1. Advanced Cell Technology, One Innovation Drive, Worcester, MA 01605, USA.
2. Lankenau Institute for Medical Research, Wynnewood, PA 19096, and the Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19104, USA.
3. Terry Fox Laboratory, British Columbia Cancer Research Center, 601 West 10 Avenue, Vancouver, BC, V5Z 1L3 Canada.
4. Department of Medicine, University of British Columbia, Vancouver, BC, V6T 2B5 Canada.