C3 and colorectal carcinoma: Elevated expression of complement components and regulators, including C2, C3, C5, FB, FI, FHR1 (factor H–related protein 1), CR4 (ITGAX), C4BPB, CD46, CD55, and CPN1, has been reported in colon adenocarcinoma tissues (103), with notable activation of the lectin pathway in patients with CRC (104).