Systemic activation and tissue infiltration of CD8 + CX3CR1 + T cells in non-small cell lung cancer treated with neoadjuvant immune checkpoint blockade.

BACKGROUND: Neoadjuvant immune checkpoint blockade (NA-ICB) shows promise in treating resectable and locally advanced non-small cell lung cancer (NSCLC), yet the specific T cell subtypes that expand and become functionally reactivated remain incompletely characterised. METHODS: We applied single-cell RNA sequencing, TCR repertoire analysis, and flow cytometry to tumour, paired normal lung tissue, and peripheral blood samples from 26 NA-ICB-treated and 14 treatment-naïve NSCLC patients to investigate responsive T cell subtypes, their tissue origins, migration patterns, and phenotype transitions. RESULTS: CD8 + CX3CR1 + T cells were significantly enriched in responsive tumours, as evidenced by increased proportions (p = 0.0027) and clonal expansion in scRNA-seq, and elevated protein-level frequencies detected by flow cytometry (p = 0.021). Longitudinal analysis revealed proliferation of these cells in peripheral blood post-treatment. Shared TCR clonotypes were identified across blood and tumour samples. Pseudotime analysis indicated differentiation of these cells into exhausted and cytotoxic NK-like CD8 + T cells upon tumour infiltration. CONCLUSION: These findings suggest that CD8 + CX3CR1 + T cells may represent circulating cytotoxic precursors associated with effective NA-ICB responses, suggesting their potential as predictive biomarkers and therapeutic targets for adoptive cell therapy.