[1] Genentech Inc, San Francisco, CA 94080 USA
[2] Washington Univ, Sch Med, St Louis, MO 14263 USA
[3] Univ Calif San Francisco, San Francisco, CA 94143 USA
[4] Univ Hosp Basel, Basel, Switzerland
[5] F Hoffmann La Roche Ltd, Basel, Switzerland
[6] Univ Penn, Perelman Sch Med, Philadelphia, PA 19104 USA