1. Department of Etiology and Carcinogenesis, Cancer Institute, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People’s Republic of China.
2. Department of Gastrointestinal Oncology, Tianjin Cancer Hospital, Tianjin, People’s Republic of China.
3. Cancer Research Center, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, People’s Republic of China.
4. Present address: Henan Cancer Hospital, Zhengzhou, Henan, People’s Republic of China.