[1] Whitehead Inst Biomed Res, Cambridge, MA 02142 USA
[2] MIT, Dept Biol, Cambridge, MA 02139 USA
[3] Univ Texas MD Anderson Canc Ctr, Dept Mol Pathol, Houston, TX 77054 USA
[4] Swiss Inst Expt Canc Res, NCCR Mol Oncol, Ecole Polytech Fed Lausanne, CH-1066 Epalinges, Switzerland
[5] Dana Farber Canc Inst, Dept Med Oncol, Boston, MA 02115 USA
[6] Harvard Univ, Sch Med, Dept Med, Boston, MA 02115 USA
[7] Harvard Univ, Sch Med, Program Biol & Biomed Sci, Boston, MA 02115 USA
[8] Univ Calif San Diego, Sch Med, Dept Pediat & Pharmacol, La Jolla, CA 92093 USA