Anticancer Compounds of Mushrooms
Medicinal mushrooms contain thousands of compounds, of which many are active against cancer. The most important anticancer compounds of mushrooms are fungal beta glucans (a type of high molecular weight polysaccharides; examples include lentinan, grifolan and GL-1). Aside from these, there are many other active compounds: polysaccharide peptides (e.g. PSP, PSK), glycans (ganoderans A, B, and C) and proteoglycans (e.g. maitake D-fraction), triterpenes and triterpenoids (e.g. ganoderic acids), protein bound polysaccharides, lignins, purines, polyphenols (esp. flavonoids), etc.
The anticancer effect is mostly the result of boosting the immune system (which makes the body fight cancer more efficiently), but also direct cytotoxic/cytostatic activity and influencing tumor cell metabolism and division.
Chihara et al. were the first to isolate lentinan (and several other anticancer substances) from shiitake mushroom (Lentinus edodes) in 1970. They found that beta glucan called lentinan inhibits sarcoma 180 with 90-100% effectiveness and leads to its complete regression. Since 1985 Lentinan is an official antitumor drug in Japan.
Additionally, powerful anticancer compounds have been discovered in the mycelium of some mushrooms, such as KS-2 and LEM from shiitake.
Another very potent and safe compound is PSK (Krestin), a polysaccharide-peptide from Trametes versicolor (= Coriolus versicolor). Registered as a drug for treating several types of cancer in Japan in the 1977, it is the best-selling anticancer drug in Japan (in 1987 it was the 9th most sold drug in the World).
Medicinal Mushrooms and Metastasis
Some medicinal mushroom compounds not only affect primary tumors, but also strongly inhibit and slow the development of metastases. Sometimes, they lead to metastatic reduction and even complete regression. Dr. Chihara (National Cancer Centre Japan) proved this for lentinan and Dr. Hiroaki Nanba (Kobe Pharmaceutical University) for maitake D-fraction from Grifola frondosa (maitake; Hen of the Woods mushroom).
Many other medicinal mushrooms exhibit similar effects. Aside from the usual host-mediated immunity and direct cytotoxic mechanisms, some compounds suppress tumor tissue vascularization, limiting the amount of nutrients the tumor cells get and making their spreading more difficult.
A great number of scientific studies have shown that medicinal mushroom metabolites block or modulate all of the processes connected with the 8 steps of carcinogenesis.
In 2012, Petrova et al. has shown that Ganoderma lucidum (reishi) contains biologically active metabolites that can influence all of these processes.
Flickr:: Luc De Leeuw (Trametes versicolor, turkey tail), caspar s (Grifola frondosa, maitake)