HDAC9 and cancer: Broad spectrum deacetylases, such as those found within the HDAC family—exemplified by HDAC4’s ability to deacetylate H3K9, 14, 18, and 23 and H4K5, 8, 12, and 16—are well known for their role in cancer biology prompting development of the HDAC inhibitors described above and in Table 1 (47).