1. National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20894, United States
2. Department of Chemistry and Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, U.K.
3. La Jolla Institute for Immunology and Sanford Consortium for Regenerative Medicine, La Jolla, California 92037, United States
4. Department of Pharmacology and Moores Cancer Center, University of California, San Diego, California 92093, United States