Abstract 2011: Attenuated levels of surface TREM1 on circulating neutrophils impair NETosis and increase infection risk in DLBCL patients

Abstract Neutrophils can undergo NETosis, but their roles in lymphoma remain unexplored. The triggering receptor expressed on myeloid cells-1 (TREM1) amplifies inflammation and may regulate NETosis. This study investigates surface TREM1's role in NETosis regulation and predicting progression-free survival (PFS), overall survival (OS), and infection risk in untreated DLBCL patients. This prospective study enrolled 118 untreated DLBCL patients. Circulating neutrophils were isolated, identified as CD45+ CD15+ using flow cytometry, and stimulated with PMA to assess NETosis by SYTOX Green or confocal microscopy. Neutrophils from healthy donors (HDs) were paired with patients to calculate normalized TREM1 or NETosis levels: (Patient - HD) / (HD) x 100%. Among 118 DLBCL patients (median age 66, 61.9% male), 39.8% were stage IV, 33.1% high-risk IPI, 23.7% had bone marrow (BM) involvement, 72.9% were non-GCB subtype, 40.7% were double expressor lymphoma (DEL), and 9.3% were Epstein-Barr virus (EBV) positive. Clinically significant infections occurred in 26 patients, with typhlitis as the most common infection focus (n = 7) and Escherichia coli as the most commonly identified pathogen (n = 10). Most patients had lower neutrophil surface-TREM1 levels than HDs (median -40.1%). High-risk IPI and non-GCB patients had significantly lower normalized TREM1 levels than their counterparts (P = 0.036 and P = 0.031, respectively). Trends were also observed for lower TREM1 levels in patients with BM involvement, DEL, and age ≥75. Patients were classified into high (≥ -43.8%; n = 66) and low (< -43.8%; n = 52) TREM1 level groups using ROC and AUC analysis. After 25.3 months of follow-up, low TREM1 patients had worse PFS (2-year PFS rate: 57.8% vs. 79.3%, log-rank P = 0.001), OS (2-year OS rate: 62.9% vs. 90.6%, log-rank P < 0.001), and a higher infection risk (cumulative incidence rate of clinically significant infection within 180 days post-DLBCL diagnosis: 36.5% vs. 10.6%, log-rank P = 0.001). Multivariate analysis showed TREM1 as an independent predictor for PFS, OS, and infection risk. Neutrophils from all 118 patients were treated ex vivo with PMA (100 nM), and the supernatant was collected to measure MPO. Patients with low TREM1 had significantly impaired NETosis (-54.6% vs. -16.8%, P < 0.001) and reduced MPO levels (61.5 vs. 82.0 ng/mL, P = 0.006). Further treatment with PMA or E. coli, followed by immunofluorescent staining and confocal microscopy, showed that neutrophils from high TREM1 patients had mildly impaired NETosis, further inhibited by the TREM1 inhibitor LP17. Neutrophils from low TREM1 patients had significantly impaired NETosis, which was restored by the TREM1 agonist PY159. In conclusion, low surface TREM1 levels on circulating neutrophils predict poorer PFS and OS, higher infection risk, and impaired NETosis in untreated DLBCL patients. These findings warrant further clinical investigation. Citation Format: Hao-Yuan Wang, Po-Chun Liu, Fu-Chen Yang, Ching-Fen Yang, Chun-Kuang Tsai, Po-Shen Ko, Yao-Chung Liu, Nien-Jung Chen. Attenuated levels of surface TREM1 on circulating neutrophils impair NETosis and increase infection risk in DLBCL patients. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2011.