Glucans and heteroglycans of fungi and their possibilities in immunotherapy of malignant neoplasms

Abstract

The present review is devoted to the oncostatic properties of glucans and heteroglycans produced by higher fungi. These are the most pharmacologically promising substances, since they are produced in large quantities both by artificially grown mycelium and fruiting bodies, do not require complex purification methods, are devoid of toxicity, and, having a complex (immune-mediated and direct) effect on tumors, do not require any complex fractionation procedures. The diversity of β-glucans produced by fungi is shown, the main types of these macromolecules are considered (according to the structural features of the macromolecule, the linear and branched forms of β-glucans are distinguished, first of all). Heteroglycans, a more diverse but less studied group of fungal compounds, have also been characterized. The effects of fungal polysaccharides and heteroglycans on immune and cancer cells described in the literature are considered. The long and branched chains of these biopolymers, as well as peptides and lipids covalently bound to them, have fragments that are complementary to the binding sites of the surface receptors of the animal cell and thus act as their agonists or antagonists. They are recognized by the receptors of antigen-representing cells of the immune system as pathogen-associated molecular patterns, what leads to the activation of the cytotoxic component of the immune system; to reduce their tolerogenic and immunosuppressive signaling. Prospects for further study of fungal glucans and heteroglycans are outlined.