The impact of β-glucan yeast extract treatment on melanoma development, tumor-cell deposit infiltration, and immune response.

Introduction: Melanoma is one of the most aggressive types of tumors, and strategies for modulating the immune response have been explored as adjuvant therapies. One notable candidate is β-glucan, a polysaccharide derived from Saccharomyces cerevisiae Objective: This study aims to evaluate the treatment effects of β-glucan contained in an extract from Methods: C57BL/6 mice were treated with β-GESc, and evaluations were conducted at different time points during tumor progression (days post-inoculation, or d.p.i). Flow cytometry was used to characterize splenic cell populations and cytokines, and histopathological assessments were performed to evaluate spleen structure. Hematological analysis was performed to assess the peripheral blood. Results: β-GESc-treatment increased spleen size and the absolute number of splenocytes, including macrophages, dendritic cells (DCs), NK cells, and NKT cells. Additionally, it enhanced MHC class II expression by DCs and promoted the formation of germinal centers, indicating immune activation in the spleen. The treatment also increased monocyte and lymphocyte counts, improved survival rates, and reduced tumor growth. Treated animals preserved the white pulp region of the spleen and showed an expansion of the T-cell zone (PALS) at 18 d.p.i., whereas untreated mice exhibited tumor cell infiltration in the spleen at 24 d.p.i. Furthermore, treated animals displayed higher absolute numbers of CD4+ and CD8+ T cells producing IFN-γ and TNF-α, particularly after anti-CD3 stimulation. Conclusions: Treatment with β-GESc demonstrates immunomodulatory potential by increasing both splenic and systemic cell frequencies, contributing to the control of experimental melanoma.