Human CA 19-9

Carbohydrate antigen 19-9 (CA 19-9) is a validated biomarker and indicator of abnormal glycosylation reflecting pancreatic cancer, as a biomarker with a sensitivity of about 80%, and as a predictor it can be used to assess the staging, prognosis, recurrence rate, and treatment outcome. The marker was first identified in 1979 when it reacted with a monoclonal antibody obtained from hybridoma cells inoculated with a human colorectal cancer cell line. CA 19-9 is also the sialylated Lewis blood group antigen, also known as siayl Lewis a (sLe^a), and the Lewis antigen is essential for its biosynthesis. There are three major steps in the biosynthesis of the CA 19-9 carbohydrate antigen. The first step is the transfer of galactose to the type 1 precursor chain catalyzed by β1,3-galactosyltransferases (B3GALTs). The second step is the addition of sialic residues to the 2,3 strand of the GlcNAc fragment catalyzed by α(2,3) sialyltransferases (S3TOs). The final step is the addition of fucose to the 1,4 residue of the GlcNAc molecule, catalyzed by the Lewis antigen (also known as FUT3).

Figure 1. Clinical value of CA19-9 in the management of pancreatic cancer
(Source: Goh SK, et al. 2017)

In pancreatic cancer, in addition to pancreatic adenocarcinoma, CA19-9 has been used to predict malignancy in intraductal papillary mucinous neoplasms (IPMN) and pancreatic neuroendocrine tumors (pNEN). For bronchial IPMNs, the mean serum CA 19-9 value was 78.72 U/mL in patients with malignant lesions and 27.03 U/mL in patients with benign lesions. In addition to pancreatic cancer, CA 19-9 has been used as a biomarker for various types of cancer, such as GI tumors. Some studies have shown that colorectal cancer patients with elevated CA 19-9 alone have a worse prognosis than those with elevated carcinoembryonic antigen alone.

Current immunoassays for CA 19-9 rely on the use of monoclonal antibodies, and because different companies use different antibodies in their assay kits and different assays use different antibodies, these commercial immunoassays are not directly comparable and the CA 19-9 values obtained are not interchangeable, despite the fact that they have acceptable analytical performance. It is important to note that CA 19-9 is not a tumor type-specific marker, as its elevation is observed in many malignant tumors, in addition to its presence in normal gastrointestinal epithelial cells and fetal tissues. High levels of CA 19-9 may occur in normal people who consume large amounts of tea, and circulating CA 19-9 can be abnormal in a variety of benign diseases, such as pancreatitis, liver injury, cystic tumors, and acute diarrhea.

Human carbohydrate antigen 19-9