1. Division of Gastroenterology, Tohoku University Graduate School of Medicine, Sendai 980-8575, Miyagi, Japan
2. Division of Cancer Stem Cell, Miyagi Cancer Center Research Institute, 47-1 Nodayama, Medeshima-Shiode, Natori 981-1293, Miyagi, Japan
3. Division of Carcinogenesis and Senescence Biology, Tohoku University Graduate School of Medicine, Natori 981-1293, Miyagi, Japan