β-glucan restores tumor-educated dendritic cell maturation to enhance antitumor immune responses.

Tumors can induce the generation and accumulation of immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs) in a tumor microenvironment, contributing to tumor escape from immunological attack. Although dendritic cell-based cancer vaccines can initiate antitumor immune responses, tumor-educated dendritic cells (TEDCs) involved in the tolerance induction have attracted much attention recently. In this study, we investigated the effect of β-glucan on TEDCs and found that β-glucan treatment could promote the maturation and migration of TEDCs and that the suppressive function of TEDCs was significantly decreased. Treatment with β-glucan drastically decreased the levels of regulatory T (Treg) cells but increased the infiltration of macrophages, granulocytes and DCs in tumor masses, thus elicited Th1 differentiation and cytotoxic T-lymphocyte responses and led to a delay in tumor progression. These findings reveal that β-glucan can inhibit the regulatory function of TEDCs, therefore revealing a novel function for β-glucan in immunotherapy and suggesting its potential clinical benefit. β-Glucan directly abrogated tumor-educated dendritic cells-associated immune suppression, promoted Th1 differentiation and cytotoxic T-lymphocyte priming and improved antitumor responses.