Long Interspersed Element-1 Methylation Level as a Prognostic Biomarker in Gastrointestinal Cancers.

Epigenetic changes play a crucial role in human cancer development. DNA methylation is a central epigenetic process that regulates levels of gene expression. Changes in DNA methylation that occur in human tumors include global DNA hypomethylation and site-specific CpG island promoter hypermethylation. Long interspersed element-1 (LINE-1) is a repetitive DNA retrotransposon that duplicates via a copy-and-paste genetic mechanism. As LINE-1 constitutes approximately 17% of the human genome, the extent of LINE-1 methylation is regarded as a surrogate marker of global DNA methylation. In a variety of gastrointestinal (GI) cancers, LINE-1 hypomethylation is strongly associated with a poor prognosis, supporting its potential role as a prognostic biomarker. In this article, we summarize current knowledge regarding LINE-1 methylation and its prognostic impact in GI cancers.