1. State Key Laboratory of Cancer Biology, National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, Xi'an, Shaanxi 710032, China
2. Department of Gastroenterology, Honghui Hospital, Xi'an, Shaanxi 710054, China
3. Department of Gastroenterology, Xianyang Center Hospital, Xianyang, Shaanxi 712099, China.