1. Division of Experimental Chemotherapy The Cancer Chemotherapy Center Japanese Foundation for Cancer Research 3‐8‐31, Ariake, Koto‐ku Tokyo 135‐8550 Japan
2. Department of Medical Genome Sciences Graduate School of Frontier Sciences The University of Tokyo 5‐1‐5, Kashiwanoha, Kashiwa‐shi Chiba 277‐8561 Japan
3. Graduate School of Pharmaceutical Sciences Kumamoto University 5‐1 Oe‐honmachi Kumamoto 862‐0973 Japan
4. Division of Protein Engineering The Cancer Institute Japanese Foundation for Cancer Research 3‐8‐31, Ariake, Koto‐ku Tokyo 135‐8550 Japan