Behold the formidable fungus.

Not quite plant and not quite animal, it grows in out-of-the-way spots, avoiding attention. But if new studies at City of Hope bear fruit, the white button mushroom may enter the spotlight.

Przemyslaw W. Twardowski (left), Melanie Palomares and Shiuan Chen are investigating whether or not eating mushrooms can reduce cancer risk. (Photo by Paula Myers)

They hope to offer men and women a way to reduce cancer risk — or even stunt cancer growth — through an addition to their diet. The potential is so enticing that the California Breast Cancer Research Program, the American Institute for Cancer Research and the National Institutes of Health supported the lab studies, and the Mushroom Council recently donated $560,000 to support the pilot clinical trials.

“Eating mushrooms would be an easy intervention,” said Shiuan Chen, Ph.D., director of the Department of Surgical Research and leader of the mushroom project. “It could provide a cost-effective, whole-food option for cancer risk reduction.”

Chen began investigating them because his lab’s studies found that ingredients in the mushrooms  suppressed the effects of a natural substance in the body called aromatase.

Blocking aromatase is a key way that physicians reduce estrogen levels among their postmenopausal breast cancer patients. About 75 percent of postmenopausal women with breast cancer have tumors that depend on estrogen to grow.

“We’ve seen that aromatase-inhibiting drugs are helpful in preventing recurrence in postmenopausal women with breast cancer,” said Melanie Palomares, M.D., M.S., assistant professor of medical oncology and population sciences, “and breast cancer survivors were found to develop fewer new breast cancers too.”

Physicians currently recommend that postmenopausal women with hormone-responsive breast cancer take these drugs, but only for two to five years.

“At the end of this period, women can feel unsure about what to do next,” Chen said. “If mushrooms can reduce risk, perhaps we can tell them to eat mushrooms instead.”

That’s the idea behind a phase I clinical trial led by Palomares.

Palomares and colleagues will recruit 24 postmenopausal breast cancer survivors for this study. Women who were diagnosed with breast cancer five or more years ago and remain free of disease will be randomly assigned to take tablets containing varying doses of freeze-dried white button mushrooms daily for 12 weeks.

Researchers will monitor aromatase activity and female hormones in participants, as well as levels of what are called conjugated linoleic acids, a group of compounds in the mushrooms that appear to be responsible for their anticancer properties. They also will study effects on the immune system, cholesterol and bone health.

A second planned trial, meanwhile, will address prostate cancer.  Przemyslaw W. Twardowski, M.D., assistant professor of medical oncology, explains that physicians have no clear answer on how to treat a specific group of prostate cancer patients: Men who were treated for cancer and appear to be cancer-free on imaging scans, but whose prostate-specific antigen (PSA) levels have begun to rise. Cancer usually returns in these patients.

“There is much interest in a natural product that could intervene in this early stage and at least delay the need for other toxic therapies,” Twardowski said. Laboratory research has shown that mushroom extract can lower levels of 5-alpha reductase, an enzyme linked to male hormones involved in prostate cancer.

Kimlin Tam Ashing-Giwa, Ph.D., professor of population sciences and director of City of Hope’s Center of Community Alliance for Research & Education, will focus on community inclusion and the recruitment of diverse breast cancer survivors.

“The beautiful thing about dietary trials is they are so practical,” Ashing-Giwa said. “It gives the community hope that there are more acceptable, natural ways of fighting cancer. It’s easier to bring these kinds of studies to the community.”