Further characterization of the mucin antigen associated with malignant transformation of human colonic mucosa, detectable with the monoclonal antibody AM-3.

The recently obtained monoclonal antibody AM-3 reacts with an antigenic determinant present in several normal and neoplastic human tissues. In the large intestine the expression of the antigen is very low, but it increases dramatically after malignant transformation. In colonic adenomas the antigen expression correlates with the grade of dysplasia. The detected epitope is membrane-bound in the epithelial membranes of the liver, kidney and esophagus, while the membrane-bound and secretory forms are detectable in the salivary gland and in transformed colonic mucosa. However, the epitope is located on different molecules in all the investigated tissues. Its resistance to denaturing agents and its sensitivity to neuraminidase treatment in preparations from every investigated tissue suggest that it is a common carbohydrate-containing epitope.