1. Division of Medical Oncology, Department of Internal Medicine, University of Utah, Salt Lake City, Utah 84112, Basic Research Program, SAIC Frederick, Chemistry Section, Laboratory of Comparative Carcinogenesis, and Macromolecular Crystallography Laboratory, National Cancer Institute at Frederick, Frederick, Maryland 21702, Liver Cancer Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, and Developmental Therapeutics Program, National Cancer Institute, Rockville, Maryland 20852