This study reveals a novel mechanism by which Ly6ghigh neutrophils promote breast cancer lung metastasis through the release of cathelicidin-containing neutrophil extracellular traps (NETs), inducing mitochondrial dysfunction and apoptosis in CD8+ T cells, offering new strategies for targeting immunosuppressive microenvironments.
Literature Overview
The article titled “Ly6ghigh Neutrophils Drive Breast Cancer Lung Metastasis via CD8+ T Cell Death”, published in Cancer Communications, reviews and summarizes how the Ly6ghigh neutrophil subset in the lung metastatic microenvironment promotes immune escape and metastatic colonization by forming neutrophil extracellular traps (NETs) and releasing the antimicrobial peptide cathelicidin, which directly induces loss of mitochondrial membrane potential and apoptosis in CD8+ T cells. By integrating single-cell RNA sequencing, gene knockout mouse models, spatial co-localization analysis, and protein interaction assays, the study systematically dissects the cellular crosstalk between neutrophils and T cells. The narrative is coherent and logically structured, concluding with a Chinese period.Background Knowledge
Breast cancer is one of the most common malignant tumors in women, and the lung is a major site of distant metastasis, significantly reducing patient survival rates. The metastatic tumor microenvironment (mTME) is highly immunosuppressive and serves as a critical niche for tumor immune evasion. Neutrophils, as key components of innate immunity, have recently been shown to promote tumor progression and metastasis through the formation of neutrophil extracellular traps (NETs). NETs are web-like structures composed of DNA, histones, and granular proteins that can trap pathogens but are often hijacked in cancer to facilitate metastasis. Cathelicidin, an antimicrobial peptide present in NETs, has been implicated in inflammation and tissue remodeling, but its role in tumor immune escape remains unclear. CD8+ T cells are central effector cells in antitumor immunity, and their functional exhaustion or depletion is closely associated with poor prognosis. Mitochondrial dysfunction is a key mechanism underlying T cell exhaustion, characterized by reduced membrane potential, diminished ATP production, and increased apoptosis. However, how extrinsic microenvironmental factors induce mitochondrial damage in CD8+ T cells remains poorly understood. This study focuses on neutrophil heterogeneity and their interactions with CD8+ T cells, filling a mechanistic gap in how NETs mediate T cell suppression and providing a theoretical foundation for developing immunotherapies targeting neutrophils or NETs.
Research Methods and Experiments
The research team established a breast cancer lung metastasis mouse model and used single-cell RNA sequencing (scRNA-seq) to systematically analyze immune cell composition in metastatic lung lesions, identifying two neutrophil subsets: Ly6ghigh and Ly6glow. Flow cytometry was employed to dynamically track the distribution of these subsets across different metastatic stages. Cathelicidin-deficient (Cramp−/−) mice were used to investigate the functional role of cathelicidin in NETs. Multiplex immunofluorescence staining was performed to analyze the spatial co-localization of apoptotic CD8+ T cells with NETs. In vitro, distinct neutrophil subsets were isolated and co-cultured with CD8+ T cells to assess their impact on T cell proliferation and apoptosis. Protein-binding assays were conducted to explore the interaction mechanism between cathelicidin and mitochondrial proteins. Furthermore, mitochondrial membrane potential assays, electron microscopy, and Western blotting were used to validate cathelicidin's regulation of mitochondrial permeability transition pore (mPTP) opening in CD8+ T cells.Key Conclusions and Perspectives
Research Significance and Prospects
This study is the first to reveal that Ly6ghigh neutrophils promote immune escape and lung metastasis by directly inducing mitochondrial dysfunction and apoptosis in CD8+ T cells via the NETs–cathelicidin–Ant1/Vdac1 axis. This expands our understanding of neutrophil heterogeneity and function, emphasizing their active regulatory role—rather than passive participation—in the pre-metastatic niche.
The findings provide new intervention points for targeting neutrophils or NETs; for example, inhibiting PADI4 or clearing cathelicidin may restore antitumor T cell function. Additionally, this mechanism may be broadly applicable to other cancers where NETs promote metastasis, warranting further investigation. Future studies could develop neutralizing antibodies or small-molecule inhibitors against cathelicidin and evaluate their combination efficacy with immune checkpoint blockade therapies.
Conclusion
This study systematically elucidates the critical pro-metastatic role of Ly6ghigh neutrophils in breast cancer lung metastasis, revealing the molecular mechanism by which they release cathelicidin via NETs to directly target CD8+ T cell mitochondria and induce apoptosis. This discovery not only deepens our understanding of the complexity of the metastatic immune microenvironment but also identifies new therapeutic targets—cathelicidin and its downstream pathways. Targeting this axis may reverse T cell exhaustion and enhance antitumor immune responses. Moreover, the study highlights the dynamic evolution of neutrophil subsets during metastasis, suggesting their potential as biomarkers of disease progression. These findings provide a crucial theoretical and experimental foundation for developing precision immunotherapies targeting the metastatic microenvironment, with the potential to improve outcomes for patients with breast cancer lung metastasis.
