Epigenetic Changes and Their Reversal in Cancer

Cancer is caused by genetic as well as epigenetic changes. Chemotherapy is considered the mainstay of cancer therapy. But multiple side effects of chemotherapy has created a demand for developing other novel and specific targets for cancer therapy. The potential reversibility of epigenetic changes have resulted in the reactivation of epigenetically silenced tumor suppressor genes being an emerging strategy for the treatment of cancer. Epigenetic modifiers like DNA methyltransferase (DNMT) inhibitors and histone deacteylase (HDAC) inhibitors induce the re-expression of epigenetically silenced genes in vitro and in vivo. Moreover, they demonstrate safety and efficacy against neoplastic diseases in clinical trials. DNMT inhibitors like 5-azacytidine and 5-aza-2’-deoxycytidine have recently been approved by FDA for the treatment of myelodysplastic syndrome. Still the mechanism of action behind their clinical efficacy remains unclear. In this review, the different epigenetic changes taking place during tumor progression and their reversal has been discussed.