Mushroom-derived polysaccharides in cancer immunotherapy: mechanisms, human evidence, and translational priorities

Abstract

Mushroom-derived polysaccharides are widely promoted as anticancer immune modulators, but interpretation is weakened by imprecise product identity, chemically non-equivalent preparations, and extrapolation across evidence levels. This critical narrative review evaluates beta-glucans, heteropolysaccharides, polysaccharide-protein complexes, crude fractions, modified derivatives, and multicomponent extracts as preparation-specific adjunct candidates. Receptor-level evidence is strongest for general fungal beta-glucan systems, particularly Dectin-1/Syk/CARD9 signaling and conditional complement receptor 3 cooperation; direct transfer of those mechanisms to individual mushroom preparations requires product-specific causal testing. Selected animal studies support myeloid remodeling, dendritic-cell and natural-killer-cell effects, and T-cell activation, but route, exposure, product characterization, and model limitations constrain translation. Human evidence remains heterogeneous: historical randomized PSK studies reported benefit in specific adjuvant chemotherapy settings, a later phase III lentinan trial was negative for overall survival, and small maitake, Agaricus , and pleuran studies mainly report immune surrogates. Direct clinical evidence with checkpoint inhibitors, therapeutic antibodies, or cancer vaccines is not established. The field should therefore move from species-level claims to product-level development with authenticated source material, orthogonal structural analysis, contaminant control, mechanism-linked potency, route-specific pharmacokinetics, tumor pharmacodynamics, and randomized testing against contemporary standard care. Mushroom-derived polysaccharide immunomodulators remain plausible research candidates, but neither the class nor unstandardized mushroom foods or supplements are clinically validated substitutes for established cancer treatment.