Unfortunately, you’d be hard pressed to find anyone that hasn’t been touched by cancer in some way or another. There is a deep need for therapeutic options that can be readily utilized to inhibit Cancer cells.
Fungi may have effective anticancer properties, and the properties that medicinal or functional mushrooms provide demonstrate the fungi’s impressive potential. One can simply visit Semantic Scholar and search for keywords like “mushrooms” and “anticancer” and find thousands of results.
How Medicinal Mushrooms Help Fight Cancer
Reishi mushrooms are one ancient example of a medicinal mushroom, as they are mentioned in the Chinese text Shen Nung Ben Cao Jing (The Classic of Herbal Medicine), thought to be written between 200 and 250 CE.  A vigorous immune system is vital in cancer treatment, and reishi mushroom polysaccharides and triterpenes stimulate cancer resistance through their immune-enhancing capabilities. This activity may be caused by inducing apoptosis (cell death) of cancerous cells or through their ability to boost immune response activity. [2,3] Reishi triterpenes, such as ganoderenic acid B, offer anti-cancer properties as well, through their toxicity to cancer cells, anti-metastatic effects, and induction of apoptosis. [4, 5]
Other mushrooms offer anticancer properties as well. An α-glucan from maitake mushrooms offers anti-tumor activity by promoting the production of cells that enhance our immune systems like tumor necrosis factor α, different interleukins, and through macrophage cell activation.  Another polysaccharide called maitake Z-fraction (MZF) also inhibited tumor growth in a preclinical model of colon cancer. 
Chaga mushrooms contain compounds such as 3β-hydroxy-lanosta-8,24-dien-21-al, inotodiol (a triterpene), and lanosterol, and each of these molecules showed effectiveness against lung, stomach, breast, and cervical cancer cell lines with low toxicity to normal cells.  These researchers first extracted the mushrooms, and subsequently purified multiple fractions that contained different phytochemicals. While all fractions had cytotoxic activity against the cancer cells, doses of 100 and 200 micrograms of one of the fractions reduced tumor volume by 24% and 34%, respectively. Molecules extracted from chaga using hot water have also shown anticancer properties against human colon cancer cells. 
The polysaccharide called krestin, or PSK in turkey tail mushrooms has also shown powerful anticancer properties, with one study measuring an increased survival in colon cancer patients who received PSK as an adjuvant immunochemotherapy. [10, 11] An adjuvant therapy seeks to keep the cancer from coming back post-treatment, and an immunotherapy targets the immune system. PSK’s effectiveness is thought to stem from its ability to invoke immunomodulation and potentiation of the process by which our immune cells identify and eradicate pre-malignant or malignant cells.  PSK from turkey tail mushrooms are regularly used for cancer treatment in Japan. 
Beta-glucans in shiitake mushrooms are known to interact with receptors on several types of immune cells. The mushrooms offer anti-tumor properties, not because they directly engage the tumor, but because they activate immune responses in the host.  The polysaccharide lentinan, for example, acts as a host defense potentiators which help hosts defend against various types of cancer.
These are just a few examples of the polysaccharides and triterpenes within several mushroom species that have demonstrated anticancer activity. As we rekindle our relationship with nature, it’s important to understand how medicinal fungi like mushrooms can convalesce our well-being. Mushrooms like reishi have been with us for antiquity, and as we evolve into the future, the power of these ancient species are being validated with science.
 Masuda Y, Nakayama Y, Tanaka A, Naito K, Konishi M. Antitumor activity of orally administered maitake α-glucan by stimulating antitumor immune response in murine tumor. PLoS One. 2017;12(3):e0173621
 Masuda Y, Ito K, Konishi M, Nanba H. A polysaccharide extracted from Grifola frondosa enhances the anti-tumor activity of bone marrow-derived dendritic cell-based immunotherapy against murine colon cancer. Cancer Immunol Immunother. 2010;59(10):1531-1541
 Chung MJ, Chung CK, Jeong Y, Ham SS. Anticancer activity of subfractions containing pure compounds of Chaga mushroom (Inonotus obliquus) extract in human cancer cells and in Balbc/c mice bearing Sarcoma-180 cells. Nutr Res Pract. 2010;4(3):177-182
 Sakamoto J, Morita S, Oba K, et al. Efficacy of adjuvant immunochemotherapy with polysaccharide K for patients with curatively resected colorectal cancer: a meta-analysis of centrally randomized controlled clinical trials. Cancer Immunol Immunother. 2006;55(4):404-411