Epigenetic opportunities and challenges in cancer

Epigenetic covalent modifications of DNA and chromatin proteins strongly affect gene expression and cellular activity, and epigenetic misregulation occurs in several diseases, especially cancer. First-generation drugs targeting the relatively promiscuous DNA methylation and histone acetylation modifiers have had successes in the treatment of haematological cancers. Second-generation drug programmes are in the discovery phase, targeting epigenetic enzymes with more tightly defined modes of action. This review highlights some of the challenges in identifying the most appropriate new targets and the issues that need to be addressed to facilitate the successful entry of second-generation epigenetic drugs into the clinic.