1. Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, Department of Experimental and Clinical Radiobiology, Maria Sklodowska-Curie Cancer Center and Institute of Oncology, 44-100 Gliwice, Poland, Peregrine Pharmaceuticals, Inc., 14272 Franklin Avenue, Suite 100, Tustin, California 92780, and Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870