Apomucin expression and association with Lewis antigens during gastric development.

In normal stomach, MUC5AC and MUC6 apomucins are associated with Lewis types 1 and 2, respectively, and this association is lost during gastric carcinogenesis. The expression of gastric (MUC5AC, MUC6) and intestinal (MUC2, MUC4) apomucins and Lewis antigens during gastric development, using single and double labeling immunohistochemistry on fetal tissues (15-41 weeks), was analyzed and related to the tumor expression patterns. Apomucin expression in other fetal tissues was also analyzed. In gastric samples, MUC2 is detected in 14 of 19 showing no correlation with fetal age, and MUC4 is not detected. MUC5AC and MUC6 are always highly detected and are coexpressed and associated with both types of Lewis antigens. These patterns change progressively with the development of the adult gastric morphology. MUC2 is detected in the small intestine, colon, and pancreas; MUC4 is expressed in the colon; MUC5AC is detected in the small intestine; and MUC6 is found in the duodenum and pancreas. The patterns of apomucin expression and association with Lewis antigens during development are complex, but there is a trend toward the establishment of the adult pattern, with the exception of MUC4, which is not detected. These patterns found in fetal stomach indicate that alterations reported in gastric tumors do not fully recapitulate a developmental phenotype.