C1R and cancer: Notably, GSEA analysis in GBM specifically revealed even more pronounced enrichment of the HALLMARK EMT pathway associated with C1R expression (size = 173, leading edge number = 102, ES = 0.79659, NES = 2.4016, p < 2e‐10) (Figure S1H), indicating that the C1R‐EMT association is particularly prominent in GBM compared to other cancer types.