Abstract
OBJECTIVE: To explore the causal relationship between inflammatory protein markers and the risk of colorectal cancer using a Mendelian randomization (MR) approach. METHODS: We obtained data pertaining to colorectal cancer from Genome-Wide Association Study (GWAS) datasets and used 91 inflammatory protein markers as the exposure variables. A two-sample MR analysis model was used to assess the causal link between the inflammatory markers and colorectal cancer risk. The robustness of the results was evaluated through heterogeneity, pleiotropy, and sensitivity analyses using 5 MR models: Inverse Variance Weighted (IVW), Weighted Median, MR Egger, Simple Mode, and Weighted Mode. We examined the mRNA expressions of PD-L1, AXIN1, and β-NGF using RT-qPCR in 86 untreated patients with colorectal adenocarcinoma admitted in Nanfang Hospital between December, 2021 and December 2023, and analyzed their correlation with the clinical characteristics of the patients. RESULTS: Using the IVW model, MR analysis revealed significant causal associations between a reduced risk of colorectal cancer and lowered expressions of AXIN1 (OR=0.866, 95% CI: 0.754-0.994, P=0.040), β-NGF (OR=0.914, 95% CI: 0.843-0.990, P=0.028; OR=0.884, 95% CI: 0.784-0.998, P=0.047 using Weighted Median model), and PD-L1 (OR=0.903, 95% CI: 0.824- 0.989, P=0.028). No significant heterogeneity or pleiotropy was observed, indicating good stability of the results. Sensitivity analysis confirmed the reliability of the findings. The clinical study demonstrated a significant correlation between PD-L1 expression and TNM staging, particularly in stage Ⅳ patients (P=0.007). AXIN1 and β -NGF expression levels were significantly correlated with the degree of tumor differentiation, and their expressions were higher in poorly differentiated samples (P<0.001). CONCLUSION: Lowered expressions of inflammatory protein markers AXIN1, β-NGF, and PD-L1 are causally correlated with a reduced risk of colorectal cancer and their expression levels are associated with TNM staging and tumor differentiation. These markers may thus serve as potential targets for colorectal cancer treatment and prevention.