HDAC9 and malignant colon neoplasm: Other epigenetic modifiers, such as histone deacetylase (HDAC) inhibitors, which include trichostatin A (TSA), vorinostat (suberoylanilide hydroxamic acid; SAHA) and valproic acid (VPA), have been reported to induce moderate resistance and cross-resistance to different HDAC inhibitors in colon cancer cells (7–9).