HDAC inhibitors have multiple cellular effects, including increasing the expression of tumor suppression genes,2 increasing the expression of cell cycle regulators,3 increasing the expression of mediators of apoptosis,4-7 decreasing proteasome-mediated degradation of tumor suppressor genes,8 decreasing oncoprotein levels via loss of hsp90-mediated protection,9-11 decreasing mitotic stability,12 and decreasing angiogenesis.13,14 HDAC inhibitors potentiate the apoptotic effect of anthracyclines on breast cancer cell lines.15 Here, HDAC9 is linked to breast cancer.