1. Philipps University of Marburg, Medical Center of the University Giessen and Marburg, Campus Marburg, Department of Hematology, Oncology and Immunology, Marburg;
2. Institute for Molecular Biology and Tumor Research, Marburg;
3. Department of Physiological Chemistry, Biocenter, Universität Würzburg, Würzburg; and
4. Bayer Schering Pharma, BU Oncology, Leverkusen, Germany