ICSAT overexpression is not sufficient to cause adult T-cell leukemia or multiple myeloma. 
ICSAT (Interferon Consensus Sequence binding protein for Activated T cells) is a lymphocyte-specific member of the interferon regulatory factor (IRF) family of transcription factors, originally identified through Southwestern screening of the ATL(Adult T-cell leukemia)-16T expression library. In this study, we created transgenic mice overexpressing ICSAT in lymphocytes. Although spontaneous tumorigenesis was not observed, IL-2 production with Concanavalin A stimulation was significantly increased in transgenic mice overexpressing ICSAT. ICSAT overexpression in lymphocytes seems insufficient for the leukemogenesis of ATL or multiple myeloma (MM), however, it may regulate T cell activation and its overexpression may lead to leukemogenesis via controlling IL-2 production. Copyright 1999 Academic Press.