SUCRASE-ISOMALTASE GENE-EXPRESSION IN BARRETT-ESOPHAGUS AND ADENOCARCINOMA

Background: Specialized Barrett's esophageal mucosa, characterized by incomplete intestinal metaplasia of the esophageal mucosa, is associated with the development of adenocarcinoma. Although the intestinal disaccharidase sucrase-isomaltase (SI) has been shown in incomplete intestinal metaplasia of the stomach, it is commonly believed that Barrett's mucosa does not express SI based on the lack of enzymatic activity. This study was undertaken to determine whether the SI gene is expressed in Barrett's epithelium and its associated adenocarcinoma at the level of messenger RNA (mRNA) and protein. Methods: Reverse transcription polymerase chain reaction was used to determine the presence of SI mRNA in Barrett's esophagus and esophageal adenocarcinomas. Cellular localization of SI protein was determined by immunohistochemistry. Results: SI mRNA was identified in 76% of Barrett's epithelium and 82% of esophageal adenocarcinomas. The transcriptional initiation site for SI in these tissues was identical to that of the small intestine. Immunohistochemical localization showed that SI was directed to the apical membrane in Barrett's epithelium in contrast to a more diffuse cytoplasmic pattern in esophageal adenocarcinomas. Conclusions: Columnar cells of specialized Barrett's epithelium express SI and are, therefore, phenotypically similar to those in incomplete intestinal metaplasia of the stomach with respect to intestinal gene expression. © 1993.