Seiji Okada M.D., Ph.D. is a Professor at Joint Research Center for Human Retrovirus Infection & Graduate School of Medicine, Kumamoto University, Japan. He received his M.D. in 1985 and his Ph.D. degree in 1992 from Jichi Medical University, where he worked on the purification and characterization of murine hematopoietic stem cells. He established several types of highly immuno-compromised mice, humanized mice, and Patient-derived tumor xenograft (PDX) models for AIDS and cancer research. His current research interest is the development of novel therapy for hematological malignancies using a mouse model system especially virus infection-derived lymphoma/leukemia such as AIDS-related lymphoma and adult T cell leukemia/lymphoma.