Polysaccharide-K (Krestin, PSK) is a protein-bound polysaccharide, which is utilized as an anticancer immunologic adjuvant in some countries. Japan began using PSK in 1977 and it is presently covered by government health insurance.
PSK is isolated from the fruitbody of Trametes versicolor. Preliminary evidence indicates PSK has anticancer activity in vitro, in vivo and in human clinical trials. Preliminary research has also demonstrated that PSK may inhibit various cancer onset mechanisms. Preliminary evidence indicates PSK may have use as an adjuvant in the treatment of gastric, esophageal, colorectal, breast and lung cancers. Human clinical trials suggest PSK may affect cancer recurrence when used as an adjuvant, and basic research has demonstrated it inhibited certain human cancer cell lines in vitro.
The MD Anderson Cancer Center reported that it is a "promising candidate for chemoprevention due to the multiple effects on the malignant process, limited side effects and safety of daily oral doses for extended periods of time." The Therapeutic Goods Administration in Australia reported that the WHO has only eight records of adverse effects with PSK and none reported for PSP.
Research summary 
In conjunction with chemotherapy, PSK has increased the survival time of cancer patients in randomized, control studies, with stomach cancer (meta-analysis of 8,009 patients), colorectal cancer (randomized, controlled study of 448 patients), non-small cell lung carcinoma, and small cell carcinoma of the lungs. PSK has produced mixed results with breast cancer, liver cancer, and leukemia. Research has shown PSK can help to restore the immune system of immuno-deficient animals, and in vitro research indicates PSK may enhance the activity of doxorubicin and etoposide.
|Tissue||Cancer cell line||Reported effect of PSK|
|Lung (spontaneous metastasis)||autochthonous tumor||Increased survival time|
|Lung (spontaneous metastasis)||human prostate cancer (DU-145M, PC-3M)||Increased survival time|
|Lung (spontaneous metastasis)||mouse melanoma (B16-BL6)||Increased survival time|
|Lung (spontaneous metastasis)||rat lung cancer||Increased survival time|
|Liver (spontaneous metastasis)||human lung cancer (AOI)||Suppressed lesion growth|
|Lymph nodes (spontaneous metastasis)||mouse leukemia (P388)||Increased survival time|
|Lymph nodes (spontaneous metastasis)||mouse liver cancer (MH134)||Suppressed lesion growth|
|Liver (artificial metastasis)||rat liver cancer (AH60C)||Suppressed lesion growth|
|Liver (artificial metastasis)||mouse leukemia||Suppressed lesion growth|
|Liver (artificial metastasis)||mouse colon cancer||Suppressed lesion growth and increased survival time|
PSK chemistry 
PSK is a protein polysaccharide consisiting of a beta-glucan β-1,4 main chain with β-1,3 and β-1,6 side chains. The approximate molecular weight of PSK is 100,000 Da, and the protein component is reported at the β-1,6 side chain. PSK is isolated from the "CM-101" strain of Trametes versicolor. The analogous compound PSP, is derived from the "COV-1" strain of Trametes versicolor.
See also 
- "Coriolus Versicolor". American Cancer Society. Retrieved 12 July 2009.
- Jiménez-Medina E, Berruguilla E, Romero I et al. (2008). "The immunomodulator PSK induces in vitro cytotoxic activity in tumour cell lines via arrest of cell cycle and induction of apoptosis". BMC Cancer 8: 78. doi:10.1186/1471-2407-8-78. PMC 2291471. PMID 18366723.
- Yamasaki A, Shoda M, Iijima H et al. (March 2009). "A protein-bound polysaccharide, PSK, enhances tumor suppression induced by docetaxel in a gastric cancer xenograft model". Anticancer Research 29 (3): 843–50. PMID 19414318.
- Oba K, Teramukai S, Kobayashi M, Matsui T, Kodera Y, Sakamoto J (June 2007). "Efficacy of adjuvant immunochemotherapy with polysaccharide K for patients with curative resections of gastric cancer". Cancer Immunology, Immunotherapy 56 (6): 905–11. doi:10.1007/s00262-006-0248-1. PMID 17106715.
- Kobayashi H, Matsunaga K, Oguchi Y (1995). "Antimetastatic effects of PSK (Krestin), a protein-bound polysaccharide obtained from basidiomycetes: an overview". Cancer Epidemiology, Biomarkers & Prevention 4 (3): 275–81. PMID 7606203.
