SCIENTIFIC NAMES: Coriolus versicolor, Trametes versicolor, Polyporus versicolor, Polystictus Figureversicolor

ALSO KNOWN AS: PSK, PSP, VPS, turkey tail, yun zhi, kawaratake, Krestin

BACKGROUND: Coriolus versicolor is a mushroom of the Basidiomycetes class. These are fungi with gills or pores, the group that includes the familiar edible mushrooms. Coriolus is used not as food, but as medicine ingested as capsules, as an extract, or as a tea. It was applied initially in traditional Chinese medicine as a tonic, but recent studies indicate immunostimulant and antitumor properties for which its proteoglycan constituents are responsible.

RESEARCH: Polysaccharide K (PSK), a proprietary product derived from Coriolus, was developed for cancer treatment in Japan. When used as an adjuvant agent, PSK enhanced immune response in vivo[1] and improved survival rates in patients with gastric[2] and colorectal cancers.[3]

Other Coriolus extracts, such as polysaccharide peptide (PSP) and versicolor polysaccharide (VPS), are available as dietary supplements. Preliminary studies show that these extracts reduce chemotherapy toxicity, increase effectiveness of chemotherapy or radiotherapy, and have antiproliferative and cytotoxic activities.[4] When used with chemotherapy, PSP may benefit patients with advanced non–small-cell lung cancer.[5]

Clinical investigations using Coriolus extract alone or in combination with other botanicals also suggest positive immunomodulatory effects.[6,7]

Barrie Cassileth DR. CASSILETH: PolysaccharideK (PSK), a protein-bound polysaccharide isolated from Coriolus versicolor, is widely used in Asia as an adjuvant agent in the treatment of cancer. Research into the biologic mechanisms underlying the anticancer effects of PSK is ongoing, but PSK appears promising. More than 2 dozen human studies of PSK have been reviewed by experts at the University of Texas M.D. Anderson Cancer Center. Almost all of these studies were done in Japan and focused on cancers of the esophagus, stomach, colon, or breast. Most of them found that people with cancer were helped by PSK. People who received PSK along with other treatments, such as surgery, chemotherapy, or radiation therapy, generally had longer disease-free periods and increased survival rates compared with patients who got only standard treatment. Side effects from PSK in these studies were very mild. Smaller studies have suggested PSK may not be as effective against liver cancer or leukemia. Adverse effects are rare with use of medicinal mushrooms. However, because over-the-counter Coriolus products are not standardized, and because medicinal mushrooms may interfere with immunosuppressant medications, patients should use caution and consult their physicians before taking medicinal mushroom supplements.

—Barrie Cassileth, PhD