HDAC9 and acute myeloid leukemia: Histone deacetylase inhibitor (HDACi) is a group of epigenetic modulators, including HDAC isoform-selective inhibitors (e.g. Entinostat, Romidepsin, Trapoxin A, and Valproic acid) and against all types of HDACs (pan-inhibitors, e.g. Trichostatin A, Vorinostat, Panobinostat, Belinostat, and Pracinostat) that have been proven to have anti-leukemia effects in AML [3].