1. Cancer Research Laboratory, Faculty of Medicine and Health Sciences, and Cancer Research and Developmental Biology, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand, Institute of Biochemistry, University of Lausanne, CH-1066 Epalinges, Switzerland, and London School of Hygiene and Tropical Medicine, University of London, Keppel Street, London WC1E 7HT, U.K.