[Update on the mechanism of action of synthetic antiestrogens].

Synthetic antiestrogens are drugs commonly used in the endocrine therapy of breast cancer. Their pharmacology is complex, most of them presenting a partial estrogenic effect. Their action via the estrogen receptor (ER) has been better understood through the use of cellular models. The antihormone-ER complex binds to estrogen responsive elements on DNA, but is unable to mimic exactly the transcriptional activation induced by the estradiol-ER complex. The antiproliferative effect of these antihormones, mainly cystostatic but also cytotoxic, is the result of the competitive inhibition of estrogens, and might also involve interaction with other cellular mediators (stimulation of inhibitory factors, and growth factors inhibition). The term antiestrogen seems therefore to be too restrictive and it may be more accurate to name them estrogen-receptor mediated drugs inhibiting cell proliferation.