[1] Univ Freiburg, Ctr Med, Div Hematol Oncol, Freiburg, Germany
[2] Univ Freiburg, Ctr Med, Dept Pediat & Adolescent Med, Freiburg, Germany
[3] Univ Erlangen Nurnberg, Dept Expt Med I, Erlangen, Germany
[4] Max Planck Inst Mol Genet, Berlin, Germany