The March 15 issue of Cancer Research, a journal of the American Association for Cancer Research, describes how a compound found in soybeans almost completely prevented the spread of human prostate cancer in mice.
Researchers say that the amount of the chemical, an antioxidant known as genistein, used in the experiments was no higher than what a human would eat in a soybean-rich diet. Scientists from Northwestern University found that genistein decreased metastasis of prostate cancer to the lungs by 96 percent compared with mice that did not eat the compound in their daily diet - making the study the first to demonstrate genistein can stop prostate cancer metastasis in a living organism.
“Diet can affect cancer and it doesn’t do it by magic,” the main author of this report, Dr. Bergan, said. “Certain chemicals have beneficial effects and now we have all the preclinical studies we need to suggest genistein might be a very promising chemopreventive drug.”
In this study, investigators fed genistein to several groups of mice before implanting them with an aggressive form of prostate cancer. The amount of genistein in the blood of the animals was comparable to human blood concentrations after consumption of soy foods, Bergan said. The researchers found that while genistein didn’t reduce the size of tumors that developed within the prostate, it stopped lung metastasis almost completely. They repeated the experiment and found the same result.
"What we found demonstrated that the compound is having a primary effect on metastasis," said the authors.
Bergan cautioned that much is unknown about use of genistein in preventing cancer spread. For example, it may be that the effects of the compound in people who have eaten soy all their lives is stronger than benefit seen in patients who have only started to use genistein.
“The problem we have faced is that epidemiology studies that found men who eat soy are at reduced risk of prostate cancer death are all associative. They don’t prove anything,” he said. “The only way we will find out how promising genistein is will be from conducting clinical trials.”
Obviously, that's the next step in this exciting new area of research.