1. Adult Stem Cell Research Center, College of Veterinery Medicine, Seoul National University, Seoul 151-742, Korea.
2. Laboratory of Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinery Medicine, Seoul National University, Seoul 151-742, Korea.
3. BK 21 program for Veterinary Sciences, College of Veterinery Medicine, Seoul National University, Seoul 151-742, Korea.