Protein-bound polysaccharide (PSK) has been used in traditional Chinese medicine (TCM) since the Ming Dynasty of China.
In the 1980s, the Japanese government approved the use of PSK for treating several types of cancers. By 1984, it ranked 19th on the list of the world's most commercially successful drugs with annual sales of $255 million.
PSK is obtained from cultured mycelia of the Coriolus versicolor, a mushroom thought to have antimicrobial, antiviral, and antitumor properties.
PSK extracts are available for clinical use in Japan, where it is widely used for cancer immunochemotherapy. In Japan, PSK is currently used as a cancer treatment, in conjunction with surgery, chemotherapy, and/or radiation. Its active ingredient can be administered as a tea or in oral capsule form. In the United States, a similar product is labeled simply Coriolus versicolor extract. Coriolus versicolor is available in limited supply in U.S. markets. In Japan, PSK is currently the best-selling cancer medicine.

Related Terms

A beta-1,4-glucan, basidiomycetes, basidiomycotinae, biological response modifier, Boletus versicolor, BRM, cloud mushroom, Coriolus versicolor, Kawaratake, Kayken Caps®, Krestin®, Polyporaceae, Polyporus versicolor, polysaccharide K, polysaccharide Kureha, Polystictus versicolor, protein-bound B-glucan, proteoglycans, PSP, Saru-no-koshikake, strain CM-101, turkey tail mushroom, Trametes versicolor, yun zhi.

evidence table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Colorectal cancer (adjuvant) (Grade: C)
PSK in addition to chemotherapy and surgery has been associated with increased disease-free survival rate for patients with colorectal cancer in various clinical trials as opposed to these pharmaceutical drugs alone. Well-designed clinical trials are needed to confirm these results along with optimal dosing regimens and optimal pharmaceutical combinations. PSK does not seem to affect the cure rate of colon cancer.
Esophageal cancer (adjuvant) (Grade: C)
A small number of clinical trials have examined the ability of PSK, in conjunction with chemotherapy and radiation, to increase survival time in esophageal cancer. Further well-designed trials are needed to fully understand PSK's potential therapeutic role in esophageal cancer.
Gastric cancer (adjuvant) (Grade: C)
Several clinical trials or case studies have investigated the use of PSK in combination with chemotherapy in the treatment of gastric cancer. Results from many of the clinical trials show that PSK administered along with chemotherapy is associated with increased 2-5 year survival rates. However, some trials found no significant effect on survival over this same period of time. No significant increase in survival has been shown in long-term (greater than five years) studies.
Leukemia (adjuvant) (Grade: C)
One preliminary human trial in patients with acute leukemia suggests that adjunct PSK therapy may prolong duration of remission and survival time. In a second study in patients with acute nonlymphocytic leukemia, no significant increases in survival were found. Well-designed clinical trials are required in order to determine if PSK therapy may in fact prolong remission and increase survival time in individuals with acute leukemia.
Liver cancer (adjuvant) (Grade: C)
Study results of PSK as an adjunct therapy for liver cancer yield mixed results. Well-designed clinical trials are needed to determine the role of PSK on survival time and remission in individuals with liver cancer.
Lung cancer (adjuvant) (Grade: C)
PSK has been studied as an adjuvant therapy in lung cancer patients. Further research is needed before a conclusion can be drawn.
Nasopharyngeal carcinoma (adjuvant) (Grade: C)
In preliminary human studies, PSK, used as adjuvant treatment to radiotherapy with or without chemotherapy, has been shown to increase the five-year survival rate following treatment. Well-designed clinical trials, with larger patient numbers, are needed to confirm these results.
Breast cancer (adjuvant) (Grade: D)
The available evidence does not support the use of PSK, in conjunction with hormone therapy, chemotherapy, and/or surgery, to increase survival rates in breast cancer patients.