DNMT3A and neoplasm: DNA hypermethylation and hypomethylation are key factors in tumor development by inhibiting tumor suppressor gene expression and inducing genomic instability (Jones & Baylin, 2002; Karpf & Matsui, 2005), which are catalyzed by kinds of DNA methyltransferases (DNMTs), such as DNMT1, DNMT3A, and DNMT3B, via transferring a methyl group to the 5′ position of cytosine in the CpG island (Robertson, 2001).