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Breast Cancer Resistance Linked to Timing of Soy Consumption
CHICAGO -- Studies exploring the relationship between soy consumption and breast
cancer have been mixed, but new research introduces a new thought: Could women
with breast cancer who began eating soy as an adult develop a tumor more resistant
to treatment?
That’s the suggestion of a new study in animal models that could provide important
hints for women with breast cancer who eat soy. The research from Georgetown
Lombardi Comprehensive Cancer Center was reported today at the American
Association for Cancer Research (AACR) Annual Meeting 2012.
For tumors that are sensitive to hormonal treatment (estrogen receptor and/or
progesterone receptor positive), tamoxifen is often given after primary treatment to
keep the cancer at bay. Unfortunately, many tumors become resistant to the
tamoxifen --meaning the drug stops working and the cancer grows again.
In the new research conducted in the laboratories of Leena Hilakivi-Clarke, PhD and
Robert Clarke, PhD, DSc, both professors of oncology at Georgetown Lombardi,
researchers looked at the impact soy consumption might have on breast tumors.
For the study, female rats were fed soy isoflavone genistein (an estrogen-like
compound in soy) at various points in their lifetime. At adulthood, all rats were
exposed to a substance that triggered mammary tumors to develop and then given
tamoxifen. The study groups were as follows: one group was never fed genistein
until tamoxifen was started; a second group was fed genistein only in youth and not
again until tamoxifen was started; a third group was fed genistein only as adults and
continued after tamoxifen was given; and finally, a fourth group was fed genistein
during youth and adulthood and continued after tamoxifen was given.
“Genistein intake in adult life which continues during tamoxifen treatment appears
to make the tumors resistant to tamoxifen,” explains Hilakivi-Clarke, the study’s
senior author. “However, if animals were fed genistein during childhood, and intake
continues before and after tumors develop, the tumors are highly sensitive to the
tamoxifen,” she explains.
“These results suggest that western women who started soy intake as adults, should
stop if diagnosed with breast cancer,” Clarke concludes.
The research was presented by the abstract’s lead author Xiyuan Zhang, M.S. Other
authors include Anni Warri, Ph.D., Idalia M. Cruz, and Katherine Cook, Ph.D.
The research was funded by the National Cancer Institute. The authors report
having no personal financial interests related to the study.
About Georgetown Lombardi Comprehensive Cancer Center
Georgetown Lombardi Comprehensive Cancer Center, part of Georgetown
University Medical Center and Georgetown University Hospital, seeks to improve
the diagnosis, treatment, and prevention of cancer through innovative basic and
clinical research, patient care, community education and outreach, and the training
of cancer specialists of the future. Georgetown Lombardi is one of only 40
comprehensive cancer centers in the nation, as designated by the National Cancer
Institute, and the only one in the Washington, DC, area. For more information, go to
http://lombardi.georgetown.edu.
About Georgetown University Medical Center
Georgetown University Medical Center is an internationally recognized academic
medical center with a three-part mission of research, teaching and patient care
(through MedStar Health). GUMC’s mission is carried out with a strong emphasis on
public service and a dedication to the Catholic, Jesuit principle of cura personalis -or "care of the whole person." The Medical Center includes the School of Medicine
and the School of Nursing & Health Studies, both nationally ranked; Georgetown
Lombardi Comprehensive Cancer Center, designated as a comprehensive cancer
center by the National Cancer Institute; and the Biomedical Graduate Research
Organization (BGRO), which accounts for the majority of externally funded research
at GUMC including a Clinical Translation and Science Award from the National
Institutes of Health. In fiscal year 2009-2010, GUMC accounted for nearly 80 percent
of Georgetown University's extramural research funding.
(Source: http://lombardi.georgetown.edu/)