HDAC9 and leukemia: Other recently described examples include mutation of DNMT3A (which occurs in approximately 20% of AML patients) [11], aberrant expression of the LSD1 (KDM1A) demethylase (which is strongly implicated in AML) [12,13,14], and overexpression of histone deacetylase 9 (HDAC9), which is associated with leukaemia and lymphoma [15,16].