1. Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan, Cancer Research Laboratory-2, Hanno Research Center, Taiho Pharmaceutical Company Ltd., Hanno 357-8527, Japan, and Cancer Research Institute, Kanazawa University, Takara-machi, Kanazawa 920-0934, Japan