HDAC9 and T-cell non-Hodgkin lymphoma: The first HDAC inhibitor to be approved was vorinostat (Zolinza, Merck, Whitehouse Station, NJ, USA), a hydroxamic acid-type HDAC inhibitor, for cutaneous T-cell lymphoma (Kelly et al, 2003, 2005; O’Connor et al, 2006; Duvic et al, 2007).