Estrogenic and antiproliferative properties of soy sapogenols in human breast cancer cells in vitro

Two soy sapogenols, soyasapogenol A (SA) and soyasapogenol B (SB) were tested for their estrogenic activities in estrogen responsive MCF-7 or estrogen-insensitive MDA-MB-231 (MDA) human breast cancer cells. SB and SA had differential actives on cell proliferation with 10 μm SB being growth inhibitory to MDA cells with no significant effect at any concentration on MCF-7 cells. SA also inhibited MDA cell proliferation at 10 μm, but at this same dose stimulated a 2.5-fold increase in MCF-7 proliferation. SA (0.1–10 μm) induced pS2 mRNA levels and the induction was blocked by co-treatment of cells with the anti-estrogen ICI 182,780. SA also induced the formation of an ER–ERE DNA complex measured by electrophoretic mobility shift assay. In summary, these results show that soyasapogenol A is estrogenic, whereas soyasapogenol B is growth inhibitory.