Although DNA methyltransferase inhibitors and histone deacetylase inhibitors are in clinical trials and show promise for the treatment of hematopoietic malignancies [32, 33, 34], treatment with vorinostat, a histone deacetylase (HDAC) inhibitor, combined with standard chemoradiation in newly diagnosed GBM in a phase II cohort did not meet efficacy objectives [35, 36]. Here, HDAC9 is linked to glioblastoma.