Changes in DNA methylation patterns is a prominent characteristic of human 
tumors. Tumor cells display reduced levels of genomic DNA methylation and 
site-specific CpG island hypermethylation. Methylation of CpG dinucleotides is 
catalyzed by the enzyme family of DNA methyltransferases (DNMTs). In this 
review, the role of DNA methylation and DNMTs as key determinants of 
carcinogenesis is further elucidated. The chromatin modifying proteins that are 
known to interact with DNMTs are also described. Finally, the role of DNMTs as 
potential therapeutic targets is addressed.