Most CpG islands in promoter regions in human cancer are hypermethylated, DNA in general is hypomethylated, and transcriptional silencing of tumor suppressor genes occurs.31–33 Dnmt3b and Dnmt3a are involved in de novo DNA methylation; however, Dnmt1 plays a key role in maintaining DNA methylation. The gene discussed is DNMT3A; the disease is neoplasm.