1. Cancer Research Laboratories, Department of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, U.K., Pharmaceutical Sciences Institute, Aston University, Birmingham B4 7ET, U.K., EORTC Screening and Pharmacology Group, New Drug Development Office, Free University, 1081 HV Amsterdam, The Netherlands, and Max-Delbrück-Centrum für Molekulare Medizin, 13122 Berlin