1. Department of Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
2. Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
3. Guangdong Provincial Key Laboratory of Digestive Disease, Department of Gastroenterology and Hepatology, Guangzhou First Municipal People's Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510180, P.R. China