Fields of aberrant CpG island hypermethylation in Barrett's esophagus and associated adenocarcinoma

Esophageal adenocarcinoma (EAC) is thought to develop through a multistage process in which Barrett's metaplasia progresses through low- and high-grad e dysplasia to invasive cancer. Transcriptional silencing of tumor suppress or genes by promoter CpG island hypermethylation has been observed in many types of human cancer. Analysis of CpG island hypermethylation in EAC has t hus far been limited to the CDKN2A (p16) gene. In this study, we extend the methylation analysis of EAC to include three other genes, APC, CDH1 (E-cad herin), and ESR1 (ER, estrogen receptor alpha), in addition to CDKN2A, Mole cular analysis can provide insight into the complex relationships between t issues with different histologies in Barrett's esophagus and associated ade nocarcinoma. Therefore, we have mapped the spatial distribution of methylat ion patterns in six esophagectomy cases in detail. Hypermethylation of the four CpG islands was analyzed by the MethyLight technique in 107 biopsies d erived from these six patients for a total of 428 methylation analyses. Our results show that normal esophageal squamous epithelium is unmethylated at all four CpG islands. CDH1 is unmethylated in most other tissue types as w ell, Hypermethylation of ESR1 is seen at high frequency in inflammatory ref lux esophagitis and at all subsequent stages, whereas APC and CDKN2A hyperm ethylation is found in Barrett's metaplasia, dysplasia, and EAC. When it oc curs, hypermethylation of APC, CDKN2A, and ESR1 is usually found in a large contiguous field, suggesting either a concerted methylation change associa ted with metaplasia or a clonal expansion of cells with abnormal hypermethy lation.