High serum levels of DUPAN2 antigen and CA19-9 in pancreatic cancer: correlation with immunocytochemical localization of antigens in cancer cells

We determined the concentration of serum DUPAN2 and CA19-9 in 43 pancreatic cancer patients by enzyme immunoassay, and compared the staining patterns of the antigens in the tissues of pancreatic cancer in order to clarify the mechanism of the elevation of serum DUPAN2 and CA19-9 levels in the patients. In 26 patients (60%), the serum DUPAN2 concentration was higher than 300 U/ml. This positive rate was not so high as that of CA19-9. However, seven out of the twelve CA19-9-negative patients were DUPAN2-positive. Using a combined assay of serum DUPAN2 and CA19-9, the diagnostic sensitivity for pancreatic cancer was 88% (38/43). Immunocytochemically, both DUPAN2 and CA19-9 were restricted to the apical surface and/or supranuclear cytoplasm in the normal pancreatic duct epithelia. In cancerous glands, however, the two were found over the entire surface and cytoplasm of the cancer cells--losing the polar distribution pattern of the antigen--and in the surrounding stroma adjacent to the cancer cells. DUPAN2 was detected in 47 (89%) out of 53 adenocarcinomas of the pancreas, and CA19-9 in 44 cases (83%). Cases with high serum antigen levels tended to display high proportions of stromal staining in the cancer tissues. These findings suggest that shedding of the antigen into the stroma adjacent to the malignant glands is one of the major mechanisms in the elevation of high serum DUPAN2 and CA19-9 levels.