Figure 1.

Unsupervised hierarchical clustering of samples obtained from four different tissue types. Clustering of the gene expression profiles of the 68 cases under study produced four main clusters. Depicted is a full-length view of the cluster dendrogram with cases orientated along the horizontal axis. Hierarchical clustering analysis is called unsupervised if the relatedness of cases is determined only by the similarity of their whole human genome expression profiles, independently of clinical or pathological parameters. Here, hierarchical cluster analysis showed that the four tissues types are clearly distinct. All 18 samples taken from healthy esophageal epithelium (NE) cluster together in the group on the left side. Carcinoma samples belong to the cluster group in the middle, encompassing two strictly separated clusters of esophageal squamous cell carcinomas (ESCC) and of esophageal adenocarcinomas (EAC). Samples taken from Barrett's esophagus (BE) form another cluster group on the right side. Please note that all samples of the different tissue types cluster together with not one mismatch.