Clinical application of the enzyme immunoassay for pancreatic oncofetal antigen.

Pancreatic oncofetal antigen (POA) purified by us has been detected in sera of patients with carcinoma of the pancreas by the micro-Ouchterlony method. In an attempt to improve the sensitivity and clinical usefulness of the serum POA assay, we established an enzyme immunoassay for POA and reported the results with this method. In this study, we investigated serum POA levels in pancreatic cancer and other diseases. The tissue localization of this POA in the pancreas was also studied. For the establishment of the enzyme immunoassay, an anti-POA-F(ab')2 fragment prepared from absorbed antiserum was conjugated with beta-D-galactosidase. The solid-phase "sandwich" principle was used. The normal upper limit of the serum POA level was defined as 400 units/ml. Among 60 patients with pancreatic cancer, 44 had elevated levels (73.3%). Of 22 cases with chronic pancreatitis, 4 had elevated levels (18.2%). In malignant diseases other than pancreatic cancer, elevated levels of serum POA were seen in 17.6% to 48.5% of the patients, most of whom had only slightly elevated levels. These results indicate that enzyme immunoassay for POA is clinically useful for making a diagnosis of pancreatic cancer. Immunoperoxidase staining showed POA to be found at the apical surface of ductular cells in fetal pancreas, at the luminal surface of glandular structures in pancreatic cancer tissue, and also at the luminal surface of the small duct in normal pancreas. Thus it is suggested that a high level of serum POA in patients with pancreatic cancer is derived from pancreatic cancer tissue.