1. X. C. Le and J. Z. Xing, Department of Public Health Sciences, Faculty of Medicine and Oral Health Sciences, University of Alberta, Edmonton, Alberta, T6G 2G3, Canada.
2. J. Lee and M. Weinfeld, Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, T6G 1Z2, Canada.
3. S. A. Leadon, Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, NC 27599–7512, USA.