Immune cells mediate the causal pathway linking circulating complements to cancer: A Mendelian randomization study

BackgroundThe role of complement in cancer remains controversial. Whether immune cells and inflammatory factors mediate the pathway from complement to cancer has not been fully elucidated.MethodsWe conducted bidirectional Mendelian randomization (MR) analysis to explore the causal association between complement components and cancer. Meta-analysis was conducted to enhance the robustness of the results. We further explored the mediation roles of immune cells and inflammatory factors in these associations.ResultsOur study identified causal associations between 11 complement components and 12 types of cancer. Furthermore, we identified five immune cells as potential mediators: BAFF-R on IgD + CD38- naive B cell mediated 7.434% of the increased risk for liver cancer from C3; CD4 on CD39 + activated CD4 regulatory T cell mediated 12.384% of the increased risk for biliary tract cancer from CD93; CD25 + + CD45RA + CD4 not regulatory T cell and Basophil %CD33dim HLA DR- CD66b- mediated 7.721% and 7.986% of the increased risk of colorectal cancer from MASP1, respectively; CD45RA on resting CD4 regulatory T cell mediated 11.444% of the increased risk of skin cancer from MASP1.ConclusionThis study revealed the causal relationships between complement components and certain cancers, with five immune cells as potential mediators.