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

Area of Science:

• Gastroenterology
• Glycobiology
• Oncology

Background:

• Colonic mucins play a role in epithelial protection and function.
• Alterations in colonic mucin oligosaccharides are associated with neoplastic transformation.
• Lectins are valuable tools for probing specific carbohydrate structures.

Purpose of the Study:

• To investigate qualitative and quantitative differences in colonic mucin oligosaccharides between normal, adenomatous, and cancerous tissues.
• To characterize the terminal and masked oligosaccharides in different colonic epithelial states using lectin binding assays.
• To assess the impact of neuraminidase digestion on lectin binding patterns.

Main Methods:

• Utilized Dolichos biflorus agglutinin (DBA) and peanut agglutinin (PNA) lectins, which bind N-acetylgalactosamine (GalNAc) and Gal beta(1-3)GalNAc respectively.
• Employed neuraminidase digestion to expose cryptic oligosaccharide residues.
• Analyzed lectin binding patterns in normal mucosa (RM), transitional mucosa (TM), adenocarcinoma (T), and adenomatous polyps.

Main Results:

• Neuraminidase digestion generally increased DBA and PNA binding across all tissue types, except for DBA in carcinomas.
• Reciprocal gradients of DBA and PNA binding were observed in untreated specimens, reflecting differentiation states.
• Post-neuraminidase digestion, most gradients were abolished, but DBA binding remained lower in T compared to TM and RM.

Conclusions:

• Qualitative and quantitative differences exist in mucins of benign and neoplastic colonic epithelium.
• The NeuAc-GalNAc dimer is a prevalent terminal oligosaccharide in benign colonic epithelium.
• The Gal beta(1-3)GalNAc dimer is a common masked oligosaccharide in benign colonic epithelium, contrary to some prior biochemical studies.