By Shi Yeung
Trametes versicolor (Coriolus versicolor), also known as turkey tail mushrooms, or Yun Zhi, has a long history of medical use in Asia. It is commonly used in traditional Chinese medicine to treat respiratory diseases. Turkey tail mushroom is a fungus with rings of black, tan, and white on its cap. It grows on dead logs worldwide and has its name because of its multicolour appearance. Despite its unappetising appearance, it is an edible and medicinal mushroom that is good for our health. There is no report on severe toxicity induced by it in humans. In Japan, it is known as kawaratake (roof tile fungus) and is prescribed as adjuvants of cancer treatment such as chemotherapy to strengthen the immune system. (PDQ® Integrative, Alternative, and Complementary Therapies Editorial Board, 2017)
The major bioactive constituents of turkey tail mushrooms are the polysaccharide peptides (PSP) and polysaccharide-Krestin (PSK). PSP and PSK polymers isolated from mycelium and fermentation broth are soluble in water. Thus, they are usually taken as a tea or in capsule form. PSK in Japan is an approved active ingredient of turkey tail mushrooms in commercial products used to treat cancer (Habtemariam, 2020). However, the U.S Food and Drug Administration (FDA) has not approved the use of turkey tail mushrooms and PSK as a treatment for cancer or any other medical condition (only several clinical trials are approved). Therefore, products containing PSK are presented as dietary supplements in the US. Since the FDA does not approve dietary supplements as safe or effective, it is the company’s responsibility to make sure their products are safe, and their descriptions are true and not misleading (PDQ® Integrative, Alternative, and Complementary Therapies Editorial Board, 2017).
According to the World Health Organization (WHO), cancer is the second most leading cause of mortality in the world. In the 1980s and 1990s, it was found that PSK has an effect on gene expression in cancer cells and could inhibit hepatic carcinogenesis in rats. Since then, more and more experimental models in vitro, in vivo and clinical trials demonstrate the anticancer effect and immunotherapy potential of PSK. The polysaccharides have also been tested as antioxidants (Habtemariam, 2020). The immunotherapeutic properties of T. versicolor and PSK have been studied extensively in Asia and a positive impact on clinical outcomes are shown. However, limited clinical trials are focusing on having T. versicolor and PSK as adjuvants along with chemotherapy and radiotherapy, and looking at their potential role in secondary prevention after completion of the standard cancer treatment in the US (Standish et al., 2008).
Previous studies have indicated PSK might act in different ways, e.g. as antioxidants, as inhibitors of enzymes involved in metastatic processes, and as inhibitors of various carcinogens activity in the cell line. While many studies focus on the immunomodulatory activity of PSK, such as the ability to activate natural killer cells and lymphocyte-activated killer cells, a study found that PSK can also inhibit tumour cell proliferation by cell cycle arrest in vitro. Moreover, the experiment suggests PSK has a synergistic effect with interleukin-2 (a cytokine signalling protein) that increase peripheral blood lymphocyte proliferation (Jiménez-Medina et al., 2008).
In a systematic review on the efficacy of T. versicolor on survival in cancer patients, it is shown that. T. versicolor results in a significant survival advantage compared to standard anti-cancer treatment alone. Results from 13 clinical trials were analysed and a 9% absolute reduction in 5-year mortality was found, which means there is one additional patient alive for every 11 patients treated. Among different types of cancer, the effect of T. versicolor is more evident in patients with breast cancer, gastric cancer, or colorectal cancer treated with chemotherapy (Eliza, Fai & Chung, 2012). The result of the report is reliable as many of the trials were randomised and controlled clinical trials (RCT). Even though some of the studies used are in poor quality (with methodological flaws when evaluated with RCT principles) and publication bias should also be taken into account, the research group suggest the conclusion is unlikely to change after the trim and fill adjustment method is used.
Lots of research and experiments have been carried out to investigate Trametes versicolor and its cancer-fighting potential in the past 40 years. From proofing the effect of T. versicolor in animal models to finding the mechanism behind the bioactive compound PSK, our understanding towards this medicinal mushroom builds up and lays a solid foundation for future studies. Ingredients in traditional Chinese herbal medicine is a huge research area worth studying as their therapeutic value is maintained in vivo following oral administration, suggesting the bioactive compound (carbohydrates, ie. PSK in T. versicolor) are not subjected to hydrolysis by intestinal enzymes. It is hard to imagine how ancient people discover and learn to use herbs as medicine in hundreds of years ago.
References:
Eliza, W. L. Y., Fai, C. K. & Chung, L. P. (2012). Efficacy of Yun Zhi (Coriolus versicolor) on Survival in Cancer Patients: Systematic Review and Meta-Analysis. Recent Patents on Inflammation & Allergy Drug Discovery, 6(1), 78–87. Available from: doi:10.2174/187221312798889310.
Habtemariam, S. (2020). Trametes versicolor (Synn. Coriolus versicolor) Polysaccharides in Cancer Therapy: Targets and Efficacy. Biomedicines, 8(5), 135. Available from: doi:10.3390/biomedicines8050135.
Jiménez-Medina, E., Berruguilla, E., Romero, I., Algarra, I., Collado, A., Garrido, F. & Garcia-Lora, A. (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(1). Available from: doi:10.1186/1471-2047-8-78.
PDQ® Integrative, Alternative, and Complementary Therapies Editorial Board. PDQ Medicinal Mushrooms: Health Professional Version. Available at: https://www.cancer.gov/about-cancer/treatment/cam/patient/mushrooms-pdq. [Accessed 23rd November 2020].
Standish, L.J., Wenner, C.A., Sweet, E.S., Bridge, C., Nelson, A., Martzen, M., Novack, J. & Torkelson, C. (2008). Trametes versicolor mushroom immune therapy in breast cancer. Journal of the Society for Integrative Oncology, 6(3), 122–8. Available from: PMID: 19087769, PMCID: PMC2845472.
Imperial Bioscience Review 