1. Cambridge Institute for Medical Research, Department of Pathology University of Cambridge Cambridge CB2 0XY UK
2. Current address: MRC Laboratory of Molecular Biology Cambridge CB2 0QH UK
3. Department of Chemistry Aarhus University Aarhus C 8000 Denmark
4. Cambridge Institute for Medical Research, Department of Clinical Biochemistry University of Cambridge Cambridge CB2 0XY UK
5. Department of Cancer and Inflammation University of Southern Denmark Odense 5000 Denmark