Epigenetic therapy of leukemia: An update.

Carcinogenesis is classically thought to result from genetic alterations in DNA sequence such as deletions, mutations, or chromosomal translocations. These in turn may lead to the activation of oncogenes, inactivation of tumor suppressor genes or formation of chimeric oncoproteins. Epigenetics, in contrast, refers to a number of biochemical modifications of chromatin, either to DNA directly or to its associated protein complexes that affect gene expression without altering the primary sequence of DNA [Robertson KD, Wolffe AP. DNA methylation in health and disease. Nat Rev Genet 2000;1:11-9; Jones PA, Baylin SB. The epigenomics of cancer. Cell. 2007;128:683-92]. A fundamental difference between genetic and epigenetic alterations is the irreversible nature of genetic lesions whereas epigenetic ones are potentially reversible, allowing for therapeutic intervention. In the last decade, it has become apparent that epigenetic changes play an important role in cancer, particularly in leukemia. Significant advances have been made in the elucidation of these processes as well as in translating this knowledge to the clinic, as in the development of new prognostic biomarkers or targeted therapies. In this review, we will focus on recent advances in epigenetic therapy in leukemia.