1. Department of Environmental Oncology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
2. Department of Gastroenterology and Hepatology, Graduate School of Medicine, Yamaguchi University, Minami Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan
3. Amaguchi University Health Administration Center, 1677-1 Yoshida, Yamaguchi 753-8511, Japan
4. Department of Oncology and Laboratory Medicine, Graduate School of Medicine, Yamaguchi University, Minami Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan