1. Department of Hematology, Fukushima Medical University Aizu Medical Center, Aizuwakamatsu, Fukushima, Japan,
2. Division of Stem Cell Regulation, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan,
3. Department of Pathology, Fukushima Medical University Aizu Medical Center, Aizuwakamatsu, Fukushima, Japan