DNA Methylation definition

DNA Methylation. Hypermethylation of the CpG island in promoter regions, resulting in loss of expression of tumor-suppressor genes, accounts for a majority of epigenetics changes during carcinogenesis (103). As reviewed by Vauhkonen et al., the hypermethylation rate is significantly higher in gastric cancers than in the mucosa of individuals with a healthy stomach (68). In particular, silencing of hMLH1 due to promoter hypermethylation was found in 32% of all gastric cancers (104) and in most of MSI-H gastric cancers (up to 90%) (96-98). Hypermethylation of the CDH1 gene is more frequent in diffuse type of gastric cancer (56-83%) than in intestinal type (28-44%) (105-108). Tamura et al. (106) found that the hypermethylation rate of CDH1 gene among early stage gastric cancer (60%) is similar to the rate among advanced stage gastric cancer (49%), suggesting that hypermethylation of CDH1 gene is an early event in gastric carcinogenesis. The promoter of the RUNX3 gene, a novel gastric tumor suppressor gene (109), is hypermethylated in approximately 65% of gastric cancers (110, 111). Using a set of 12 genes, Esterller et al. (104) reported that APC (34%), p16 (36%), p14 (26%), and MGMT (16%) are frequently hypermethylated in gastric cancer. However, in some cases promoter hypermethylation results in activation of genes (69). Human telomerase reverse transcriptase gene (hTERT) is one example where promoter hypermethylation is positively correlated with gene expression (112). Reactivation of telomerase activity is necessary for the immortality of cancer cells and is normally inhibited in gastric cells. The activity of hTERT is increased in almost all gastric cancers (70).
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Examples of DNA Methylation in a sentence

  • Predicting DNA Methylation State of CpG Dinucleotide Using Genome Topological Features and Deep Networks.

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