Effect of flavonoids on cell proliferation: comparison with estrogen

Abstract

Some flavonoids are structurally similar to 17β-estradiol and have been considered to be phytoestrogen or plant derived compounds with estrogenic actions. Our previous studies indicated that 17β-estradiol and certain flavonoids relaxed and favorably modulated vascular reactivity in porcine coronary arteries. These vascular actions of 17β-estradiol appeared to be mediated by receptors other than the classical estrogen receptors. In the present study, the potential of flavonoids to mimic the hormonal actions of 17β-estradiol were investigated. The effect of different flavonoids on the proliferation of the breast cancer cell line, MCF-7 cells, was examined by using the MTT assay. 17β-estradiol (10−6 M) significantly increased the rate of proliferation of MCF-7 cells, and this increase was inhibited by the classical estrogen receptor antagonist, ICI 182780 (10−9 M). None of the 13 different flavonoids tested, at concentrations ranging from 10−9 to 10−5 M, significantly affected the proliferation of MCF-7 cells. However, these flavonoids (10−9 to 10−6 M), except quercetin, inhibited the proliferating action of 17β-estradiol (10−6 M) on MCF-7 cells. These results suggested that flavonoids bind to the classical estrogen receptors without activating them. Thus flavonoids elicit similar vascular actions to 17β-estradiol but they do not induce the hormonal effects. (Supported by the Research Grant Council of Hong Kong)