Immunohistochemistry of Human Gastrointestinal Cancer‐associated Antigen Detected by Monoclonal Antibody PA 8‐15

A murine monoclonal antibody (MAb), PA 8‐15, was produced against a newly established human pancreatic adenocarcinoma cell line, SUIT‐2. With the avidin‐biotin immunoperoxidase technique, PA 8‐15 MAb reacted strongly with 27 of 28 formalin‐fixed paraffin‐embedded pancreatic adenocarcinoma tissues. All six gall bladder carcinomas and all nine biliary tract carcinomas also showed positive reactions. In addition, PA 8‐15 MAb reacted with gastric carcinomas (6/10), colorectal carcinomas (7/11), and some other primary adenocarcinomas. The distribution of PA 8‐15 antigen on the same tissues of pancreatic cancer was different from those of CA 19‐9 and DU‐PAN‐2 antigens and CEA. PA 8‐15 MAb stained only the epithelium of the pancreatic duct, gall bladder and bile duct in normal adult tissues, and some normal fetal glandular epithelial cells. However, PA 8‐15 MAb was not reactive with inflammatory or benign tumors of the digestive system except for the epithelium, as was seen in normal adults. Reactivity of PA 8‐15 MAb with tissue specimens largely disappeared after treatment with neuraminidase, while oxidation with periodate or trypsin digestion did not alter the staining intensity, indicating that antigenic determinants may be at least partly of sialylated carbohydrate nature. These results suggest that PA 8‐15 MAb detects a new oncofetal antigen in gastrointestinal cancers, especially of the pancreatico‐biliary tract.