GSEA analysis revealed that RRM2 was involved in immune-related signaling pathways in diverse cancers, especially for the antigen that activates the B cell receptor (BCR) leading to generation of second messengers, CD22 mediated BCR regulation, FCGR3A mediated IL10 synthesis, creation of C4 and C2 activators, initial trigging of complement, binding and uptake of ligands by scavenger receptors, signaling by the BCR, complement cascade, etc. (Figure 6A–F). Here, C4A is linked to cancer.