Triple-negative breast cancer influences a mixed M1/M2 macrophage phenotype associated with tumor aggressiveness.

Triple-negative breast cancer (TNBC) is characterized by excessive accumulation of tumor-infiltrating immune cells, including tumor-associated macrophages (TAMs). TAMs consist of a heterogeneous population with high plasticity and are associated with tumor aggressiveness and poor prognosis. Moreover, breast cancer cells can secrete factors that influence TAM polarization. Therefore, this study aimed to evaluate the crosstalk between cancer cells and macrophages in the context of TNBC. Cytokine-polarized M2 macrophage were used as control. Distinct from the classical M2 macrophage, TAMs generated from TNBC-conditioned media upregulated both M1- and M2-associated genes, and secreted both the anti-inflammatory cytokine interleukin IL-10 and the proinflammatory cytokine IL-6 and tumor necrosis factor- α. Theses TNBC-induced TAMs exert aggressive behavior of TNBC cells. Consistently, TCGA and MTABRIC analyses of human breast cancer revealed upregulation of M1- associated genes in TNBC comparing with non-TNBC. Among these M1-associated genes, CXCL10 and IL1B were revealed to be independent prognostic factors for disease progression. In conclusion, TNBC cells induce macrophage polarization with a mixture of M1 and M2 phenotypes. These cancer-induced TAMs further enhance tumor cell growth and aggressiveness.