title: Essential role of cooperative NF-κB and Stat3 recruitment to ICAM-1 intronic consensus elements in the regulation of radiation-induced invasion and migration in glioma.
abstract: Although radiotherapy improves survival in patients, glioblastoma multiformes (GBMs) tend to relapse with augmented tumor migration and invasion even after ionizing radiation (IR). Aberrant nuclear factor-κB (NF-κB) and signal transducer and activator of transcription factor 3 (Stat3) activation and interaction have been suggested in several human tumors. However, possible NF-κB/Stat3 interaction and the role of Stat3 in maintenance of NF-κB nuclear retention in GBM still remain unknown. Stat3 and NF-κB (p65) physically interact with one another in the nucleus in glioma tumors. Most importantly, glutathione S-transferase pull-down assays identified that Stat3 binds to the p65 transactivation domain and is present in the NF-κB DNA-binding complex. Irradiation significantly elevated nuclear phospho-p65/phospho-Stat3 interaction in correlation with increased intercellular adhesion molecule-1 (ICAM-1) and soluble-ICAM-1 levels, migration and invasion in human glioma xenograft cell lines 4910 and 5310. Chromatin immunopreicipitation and promoter luciferase activity assays confirmed the critical role of adjacent NF-κB (+399) and Stat3 (+479) binding motifs in the proximal intron-1 in elevating IR-induced ICAM-1 expression. Specific inhibition of Stat3 or NF-κB with Stat3.siRNA or JSH-23 severely inhibited IR-induced p65 recruitment onto ICAM-1 intron-1 and suppressed migratory properties in both the cell lines. On the other hand, Stat3C- or IR-induced Stat3 promoter recruitment was significantly decreased in p65-knockdown cells, thereby suggesting the reciprocal regulation between p65 and Stat3. We also observed a significant increase in NF-κB enrichment on ICAM-1 intron-1 and ICAM-1 transactivation in Stat3C overexpressing cells. In in vivo orthotopic experiments, suppression of tumor growth in Stat3.si+IR-treated mice was associated with the inhibition of IR-induced p-p65/p-Stat3 nuclear colocalization and ICAM-1 levels. To our knowledge, this is the first study showing the crucial role of NF-κB/Stat3 nuclear association in IR-induced ICAM-1 regulation and implies that targeting NF-κB/Stat3 interaction may have future therapeutic significance in glioma treatment.
authors.affiliation: Department of Cancer Biology & Pharmacology, University of Illinois College of Medicine at Peoria, Peoria, IL, USA.
authors.forename: D
authors.initials: D
authors.lastname: Kesanakurti
authors.forename: C
authors.initials: C
authors.lastname: Chetty
authors.forename: D
authors.initials: D
authors.lastname: Rajasekhar Maddirela
authors.forename: M
authors.initials: M
authors.lastname: Gujrati
authors.forename: J S
authors.initials: JS
authors.lastname: Rao
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000528:radiation effects; D016384:Consensus Sequence; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D005910:Glioma / Q000235:genetics* / Q000473:pathology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism*; D007438:Introns / Q000235:genetics; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D009361:Neoplasm Invasiveness / Q000235:genetics; D011827:Radiation; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D016328:NF-kappa B; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D018799:Intercellular Adhesion Molecule-1