Epigenetics and micrornas in cancer

MicroRNAs (miRNAs) are small noncoding RNA which regulate gene expression. In addition to their “classical” mechanism of action (targeting of messenger RNAs by binding to partially complementary sequences in their 3′-untranslated region), it has been shown that miRNAs can also regulate gene expression by affecting the epigenetics status of genes. These miRNAs, called epi-miRNAs, act by directly silencing key effectors of the epigenetic machinery, such as DNA methyltransferases (DNMTs), histone deacetylases (HDACs), and Polycomb Repressive Complex (PRC) genes. Moreover, miRNAs, like any other protein coding gene, are also regulated by epigenetic mechanisms. Overall, this two-way interaction between the miRNome and the epigenome is critically involved in the dysregulation of miRNAs observed in human cancer, and at least in part responsible for human carcinogenesis. A better understanding of the dynamic between miRNAs and epigenetics in cancer is leading to the identification of new molecular anticancer targets.