1. Tsukuba Research Laboratories, Kyowa Hakko Kogyo Company Limited, Tsukuba-shi, Ibaraki 305-0841, Japan
2. Tokyo Research Laboratories, Kyowa Hakko Kogyo Company Limited, Machida-shi, Tokyo 194-8533, Japan
3. Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan