1. Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
2. Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02114, USA.
3. MGH Biostatistics Center, Massachusetts General Hospital, Boston, MA 02114, USA.
4. Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115, USA.
5. Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
6. Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.