Distribution of Tn antigen recognized by an anti-Tn monoclonal antibody (MLS128) in normal and malignant tissues of the digestive tract.

Alterations in the normal glycosylation process are often associated with oncogenic transformation. Using an anti-Tn monoclonal antibody, MLS128, we have investigated the immunohistochemical localization of Tn antigen in normal and malignant tissues of the digestive tract. In normal tissues, MLS128 was immunoreactive with the squamous epithelium of the esophagus and was weakly reactive with the columnar epithelia of the stomach, duodenum, colon, bile duct and pancreatic duct. In malignant tissues, positive immunostaining was detected with high frequency (75%-100%) in carcinomas of the esophagus, stomach colon, biliary tract and pancreas, whereas 2 of 11 (18%) hepatocellular carcinomas were positive. Tn antigen was detected in the upper two-thirds of the normal squamous epithelium, and was often detected in squamous cell carcinomas with cancer pearls (keratinization). These results suggest that the expression of Tn antigen is related to the differentiation of squamous epithelium, or to keratinization. In normal columnar epithelial cells. Tn antigen was localized mainly to the Golgi area. This intracellular localization was preserved in well-differentiated papillary adenocarcinomas of the colon, but was lost in most cases of tubular adenocarcinomas.