To investigate the causal relationship between neutrophil extracellular traps (NETs) and head and neck squamous cell carcinoma (HNSCC) using Mendelian randomization (MR) methods, and to explore the clinical significance of NETs in the occurrence and development of HNSCC.

Data related to NET biomarker myeloperoxidase-DNA complex (MPO-DNA) complex and HNSCC were obtained from the pooled statistical data of the Genome-Wide Association Study database (GWAS). This study was reviewed and approved by the Medical Ethics Committee, and informed consent was obtained from patients. Patients with HNSCC admitted to Department of Oral Maxillofacial, the First Affiliated Hospital of Harbin Medical University were included as the research group, and volunteers matched for age and gender were randomly selected from the Clinical Examination Center as the control group. The levels of MPO-DNA and citrullinated histone H3 (CitH3), two markers of NETs, as well as the levels of soluble adhesion factor CD44 variant 6 (CD44v6) and leukocyte differentiation antigen CD109, markers of lymph node metastasis, were measured in all subjects. Blood coagulation indicators, including plasma prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), D-dimer (DD), and fibrinogen levels (FIB), were recorded to analyze the relationship and potential mechanisms between NETs and HNSCC.

MR results indicated a possible causal relationship between NETs and HNSCC. The inverse variance weighted P values for the four datasets were P₁ = 0.037, P₂ = 0.017, P₃ = 0.004, and P₄ = 0.023. Ultimately, 52 patients with head and neck squamous cell carcinoma and 20 healthy individuals were included. Compared with the control group, the expression levels of NETs markers MPO-DNA, CitH3, lymph node metastasis markers CD44v6 and CD109, and coagulation indicators FIB and DD were significantly elevated in the group with head and neck squamous cell carcinoma, with statistically significant differences (all P<0.001). In correlation studies between NETs markers and lymph node metastasis markers, as well as coagulation indicators, the Pearson correlation coefficient was 0.686, 0.531, 0.7, and 0.5 for MPO-DNA and DD, FIB, CD44v6, and CD109, respectively, and the Pearson correlation coefficient was 0.456, 0.503, 0.525, and 0.603 for CitH3 and DD, FIB, CD44v6, and CD109, respectively (P<0.05). In terms of diagnostic efficacy, the area under the curve (AUC) for MPO-DNA, CitH3, and MPO-DNA + CitH3 in patients with head and neck squamous cell carcinoma was 0.863, 0.892, and 0.905, respectively, with an increasing AUC of the receiver operating characteristic curve (ROC) in the order mentioned. Levels of MPO-DNA and CitH3 in patients with early-stage head and neck squamous cell carcinoma were (132.4 ± 16.4) ng/mL and (21.3 ± 2.9) ng/mL, respectively, which were lower than those in patients with advanced head and neck squamous cell carcinoma, who had MPO-DNA and CitH3 levels of (199.3 ± 33.1) ng/mL and (26.6 ± 3.7) ng/mL, respectively. The serum concentrations of FIB, DD, CD44v6, and CD109 in patients with high MPO-DNA expression were significantly higher than those in patients with low MPO-DNA expression (all P<0.05). The serum concentrations of FIB, CD44v6, and CD109 in patients with high CitH3 expression were significantly higher than those in patients with low CitH3 expression (all P<0.05).

The study indicates a potential causal relationship between NETs and HNSCC. NETs-related markers may serve as potential biomarkers for HNSCC, as they correlate with the hypercoagulable state of the cancer. NETs-related markers have potential diagnostic utility for HNSCC and are associated with tumor progression.

To investigate the prognostic significance and biological functions of neutrophil extracellular traps (NETs) related genes in oral squamous cell carcinoma (OSCC).

A total of 333 transcriptome datasets and 6 single-cell sequencing datasets of OSCC were retrieved from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Based on 69 NETs related gene sets, univariate Cox and Lasso-Cox regression were used to construct a prognostic risk model for OSCC. The model's efficacy was evaluated through Kaplan-Meier analysis and receiver operating characteristic (ROC) curves, and risk scoring and nomogram analysis were conducted. Further, the relationship between NETs risk scores and angiogenesis, epithelial-mesenchymal transition (EMT), and cell cycle was explored. Enrichment analysis was performed to annotate the functional characteristics of relevant pathways. Kaplan-Meier analysis was employed to screen for prognostic key genes. Candidate targets were validated through drug prediction and molecular docking assays. Single-cell RNA sequencing was utilized to characterize the expression profile of the key gene cathepsin G (CTSG) within the tumor microenvironment (TME). Using pan-cancer and OSCC related data retrieved from the TCGA database, we analyzed the differences in CTSG expression between tumor tissues and normal tissues. Subsequently, immunohistochemical staining experiments were performed on tissue microarrays to validate its expression at the protein level.

