[CA 19-9 like epitope(s) on carcinoembryonic antigen molecules]

CA 19-9 epitope(s) on carcinoembryonic antigen (CEA) was studied by a method designated the hybrid immunoradiometric-assay (hybrid IRMA) using solid phase CEA antibody to capture the CEA molecule and radio-labeled NS 19-9 antibody as a detector. The radioactivities of the hybrid IRMA of respective sera with certain cancers differed from that of normal sera. The specific radioactivities of hybrid IRMA did not disappear on washing with a reaction mixture containing Triton X-100 as a detergent. Treatment of the sample with neuraminidase or periodate diminished the specific bound radioactivities, similar to CA 19-9 antigen. Furthermore, the treatment of CEAs by PI-PLC had no effect on the radioactivities. Taken together, it was suggested that CEA sugar moieties contain CA 19-9 like epitope(s).