Whole methylome changes in Barrett's metaplasia, dysplasia, and cancer

The clinical management of Barrett's esophagus (BE) and the risk of esophageal adenocarcinoma (EAC) is dependent on the presence or absence of dysplasia. The histopathological diagnosis of dysplasia is unreliable however, and would benefit from additional diagnostic criteria. Here, we obtained EM-seq whole-genome methylation profiles from 86 samples across the BE/EAC disease spectrum, notably supplementing the scant existing methylation evidence for low-grade and high-grade dysplasia. While the bulk of methylation changes occur in the transition from normal squamous epithelium to intestinal metaplasia (non-dysplastic Barrett's esophagus), we identified a smaller set of changes that mark the onset of dysplasia and progression to EAC. Methylation changes were broadly independent of copy number variation. They were tightly anticorrelated with RNA-seq expression for some genes. Deconvolution of the bulk methylation signatures into constituent cell types revealed four sample groupings enriched with a particular cell type (squamous, columnar, lymphoid and erythroid cells), somewhat reflecting existing clinical classifications. We outline potential markers that could improve the diagnosis of metaplasia and dysplasia in EAC.