Main articles: DNA methylation in cancer and Regulation of transcription in cancer

In many disease processes, such as cancer, gene promoter CpG islands acquire abnormal hypermethylation, which results in transcriptional silencing that can be inherited by daughter cells following cell division. Alterations of DNA methylation have been recognized as an important component of cancer development. Hypomethylation, in general, arises earlier and is linked to chromosomal instability and loss of imprinting, whereas hypermethylation is associated with promoters and can arise secondary to gene (oncogene suppressor) silencing, but might be a target for epigenetic therapy.^[37]

Global hypomethylation has also been implicated in the development and progression of cancer through different mechanisms.^[38] Typically, there is hypermethylation of tumor suppressor genes and hypomethylation of oncogenes.^[39]

Generally, in progression to cancer, hundreds of genes are silenced or activated. Although silencing of some genes in cancers occurs by mutation…