1. D. J. Dumont, Ontario Cancer Institute and Amgen Institute, Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada M5G 2C1. L. Jussila, J. Taipale, A. Lymboussaki, T. Mustonen, K. Pajusola, K. Alitalo, Molecular/Cancer Biology Laboratory, Haartman Institute, University of Helsinki, PL 21 (Haartmaninkatu 3), 00014 Helsinki, Finland. M. Breitman, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada.