1. Department of Gastroenterology, Beijing Friendship Hospital, Capital Medical University, National Clinical Research Center for Digestive Disease, Beijing 100050, China;
2. Department of Gastrointestinal Surgery, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Peking University Cancer Hospital and Institute, Beijing 100142, China;
3. Department of Gastroenterology and Hepatology, the First Medical Center, Chinese People’s Liberation Army General Hospital, Beijing 100853, China.