HDAC9 and neoplasm: Histone deacetylase inhibitors (HDAC-Is) represent a new class of anticancer agents that modulate the expression of cell cycle regulation, survival and differentiation genes by enhancing histone acetylation, thus affecting multiple pathways in tumour cells with minimal effects on normal tissues (Budillon et al, 2005, 2007; Marks, 2007; Lane and Chabner, 2009).