HDAC9 and cancer: Aberrant promoter methylation inactivates the expression of tumor suppressor genes which leads to blockage of differentiation and deregulated proliferation.1, 2 Targeting the epigenetic modifying enzymes like DNA methyltransferases, histone methyltransferases or histone deacetylase (HDAC) becomes an important area for the development of anti-cancer drugs.3, 4 Currently, several epigenetic drugs have been approved for cancer treatment.