title: STAT-3 activates NF-kappaB in chronic lymphocytic leukemia cells.
abstract: NF-κB plays a major role in the pathogenesis of B-cell neoplasms. A broad array of mostly extracellular stimuli has been reported to activate NF-κB, to various degrees, in chronic lymphocytic leukemia (CLL) cells. Because CLL cells harbor high levels of unphosphorylated STAT-3 (USTAT-3) and USTAT-3 was reported to activate NF-κB, we sought to determine whether USTAT-3 activates NF-κB in CLL. Using the electrophoretic mobility shift assay (EMSA), we studied peripheral blood low-density cells from 15 patients with CLL and found that CLL cell nuclear extracts from all the samples bound to an NF-κB DNA probe, suggesting that NF-κB is constitutively activated in CLL. Immunoprecipitation studies showed that STAT-3 bound NF-κB p65, and confocal microscopy studies detected USTAT-3/NF-κB complexes in the nuclei of CLL cells, thereby confirming these findings. Furthermore, infection of CLL cells with retroviral STAT-3-short hairpin RNA attenuated the binding of NF-κB to DNA, as assessed by EMSA, and downregulated mRNA levels of NF-κB-regulated genes, as assessed by quantitative PCR. Taken together, our data suggest that USTAT-3 binds to the NF-κB p50/p65 dimers and that the USTAT-3/NF-κB complexes bind to DNA and activate NF-κB-regulated genes in CLL cells.
authors.affiliation: Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Liu
authors.forename: Inbal
authors.initials: I
authors.lastname: Hazan-Halevy
authors.forename: David M
authors.initials: DM
authors.lastname: Harris
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: Alessandra
authors.initials: A
authors.lastname: Ferrajoli
authors.forename: Stefan
authors.initials: S
authors.lastname: Faderl
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Keating
authors.forename: Zeev
authors.initials: Z
authors.lastname: Estrov
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D052002:NF-kappa B p50 Subunit / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D052002:NF-kappa B p50 Subunit; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D051996:Transcription Factor RelA