[1] Karolinska Inst, Dept Cell & Mol Biol, Stockholm, Sweden
[2] Univ Cambridge, Med Res Council, Epidemiol Unit, Cambridge, England
[3] Karolinska Inst, Dept Oncol Pathol, Stockholm, Sweden
[4] Deutsch Krebsforschungszentrum Julich, Infect & Canc Epidemiol Div, Heidelberg, Germany
[5] Cambridge Biomed Res Ctr, Dept Med, Cambridge, England