A prognostic risk model based on six NETs related genes (F3, AKT1, CTSG, VNN3, MPO, and IL17A) was successfully established. Patients in the high-risk group exhibited significantly shorter overall survival (OS) (P<0.0001). The area under the ROC curve (AUC) of the established model for predicting 1-, 3-, and 5-year overall survival (OS) rates was 0.718, 0.820, and 0.805, respectively. The NETs related risk score was identified as an independent prognostic factor (P<0.001), with the constructed nomogram demonstrating good calibration. The NETs related risk score correlated with angiogenesis (r = -0.20,, P<0.001), EMT (r = 0.17, P<0.01), G1/S phase transition (r = 0.11, P<0.05), and G2/M phase transition (r = 0.17, P<0.01). GSEA (gene set enrichment analysis) revealed that the high-risk group was significantly enriched in pathways including basal cell carcinoma, whereas the low-risk group exhibited significant enrichment in pathways such as alpha-linolenic acid metabolism (P<0.05). Kaplan-Meier analysis revealed that patients with low expression of CTSG had a poorer prognosis (P<0.001). Molecular docking assays demonstrated a stable binding interaction between CTSG and glutathione (binding energy: -7.4 kcal/mol). Single-cell RNA sequencing analysis further showed that CTSG was highly expressed in mast cell subsets but weakly expressed in malignant cells (P<0.001). TCGA pan-cancer analysis revealed that CTSG is underexpressed in multiple cancer tissues, including OSCC (P<0.05). Immunohistochemical staining confirmed that CTSG protein expression was lower in tumor tissues than in paracancerous tissues (P<0.01).

The NETs related prognostic model established in this study exhibits robust predictive performance. CTSG was identified as a key prognostic gene, thereby providing a novel biomarker and potential therapeutic target for prognostic evaluation and targeted therapy of OSCC.

To construct a molecular classification system for head and neck squamous cell carcinoma (HNSCC) utilizing hypoxia-related gene (HAG) expression profiles, and to comprehensively examine the clinicopathological significance and biological functions of the hypoxia gene stanniocalcin 2 (STC2) in HNSCC.

Transcriptomic data and clinical information of 546 HNSCC samples were obtained from The Cancer Genome Atlas (TCGA) database, and based on the expression profiles of 200 HRGs, HNSCC was classified subclasses using non-negative matrix factorization (NMF). HNSCC was classified into three subclasses (C1, C2, and C3), and the molecular characteristics and prognostic differences of the subclasses were assessed by comparing the tumor mutation load, functional enrichment analysis, drug sensitivity, and clinical features among the subclasses. LASSO-Cox regression was used to screen prognosis-related genes and construct prognostic models. Using oral squamous cell carcinoma (OSCC)-related data in the TCGA database, we analyzed the expression differences of STC2 in OSCC and control samples, and detected the mRNA and protein expression of STC2 in oral squamous carcinoma samples using qRT-PCR and immunohistochemistry. We knocked down STC2 in CAL-27 cells and verified the knockdown efficiency by qRT-PCR and Western blot. CCK-8 assay and cell scratch assay were used to assess the effect of STC2 on cell proliferation and migration ability.

Based on HRGs expression profiles, HNSCC was categorized into three subclasses (C1, C2, and C3). Subclass C1 had moderate hypoxic activity and good prognosis; subclass C2 had the highest hypoxic activity, poor prognosis, and poor sensitivity to CTLA-4 inhibitors (P＜0.05); subclass C3 had the lowest hypoxic activity and moderate prognosis, and STC2 belonged to subclass C3. The frequency of cyclin-dependent kinase inhibitor 2A (CDKN2A), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and tumor protein p53 (TP 53) mutations was higher in HNSCC. C1 genomic gain and deletion burden were significantly higher than C3 subclass (P＜0.05) and C2 genomic gain than C3 subclass (P＜0.05). The C2 subclass was significantly enriched in hypoxia-associated pathways, such as glycine metabolism and base excision repair (P＜0.05). The C1, C2, and C3 subclasses were significantly positively correlated in terms of sex (male) (Cramer’s V=0.15), radiation exposure (Cramer’s V=0.12), medication (Cramer’s V=0.18), and pathological grading (G1/G2) (Cramer’s V=0.25) (P＜0.05). Nine prognosis-related genes were screened by LASSO-Cox regression, among which high expression of STC2 was positively correlated with poorer overall survival (OS) in HNSCC patients (P＜0.01). Bioinformatics analysis showed that STC2 mRNA expression was higher in OSCC than in normal controls (P＜0.05). qRT-PCR and immunohistochemistry confirmed that both mRNA and protein expression of STC2 were significantly upregulated in OSCC tissues and cells (P＜0.01). In vitro experiments showed that STC2 expression was knocked down to approximately 80% in CAL-27 cells (P＜0.001), and the STC2 knockdown group had a reduced value-added rate (P＜0.001) and a reduced percentage of scratch closure (P＜0.05) compared with the control group.

We successfully constructed a molecular typing system for HNSCC based on the expression profiles of HRGs and categorized HNSCC into three subclasses with significant prognostic differences, among which the C2 subclass had the highest hypoxic activity and the poorest prognosis. STC2 was highly expressed in HNSCC and suggested a poor prognosis, demonstrating that it may be a potential target for HNSCC treatment.