1,2 1Division of Molecular Pathology, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands; 2Oncode Institute, 3521 AL Utrecht, The Netherlands; 3Division of Cell Systems and Drug Safety, Leiden Academic Center for Drug Research, Leiden University, 2333 CC Leiden, The Netherlands Corresponding authors: j.jonkers{at}nki.nl, s.moser{at}nki.nl, r.j.p.bouwman{at}lacdr.leidenuniv.nl Footnotes Supplemental material is available for this article. Article published online ahead of print.