1. Department of Gastroenterology and Hepatology Hakodate Municipal Hospital Hakodate Japan
2. Department of Gastroenterology Kushiro Rosai Hospital Kushiro Japan
3. Division of Endoscopy Hokkaido University Hospital Sapporo Japan
4. Genomics Unit, Keio Cancer Center Keio University School of Medicine Tokyo Japan
5. Department of Gastroenterology and Hepatology Hokkaido University Hospital Sapporo Japan