by Kathleen O’Neil
White button mushrooms may help prevent breast cancer by suppressing estrogen production in the body, according to a study led by City of Hope researchers.
The mushrooms may wield their greatest preventive effect on postmenopausal women by blocking the important enzyme known as aromatase, according to the study published in the Dec. 15 issue of Cancer Research. Aromatase is a substance that helps the body make estrogen.
“We decided to look at mushrooms because we know that synthetic aromatase inhibitors can prevent breast cancer recurrence,” said Shiuan Chen, Ph.D., director of the Department of Surgical Research and lead author of the study.
About 60 percent of premenopausal women and 75 percent of postmenopausal women have breast cancers that depend on estrogen to grow; controlling estrogen levels in the body can help limit or prevent cancer growth. And inhibiting aromatase is an important way to control estrogen levels among postmenopausal women.
Before menopause, the brain governs the body’s estrogen levels by controlling the ovaries’ production of estrogen from aromatase. The brain can override attempts to inhibit aromatase in these women. But after menopause, estrogen primarily is created in fat and other tissues, independent of control by the brain. Consequently, blocking aromatase will block estrogen production.
Aromatase is normally expressed in tissues such as ovary, placenta, fat and bone; it also is expressed at higher levels in breast cancer tissue than in normal breast tissue.
The researchers tested seven vegetable extracts for aromatase-inhibiting activity. They found that mushrooms had the most effective anti-aromatase effect due to one phytochemical: conjugated linoleic acid. They were surprised to find that mushrooms contain conjugated linoleic acid, a compound previously shown to have anticancer properties, because it is mainly present in animal-based foods.
They found celery to have a moderate effect on aromatase, while green onion, carrot, bell pepper, broccoli and spinach extracts did not significantly reduce aromatase levels. The group then tested other mushrooms and found that white stuffing mushrooms had the strongest effect, but shiitake, white button, portobello, crimini and baby button mushrooms also had significant inhibitory effects on aromatase, even when cooked.
After confirming the presence of anti-aromatase chemicals in white button mushrooms, the researchers used laboratory and mouse studies to confirm that the anti-aromatase compounds could stop the growth of breast cancer cells. They found that mice that were fed mushroom extract had a 58 percent reduction in breast tumor growth.
Chen said the research team is now carrying out similar research on the effect of anti-aromatase compounds from food on prostate cancer. They also are planning a clinical trial to test the effect of mushrooms on estrogen levels in women.
“The idea of exploring foods for cancer prevention is very important, because prevention is much better than treating a disease,” Chen said. “You don’t need a strong effect to cause cancer prevention. Eating 100 grams [about 3.5 ounces] or even less of mushrooms per day could have an effect on preventing new breast cancers.”
Other City of Hope researchers included Sei-Ryang Oh, Ph.D., Sheryl Phung, Gene Hur, Jing Jing Ye, Sum Ling Kwok, Lynn Adams, Ph.D., and Dudley Williams, Ph.D., as well as Gayle Shrode, Ph.D., and Martha Belury, Ph.D., of The Ohio State University.
The research was supported by the California Breast Cancer Research Program, the National Institutes of Health and the Mushroom Council.