Epigenetics in health and illness

Epigenetics can be defined as the study of the function of the genome not associated with the DNA sequence as such, and which helps to establish the patterns of gene expression. Until only a few years ago, it was thought that genetic alterations (mutations and other structural alterations that lead to the activation of oncogenes and the inactivation of suppressor genes) were responsible for the initiation and progression of the cancer. However, more recently it has been proven that epigenetic alterations are also very important in carcinogenesis. The two most-studied epigenetic phenomena (though not the only ones) are DNA methylation and the state of acetylation of histones. Unlike genetic alterations, which are irreversible, the reversible nature of these two epigenetic phenomena and the availability of agents for inhibiting methylation and of histone deacetylase mean that epigenetics has begun to be studied in clinical tests based on the significant antitumour activity of the combination of these agents in preclinical models.