1. Chemical Biology Laboratory, National Cancer Institute, Frederick, Maryland 21702, United States
2. Department of Pathology, Cancer Research Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, United States
3. National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States
4. Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, United States
5. Molecular Pharmacology Laboratories, Applied and Developmental Research Directorate, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, United States