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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASESeptember 15-18, 1996
Brussells, Belgium
SCIENTIFIC PROGRAM
(Oral Abstracts)Soy and Cancer
Animal studiesParadoxical Effects of the Soy Phytoestrogen, Genistein on Growth of Human Breast Cancer Cells In Vitro and In Vivo
William G. Helferich.
Dept. of Food Science & Human Nutrition, Michigan State University, E. Lansing, MI 48824.Genistein, found in soy products, is a phytochemical with several potent biological activities. Our research has focused on the effects of genistein on growth of both estrogen (E)-dependent and E-independent human breast cancer cells at concentration as low as 200nM achieving similar effects to that of estradiol at 1nM. Expression of the estrogen-responsive gene, pS2 was also induced in response to treatment with genistein. However, at higher concentrations genistein inhibits growth of both E-dependent and E-independent human breast cancer cells. To evaluation whether these proliferative or anti-proliferative effects observed in vitro could be reproduced in vivo, E-dependent cells were implanted into 4 subcutaneous sites in ovariectomized athymic mice. Negative control animals received AIN-93G diet, the positive control group received a new subcutaneous estradiol (2mg) pellet, and the third group received genistein at 750ppm in the AIN-93G diet. Tumor size was measured weekly. Tumor size was larger in the 750 ppm genistein treated compared to the negative control group, indicating that genistein was able to act as an estrogen agonist to stimulate growth of E-dependent breast cancer cell tumors in vivo. Similar studies were conducted using E-independent breast cancer cells in intact athymic nude mice. However, no change in growth of E-independent breast cancer cells was observed. In summary, genistein can block cell proliferation at high concentrations in vitro, however these effects were not observed in vivo. Additionally, genistein acts as an estrogen agonist resulting in proliferation of E-dependent human breast cancer cells in vitro and enhances growth of MCF-7 cell tumors (in vivo) implanted into ovariectomized athymic mice.
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