A pan-HDAC inhibitor (Kis = 7, 19, 8.2, 17, 280, and 24 nM for HDAC1, HDAC2, HDAC3/SMRT, HDAC6, HDAC8, and HDAC10, respectively; prevents the growth of tumor cells in vitro, inducing apoptosis, as well as in mice harboring HCT116 or DLD-1 colon tumor xenografts