1 Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. Electronic address: keigokbys@keio.jp.
2 Division of Cancer Biology, Institute for Genetic Medicine, Hokkaido University, N15, W7, Kita-Ku, Sapporo 060-0815, Japan. Electronic address: m_noguch@igm.hokudai.ac.jp.