State key Laboratory of Cancer Biology and National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, P.R. China. School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China. Department of Histology and Embryology, School of Basic Medicine, Xi'an Medical University, Xi'an, 710021, China. Department of Nutrition, Xinqiao Hospital, Army Military Medical University, Chongqing, 40038, China. State key Laboratory of Cancer Biology and National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, P.R. China. hongliu1@fmmu.edu.cn.