BIOCHEMICAL-CHARACTERIZATION AND SEROLOGICAL IMMUNOASSAY OF A PANCREATIC CARCINOMA-ASSOCIATED ANTIGEN DEFINED BY MONOCLONAL-ANTIBODY LD-B1

Several glycosylated macromolecules associated with normal and malignant pancreatic ductal cells have been described. We have generated a monoclonal antibody, LD-B1, by immunizing Balb/c mice with the postmicrosomal extract of fresh human pancreatic ductal carcinoma tissue and used it in this study to characterize the nature of the target antigen. The antigen detected by LD-B1 antibody was purified to homogeneity by affinity chromatography. Enzymatic and biochemical analysis showed it to be a nonsialylated glycoprotein that on Western blotting and immunoprecipitation analyses had an apparent molecular weight of 300-400 kDa. The mobility on gels was not affected by reducing or denaturing conditions. Competitive inhibition assays with various MoAbs and lectins indicated that the epitope recognized by LD-B1 antibody involves the carbohydrate sequence Galβ1 → 3Galβ1 → 3(or 4)GlcNAcβ1 → 3Gal. Using a double determinant sandwich ELISA, elevated antigen levels were detected in the sera of 5 of 6 patients with pancreatic carcinoma, 0 of 3 patients with chronic pancreatitis, and 12 of 137 normal controls. These results suggest that patients with pancreatic carcinoma exhibit altered expression of a heavily glycosylated molecule related to a blood group precursor immunodeterminant. © 1990.