DNA methylation is a modification of cytosine nucleotides catalyzed by DNA methyltransferases.¹ This process is important for genomic stability and epigenetic gene silencing in normal cells as well as cellular differentiation during development.^2,3 Methylation occurs at CpG dinucleotides, which are often enriched at promoter regions of genes.^2,4 In normal tissues, promoter regions are usually unmethylated. Aberrant DNA hypermethylation contributes to gene silencing, including that of tumor suppressor genes, which may promote development and progression of certain cancers.^4-9 Aberrant DNA methylation has been observed in correlative studies in a number of malignancies, including myelodysplastic syndromes (MDS), acute myeloid leukemia (AML), breast cancer, and lung cancer.^6-11

As the roles of epigenetic modifications in various malignancies are dissected, epigenetic modifying therapies may increasingly play a role in the treatment of cancer.¹²

mRNA, messenger RNA.