The process of DNA methylation is controlled at several different levels in normal and diseased cells. A family of enzymes, DNA methyltransferases (DNMTs) carry out the addition of methyl group. Five DNMT isoforms, DNMT1, DNMT2, DNMT3a, DNMT3b, and DNMT3L are in genomic, however only three DNMTs (DNMT1, DNMT3A, and DNMT3B) are involved in the establishment and maintenance of DNA methylation patterns.