1. Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, 1066 Epalinges, Switzerland
2. Institute of Clinical Molecular Biology and Tumor Genetics, GSF-National Research Center for Environment and Health, 81377 Munich, Germany
3. Swiss Institute for Experimental Cancer Research, 1066 Epalinges, Switzerland
4. Institut National de la Santé et de la Recherche Médicale, U591, Université Paris V, 75730 Paris Cedex 15, France