Abstract 2706: Identification and characterization of cancer-associated polymorphonuclear cell subsets in mice

Abstract

Abstract Background: Neutrophils are the main type of polymorphonuclear cells (PMN) and comprise most immune cells in the body. PMN cells are upregulated in cancer and accumulate in the tumors. Tumor-associated PMNs comprise a heterogeneous population consisting of immunologically active mature neutrophils and immature polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). The phenotype of these cells evolves with disease progression and is implicated in modulating immune response. However, there is yet to be a consensus to define PMN populations in tumors and blood. Methods: Here, we used single-cell RNA-seq, bulk RNA sequencing, flow cytometry, and immunohistochemistry (IHC) analysis to characterize cancer-associated PMN-MDSCs in tumor-bearing mice. Results: Single-cell RNA-seq data from lung tumors and healthy individuals revealed five metaclusters (MC): MCA, MCB, MCC, MCD, and MCE. MCA and MCB made up 34.4 and 65.1% of PMNs in healthy tissues, respectively. MCA, MCB, MCC, MCD, and MCE comprised 3.8%, 23.5% 3.3% 14.6%, and 54.7% of PMNs in tumors, respectively. Genes enriched in MCA and MCE were associated with MDSCs and myeloid progenitor cells. MCB and MCC were associated with inflammatory responses mediated by TNF-alpha signaling and neutrophil degranulation. MCD was associated with a CD33 myeloid cell phenotype and had high expression levels of CD274, Pdcd1lg2, Havcr2, and Tigit genes. Cells from MCE were associated with protein translation signatures and had elevated levels of Nt5e. Gene expression signatures from single-cell RNA-seq data were compared with bulk transcriptomic data from healthy mouse prostates and Pten-null prostate tumors characterized by high PMN cell infiltration. Gene set enrichment analysis showed enrichments after androgen deprivation therapy and Cluster MCE was associated with castration-resistant tumors. Flow cytometric and IHC analysis confirmed the enrichment of PMN cells expressing elevated levels of proteins identified from gene expression analysis including CD73, PD-L1, and PD-L2. Conclusion: This study offers further insights into the distinct subsets of PMN-MDSCs present in tumors. Citation Format: Marco A. De Velasco, Yurie Kura, Kazuko Sakai, Takashi Kikuchi, Yasunori Mori, Takafumi Minami, Kazuhiro Yoshimura, Kazutoshi Fujita, Kazuto Nishio, Hirotsugu Uemura. Identification and characterization of cancer-associated polymorphonuclear cell subsets in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2706.