GATA6 expression in Barrett’s metaplasia development and malignant progression.

Abstract

26 Background: Barrett’s metaplasia is characterized by the presence of a columnar metaplastic epithelium in the esophagus. Barrett’s metaplasia can show malignant progression towards esophageal adenocarcinoma by a metaplasia-dysplasia-carcinoma sequence. The underlying mechanisms of Barrett’s metaplasia development and malignant progression are poorly understood. The transcription factor GATA-6 is known to be involved in columnar differentiation and carcinogenesis. GATA6 gene amplification was recently linked with aggressiveness in esophageal adenocarcinoma. Here, we studied GATA6 protein expression in normal squamous, metaplastic, dysplastic and esophageal adenocarcinoma tissues in order to identify a possible role of GATA-6 in the development and malignant progression of Barrett’s metaplasia. Methods: Samples of squamous epithelium (N=37), Barrett’s non-intestinal metaplasia (N=16), Barrett’s intestinal metaplasia (N=29), high-grade dysplasia (N= 39), in situ esophageal adenocarcinoma (N=29) and an esophageal adenocarcinoma tissue microarray (N=95) were stained with a polyclonal antibody against GATA6. Staining intensity was categorized as absent, weak, normal or strong. Scoring was performed by two independent observers and validated by a pathologist. Results: GATA6 expression was absent in squamous epithelium but expressed in all samples of Barrett’s metaplasia, preferentially in the lower half of the crypt. Expansion of GATA6-positive cells throughout the crypt was observed in high-grade dysplasia. While all cases of in situ esophageal adenocarcinoma showed GATA6 expression we observed complete loss of GATA6 expression in 17% of esophageal adenocarcinoma samples. Conclusions: GATA6 is absent in squamous epithelium but its expression increases along the metaplasia-dysplasia carcinoma sequence. GATA6 expression remains predominantly present in esophageal adenocarcinoma, however, its expression is lost in a subset of samples. Analysis of the relation between GATA6 expression and clinicopathological characteristics in esophageal adenocarcinoma is pending.