title: Activation of NF-κB by SOD2 promotes the aggressiveness of lung adenocarcinoma by modulating NKX2-1-mediated IKKβ expression.
abstract: Magnesium superoxide dismutase (SOD2) has been shown to cause dysfunction of p53 transcriptional activity, whereas, in turn, SOD2 expression is regulated by p53 to modulate lung tumorigenesis. In this study, we found that the level of SOD2 expression in a panel of lung cancer cells was negatively correlated with that of NK2 homeobox 1 (NKX2-1) but was not associated with p53 status. Mechanistic studies indicated that a decrease in NKX2-1 caused by SOD2-activated IKKβ transcription was achieved by derepression of binding of Sp1 to the IKKβ promoter. Immunoprecipitation, glutathione S-transferase pull-down experiments and electrophoretic mobility shift assays demonstrated a direct interaction between NKX2-1 and Sp1, blocking Sp1-mediated IKKβ transcription. SOD2-mediated nuclear factor-kappaB activation, via elevation of IKKβ transcription, promoted anchorage-independent soft-agar growth, invasion and xenograft tumor formation, because of development of the epithelial-to-mesenchymal transition. The expression level of NKX2-1 messenger RNA was negatively associated with the extent of SOD immunostaining and the IKKβ messenger RNA expression level in lung tumors. The extent of SOD2 immunostaining and IKKβ messenger RNA levels may independently predict overall survival and relapse-free survival in lung adenocarcinoma patients. In summary, we found that SOD2 activates nuclear factor-kappaB signaling by increasing IKKβ transcription, which results in progression of lung adenocarcinoma and poorer patient outcomes. We suggest that IKKβ may potentially be targeted to improve outcomes in patients with SOD2-positive tumors.
authors.affiliation: Graduate Institute of Cancer Biology and Drug Discovery, Taipei Medical University, Taipei 115, Taiwan.
authors.forename: Po-Ming
authors.initials: PM
authors.lastname: Chen
authors.forename: Tzu-Chin
authors.initials: TC
authors.lastname: Wu
authors.forename: Yao-Chen
authors.initials: YC
authors.lastname: Wang
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Cheng
authors.forename: Gwo-Tarng
authors.initials: GT
authors.lastname: Sheu
authors.forename: Chih-Yi
authors.initials: CY
authors.lastname: Chen
authors.forename: Huei
authors.initials: H
authors.lastname: Lee
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics* / Q000378:metabolism; D007124:Immunoenzyme Techniques; D008156:Luciferases / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53; D000099156:Superoxide Dismutase 2
chemical_list: D051550:I-kappa B Kinase; D008156:Luciferases; D016328:NF-kappa B; D009687:Nuclear Proteins; D012333:RNA, Messenger; D013482:Superoxide Dismutase; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D000099156:Superoxide Dismutase 2; C000614414:Nkx2-1 protein, mouse