[Clinical application of carcinoembryonic antigen (CEA) monoclonal antibodies (McAbs)]

CEA McAbs, recognizing three different epitopes on CEA molecules, were used to measure serum CEA level in cancer patients by enzyme-immunoassay (EIA). The results, as compared with those using polyclonal antibodies, indicated that the positive rate was higher while the false positivity was lower. Immunohistochemistry of tumour sections showed that the CEA McAbs are bonded to 80-90% of gastrointestinal cancers. Although the normal colon epithelium occasionally reacted with CEA McAbs, other normal tissues did not. After in vivo administration of radio-labeled CEA McAbs to nude mice xenograft with human colon cancer, the radio-isotope was found to be concentrated preferentially in the tumour. The ratio of tumour and normal tissue was 3.6-11.8 after 48 hours following administration. Thus, the CEA McAbs can be used clinically not only for serum CEA determination but also for diagnostic imaging.