Antiestrogenic Action of 3-Hydroxytamoxifen in the Human Breast Cancer Cell Line MCF-723

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Abstract
The antiestrogenic action of 3-hydroxytamoxifen [trans-1-(4-β-dimethylaminoethoxyphenyl)-1-(3-hydroxyphenyl)-2-phenylbut-1-ene] was characterized in vitro and compared with that of tamoxifen [trans-1-(4-β-dimethylaminoethoxyphenyl)-1,2-diphenylbut-1-ene]. The relative binding affinities of 3-hydroxytamoxifen to estrogen receptor were 3.3% in cytosol of MCF-7 cells and 1.5% in human mammary carcinoma cytosol compared to values of 0.2 and 0.3% for tamoxifen (the affinity of 17β-estradiol considered to be 100%). The concentration of 3-hydroxytamoxifen necessary to suppress the 17β-estradiol-induced growth stimulation of MCF-7 cells was about tenfold lower than that for tamoxifen. The induction of progesterone receptor in MCF-7 cells by 17β-estradiol was inhibited by 3-hydroxytamoxifen. In the absence of 17β-estradiol, 3-hydroxytamoxifen gave rise to a moderate increase in the progesterone receptor levels, which demonstrates the partially estrogenic character of hydroxytamoxifen.

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