Inflammatory cytokines and oral cancer risk: an integrated study combining two-sample Mendelian randomization with experimental validation.

OBJECTIVE

This study aimed to investigate the causal relationship between inflammatory cytokines and oral cavity cancer risk using Mendelian randomization analysis and experimental validation.

METHODS

Two-sample Mendelian randomization was conducted using summary-level genome-wide association study data on 41 inflammatory cytokines and oral cavity cancer risk in Europeans. Single nucleotide polymorphisms associated with cytokines (p < 5 × 10-6) and oral cancer were selected as instrumental variables, excluding those in linkage disequilibrium. Inverse-variance weighted analysis was used as the primary method, supplemented by MR Egger, weighted median, simple and weighted mode methods. Sensitivity analyses included heterogeneity, horizontal pleiotropy, leave-one-out, and funnel plot assessments. Multivariable MR analysis adjusted for smoking, alcohol, periodontitis and malnutrition was performed. The findings were further validated through expression analysis in TCGA database and clinical samples, as well as functional studies in oral cancer cells.

RESULTS

In univariate MR analysis, increased beta-nerve growth factor (OR: 1.53, 95% CI: 1.06-2.20), and decreased macrophage colony stimulating factor (OR: 0.87, 95% CI: 0.78-0.98) and interleukin-18 (OR: 0.80, 95% CI: 0.65-0.98) were causally associated with higher oral cancer risk. In multivariable MR analysis, the effects remained significant after adjusting for exposures. No reverse causation was found. Expression analysis revealed significant upregulation of NGF in oral cancer tissues compared to adjacent normal tissues, while CSF1 and IL-18 showed no significant differences. Functional studies demonstrated that NGF overexpression promoted cell proliferation, colony formation, invasion, and migration while inhibiting apoptosis in oral cancer cells.

CONCLUSIONS

This integrated study combining MR analysis and experimental validation provides evidence for causal effects of increased beta-nerve growth factor along with decreased macrophage colony stimulating factor and interleukin-18 on higher oral cavity cancer risk, independent of known risk factors. The oncogenic role of NGF was further confirmed through functional studies, suggesting these inflammatory cytokines may represent etiologic targets for oral cancer prevention.