State Key Laboratory of Cancer Biology, National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi 710032, China. Department of Gastroenterology, Honghui Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi, China. State Key Laboratory of Cancer Biology, National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi 710032, China. Electronic address: panyanglin@gmail.com.