HDAC9 and malignant colon neoplasm: To investigate whether any of the phenotypic effects mediated by Cubisbel were due to synergy provided from Cu(II) complexation, HDAC activity, apoptosis and cell cycle activity was additionally examined in the colon cancer cells treated with CuCl2 at equivalent doses to that of Cubisbel 72 h IC50 (Supplementary Fig. 7).