Edible and medicinal fungal polysaccharides inhibit the immunosuppressive functions of myeloid-derived suppressor cells (MDSCs) on cancers

Abstract:

Myeloid-derived suppressor cells (MDSCs) are heterogeneous immunomodulatory cells. In the instance of cancers, they exert immunosuppressive functions. To be specific, they induce T cell exhaustion and apoptosis through multiple pathways to promote the escape of tumor cells from destruction by the immune system and sustain cancer progression. Thus, they are the main obstacle in the fight against cancers. At the moment, MDSCs are the focus in development of anti-cancer drugs and the key targets of the drugs. It has been reported that polysaccharides reduced the count and proportion of MDSCs in cancer patients and tumor-bearing mice and eliminate the immunosuppression. Natural edible and medicinal fungal polysaccharides can activate immune response to tumors through multiple pathways, and there has been an explosion of research on the suppression of the immunosuppressive function of MDSCs. The currently available studies mainly focus on polysaccharides from Lentinula edodes and Ganoderma lucidum. In this review, we briefed the immunosuppressive mechanism of MDSCs in the cases of cancers, and then summarized the effects of edible and medicinal fungal polysaccharides on MDSCs, hoping to provide a new mindset for the development of anti-tumor drugs and auxiliary enhancement of immunotherapy such as immune checkpoint inhibitors with edible and medicinal fungal polysaccharides.