A natural mushroom-soy supplement, called GCP, has been shown to combat prostate cancer tumors and could lengthen the life expectancy of men with advanced cases of the disease, according to new research by the University of California-Davis. The nontoxic product — called genistein-combined polysaccharide (GCP), marketed by Amino-Up of Sapporo, Japan — is sold in health stores and made from an extract cultured from soybeans and shiitake mushrooms. The study, published in the journal Endocrine-Related Cancer, found the combination of compounds in GCP helps block a key mechanism used by prostate cancer cells to survive in the face drug therapies that seek to lower testosterone, which fuels tumor growth. Paramita Ghosh, an associate professor in the UC-Davis School of Medicine who helped conduct the study, explained that men with prostate cancer that has spread to other parts of the body, known as metastatic cancer, and who have had their testosterone lowered with drug therapy are most likely to benefit from GCP. Such drugs, known as androgen-deprivation therapy, are often used to treat patients with metastatic prostate cancer, but they aren't effective for everyone. Although the new study was conducted in prostate cancer cells and in mice, the researchers said the findings hold promise for GCP therapy as a way to extend life expectancy of patients with low response to androgen-deprivation therapy. The team is now seeking funding to start GCP trials in human cancer patients. Because GCP is a natural product and not a drug, those clinical trials could begin soon because they will require fewer government approvals. Ralph de Vere White, a professor of urology and director of the UC-Davis Comprehensive Cancer Center, said results could be available within a year. "We should know within the first eight months or so of human clinical trials if GCP works to reduce PSA levels," said de Vere White, referring to prostate-specific antigen levels, a tumor marker to detect cancer. "We want to see up to 75 percent of metastatic prostate cancer patients lower their PSA levels, and GCP holds promise of accomplishing this goal. If that happens, it would probably be a greater therapy than any drug today."
