Neutrophils activated by cancer cells and M2 macrophages promote gastric cancer progression during PD-1 antibody-based immunotherapy

Biomarkers of immune checkpoint inhibitors (ICIs) in advanced gastric cancer (AGC) are under investigation. In present study, correlation between neutrophil-to-lymphocyte ratio (NLR) and efficacy of ICIs treatment in AGC patients as well as its underlying mechanisms were investigated based on clinical cases and single-cell RNA sequencing (scRNA-seq) analysis. NLRs early after treatment were correlated with disease progression and poor progression-free survival (PFS) of AGC patients. Neutrophil cluster1 (NE-C1) divided by scRNA-seq was the major cluster in peripheral blood samples and its proportion increased after PD-1 antibody treatment. NE-C1 had a neutrophil activation phenotype with high expression of MMP9 , S100A8 , S100A9 , PORK2 , and TGF-β1. Subclusters of malignant epithelial cells (EP-C4) and M2 macrophages (MF-C1, MF-C2) showed high neutrophil activating phenotypes. Strong interactions among NE-C1, EP-C4, MF-C1 and MF-C2 were identified. In summary, posttreatment NLR can be an early prognostic biomarker of AGC patients treated by PD-1 antibody-based therapy. Neutrophils activated by both tumor cells and M2 macrophages participate in promoting gastric cancer progression during PD-1 antibody-based treatment.