| Estrogen plays a major role in breast cancer development and progression making those enzymes involved in its metabolism and synthesis, both systemically and locally, targets for breast cancer treatment and prevention. Flaxseed and soy are major dietary sources of phytoestrogens, lignans and isoflavones respectively. In postmenopausal women flaxseed, but not soy, altered the metabolism of estrogen as indicated by the urinary excretion of 2- and 16α-hydroxyestrone. Flaxseed shifted the metabolism of estrogen to the less biologically active estrogen, 2-hydroxyestrone. In vitro, the effect of purified lignans (enterolactone, enterodiol) and isoflavones (genistein) on estrogen synthesis were examined in MCF-7 cells. Enterolactone, enterodiol and genistein significantly decreased the amount of estrogen produced by aromatase and enterolactone and genistein by 17β-HSD type 1, key enzymes involved in estrogen synthesis. Changes in enzyme activity were significantly related to changes in cell proliferation. |
