Investigating the Causality and Pathogenesis of Primary Sclerosing Cholangitis in Colorectal Cancer Through Mendelian Randomization and Bioinformatics

<b>Introduction:</b> The relationship between autoimmune diseases and cancer risk has been increasingly studied. Colorectal cancer, a common malignancy with high morbidity and mortality, has been closely linked to inflammatory bowel disease (IBD) in previous research. However, the association and pathogenesis between primary sclerosing cholangitis (PSC) in autoimmune diseases and colorectal cancer remain incompletely understood. Our study directly investigated the relationship between PSC and colorectal cancer, excluding the influence of IBD, and provided new insights into this association. <b>Methods:</b> Mendelian randomization (MR) analysis was first used to investigate the potential causal relationship between PSC and colorectal cancer. Sensitivity analyses were performed to verify the reliability of the MR results. Transcriptomic data were then analyzed based on the Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) database, combined with clinical prognostic data for the final identification of core differential genes. <b>Results:</b> MR analysis demonstrated that genetic susceptibility to PSC was associated with an increased risk of colorectal cancer in a European population cohort (ratio: 1.038, 95% confidence interval: 1.016-1.060, and <i>p</i> < 0.001). Furthermore, sensitivity analyses confirmed the robustness of the MR results. Univariate and multivariate Cox analyses identified five core genes: NEDD4L, PPP1R1A, NRG1, KCNJ16, and NECAB2. Patients grouped according to high or low expression of NRG1 showed significant differences in their prognosis (<i>p</i> < 0.001). <b>Conclusion:</b> Our MR study provides evidence that genetic susceptibility to PSC is significantly associated with an increased risk of colorectal cancer in European populations. Analysis of transcriptomic data suggests that NRG1 can be used as a novel biomarker to predict patient prognosis when colorectal cancer and PSC coexist.