Bauhinia purpurea agglutinin (BPA) binding sites in human gastrointestinal tract

The binding of biotinylated BPA to parraffin sections of 18 normal gastrointestinal tract mucosa, 5 nonneoplastic polyps (NNP), 12 adenomas, and 59 carcinomas was studied by using avidinbiotin peroxidase complex (ABC) technique. In normal mucosa BPA appeared to bind both mucus and nonmucus glycoproteins but goblet cell mucus showed a decrease in binding and increase in binding of nonmucus glycoproteins as the cells lose their differentiation. BPA showed characteristic binding patterns in adenoma and carcinoma that differed from the pattern in normal mucosa. In normal mucosa linear binding to the apical cytoplasm in the columnar cells of the surface epithelium was observed, whereas in adenomas and carcinomas, in addition to the linear binding to the apical cytoplasm, diffuse cytoplasmic and granular deposits in the supranuclear, paranuclear or infranuclear zones were seen. Our findings suggest that BPA binding patterns in normal and neoplastic mucosa are related to the degree of cellular differentiation. In the process of malignant transformation the carbohydrate distribution undergoes progressive changes through the adenoma carcinoma sequence. These changes are related to the degree of dysplasia in adenomas and to the degree of differentiation in carcinomas.