Serum Neutrophil Extracellular Trap‐Related Proteins Serving as Potential Diagnostic and Disease Activity Biomarkers of Cronkhite–Canada Syndrome

OBJECTIVE: To explore the involvement of neutrophil dysregulation in Cronkhite-Canada syndrome (CCS) and to identify serum biomarkers for its diagnosis and disease activity assessment. METHODS: We performed comprehensive serum proteomic analysis using data-independent acquisition (DIA) on samples from patients with active CCS (aCCS) and healthy controls (HCs). Candidate proteins were further evaluated by parallel reaction monitoring (PRM). An independent validation cohort including cases with aCCS, remitting CCS (rCCS), and HCs was then assessed using enzyme-linked immunosorbent assay (ELISA). In addition, previously generated transcriptomic data and immunofluorescence staining of colonic polyps were used to assess local neutrophil extracellular trap (NET)-related immune changes in intestinal tissues. RESULTS: Proteomic screening identified 362 differentially expressed proteins, and bioinformatic analysis consistently highlighted pathways related to neutrophil activation, acute inflammation, and NET formation. Key neutrophil-associated proteins, including myeloperoxidase (MPO), lipocalin-2 (LCN2), and matrix metalloproteinase-9 (MMP-9), were significantly upregulated. PRM validated seven upregulated candidate proteins. In the independent validation cohort, compared with HCs, serum MPO-DNA complexes, LCN2, and MMP-9 were significantly elevated in aCCS patients, whereas MPO-DNA complexes and MMP-9 were significantly reduced in rCCS cases. Tissue-level transcriptomic and immunofluorescence analyses further supported NET-related immune activation in CCS colonic polyps. Receiver operating characteristic curve analysis demonstrated favorable diagnostic performance for these biomarkers. CONCLUSIONS: Our findings support the involvement of neutrophil dysregulation and NET-associated pathways in CCS pathobiology. Serum MPO-DNA complexes, LCN2, and MMP-9 may serve as promising non-invasive biomarkers for diagnosis and disease activity monitoring. Further studies incorporating disease control cohorts and mechanistic validation are warranted.