Interactions between neutrophils and macrophages harboring gram-negative bacteria promote obesity-associated breast cancer

SUMMARY Obesity promotes a more aggressive breast cancer phenotype. Through spatial and single-cell-based analysis of hormone receptor-negative breast cancers, we identify a subset of tumor-associated neutrophils (TANs) positive for granzyme B (GZMB) enriched in the tumor microenvironment of obese patients. In breast tumors evolved in obese environments, TANs are in proximity of M2 polarized macrophages containing lipopolysaccharides (LPS) from gram-negative bacteria. Pyroptosis of macrophages releases bacterial LPS, activating local GZMB + TANs. This induces release of the S100 family member S100A8 that promotes tumor progression. In sum, we describe an obesity associated cellular network of cancer cells, neutrophils and M2 polarized macrophages that promotes tumor growth.