1. Department of Pathology, University of Cambridge, Cambridge CB2 1QP, England, UK
2. Department of Obstetrics and Gynecology, St. James University Hospital, Leeds LS9 7TF, England, UK
3. Department of Medicine, University of Cambridge Clinical School, Addenbrooke's Hospital, Cambridge CB2 2QQ, England, UK
4. Nuffield Department of Obstetrics and Gynecology, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DZ, England, UK
5. Basic Research Program, SAIC-Frederick, Inc., National Cancer Institute-Frederick, Frederick, MD 21702