Constitutive activation of LIL-Stat in adult T-cell leukemia cells

The activation status of a recently identified STAT (signal transducers and activators of transcription) factor, LIL-Stat (lipopolysaccharide [LPS]/IL -1-inducible Stat) in adult T-cell leukemia (ATL) cells was investigated by electrophoretic mobility shift assays using nuclear extracts of leukemic c ells from 7 patients with ATL and a GAS (gamma interferon activation site)- like element termed LILRE (LPS/IL-1-responsive element), which is found in the human prointerleukin 1 beta (IL1B) gene. Spontaneous DNA binding of LIL -Stat was observed in all ATL cells examined. However, in normal human peri pheral lymphocytes, DNA binding of LIL-Stat was detected only after stimula tion with IL-1. These results demonstrated that LIL-Stat is constitutively activated in ATL cells. Furthermore, our transient transfection studies usi ng LILRE chloramphenicol acetyltransferase (CAT) reporters argue that LIL-S tat in ATL cells functions as a transcriptional activator through binding t o the LILRE in the IL1B gene. (Blood. 2000;95:2715-2718) (C) 2000 by The Am erican Society of Hematology.