C5 and neoplasm: Although there were no previous reports associating C5A with CRC, another complement anaphylatoxin, C3A, was proposed as a potential CRC diagnostic biomarker.35 Moreover, several studies suggest that C5A may promote CRC tumorigenesis, metastasis, and immunosuppressive microenvironment within the tumor.35, –37 However, further validation studies are needed to confirm the association between C5A plasma levels and CRC.