title: Clinical implications of the LINE-1 methylation levels in patients with gastrointestinal cancer.
abstract: Epigenetic alterations, such as DNA methylation, histone modification and the loss of genome imprinting, are important indicators of human carcinogenesis. DNA methylation is a fundamental epigenetic process that modulates the gene expression levels. In cancer cells, DNA methylation may be altered in two principle ways: global DNA hypomethylation and site-specific CpG island promoter hypermethylation. Long interspersed element-1 (LINE-1 or L1) is a repetitive DNA retrotransposon that duplicates via a copy-and-paste genetic mechanism. Since LINE-1 constitutes a substantial portion (approximately 17 %) of the human genome, the extent of LINE-1 methylation is regarded to be a surrogate marker of global DNA methylation. Measuring the level of LINE-1 methylation using pyrosequencing technology has emerged as a cost-effective and high-throughput method for assessing the global DNA methylation status. In some types of gastrointestinal (GI) cancers, LINE-1 hypomethylation is strongly associated with a poor prognosis, supporting its potential role as a prognostic marker. In addition, the LINE-1 methylation level may prove to be a useful clinical biomarker for assessing the risk of cancer or predicting the chemotherapeutic efficacy of treatment in patients with GI cancers. In this article, we summarize current knowledge regarding LINE-1 methylation and its clinical implications in GI cancers, including colorectal cancer, gastric cancer and esophageal cancer.
authors.affiliation: Department of Gastroenterological Surgery, Graduate School of Medical Science, Kumamoto University, 1-1-1 Honjo, Kumamoto, 860-8556, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Baba
authors.forename: Asuka
authors.initials: A
authors.lastname: Murata
authors.forename: Masayuki
authors.initials: M
authors.lastname: Watanabe
authors.forename: Hideo
authors.initials: H
authors.lastname: Baba
mesh_terms: D014408:Biomarkers, Tumor; D018899:CpG Islands / Q000235:genetics; D004247:DNA / Q000235:genetics; D019175:DNA Methylation; D044127:Epigenesis, Genetic / Q000235:genetics*; D005770:Gastrointestinal Neoplasms / Q000235:genetics*; D015894:Genome, Human / Q000235:genetics; D006801:Humans; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D011379:Prognosis; D012091:Repetitive Sequences, Nucleic Acid; D018626:Retroelements; D012306:Risk
chemical_list: D014408:Biomarkers, Tumor; D018626:Retroelements; D004247:DNA