What this is about
Trametes versicolor (Turkey Tail, Yun Zhi) is a wood-decay fungus with a concentrically banded cap that has been studied for decades in Japan and China as the source of two polysaccharide fractions:
- PSK (polysaccharide-K, "Krestin") — a protein-bound β-(1→3)/(1→6)-glucan isolated from T. versicolor mycelium strain CM-101 in Japan. Registered as an adjuvant drug in Japan since the 1970s.
- PSP (polysaccharide-peptide) — a similar fraction developed in China on the Cov-1 strain.
Both fractions belong to adjuvant therapy: they are prescribed not instead of but together with standard treatment (surgery, chemotherapy, radiotherapy). The species card is at Trametes versicolor.
How it works pharmacologically
PSK and PSP are not "cancer drugs" in the direct sense. Their action is attributed to several mechanisms:
- Immunomodulation. Stimulation of macrophages, NK cells, T-lymphocytes; increased production of interleukins and interferons.
- Apoptosis modulation. In laboratory work — increased tumour-cell sensitivity to chemotherapeutic agents.
- Antioxidant protection. Reduced oxidative stress, including that caused by chemotherapy.
- Microbiota effects. Altered gut-microbiota composition, indirectly influencing the immune response.
These data are collected in the review on PubMed on PSK and adjuvant therapy and in our article Beta-glucans and immunity, which also describes the general biochemistry of β-glucans.
Clinical data: what studies showed
Gastric cancer
The most extensive evidence base is for gastric cancer. A series of Japanese RCTs (mostly from the 1980s–2000s) showed that adding PSK to standard chemotherapy improves 5-year survival of patients after radical surgery. In the Cochrane review on PSK for gastric cancer, these data are acknowledged as statistically significant, with a caveat about the quality of individual studies (no blinding, small samples).
Colorectal cancer
For colorectal cancer, results of several Phase III RCTs were published in which PSK was added to adjuvant chemotherapy. Some studies showed improved relapse-free survival; results differ across patient subgroups. Meta-analyses confirm the general trend but point to the need for larger modern trials.
Other nosologies
PSK and PSP have also been studied in lung, breast, liver and prostate cancer. Individual studies recorded improved survival and quality-of-life measures, but study designs vary, and no large multicentre RCTs meeting modern standards have been published.
Quality of life and side effects
Several studies address the effect of PSK/PSP on the quality of life of patients undergoing chemotherapy. Some noted reduced fatigue, improved appetite and subjective tolerability of treatment. Side effects in the available studies are rare and limited to mild dyspeptic symptoms.
Context for these data
- Age of the studies. Most PSK RCTs were conducted in the 1980s–2000s. In the decades since, new work and refined protocols have appeared; the overall picture is gradually expanding.
- Product heterogeneity. PSK and PSP are not the same substance. Differences in strains, extraction methods and standardization reflect the products' long evolution.
- Geography of registration. In Japan, China and several Asian countries PSK is registered as an adjuvant agent. In Europe, the US and Russia it is registered in the dietary-supplement category.
- Population data. Most studies were conducted in Asian populations; in 2020–2025 work in other regions has appeared.
These limitations are reproduced in the review Trametes versicolor and the PSK/PSP work in the Mushrooms and immunity topic hub, and in the Beta-glucans and immunity review.
Where T. versicolor intersects with other fungi in our catalog
- Reishi (Ganoderma lucidum) — another wood-decay polypore with a studied β-glucan fraction; see the reishi card and Beta-glucans and immunity.
- Agarikon (Laricifomes officinalis) — studied for antimicrobial activity; see the agarikon card.
- Lion's mane (Hericium erinaceus) — another "medicinal" fungus studied for neuroprotection; see Lion's mane and neurogenesis and the lion's mane card.
- Chaga (Inonotus obliquus) — another wood-decay fungus with rich phytochemistry; see Chaga: antioxidant and metabolic effects and the chaga card.
What is important to keep in mind
- PSK and PSP are adjuvants, not a replacement for standard therapy. In Japan and China PSK is part of approved adjuvant-therapy protocols for oncology; in European countries, North America and Russia PSK and PSP are registered as dietary supplements.
- Standardization is critical. Different commercial products labelled "Turkey Tail" or "Yun Zhi" contain different strains and different fractions, making them incomparable.
- The evidence base is expanding. In 2020–2025 new RCTs have appeared, including in Europe and North America — the overall picture is gradually being refined.
Related materials
- Species card: Trametes versicolor
- Medicinal-fungi catalog: Mushroom catalog
- General β-glucan review: Beta-glucans and immunity
- Topic hub: Mushrooms and immunity
- Other wood-decay fungi: Reishi, Agarikon, Lion's mane, Chaga
- Sources