A B S T R A C T Epigenetic alterations, including DNA methylation, histone modifi cation, loss of genome imprinting, chromatin remodeling and non-coding RNAs, are associated with human carcinogenesis. Among them, DNA methylation is a fundamental epigenetic process to modulate gene expression. In cancer cells, altered DNA methylation includes hypermethylation of site-specifi c CpG island promoter and global DNA hypo-methylation. Detection of aberrant gene promoter methylation has been applied to

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... the clinic to stratify risk in cancer development, detect early cancer and predict clinical outcomes. Environmental factors associated with carcinogenesis are also signifi cantly related to aberrant DNA methylation. Importantly, epigenetic changes, including altered DNA methylation, are reversible and thus, used as targets for cancer therapy or chemoprevention. An increasing number of recent studies reported DNA methylation level to be a useful biomarker for diagnosis, risk assessment and prognosis prediction for gastrointestinal (GI) cancers. This review summarized the accumulated evidence for clinical application to use aberrant DNA methylation levels in GI cancers, including colorectal, gastric and esophageal cancer.