By DAVID WILLIAMSON UNC-CH News Services
CHAPEL HILL -- A component of soybeans called genistein so far looks extremely promising in preventing cancer, according to medical scientists at the University of North Carolina at Chapel Hill.
UNC-CH researchers have launched a new study of the protein, which stops human tumor cells from growing in laboratory culture and inhibits cancer in rats, to investigate the possibilities.
"We know the Japanese, who eat diets rich in soybeans, take in about 80 milligrams of genistein a day, and that's as much as 80 times more than we Americans do," said Dr. Steven Zeisel, chairman of nutrition at the UNC-CH schools of public health and medicine. "Japanese people eat much of their genistein in the form of soybean curd they call tofu, and they have very low rates of breast and prostate cancer compared to us."
Because no scientific data exist yet on what genistein does in humans, the National Cancer Institute has asked the UNC-CH researchers to look into it and is providing purified genistein as well as assisting in the study design. The institute is supporting their work with $785,000 for the first year and likely will expand the studies later.
"The institute has asked us to do two things," Zeisel said. "First, we will study healthy people and patients with prostate cancer to determine how high a dose people can take without having side effects. Once we establish that, we have an understanding that NCI will fund a larger study in which patients newly diagnosed with prostate cancer are randomly assigned either to receive nothing or receive medium to high doses of the protein."
Several weeks later, when patients go into surgery, researchers will compare their tumors to see if treatment with genistein has affected tumor growth.
"We expect that that the protein should be able to convert cancer cells in a way that makes them less able to divide and grow," said Zeisel, a member of the UNC Lineberger Comprehensive Cancer Center. "We believe that treatment will inhibit the signal that cells use to tell themselves to grow and multiply."
If the research turns out as hoped, it will provide the first evidence that genistein can stop or retard cancer in humans, he said. The institute then will fund a large study of its effectiveness at multiple medical centers across the country.
"There is no reason to think genistein will not be safe because the Japanese already are consuming so much," the scientist said. "We will determine how it is delivered into the blood, the rate at which delivery occurs and whether patients should be dosed twice or three times a day."
Besides research dietitian Marjorie Busby, the UNC-CH investigators include Drs. William D. Heizer, professor of medicine; Gary J. Smith, professor of pathology and laboratory medicine; James L. Mohler, associate professor of surgery; and Paul Godley, assistant professor of medicine. The scientists will collaborate with others at Research Triangle Institute who will conduct biochemistry studies.
Genistein is known as a phytoestrogen. It is believed to slow cancer to the point where the immune systems of animals --and hopefully humans -- can catch up with cancers and eliminate them.
Note: Zeisel can be reached at (919) 966-7218 for details.