Use of Carcino-Embryonic Antigen for Cancer Diagnosis

Abstract

A simple and rapid method is described for the purification of carcinoembryonic antigen (CEA) from malignant tissues. Carcinoembryonic antigen was extracted from rectal carcinoma, chest sarcoma and hip sarcoma in acetate buffer (0.02 M sodium acetate ph 5.0), and purified by ion exchange chromatography through CM-sephandex, followed by DEAE-Sephandex chromatography. Gel filteration, through sepharose-4B was used as final purification step. Carcinoembryonic antigen activity was monitored at each purification step by a specific double antibody radioimmunoassay procedure (Thomson et al., 1969). Carcinoembryonic antigen in the initial extract (21 ug/g tissue) was purified 2.6-fold after CM-Sephandex chromatography and 10-fold after DEAE-Sephandex chromatography. A 202-fold purification was achieved in the final purification step (yield 7.3 ug/g tissues). The CEA, purified at each step was characterized by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). In SDS-PAGE the purified CEA preparation resolved into two immunologically related species with a molecular weight of 185 Kd and 165 Kd respectively. Analysis of the CEA content of malignant tissues indicate that CEA is synthesized in substantial quantities by the colo rectal tissue (upto 21 ug/g tissue), followed by tongue, mandible, hip and chest sarcomas. No comparison of these data could be made with those of the corresponding normal tissues. Serum samples from 88 cancer patients and 23 normal subjects were analyzed for CEA activity. Highest level of CEA was obtained in the sera of patients with colo rectal cancer (44.65± 21.13 ng/ml Vs 3.8± 2.34). the analysis of the data of serum samples of patients suffering from 13 different types of cancers provide the information that the colorectal cancer, the lung cancer and oesophageal cancer all of which have endothelial origin, do secrete large quantities of CEA. Furthermore, the data clearly show that measurement of serum levels of CEA can be used as an effective index for the diagnosis of these types of cancer.