Quantitation and immunochemical characterization of carcinoembryonic antigen and glucose phosphate isomerase in blood and washings of patients with gastric and colonic diseases.

Circulating levels of carcinoembryonic antigen (CEA) and glucose phosphate isomerase (GPI) have been measured and compared in 51 subjects with gastric and colonic diseases. Levels were higher in gastric and colonic cancer patients than in normals or patients with other diseases. Elevations of both these markers were most frequent in patients with metastases. Concentrations of CEA and GPI in gastrointestinal washings were also measured. No correlation was found between total protein content and concentrations of CEA or GPI in the washings. Further characterization of the perchloric acid-soluble material from colon washings by gel filtration indicated that the CEA-like substance from colon cancer patients was higher in molecular weight than standard radiolabeled CEA and CEA from normal colon washings. When tested against anti-CEA antiserum and pure CEA from a colonic cancer metastasis, all CEA preparations showed immunological identity in gel-diffusion plates; on immunoelectrophoresis similar mobility was indicative of a similar charge.