Abstract
BACKGROUND AND OBJECTIVES: Currently, research on the role of B cells in esophageal cancer (EC) is limited, and existing studies on their impact are controversial. Therefore, this study was conducted to elucidate the complex causal relationship between B cells and EC, expand the understanding of esophageal cancer immunology. METHODS: Bidirectional two-sample Mendelian randomization (MR) was performed to assess the causal relationships between 190 B cell phenotypes and EC. To complement the MR analysis, Bayesian Weighted Mendelian Randomization (BWMR) was employed, and sensitivity analyses were conducted to evaluate the robustness of the findings. Positive results were further validated in independent cohorts of esophageal cancer studies. In addition, RNA sequencing (RNA-seq) data from The Cancer Genome Atlas (TCGA) were utilized for validation, incorporating B cell-related gene expression analysis and functional enrichment analysis to support the MR findings. RESULTS: In the primary analysis, significant causal relationships were observed between 5 B cell types and the risk of EC; the onset of EC was causally linked to 3 B cell phenotypes. Validation in other cohorts revealed that 4 outcomes aligned with the primary analysis, included were CD19 on IgD + CD38-, CD20 on IgD- CD27-, CD20 on IgD- CD38br, and CD38 on PB/PC. Further validation using RNA-seq data showed that CD38 mRNA was significantly overexpressed in EC tissues, whereas CD19 and MS4A1 mRNA levels did not differ significantly between tumor and normal tissues. Functional enrichment analysis revealed that CD19, MS4A1, and CD38 are involved in multiple tumor-related immune pathways, suggesting their pivotal role in regulating the tumor immune microenvironment. CONCLUSIONS: Our study suggests a potential connection between B cell phenotypes and EC through bidirectional two-sample MR combined with BWMR analysis, providing a preliminary basis for future research.