C1QB was found upregulated in tumor tissue versus normal-matched tissue but not in CRC patients’ plasma.33 Another novel complement protein with enhanced plasma level is C4B, which is a non-enzymatic component of C3/C5 convertases and was reported as upregulated in the serum of ApcMin/+ CRC mice versus wild-type mice.31 In our study, increased C4B was found in advanced-stage CRC patients, suggesting that this complement protein might play a key role in the disease progression. Here, C3 is linked to neoplasm.