Background: While neutrophil extracellular traps (NETs) have been shown to contribute to cancer progression, including that of lung adenocarcinoma, the mechanisms underlying NET formation within the tumor immune microenvironment (TIME) remain incompletely understood. Notably, neutrophil infiltration has been strongly linked to tumor necrosis factor alpha-inducible protein 6 (TNFAIP6) expression. Methods: In vitro and in vivo experiments were performed. DNA pulldown coupled with mass spectrometry, bioinformatics analyses, immunohistochemistry, and dual-luciferase reporter assays were conducted. DNA pulldown Western blotting, chromatin immunoprecipitation–quantitative PCR, and dual-luciferase reporter assays using truncated promoter constructs were also employed. Results: TNFAIP6 expressed by lung adenocarcinoma cells was shown to induce NET formation (a form of programmed cell death called NETosis). Mechanistically, TNFAIP6 interacted with CD44 in lung adenocarcinoma cells, leading to increased extracellular availability of secreted phosphoprotein 1 (SPP1) within the TIME and the subsequent promotion of NETosis. Additionally, nucleophosmin 1 (NPM1) significantly enhances the transcriptional activation of TNFAIP6 and associates with the −2000 to −1700 bp region of its promoter. Conclusions: These findings delineate a regulatory model in which lung adenocarcinoma cells directly stimulate NETosis through the NPM1–TNFAIP6–CD44–SPP1 axis, suggesting that therapeutic targeting of this pathway may attenuate tumor progression.

Background: Neutrophil extracellular traps (NETs) promote tumor progression and immune evasion across multiple cancers. However, the mechanisms governing NET formation (NETosis) within the tumor immune microenvironment remain incompletely understood. Low P2RY13 expression is associated with the pro-tumor activity of neutrophils in lung adenocarcinoma. Methods: Pan-cancer bioinformatics analyses were performed, including differential gene expression, prognostic, tumor-infiltrating immune cell, and NET scoring analyses. Single-cell profiling was conducted using the Tumor Immune Single-cell Hub 2 database. Immunohistochemical (IHC) and multiplex immunofluorescence (mIF) staining of tissue microarrays (TMAs) was performed to validate findings in lung adenocarcinoma (LUAD), liver hepatocellular carcinoma (LIHC), and colorectal cancer (CRC). In vitro validation was conducted using gene modulation, tumor-cell-conditioned medium (CM) education, tumor-associated macrophage (TAM)-like macrophage CM transfer, immunofluorescence staining, and ELISA. Results: Bioinformatics analyses suggested that P2RY13 is frequently dysregulated in multiple cancers and that low P2RY13 expression is associated with poor prognosis and reduced immunotherapy responsiveness. Single-cell analyses revealed that P2RY13 is predominantly expressed in TAMs rather than tumor cells. Macrophages without detectable P2RY13 transcripts were markedly enriched in tumor tissues compared with paired normal tissues, and their high infiltration appeared to be associated with elevated NET scores. Tissue microarray-based IHC and mIF analyses further validated this infiltration pattern in LUAD, LIHC, and CRC. In vitro, CM from P2RY13-silenced, tumor-educated TAM-like macrophages enhanced neutrophil NETosis, whereas P2RY13 re-expression attenuated this effect. Furthermore, TMA staining indicated a positive correlation between P2RY13⁻CD68⁺ TAM infiltration and NET expression in the three malignancies. Conclusions: We identified a potentially conserved NETosis-regulating pattern in multiple cancers in which P2RY13-negative TAMs promote NET formation and are associated with adverse clinical outcomes. These findings suggest a previously unrecognized tumor-promoting mechanism and highlight potential therapeutic targets for cancer treatment.