens, maximal inhibition of cell proliferation in the presence of E2 was achieved by the combination of the antiestrogen and 5 alpha-DHT. Supraphysiological concentrations of E2 (up to 1 microM) were needed to completely reverse the growth inhibitory effect of a submaximal concentration of 5 alpha-DHT (1 nM). The antiproliferative effect of androgens was competitively reversed by the antiandrogen hydroxyflutamide, thus indicating an androgen receptor-mediated mechanism. The present data suggest the potential benefits of an androgen-antiestrogen combination therapy in the endocrine management of breast cancer.

“…The direct activity of androgens via androgen receptor-mediated mechanisms in breast cancer cells is also supported by the demonstration of their inhibitory effect on estrogen-induced progesterone receptor levels in MCF7 cells [12,36]. Moreover, in the T-47D and ZR-75-1 human breast cancer cell line, DHT specifically induces the secretion of several proteins, an effect which is reversed by the antiandrogen Flutamide [37,38].…”

Section: Discussionmentioning

confidence: 87%

“…A most pertinent recent observation is that physiological concentrations of androgens strongly decrease basal as well as estrogen-induced cell proliferation through a specific interaction with the androgen receptor in the estrogen responsive ZR-75-1 human breast cancer cell line [11]. An antiestrogen effect of an-drogens on progesterone receptor levels has been described in MCF-7 cells [12].…”

Section: Introductionmentioning

confidence: 99%

Inhibitory effect of androgens on DMBA-induced mammary carcinoma in the rat

Dauvois

Martel

et al. 1989

Constant release of the androgen 5 alpha-dihydrotestosterone (DHT) in ovariectomized rats bearing DMBA-induced mammary carcinoma caused a marked inhibition of tumor growth induced by 17 beta-estradiol (E2). That DHT acts through interaction with the androgen receptor is supported by the finding that simultaneous treatment with the antiandrogen Flutamide completely prevents DHT action. Particularly illustrative of the potent inhibitory effect of DHT on tumor growth are the decrease by DHT of the number of progressing tumors from 69.2% to 29.2% in E2-treated animals and the increase by DHT of the number of complete responses (disappearance of palpable tumors) from 11.5% to 33.3% in the same groups of animals. The number of new tumors appearing during the 28-day observation period in E2-treated animals decreased from 1.5 +/- 0.3 to 0.7 +/- 0.2 per rat during treatment with DHT, an effect which was also reversed by the antiandrogen Flutamide. The present data demonstrate, for the first time, that androgens are potent inhibitors of DMBA-induced mammary carcinoma growth by an action independent of inhibition of gonadotropin secretion, and suggest an action exerted directly at the tumor level.