EXPRESSION OF CA19-9, DU-PAN-2, AND SPAN-1 ANTIGENS ON 2 TYPES OF NORMAL SALIVARY MUCINS

Mucins are important in cancer diagnosis and therapy. A better underst anding of the characteristics of mucins in normal and malignant tissue s could make them more effective clinical targets. Levels of the sialy lated carbohydrate mucin antigens CA19-9, DU-PAN-2, SPan-1, and TAG-72 are elevated in sera from patients with pancreatic cancer. In this st udy we examined normal saliva for the presence of these antigens. TAG- 72 reactivity was not detected in the samples examined. SPan-1 express ion correlated with the expression of CA19-9 except in Le(a-) individu als. In these individuals CA19-9 was absent; SPan-1 was expressed to v arying degrees. Little, if any, reactivity was detected with four mono clonal antibodies directed against the MUC1 mucin peptide. A high-buoy ant-density-fraction (1.35 to 1.55 g/mL) of normal saliva, containing most of the sialic acids and O-linked oligosaccharides, was separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE ). Western blots showed that CA19-9, DU-PAN-2, and SPan-1 antigens wer e found on two forms of mucins. DU-PAN-2 reactivity was detected only in the absence of the sulfhydryl reducing agent beta-mercaptoethanol. The two main forms of antigens differed in molecular size (150 kDa and greater than 400 kDa) and buoyant density (1.38 and 1.49 g/mL) and ha ve been reported to differ in aminoacid composition. In colon or pancr eas, the CA19-9, DU-PAN-2, and Span-1 carbohydrate structures have bee n reported to be present on the MUC1 mucin peptide. Our present result s suggest that in saliva, these carbohydrate antigens may be found on mucin peptides other than MUC1.