Mendelian Randomization and Single-Cell Analyses Identify the Links Between IL6 and Pan B Cells in Clear Cell Renal Cell Carcinoma

Background Although several risk factors associated with renal cell carcinoma (RCC) have been identified, the etiology of the disease remains unclear. While certain cytokines have been observed in RCC patients compared to healthy individuals, the role of cytokines in promoting RCC development and progression remains uncertain. Methods We conducted a two-sample bidirectional Mendelian randomization (MR) analysis to explore the causal effects of cytokines on clear cell RCC (ccRCC). Integrated bulk RNA sequencing (RNA-seq) and single-cell RNA sequencing (scRNA-seq) analyses were employed to unveil potential mechanisms, which were further corroborated by immunohistochemical staining and plasma cytokine detection using ELISA. Additionally, we developed a diagnostic model using logistic regression analysis. Finally, sensitivity to immunotherapy and targeted therapy was estimated using the R package. Results We found bidirectional causal effects of interleukin (IL) 6 in ccRCC, indicating a complementary and mutually reinforcing relationship. Although no statistical differences were observed in IL6 expression between ccRCC and normal tissues, plasma IL6 levels in ccRCC patients were significantly higher than in control cases, positively correlating with T stage. To mitigate potential bias from RNA-seq, we conducted scRNA-seq analysis, confirming IL6 expression in both tumor and normal tissues, consistent with RNA-seq results. Moreover, IL6 expression was found to be unevenly distributed in the B cell cluster, predominantly in the Pan B cell. Trajectory and pseudotime analyses suggested that the malignant progression of cells may be driven by interactions between IL6 and Pan B cells. Subsequently, we identified 13 Pan B cells-specific oncogenes. Using these genes, we constructed a diagnostic model with an area under the curve of 0.988, identifying ZFAS1 (Zinc finger antisense RNA 1) and BCL2A1 (BCL2 related protein A1) as independent risk factors. Finally, we demonstrated that IL6 not only influences immunotherapy response but also affects targeted therapy response. Conclusion Our analysis confirms a causal correlation between IL6 and ccRCC, suggesting that IL6 may serve as a potential target for diagnostic, therapeutic, and prognostic interventions in ccRCC.