Histone deacetylases (HDACs) and histone acetyltransferases are key enzymes in histone acetylation, and the inhibition of HDACs induces the differentiation and suppresses the proliferation of cancer cells through the modulation of early growth response 1; thus, HDAC inhibitors have been proposed as effective epigenetic therapy for cancer (Gottlicher et al., 2001; Sharma et al., 2010). The gene discussed is HDAC9; the disease is cancer.