Estrogen Found In Soy Stimulates HumanBreast Cancer Cells In
Mice
Public
release date: 1-Nov-2001
Contact:
Jim Barlow
b-james3@uiuc.edu
217-333-5802
University
of Illinois at Urbana-Champaign
CHAMPAIGN, Ill. - The increasingly consumed isoflavone genistein - a
plant estrogen linked to the health benefits of soy - has been shown in
a series of University of Illinois studies to stimulate the growth of
estrogen-dependent human breast-cancer cells implanted into laboratory
mice.
The findings of three studies, funded by the National Institutes of
Health, are detailed in the Journal of Nutrition (November),
Carcinogenesis (October) and Cancer Research (July).
The results demonstrate that genistein in various forms stimulates
tumor growth. They also suggest that women with estrogen-dependent
breast cancer or a predisposition to it may want to reduce their
consumption of soy products with a high isoflavone content, said
William G. Helferich, a UI professor of food science and human
nutrition. Many soy isoflavone-containing products are marketed to
women over age 50 for the relief of menopausal symptoms.
"Our pre-clinical laboratory animal data suggest that caution is
warranted regarding the use of soy supplements high in isoflavones for
women with breast cancer, particularly if they are menopausal," said
Helferich, who was the principal researcher on the papers.
For most people, soy is a healthy food and can be used as part of a
healthy diet, he said. Isolated soy protein had been found in previous
UI studies to effectively lower cholesterol. Studies elsewhere have
shown potential relief of menopausal symptoms and protection against
cancer.
In the Journal of Nutrition, Helferich and colleagues show
that the estrogen-dependent tumors implanted into experimental mice
models grow at a rate in proportion to the levels of genistein
consumed. Researchers used athymic mice that lack the ability to reject
human cancer cells. After inserting breast cancer cells, researchers
were able to closely monitor the dietary estrogen to stimulate tumor
growth.
Genistein at or above 250 parts per million, a dosage that produces
blood levels similar to what is observed in women consuming soy diets,
was enough to stimulate tumor growth.
In the paper in Carcinogenesis, the researchers compared
the isoflavone in its two forms, as a glycoside (genistin, as it
appears in plants) and aglucone (genistein). They found that both forms
produced similar tumor growth rates, and that the conversion of
genistin to genistein in the body begins with contact with saliva in
the mouth.
In Cancer Research, Helferich compared soy protein isolates
containing varying levels of isoflavones. The researchers found that
estrogen-dependent tumor growth increased as the isoflavone content
increased in the soy-containing diet.
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