1. INSERM U-524 et Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, IRCL, Place de Verdun, 59045 Lille, France, School of Chemistry, Queen's University Belfast, Belfast BT9 5AG, Northern Ireland, and Cancer Research UK Biomolecular Structure Group, The School of Pharmacy, University of London, 29−39 Brunswick Square, London WC1N 1AX, U.K.