Soy Protein Protects Mice from Skin Cancer

Lotion wards off dangerous DNA changes, says study

MONDAY, Oct. 15, 2001 (HealthDayNews) -- California researchers say a cream rich in a particular soy protein delays and even prevents skin cancer in mice.

The compound, called lunasin, helps ward off cancerous changes to DNA, the long molecule that holds all the biological instructions for life, says a report in today's issue of the journal Cancer Research.

Study co-author Alfredo Galvez, president and CEO of FilGen BioSciences of Fairfield, Calif., which helped fund the latest work, says his company hopes to create a "cosmeceutical" form of lunasin that can be marketed as a skin cream to fight both skin tumors and breast cancer. Food and Drug Administration (FDA) regulations for topical medications are less stringent than they are for other prescription drugs, meaning FilGen could have a lotion on the market in several years as opposed to a decade or so for a medication taken internally, he says.

Soy has achieved cult status as a cure-all for everything from cardiovascular disease to cancer, with advocates pointing to lower rates of these illnesses in Asia, where soy is a staple.

Two years ago the FDA said it would permit food labels to say that eating 25 milligrams a day of soy protein may help cut the risk of heart disease.

A number of compounds in soybeans, including isoflavones and a molecule called BBI, have shown promise in treating cancer, and mounting research suggests that lunasin also may have potent anti-cancer properties.

In a study two years ago, Galvez and his colleagues showed that when the protein is injected into tumor cells, the cells stop dividing and die in a process known as apoptosis.

Lunasin behaves like a backup tumor suppressor, stepping in when the genes that normally quash runaway cell growth fail, as they do when cancer forms. "It seems like lunasin is selectively killing cells that are being transformed or are in the process of transformation into cancerous tissue," says Ben de Lumen, professor of food science at the University of California at Berkeley and a co-founder of FilGen.

De Lumen says the protein in soybeans appears to help seeds churn out DNA without having to divide. Since mammalian cells can't perform this trick, when the plant protein enters them "it messes up the cell."

In the new study, Galvez, de Lumen and others tested a topical lotion laced with lunasin on the skin of mice, applying it regularly for 19 weeks. They also exposed the animals to chemical carcinogens known to promote skin tumors.

Mice that received the largest dose of the cream -- 125 micrograms (millionths of a gram) twice a week -- were 70 percent less likely to develop skin tumors than untreated rodents, the researchers say. And when they did get cancer, they tended to have fewer tumors, and those appeared about two weeks later than those in the animals that didn't receive the lotion.

Early work with the protein shows it can penetrate into the basal layer of skin, where cell division is most rapid. Galvez says whether lunasin works against tumors triggered by exposure to ultraviolet radiation, which is the leading cause of skin cancer in humans, remains to be seen.

Although the compound seems safe for mice, when the gene for lunasin was injected into tumors, it killed both diseased and healthy tissue, says Galvez. FilGen is preparing to conduct toxicity studies with the protein.

As for other tumors, such as breast cancer, Galvez says the trick will be to find a way to make lunasin digestible. "The only stumbling block is to develop orally delivered lunasin that can get into the blood and deposit it into the tissue where it can be a preventative agent," Galvez says.

Carol MacLeod, a professor of medicine at the University of California, San Diego, Cancer Center, is planning a study to test the effectiveness of lunasin against breast cancer in mice. MacLeod is receiving funding for the work from the company and the state of California, an "arm's length" pairing she says will help enhance the credibility of the findings. MacLeod says she's not expecting any data from the study for many months.

What To Do: To find out more about soy, try this Web site dedicated to the legume. For more on skin cancer, try The Skin Cancer Foundation or the Centers for Disease Control and Prevention.

SOURCES: Interviews with Ben O. de Lumen , Ph.D., professor of food science, University of California, Berkeley; Carol MacLeod, Ph.D., professor of medicine, University of California, San Diego, Cancer Center, and Alfredo Galvez, Ph.D., president and CEO, FilGen BioSciences, Inc., Fairfield, Calif.; Oct. 15, 2001, Cancer Research
Consumer News