Protein-Bound Polysaccharides from Coriolus Versicolor Fungus Disrupt the Crosstalk Between Breast Cancer Cells and Macrophages through Inhibition of Angiogenic Cytokines Production and Shifting Tumour-Associated Macrophages from the M2 to M1 Subtype.

Abstract

The tumour microenvironment is rich in multiple cells that influence cancer development. Among them, macrophages are the most abundant immune cells, which secrete factors involved in carcinogenesis. Since protein-bound polysaccharides (PBP) from the Coriolus versicolor fungus are believed to inhibit the growth of cancers, in the present study, we investigated whether these PBP influence crosstalk between triple-negative 4T1 breast cancer cells and RAW 264.7 macrophages. 4T1 cells were cultured in conditioned media (CM) collected after: stimulation of the macrophages with PBP (CM-PBP) or incubation of non-treated macrophages (CM-NT). A co-cultured model of both cell lines was also employed to investigate the crosstalk between the cells. Cell viability was measured using the MTT assay. The levels of cytokines and chemokines were determined by ELISA methods. Commercial assay kits were used to assess the activity of both arginase 1 and inducible nitric oxide synthase (iNOS) and the level of cell migration. The results revealed that CM-NT promotes proliferation and migration of 4T1 cells, and increases the secretion of pro-angiogenic factors (VEGF, MCP-1) by cancer cells. In contrast, CM-PBP inhibits 4T1 cell growth and migration, decreases the secretion of pro-angiogenic factors (VEGF, MCP-1) and upregulates the production of pro-inflammatory mediators (IL-6, TNF-α) with certain anti-tumoral properties Moreover, PBP-treated CM significantly decreases the level of M2 macrophage markers (arginase 1 activity, IL-10 and TGF-β concentrations), but upregulates iNOS activity and IL-6 and TNF-α production, which are M1 cell markers. The results suggest that PBP suppress the favourable tumour microenvironment by inhibiting the crosstalk between 4T1 cells and macrophages through the regulation of production of angiogenic and inflammatory mediators, and modulating the M1/M2 macrophage subtype.