1. Department of Hematology, Hokkaido University Faculty of Medicine and Graduate School of Medicine, Sapporo 060-8638, Japan.
2. Department of Gastroenterology and Hepatology, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan.
3. Department of Surgical Pathology, Hokkaido University Hospital, Sapporo 060-8648, Japan.
4. Division of Cancer Epidemiology and Prevention, Aichi Cancer Center Research Institute, Nagoya 464-8681, Japan.
5. Department of Cancer Epidemiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
6. Department of Microbiology and Immunology, Graduate School of Medicine, WPI Immunology Frontier Research Center, Osaka University, Suita 565-0871, Japan.