DNA methyltransferases catalyze the methylation of cytosine residues of CpG dinucleotides in DNA and are encoded by the human genes DNMT1, DNMT3A, and DNMT3B. DNMT3A mutations in AML have only been recently described [63–65] and found to be present in approximately 20–22% of patients with de novo AML. This evidence concerns the gene DNMT3B and acute myeloid leukemia.