Author Interviews, Breast Cancer / 07.02.2017
Link Between Soy Consumption and Breast Cancer Remains Complicated
MedicalResearch.com Interview with:
Xiyuan Zhang PhD
and Leena Hilakivi-Clarke, PhD
Professor of Oncology
Georgetown University
Research Building, Room E407
Washington, DC 20057
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Breast cancer is the most common cancer type in women and it also is the second leading cause of death by cancer in the United States. Every year, over 200,000 new cases of breast cancer are diagnosed in the US and this number reached over 1.5 million worldwide in 2012.
Asian women exhibit much lower risk of breast cancer than Caucasian women, accounting for about one fifth of the breast cancer incidence in Western women. Therefore, researchers have been intensively studying and aiming to decipher the difference between these two populations. Results of previous research from our laboratory and by others, in animal models and humans, indicate that higher intake of soy foods or soy isoflavone genistein during childhood is associated with reduced breast cancer risk. However, findings done using human breast cancer cells indicate that soy isoflavones stimulate growth of breast cancer cells. Thus, there is an apparent controversy regarding soy isoflavones and breast cancer.
70% of all breast cancer cases are estrogen receptor positive (ER+) and are therefore treated with endocrine therapy, including with tamoxifen. Although these treatments effectively prevent recurrence in half of the ER+ breast cancer patients, the other half are resistant or develop resistance to the endocrine therapy and recur. Intriguingly, several studies done using human breast cancer cells in culture or in mice found that soy isoflavone genistein negates tamoxifen’s effects. However, observational studies in women suggest that those patients who consume most soy foods have the lowest risk of breast cancer recurrence. The present study was designed to address these conflicting findings using a preclinical animal model and to determine if lifetime isoflavone intake has different effect on tamoxifen’s ability to treat breast cancer than intake that starts when cancer is detected.
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