Preparation and partial characterization of a pancreatic cancer-associated glycoprotein expressing CA50

In our previous study, two antigens associated with pancreatic cancer were prepared from ascites of the patients by using a newly developed affinity chromatography technique; one expressed CA19-9, CA50, Span-1, sialyl SSEA-1, and Dupan-2. This report describes the other part of the antigens, which was scarcely found in normal sera. This antigen was a glycoprotein with a high molecular weight of 1,000,000 in its native state, estimated by size exclusion chromatography on Sephacryl S400. After sodium dodecyl sulfate polyacrylamide gel electrophoresis and blotting analysis, the antigenic activity was observed on the 200-Kd band, and monoclonal antibody of CA50 showed intense reactivity to it. By means of an enzyme immunoassay, CA19-9 determinant was also recognized on it to a lesser extent, although sialyl SSEA-1 and Dupan-2 determinants were scarcely observed. From these observations, the present antigen was considered to be a serum glycoprotein carrying type-1 polylactosamine determinant and differs from previously reported glycoprotein carrying CA19-9 in its insolubility in perchloric acid solution because of its lesser degree of glycosilation. Serum levels of the antigen measured by enzyme-linked immunosorbent assay demonstrated that highly positive rates were observed in 78% of pancreatic cancers, 82% of biliary tract cancers, and 96% of hepatocellular carcinomas.