Identification of LIL-STAT in monocytic leukemia cells and monocytes after stimulation with interleukin-6 or interferon γ

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Abstract
In acute myelogenous leukemia (AML) and adult T-cell leukemia, it has been demonstrated that the transcription factor LIL-STAT is constitutively activated. To identify and characterize this unknown LIL-STAT protein, electrophoretic mobility shift assay (EMSA) and oligoprecipitation assays were performed by using lipopolysaccharide/interleukin-1 (IL-1)–responsive element (LILRE) oligonucleotide probes. EMSA demonstrated a significant increase in LIL-STAT binding to the LILRE oligonucleotides after interferon γ (IFN-γ) and IL-6 stimulation of THP-1 cells. In unstimulated THP-1 and AML cells, LILRE oligonucleotide probes bound only to STAT1 α and β isoforms. The LILRE element showed a significant increase in binding of both α and β isoforms of STAT1 and STAT3 upon IFN-γ and IL-6 stimulation. Similar results were observed with human monocytes upon IL-6 or IFN-γ stimulation. These studies indicate that LIL-STAT consists of STAT1 and STAT3 proteins that bind to the LILRE DNA consensus site in a stimulus-dependent way.