The role of gut microbiota in prostate cancer progression: A Mendelian randomization study of immune mediation

The potential relationship between the gut microbiota and prostate cancer, possibly influenced by immune cells, remains unclear. This study employed the mediation Mendelian randomization (MR) technique to investigate the causal link between the gut microbiota, immune cells, and prostate cancer. Data on immune cell activity were sourced from Valeria Orr & ugrave;'s research, whereas the genome-wide association study outcome dataset was obtained from the Integrative Epidemiology Unit database. The bidirectional MR analysis utilized 5 different methods: inverse variance weighted (IVW), weighted median, MR-Egger regression, weighted mode, and simple mode. In addition, the mediating effect of immune cells on the gut microbiota and prostate cancer was explored using mediation analysis. Eighty-three single nucleotide polymorphisms associated with prostate cancer were screened as instrumental variables. In a positive MR analysis with gut microbiota as the exposure factor, IVW showed an association between 8 gut microbiota and prostate cancer. Additionally, 9 types of immune cells have been found to be associated with prostate cancer using methods such as IVW. MR analysis of the gut microbiota on immune cells (beta1) revealed a negative correlation between Bifidobacterium and CD39+ T regulatory cells (Tregs; odds ratio [OR] = 0.785, 95% confidence interval [CI] = 0.627-0.983, P = .03). Furthermore, MR analysis of immune cells in prostate cancer disease (beta2) showed that CD39+Tregs are a risk factor for prostate cancer (OR = 1.215, 95% CI = 1.027-1.354, P = .04). Moreover, MR analysis of gut microbiota in prostate cancer (total effect) indicated that Bifidobacterium is a protective factor for prostate cancer (OR = 0.905, 95% CI = 0.822-0.977, P = .04). The sensitivity analysis verified the robustness of the above results. Mediation analysis demonstrated that CD39+Tregs partially mediate the causal relationship between Bifidobacterium and prostate cancer. This study demonstrates that Bifidobacterium inhibits prostate cancer progression through CD39+Tregs as mediators, providing new ideas and approaches for the treatment and prevention of prostate cancer.