Identification of LIL-STAT in monocytic leukemia cells and monocytes afterstimulation with interleukin-6 or interferon gamma

In acute myelogenous leukemia (AML) and adult T-cell leukemia, it has been demonstrated that the transcription factor LIL-STAT is constitutively activ ated. To identify and characterize this unknown LIL-STAT protein, electroph oretic mobility shift assay (EMSA) and oligoprecipitation assays were perfo rmed by using lipopoiysaccharide/interleukin-1 (IL-1)responsive element (LI LRE) oligonucleotide probes. EMSA demonstrated a significant increase in LI L-STAT binding to the LILRE oligonucleotides after interferon gamma (IFN-ga mma) and IL-6 stimulation of THP-1 cells. In unstimulated THP-1 and AML cel ls, LILRE oligonucleotide probes bound only to STAT1 alpha and beta isoform s. The LILRE element showed a significant increase in binding of both alpha and beta isoforms of STAT1 and STAT3 upon IFN-gamma and IL-6 stimulation. Similar results were observed with human monocytes upon IL-6 or IFN-gamma s timulation. These studies indicate that LIL-STAT consists of STAT1 and STAT 3 proteins that bind to the LILRE DNA consensus site in a stimulus-dependen t way. (C) 2001 by The American Society of Hematology.