Characterization of CA 19-9 bearing mucins as physiological exocrine pancreatic secretion products

The monoclonal antibody CA 19-9 reacts with a carbohydrate epitope (sialylated lacto-N-fucopentaose II), which was shown to be part of a ganglioside extracted from a colon carcinoma cell line as well as of a mucin isolated from gastrointestinal tract tumor patients' sera. Recently, when we compared CA 19-9 levels in pancreatic juices and corresponding serum samples from a large group of patients, we showed the high serum values to be indicative solely for a malignant disease. In contrast, the overall high CA 19-9 content in pancreatic juices from all diagnostic groups raised the question about the antigenic moieties in these samples. By means of thin layer chromatography of glycolipids with subsequent antibody overlay, gel chromatography, and density gradient analysis, we found only the mucin form in all sources investigated. Thus we conclude that the discrimination potential of the CA 19-9 assay in serum is based on an altered secretion or distribution in pancreatic tumors.