Comparative studies on expression of CA 19-9 and DU-PAN-2 in pancreatic cancer tissue.

Thirty-eight human pancreatic cancer cases were examined by immunohistochemistry for expression of CA 19-9 and DU-PAN-2 antigens by the respective monoclonal antibodies. CA 19-9 was expressed in 82% and DU-PAN-2 in 87% of cases. A combination of two antibodies increased the reactivity to 97%. Six CA 19-9-negative cases were DU-PAN-2 positive and 4 DU-PAN-2-negative cases expressed CA 19-9. In only 1 case (an anaplastic carcinoma), neither of the antibodies was reactive with cancer cells. The reactivity of tumor cells with each of the antibodies varied from case to case, and, within the same tumor, from one area to another. Histologically, all but one tumor were adenocarcinomas. Thirty-five cases showed areas of either a moderate degree of differentiation (16 cases), poor differentiation (11 cases) or anaplastic areas (8 cases). Although both antigens were expressed in a greater number of cancer cells in well differentiated areas, and less frequently in poorly differentiated and anaplastic regions, the difference in antigen expression in relation to the degree of tumor differentiation was not statistically significant. The cellular localization of the antigens varied. DU-PAN-2 was primarily localized within the cytoplasm, whereas CA 19-9 was found mostly on the luminal cell surface and in luminal content of the glandular structure. In tumor-free pancreatic tissue, adjacent to the tumor, CA 19-9 was detected almost exclusively in the cells of large and medium sized ducts, whereas DU-PAN-2 was primarily expressed in terminal ductular and centrocinar cells. The results indicate that a cocktail of CA 19-9 and DU-PAN-2 antibodies could increase the likelihood of identifying a biomarker in most patients with pancreatic cancer.