HDAC9 and cancer: Numerous studies show synergisms or additive effects of HDAC inhibitors and DNA damaging agents such as topoisomerase inhibitors, DNA intercalators, inhibitors of DNA synthesis, covalently modifying DNA agents (i.e., doxorubicin, epirubicin, etoposid, CDDP, melphalan, and temozolomide) and ionizing radiation in many cancer cell lines (reviewed in [37]).