Immunoperoxidase detection of pancreatic oncofetal antigen in human tissues

Normal human adult tissues (from the pancreas, stomach, small intestine, colon and rectum), human fetal pancreas and various human tumor tissues were investigated for the expression of pancreatic oncofetal antigen (POA) by the peroxidase-antiperoxidase complex method. The antibody used in this study was raised by immunization of rabbit with POA purified from ascites of a patient with pancreatic cancer; it was the same as in our previous report on enzyme immunoassay for serum POA. POA was localized in the ductal cells of human fetal pancreas and ductal cell type pancreatic cancer tissue. It was hardly seen in acinar cells of human fetal or adult pancreas, or in acinar cell type pancreatic cancer tissue. Several cancer tissues other than the pancreas revealed positive POA-staining but less frequently. POA was also detected in small amounts in the small duct of normal adult pancreas. In other normal human tissues, POA was recognized in deep crypts of the small intestine and colon. These results indicate that POA is present abundantly in immature ductal cells of the pancreas such as in fetal pancreas and pancreatic cancer, and that high serum levels of POA seen in patients with pancreatic cancer and other malignant tumors may originate from these malignant tissues.