1. Vilhelm Magnus Laboratory, Institute for Surgical Research, University of Oslo, Oslo, Norway
2. Department of Neurosurgery, Ulleval University Hospital, Oslo, Norway
3. Department of Tumor Biology, Rikshospitalet-Radiumhospitalet, Oslo, Norway
4. Department of Oncology-Pathology, Karolinska Institute, Stockholm, Sweden
5. Department of Neurosurgery, Rikshospitalet-Radiumhospitalet, Oslo, Norway