Ferroptotic Neutrophils Induce Immunosuppression and Chemoresistance in Breast Cancer.

Inducing ferroptosis in tumor cells is emerging as a strategy for treating malignancies that are refractory to traditional treatment modalities. However, the consequences of ferroptosis of immune cells in the tumor microenvironment (TME) need to be better understood in order to realize the potential of this approach. In this study, we discovered that neutrophils in chemoresistant breast cancer are highly sensitive to ferroptosis. Reduction of the acyltransferase MBOAT1 in chemoresistance-associated neutrophils induced phospholipid reprogramming, switching the preference from monounsaturated fatty acids to polyunsaturated fatty acids, which increased their susceptibility to ferroptosis. Ferroptotic neutrophils secreted PGE2, IDO and oxidized lipids that suppressed the proliferation and cytotoxicity of antitumor CD8+ T cells. Furthermore, neutrophil ferroptosis was closely related to a distinct subset of IL-1beta+CXCL3+CD4+ (Fer-CD4) T lymphocytes, which were enriched in chemoresistant tumors. Fer-CD4 T cells orchestrated neutrophil ferroptosis by modulating MBOAT1 expression via IL-1beta/IL-1R1/NF-kappaB signaling. Moreover, Fer-CD4 T cells secreted CXCL3, IL-8 and S100A9 to replenish the neutrophil pool in the TME. Ferroptotic neutrophils in turn fostered Fer-CD4 T cell differentiation. In spontaneous tumorigenesis mouse models, targeting IL-1beta+ CD4+ T cells or IL-1R1+ neutrophils broke the crosstalk, restraining neutrophil ferroptosis, enhancing antitumor immunity, and overcoming chemoresistance. Overall, these findings uncover the role of neutrophil ferroptosis in shaping the immune landscape and propose appealing targets for restoring immunosurveillance and chemosensitivity in breast cancer.