Proposed mechanism of action of vorinostat in inducing tumor cell-cycle arrest and apoptosisa . HDAC, histone deacetylase; TS, thymidylate synthase; VEGF, vascular endothelial growth factor; 17-AAG, 17-allylamino-17-demethoxygeldanamycin; 5-FU, 5-fluorouracil. Reprinted by permission from Macmillan Publishers Ltd: Richon VM. Cancer biology: mechanism of antitumour action of vorinostat (suberoylanilide hydroxamic acid), a novel histone deacetylase inhibitor. Br J Cancer 2006; 95 (Suppl 1): S2–S6, copyright 2006.