Mushrooms may mean more might for the cancer fight

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

City of Hope scientists are on their way toward incorporating mushrooms in a cancer-fighting strategy.

Powder made from white button mushrooms appears able to lower PSA levels in men previously treated for prostate cancer. In a study led by City of Hope researchers, a powder made of white button mushrooms was found to reduce the levels of prostate specific antigen, or PSA, in prostate cancer patients whose PSA levels had been rising. And, even better, the powder caused no ill effects.

Here's why that matters. A rise in PSA levels in men already treated for prostate cancer can be a harbinger of disease recurrence. So when those levels rise – and continue to rise – men know that further treatment is likely necessary. Men need a way to keep those PSA levels down or, more to the point, help prevent cancer’s recurrence. White button mushrooms could be it.

The City of Hope researchers treated 36 prostate cancer patients with the powder, assessing their PSA levels' responsiveness to different doses of the powder and whether the men experienced any ill effects. After three months of daily use of the powder, 36 percent of patients experienced some reduction in PSA, with two patients experiencing a remarkable complete response, meaning their PSA levels dropped to undetectable levels. Of note, that complete response continued for 72 and 53 months.

Two additional patients experienced partial responses (PR). Another five patients currently stay on protocol treatment because of their stable PSA values. Minimal side effects were noted with mushroom intake. The mean compliance with protocol-defined mushroom treatment was 98.6%. These results suggest that mushroom intake should not alter the physical and mental health of the patients currently receiving non-mushroom treatment.

Mushrooms and Breast Cancer

Over the last decade, City of Hope researchers identified and tested cancer-inhibiting compounds in the common supermarket mushroom. Their work has moved into clinical trials at City of Hope, including one that tested whether consuming mushroom extract could stave off breast cancer recurrence in postmenopausal patients.

Early findings from that study showed that the doses of mushroom extract that were tested blocked activity of an enzyme important to breast cancer, but not at levels likely to deter the disease. The work encourages scientists to hone their potential strategy for prevention.

In earlier work, Shiuan Chen, Ph.D., chair and professor of City of Hope’s Department of Cancer Biology, found that phytochemicals — naturally occurring plant chemicals — in mushrooms can block the activity of the enzyme called aromatase.

Aromatase helps the body produce the hormone estrogen, which many breast cancers need to grow. Blocking the enzyme chokes off the supply of estrogen to tumor cells, stunting their growth. Several drugs that block aromatase are already part of medicine’s arsenal against breast cancer.

Mushrooms’ natural aromatase-inhibiting properties might offer a dietary, non-drug intervention to help prevent recurrence of hormone-dependent breast cancers, according to the researchers.

The current study, which aimed to find an effective dose of mushroom extract, centered on postmenopausal breast cancer survivors who were cancer-free after they finished their treatment.

Women in the study took white button mushroom extract daily for 12 weeks. They were divided into groups that received either 5-, 8-, 10- or 13-gram doses. The researchers checked patients’ responses by measuring blood levels of estradiol, a close chemical relative of estrogen. Women whose estradiol level dropped by 50 percent or more were deemed to have responded to the intervention.

Patients tolerated the extract well, but the estradiol level failed to drop by 50 percent or more in any group. The researchers did see evidence of modest aromatase inhibition that lasted as long as six hours at the highest dose level. The result suggested that eating mushrooms can weakly inhibit aromatase in patients, but much higher amounts likely are necessary for a clinically significant result.

“Over the course of 12 weeks, we were able to observe phytochemical activity, but not at high enough concentrations to significantly reduce circulating estrogen levels in our patients,” Palomares said. In addition to trying higher concentrations of mushroom extract in future studies, the scientists also may change the way they measure estrogens in the body. “The local estrogen level in the breast is likely more significant clinically than what circulates in the bloodstream.”