1. Department of Pharmacology and Cancer Biology, Duke University, 450 Research Drive, Durham, NC 27710, USA.
2. Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA.
3. Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
4. Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA.
5. University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
6. Massachusetts General Hospital Cancer Center, 55 Fruit Street, Boston, MA 02114, USA.