The radioimmunoassay of circulating carcinoembryonic antigen of the human digestive system

Radioimmunoassay of carcinoembryonic antigen in serum of normal subjects and patients with colonic carcinoma

Sera from 14 normal subjects and 43 patients with colonic carcinoma were evaluated for the presence of carcinoembryonic antigen (CEA). Inhibiting material which behaved in the assay in a similar manner to CEA was found in normal serum at concentrations below 2.8 ng/ml. Its nature has not so far been established. Thirty-eight of the 43 patients with colonic carcinoma showed levels of serum CEA in excess of 2.8 ng/ml. The concentration of CEA in serum was correlated with the extent of the disease as classified by a staging procedure similar to that of Dukes (1932). Examination of a small number of specimens of colonic carcinoma and normal colonic mucosa suggested that the concentration of CEA in different adenocarcinomata may vary, and that traces of cross-reacting material may be found in some normal mucosae.

Carcinoembryonic antigen in faeces

Carcinoembryonic antigen (C.E.A.) was detected in the faeces of 5 out of 10 healthy volunteers, 12 out of 18 patients suffering from gastrointestinal cancer (including 10 out of 11 cases of colonic cancer), and 3 out of 13 patients suffering from non-neoplastic disease. It is suggested that C.E.A. may be present in small amounts in normal faeces but that in malignant conditions of the bowel the amount increases.

Studies of colonic carcinoma antigens

Extracts of human colonic adenocarcinomata were made with perchloric acid and shown to contain antigens which were not present in pooled samples of normal colonic mucosa or in healthy colonic mucosa from patients providing the tumours. Antisera prepared against the tumour extracts gave two precipitin lines on immunodiffusion, and antiserum prepared in Montreal according to the methods devised by Gold and Freedman (1965a and b) also gave two lines of precipitation when tested against some of these extracts; one of these precipitin lines gave a reaction of identity with that given by the antiserum produced here. The results suggest that perchloric acid may extract two antigens from colonic carcinomata.

Antibody-producing capacity in human cancer

The antibody response to primary immunization with monomeric flagellin from Salmonella adelaide was studied in 61 patients with cancer and antibody-producing capacity was correlated with survival. In 27 patients suffering from "active" cancer, antibody-producing capacity was significantly depressed (P<0.05) as compared with sick but not cancerous controls; in 13 such patients who survived more than 6 months after immunization, antibody-producing capacity was moderately depressed, whereas in 14 who survived less than 6 months, the capacity was markedly depressed. In 34 patients with "cured" cancer, by surgery and/or radiotherapy, antibody-producing capacity was significantly greater than that of the "hospital" controls and patients with "active" cancer, but yet was significantly less than that of healthy subjects. Three explanations for the findings were considered: an immunodepressive effect of general debility, an immunodepressive effect specific to cancer and, on the other hand, the occurrence of cancer preferentially in individuals with an impaired capacity for antibody production. The present findings gained added relevance from recent evidence that a specific humoral immune response is evoked by antigens of certain types at least of human cancer.