- Fisher M, Yang LX (2002). "Anticancer effects and mechanisms of polysaccharide-K (PSK): implications of cancer immunotherapy". Anticancer Research 22 (3): 1737–54. PMID 12168863.
- Sugimachi K, Maehara Y, Ogawa M, Kakegawa T, Tomita M (1997). "Dose intensity of uracil and tegafur in postoperative chemotherapy for patients with poorly differentiated gastric cancer". Cancer Chemotherapy and Pharmacology 40 (3): 233–8. doi:10.1007/s002800050652. PMID 9219507.
- Hsieh TC, Wu JM (January 2001). "Cell growth and gene modulatory activities of Yunzhi (Windsor Wunxi) from mushroom Trametes versicolor in androgen-dependent and androgen-insensitive human prostate cancer cells". International Journal of Oncology 18 (1): 81–8. PMID 11115542.
- Dong Y, Yang MM, Kwan CY (1997). "In vitro inhibition of proliferation of HL-60 cells by tetrandrine and coriolus versicolor peptide derived from Chinese medicinal herbs". Life Sciences 60 (8): PL135–40. doi:10.1016/S0024-3205(96)00695-9. PMID 9042394.
- Yang MM, Chen Z, Kwok JS (1992). "The anti-tumor effect of a small polypeptide from Coriolus versicolor (SPCV)". The American Journal of Chinese Medicine 20 (3–4): 221–32. doi:10.1142/S0192415X92000230. PMID 1471606.
- "Coriolus versicolor". Complementary and alternative therapies for cancer patients. San Diego: University of California.
- Mitomi T, Tsuchiya S, Iijima N, et al. (February 1992). "Randomized, controlled study on adjuvant immunochemotherapy with PSK in curatively resected colorectal cancer. The Cooperative Study Group of Surgical Adjuvant Immunochemotherapy for Cancer of Colon and Rectum (Kanagawa)". Diseases of the Colon and Rectum 35 (2): 123–30. doi:10.1007/BF02050666. PMID 1735313.
- Hayakawa K, Mitsuhashi N, Saito Y, et al. (1997). "Effect of Krestin as adjuvant treatment following radical radiotherapy in non-small cell lung cancer patients". Cancer Detection and Prevention 21 (1): 71–7. PMID 9043766.
- Iino Y, Yokoe T, Maemura M, et al. (1995). "Immunochemotherapies versus chemotherapy as adjuvant treatment after curative resection of operable breast cancer". Anticancer Research 15 (6B): 2907–11. PMID 8669887.
- Suto T, Fukuda S, Moriya N, et al. (1994). "Clinical study of biological response modifiers as maintenance therapy for hepatocellular carcinoma". Cancer Chemotherapy and Pharmacology. 33 Suppl: S145–8. PMID 8137477.
- Ohno R, Yamada K, Masaoka T, et al. (1984). "A randomized trial of chemoimmunotherapy of acute nonlymphocytic leukemia in adults using a protein-bound polysaccharide preparation". Cancer Immunology, Immunotherapy 18 (3): 149–54. doi:10.1007/BF00205503. PMID 6391658.
- Tsukagoshi S, Hashimoto Y, Fujii G, Kobayashi H, Nomoto K, Orita K (June 1984). "Krestin (PSK)". Cancer Treatment Reviews 11 (2): 131–55. doi:10.1016/0305-7372(84)90005-7. PMID 6238674.
- Wan JM, Sit WH, Louie JC (2008). "Polysaccharopeptide enhances the anticancer activity of doxorubicin and etoposide on human breast cancer cells ZR-75-30". Int J Oncol 32 (3): 689–99. PMID 18292947.
- Hui KP, Sit WH, Wan JM (2005). "Induction of S phase cell arrest and caspase activation by polysaccharide peptide isolated from Coriolus versicolor enhanced the cell cycle dependent activity and apoptotic cell death of doxorubicin and etoposide, but not cytarabine in HL-60 cells". Oncol Rep 14 (1): 145–55. PMID 15944782.
- American Cancer Society's page for Trametes versicolor and Polysaccharide-K.
- Memorial Sloan-Kettering Cancer Center's page for Trametes versicolor and Polysaccharide-K.
- A "Detailed Scientific Review of Trametes versicolor and Polysaccharide-K" by the MD Anderson Cancer Center.
- Trametes versicolor and Polysaccharide-K information from Drugs.com.