1. Department of Veterans Affairs Medical Center, 151M, and Huntsman Cancer Institute, Department of Oncologic Sciences and Department of Medicine (Hematology/Oncology) University of Utah Health Sciences Center, 500 Foothill Blvd., Salt Lake City, UT 84148, U.S.A.
2. Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Davidson Building, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
3. ICOS Corporation, 22021 20th Avenue S.E., Bothell, WA 98021, U.S.A.