Immunosuppressive JAG2+ tumor‐associated neutrophils hamper PD‐1 blockade response in ovarian cancer by mediating the differentiation of effector regulatory T cells

Abstract Background Tumor‐associated neutrophils (TANs) play a critical role in modulating immune responses and exhibit significant heterogeneity. Our previous study demonstrated that jagged canonical Notch ligand 2 (JAG2) + TANs were associated with an immunosuppressive microenvironment in high‐grade serous ovarian cancer (HGSOC), but the underlying mechanism remains unclear. This study aimed to elucidate the role of JAG2 + TANs in tumor immunosuppressive microenvironment in HGSOC. Methods HGSOC samples were collected, with 274 samples constituting two independent cohorts (training and validation cohorts) and an additional 30 samples utilized to establish patient‐derived tumor organoids (PDTOs). We characterized the number and phenotype of JAG2 + TANs by multiplex immunohistochemistry, flow cytometry, and single‐cell RNA sequencing (scRNA‐seq). We investigated the biological functions of JAG2 in immune evasion using in vitro co‐culture systems, flow cytometry, tumor‐bearing mouse models, and PDTOs. Results JAG2 + TANs expressed elevated levels of immunosuppressive molecules, including programmed cell death ligand 1 and CD14, and had independent prognostic value for the overall survival of patients with HGSOC. scRNA‐seq analysis revealed that JAG2 + TANs exhibited a terminally mature phenotype. The infiltration of JAG2 + TANs was positively correlated with the abundance of effector regulatory T cells (eTregs). Interaction with JAG2 + TANs skewed CD4 + T cells towards an eTreg phenotype, a process that was suppressed by the Notch inhibitor LY3039478 and induced by recombinant Jagged2. Furthermore, we demonstrated that JAG2 + TANs enhanced Notch signaling activation, ultimately promoting recombination signal binding protein for immunoglobulin kappa J region (RBPJ)‐induced differentiation of naïve CD4 + T cells into eTregs. Clinically, JAG2 + TANs could serve as a biomarker for assessing immunotherapy resistance in various solid tumors. Pharmacological targeting of Notch signaling with LY3039478 or JAG2 neutralization antibodies enhanced the efficacy of programmed cell death protein 1 (PD‐1) monoclonal antibodies (mAbs) in both xenograft and PDTO models. Conclusions The emergence of JAG2 + TANs is crucial for the differentiation of eTregs, which triggers immune evasion and resistance to anti‐PD‐1 therapy. Inhibiting Notch signaling with LY3039478 or JAG2 neutralization antibodies may overcome this anti‐PD‐1 resistance in HGSOC.