Soy isoflavone extracts stimulate the growth of nude mouse xenografts bearing estrogen-dependent human breast cancer cells (MCF-7).
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596079/pdf/jbr-26-01-044.pdf
We explored the effects of different lifetime exposures to soy isoflavone extracts on the growth of estrogen-dependent human breast cancer cells (MCF-7) implanted into athymic mice of different ovarian statuses. The athymic mice, ovariectomized or not, were implanted with MCF-7 cells. Mice were fed with low, moderate and high doses of soy isoflavone extract, at dietary concentrations of 6.25, 12.5 and 25 g/kg, in different reproductive models, respectively. The expression of ki-67 was detected by immunohistochemistry. pS2 expression in tumors was analyzed by real-time PCR. Estrogen level in the serum was measured by chemiluminescence enzyme immunoassay. Total genistein and daidzein levels in serum and urine were determined by liquid chromatography-electrospray tandem mass spectrometry (LC-ES/MS/MS). In Group A, on week 4, nude mice were exposed to different doses of soy iosflavone extracts. In Group B, the experimental diets were given to the nude mice following ovariectomy and tumor implantation. In both groups, 6.25 and 12.5 g/kg soy isoflavone extracts stimulated the growth of MCF-7 xenografts, increased pS2 expression, proliferation and estrogen level in serum. In both Group B (postmenopausal mouse model) and Group C (premenopausal mouse model), soy isoflavone extracts at doses of 6.25 and 12.5 g/kg showed stimulatory effects on the growth of MCF-7 tumors. In conclusion, administration of soy isoflavone extracts at doses of 6.25 and 12.5 g/kg during adolescence or later in life stimulated tumor growth in both menopausal and postmenopausal mouse models.
Estrogen Found In Soy Stimulates Human Breast-Cancer Cells In Mice
http://www.sciencedaily.com/releases/2001/11/011105073548.htm
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.
Soy for Breast Cancer Survivors: A Critical Review of the Literature
http://jn.nutrition.org/content/131/11/3095S.full.pdf
ABSTRACT A variety of health benefits, including protection against breast cancer, have been attributed to soy
food consumption, primarily because of the soybean isoflavones (genistein, daidzein, glycitein). Isoflavones are
considered to be possible selective estrogen receptor modulators but possess nonhormonal properties that also
may contribute to their effects. Concern has arisen over a possible detrimental effect of soy in breast cancer
patients because of the estrogen-like effects of isoflavones. Genistein exhibits a biphasic effect on the growth of
MCF-7 cells in vitro, stimulating proliferation at low concentrations but inhibiting it at high concentrations. In
ovariectomized athymic mice implanted with MCF-7 cells, both genistein and soy protein stimulate tumor growth
in a dose-dependent manner. In contrast, in intact mice fed estrogen, genistein inhibits tumor growth. Although two
studies in premenopausal women suggested that soy exerts estrogenic-like effects on breast tissue, recently
conducted year-long studies indicated that isoflavone supplements do not affect breast tissue density in pre-
menopausal women and may decrease density in postmenopausal women. These latter effects are opposite to
those of hormone replacement therapy (HRT). Importantly, substantial data suggest that the progestogen, not the
estrogen, component of HRT increases risk of developing breast cancer. Furthermore, recently conducted studies
have failed to find that even HRT reduces survival in breast cancer patients. Overall, the data are not impressive
that the adult consumption of soy affects the risk of developing breast cancer or that soy consumption affects the
survival of breast cancer patients. Consequently, if breast cancer patients enjoy soy products, it seems reasonable
for them to continue to use them. J. Nutr. 131: 3095S–3108S, 2001
Do soy foods increase cancer risk?
http://www.mdanderson.org/patient-and-cancer-information/cancer-information/cancer-topics/prevention-and-screening/food/soyandcancer.html
Because natural soy foods contain isoflavones, similar to estrogen, some people fear that soy may raise their risks for certain cancers. This is because estrogen is linked to hormonally-sensitive cancers, like breast cancer.
But according to the American Cancer Society, when it comes to soy, isoflavones may act like estrogen, but they have anti-estrogen properties as well. Some studies even show that people who ate soy were less likely to get breast cancer.
“The current research does not support avoiding whole soy foods--even for cancer patients or survivors,” McKindley says.
The latest on soy and breast cancer: What you need to know
http://www.today.com/health/latest-soy-breast-cancer-what-you-need-know-2D80192077
Could your daily soy lattes up your risk of breast cancer or lend a protective effect?
So far, the research has been conflicting. While some studies have shown that soy can increase tumor growth at the cellular level, other research has found that soy may actually have a protective effect. However, most of what we know about this link comes from epidemiological studies (looking at broad population data), which have not been able to find a clear cause-and-effect link between soy and breast cancer.
what's The Deal With Soy And Breast Cancer?
http://www.huffingtonpost.com/2014/06/20/how-much-soy-should-you-eat-breast-cancer_n_5249925.html
About 75 percent of breast cancer tumors have estrogen receptors, meaning they grow in response to estrogen. And so, if breast cancer runs in your family, it stands to reason that you'd want to closely regulate exposure to a hormone that promotes tumor growth. For many people, doing so includes avoiding soy -- but luckily for those who love their edamame or veggie burgers, this isn't necessary at all. Yes, soy mimics estrogen and estrogen is linked to some hormonally active cancers, but that does not mean that soy itself is linked to cancer.
"There has been concern over the years regarding soy consumption and development or recurrence of breast cancer, and the basis for this concern is isoflavones, a compound in soy with a similar chemical structure to estrogen," Dr. Erica Mayer, M.D., M.P.H., a medical oncologist at the Susan F. Smith Center for Women's Cancers at Dana-Farber, explains to HuffPost. "The idea is that this could potentially fuel growth of breast cancer, but that doesn't bear out in the data."
Soy
Breast Cancer Risk Reduction → Foods To Consider → Soy
Until the issue becomes clearer, many doctors recommend that women who take hormonal therapy or who have estrogen-receptor-positive breast cancer avoid soy supplements because they contain high concentrations of isoflavones. But in general, it's fine to eat moderate amounts of soy foods as part of a balanced diet. One to 3 servings of soy a day (a serving is about a half cup) is similar to an average Japanese woman's daily soy intake. If you are taking hormonal therapy to fight off a hormone-receptor-positive breast cancer, and you are concerned about any phytoestrogen effects, ask your doctor or registered dietitian about how much soy you can eat.
