Epigenetic corresponds to the modifications of gene expression which do not arise from modifications of the DNA sequence. The most important events are : DNA methylation at CpG islets and post-translational modification of histones .
In normal cells, these modifications allow to modulate gene expression and numerous factors are involved in these mechanisms (DNA methyltransferase, histone deacetylase and histone acetyltransferase, sirtuin, aurora kinase,...) . All these factors interact together to modulate gene expression, which notably lead to cell differenciation of totipotent cell .
In cancer, tumor cells modulate epigenetic factors to their advantage. These mechanisms lead to transcription activation of genes involved in signaling pathways, ordinary inactive (migration, invasion, cell proliferation, ...) .
Epigenetic control of adult stem cell function(4)
These activations are due to global DNA hypomethylation with a localised hypermethylation (tumor suppressor genes and cell cycle checkpoints). Histones are also modified in order to let the chromatin more accessible .