Cancer epigenomics

Epigenetics is the study of informationmaintained duringmitotic division other than the DNA sequence itself and includes DNA methylation, and modifi- cation of chromatin histone tails. Both DNA methylation and chromatin structure are essential to normal growth and development in mammals and regulate diverse functions such as imprinting, genomic stability, and gene transcription. Incorrect establishment, maintenance, or recognition of epigenetic marks can lead to a wide range of human diseases including immunodeficiency, centromeric region instability and facial anomalies syndrome (ICF), Rett syndrome, and cancer. In human cancer, both global hypomethylation of DNA across the genome and locus specific hypermethylation of DNA in promoters are common, thus are hallmarks of malignancy. Changes in transcription of histone tail modifying enzymes have also been well documented in a variety of human tumors. Although a great deal is known about epigenetic changes in cancer at the single gene level, little is known about the cancer epigenome; a genome-wide approach is likely to reveal important new insights that can not been seen from the single gene viewpoint. In this chapter we will describe new technologies used to study the epigenome and review what we have learned about the cancer epigenome using these new approaches.