Physicochemical and immunochemical properties of carcinoembryonic antigen (CEA) from different tumour sources

The physical, chemical and immunochemical properties of carcinoembryonic antigen (CEA) purified from hepatic metastases of eight tumours, originating in the colon (6), stomach (1) and lung (1), have been examined. Differences were observed in the overall molecular charge, and also in the carbohydrate composition of the different preparations (both total % carbohydrate, and mole % of the individual sugars). Negligible differences in amino acid composition were found. Gel filtration analysis of these CEA preparations and an additional four partially purified preparations (from pancreatic, hepatic, breast and oesophageal tumour tissues) revealed a single CEA-active peak of similar molecular weight (about 200,000-300,000 daltons) in all preparations. Radioimmunoassay data for the twelve CEA preparations indicated that all preparations contain the same antigenic determinants, as detected by our antiserum, but that there are differences in the expression of these determinants in different preparations.