Immunological comparison of carcinoembryonic antigen (CEA) extracted from tumours of various organs: their use in radioimmunological CEA determinations.

CEA was extracted by the perchloric acid method from primary adenocarcinomas of the colon and the ovary, from ascitic and pleural fluids from patients with pancreatic, lung and breast cancer, and from the cyst fluid of a benign ovarian cystadenoma. Further purification included gel filtration and affinity chromatography. Antisera against CEA from colon, breast, ovary, lung and pancreatic cancer were produced in rabbits. In double diffusion experiments, all these CEA samples showed a reaction of complete immunological identity with all the anti-CEA sera, whatever their origin. CEA from colon, breast, pancreas and ovary were labelled with 125I and used in radioimmunological experiments. In a radioimmunological system where the tracer and the antiserum were constant, all the CEA used as standards gave parallel inhibition curves, having nearly identical slopes. This was another criterion of immunological identity. Sera of numerous cancer patients were assayed in several RIA systems, one of them being the classical system with colonic CEA as tracer and anti-colonic CEA as antiserum, the others being "organ specific" systems. The values obtained in these assays were found to be highly correlated: the rank coefficient of correlation between colonic and breast cancer RIA systems was rs = 0.96, that between colonic and ovarian RIA systems, 0.92, that between colonic and pancreatic RIA systems, 0.97 and that between colonic and lung RIA systems 0.96. It is thus concluded that by use of different organ-derived CEA preparations and their corresponding polyclonal antisera, no significative differences in serum CEA levels may be expected. No evidence of organ specificity of serum CEA was found.