Epigenetics are types of mechanisms that that occur in a cell that do not permanently alter the DNA code but can contribute to the regulation of genes. DNA methylation is part of a complex mechanism that affects the chromosomal structure of a gene. It is known that aberrant DNA methylation occurs in cancer cells and can silence genes that would normally prevent cancer formation. Hypermethylation of these "tumor suppressor genes" has been shown to affect nearly all adult and pediatric cancers.