Tumor-associated neutrophils upregulate Nectin2 expression, creating the immunosuppressive microenvironment in pancreatic ductal adenocarcinoma

Background: Tumor-associated neutrophils (TANs) constitute an abundant component among tumor-infiltrating immune cells and have recently emerged as a critical player in pancreatic ductal adenocarcinoma (PDAC) progression. This study aimed to elucidate the pro-tumor mechanisms of TAN and identify a novel target for effective immunotherapy against PDAC. Methods: Microarray and cytokine array analyses were performed to identify the mechanisms underlying the function of TANs. Human and mouse TANs were obtained from differentiated HL-60 cells and orthotopically transplanted PDAC tumors, respectively. The interactions of TANs with cancer and cytotoxic T-cells were evaluated through in vitro co-culture and in vivo orthotopic or subcutaneous models. Single-cell transcriptomes from patients with PDAC were analyzed to validate the cellular findings. Results: Increased neutrophil infiltration in the tumor microenvironment was associated with poor survival in patients with PDAC. TANs secreted abundant amounts of chemokine ligand 5 (CCL5), subsequently enhancing cancer cell migration and invasion. TANs subpopulations negatively correlated with cytotoxic CD8⁺ T-cell infiltration in PDAC and promoted T-cell dysfunction. TANs upregulated the membranous expression of Nectin2, which contributed to CD8⁺ T-cell exhaustion. Blocking Nectin2 improved CD8⁺ T-cell function and suppressed tumor progression in the mouse model. Single-cell analysis of human PDAC revealed two immunosuppressive TANs phenotypes: Nectin2⁺ TANs and OLR1⁺ TANs. Endoplasmic reticulum stress regulated the protumor activities in TANs. Conclusions: TANs enhance PDAC progression by secreting CCL5 and upregulating Nectin2. Targeting the immune checkpoint Nectin2 could represent a novel strategy to enhance immunotherapy efficacy in PDAC.