Colonic oligosaccharide structures deduced from lectin-binding studies before and after desialylation.

Dolichos biflorus agglutinin (DBA) binds N-acetylgalactosamine (GalNAc), and peanut agglutinin (PNA) binds Gal beta(1-3)GalNAc residues (Gal = galactose). We used these lectins with neuraminidase to probe colonic oligosaccharides. Tissues included normal epithelium, adenocarcinomas (T) with contiguous transitional (TM) and normal mucosae (RM), and adenomatous polyps. Except for DBA binding in carcinomas, neuraminidase digestion increased DBA and PNA binding in all epithelia. In untreated specimens, reciprocal gradients for binding by DBA (T less than TM and TM less than RM) and PNA (T greater than TM and T greater than RM) were seen. After neuraminidase, all gradients were abolished except for T less than TM and T less than RM with DBA. We conclude that (1) qualitative as well as quantitative differences may exist between the mucins of benign and neoplastic colonic epithelium, (2) the NeuAc-GalNAc dimer is a widely prevalent terminal oligosaccharide in benign epithelium at all stages of differentiation (NeuAc = sialic acid), and (3) in contrast with evidence from recent biochemical studies, the Gal beta(1-3)GalNAc dimer is a common masked oligosaccharide in benign epithelium.