Interleukin-9 (IL-9) is a multifunctional cytokine secreted from Th2 cell. Besides its role in immune and inflammatory responses, its growth promoting and antiapoptotic activities on multiple transformed cells suggest a potential role in tumorigenesis. We previously reported over-expression and activation of the receptor of IL-9 (IL-9R) in radiation-induced mouse T-cell leukemia (TL), which is an animal model of human T-cell acute lymphoblastic leukemia. In this study we established an Il9r-highly-expressing TL cell line, and examined the promoter activity with luciferase reporter assay. We found that promoter regulatory region was located at a 5` AT-rich region from -410 bp to -487 bp upstream translation start codon. EMSA and ChIP assay were also carried out to investigate the associated transcription factor(s).68th Annual Meeting of the Japanese Cancer Associatio