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 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 MOAT1 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 IL1β+CXCL3+CD4+ (Fer-CD4) T lymphocytes, which were enriched in chemoresistant tumors. Fer-CD4 T cells orchestrated neutrophil ferroptosis by modulating MOAT1 expression via IL1β/IL1R1/NF-κB signaling. Moreover, Fer-CD4 T cells secreted CXCL3, IL8, and S100A9 to replenish the neutrophil pool in the tumor microenvironment. Ferroptotic neutrophils in turn fostered Fer-CD4 T-cell differentiation. In spontaneous tumorigenesis mouse models, targeting IL1β+ CD4+ T cells or IL1R1+ neutrophils broke the cross-talk, 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. Significance: In chemoresistant breast cancer, IL1β+CXCL3+CD4+ T cells mediate neutrophil ferroptosis that suppresses antitumor immunity, indicating that interfering with this intercellular cross-talk could be an attractive strategy to reverse chemoresistance.