March 14, 2008 -- Dietary levels of genistein, a soy protein, stopped the spread of prostate cancer in mouse studies, Northwestern University researchers report.
Men who live in countries with high soy consumption are less likely to die of prostate cancer than are men in the U.S. and Europe. Genistein, a protein from soybeans, keeps prostate cancer cells from spreading in test-tube studies.
Now a study led by Raymond C. Bergen, MD, director of experimental therapeutics for the Robert H. Lurie Comprehensive Cancer Center at Northwestern University, shows that genistein fights human prostate cancers implanted in living animals.
The soy compound doesn't make prostate cancer go away. It doesn't even make prostate tumors smaller. But it does keep the cancer cells from spreading through the body. Like some other cancers, prostate cancer is not deadly unless it spreads through the body -- a process known as cancer metastasis.
"These impressive results give us hope that genistein might show some effect in preventing the spread of prostate cancer in patients," Bergen says in a news release. "Now we have all the preclinical studies we need to suggest genistein might be a very promising chemopreventive drug."
A 2003 human study showed that when men with prostate cancer took genistein preparations, their blood levels of genistein reached concentrations that had anticancer effects in the test tube. These are the same genistein blood levels that protected mice in the current study.
Bergan and colleagues note that a larger clinical trial of genistein is under way. Other researchers are studying the compound in patients with breast cancer, kidney cancer, endometrial cancer, pancreatic cancer, and melanoma.
Bergan and colleagues report their findings in the March 15 issue of Cancer Research.