1. Division of Human Biology, Fred Hutchinson Cancer Research Center, Post Office Box 19024, 1100 Fairview Avenue North, D4-100, Seattle, WA 98109–1024, USA.
2. Division of Clinical Research, Fred Hutchinson Cancer Research Center, Post Office Box 19024, 1100 Fairview Avenue North, D4-100, Seattle, WA 98109–1024, USA.
3. Molecular and Cellular Biology Program, University of Washington, Box 357275, Seattle, WA 98195–7275, USA.
4. Department of Genome Sciences, University of Washington, Box 351800, Seattle, WA 98195–7275, USA.
5. Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA.