Epigenetic Modifications: Basic Mechanisms in Normal and Cancerous Cells

Epigenetics is one of the most rapidly expanding fields in biology that refers to the somatically heritable differences in gene expression that are not coded in the DNA sequence itself and work with genetic mechanisms to determine transcriptional activity. Aberrant epigenetic modifications including, DNA methylation, histone modifications, and small noncoding microRNAs (miRNA), probably occur at a very early stage in neoplastic development, and they are widely described as important players in cancer progression. However, the reversible nature of epigenetic alternations has encouraged the development of pharmacologic inhibitors as anticancer therapeutics. In this case, histone deacetylase inhibitors and DNA methylation inhibitors have been FDA-approved for several years and are clinically successful. In this article, we review the mechanisms of each epigenetic modification in both normal and tumor cells. Also, the potential of epigenetic alternations as a new emerging target in cancer therapy has been discussed