title: Nickel ion inhibits nuclear factor-kappa B activity in human oral squamous cell carcinoma.
abstract: BACKGROUND
  The spontaneous IL-8 secretion observed in OSCC is partially dependent on the disregulated activity of transcription factor NF-κB. Nickel compounds are well established human carcinogens, however, little is known about the influence of nickel on the spontaneous secretion of IL-8 in oral squamous cell carcinoma (OSCC) cells. The aim of the present study was to investigate whether Ni(2+) ions can influence on IL-8 secretion by OSCC.
  
  
  RESULTS
  The IL-8 secretion was measured by ELISA. The expression of IL-8 mRNA was examined by real-time PCR. The NF-κB activity was measured by luciferase assay. The phosphorylation status and nuclear localization of NF-κB subunits were examined by Western blotting or Transfactor kit and immunofluorescence staining, respectively. The interaction of NF-κB p50 subunit and Ni(2+) ions was examined by Ni(2+)-column pull down assay. The site-directed mutagenesis was used to generate a series of p50 mutants. Scratch motility assay was used to monitor the cell mobility. Our results demonstrated that, on the contrary to our expectations, Ni(2+) ions inhibited the spontaneous secretion of IL-8. As IL-8 reduction was observed in a transcriptional level, we performed the luciferase assay and the data indicated that Ni(2+) ions reduced the NF-κB activity. Measurement of p50 subunit in the nucleus and the immunofluorescence staining revealed that the inhibitory effect of Ni(2+) ions was attributed to the prevention of p50 subunit accumulation to the nucleus. By Ni(2+)-column pull down assay, Ni(2+) ions were shown to interact directly with His cluster in the N-terminus of p50 subunit. The inhibitory effect of Ni(2+) ions was reverted in the transfectant expressing the His cluster-deleted p50 mutant. Moreover, Ni(2+) ions inhibited the OSCC mobility in a dose dependent fashion.
  
  
  CONCLUSIONS
  Taken together, inhibition of NF-κB activity by Ni(2+) ion might be a novel therapeutic strategy for the treatment of oral cancer.
authors.affiliation: Department of Partial Denture Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Shionome
authors.forename: Shigeki
authors.initials: S
authors.lastname: Endo
authors.forename: Daisuke
authors.initials: D
authors.lastname: Omagari
authors.forename: Masatake
authors.initials: M
authors.lastname: Asano
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Toyoma
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Ishigami
authors.forename: Kazuo
authors.initials: K
authors.lastname: Komiyama
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression; D020450:Heavy Ions / Q000009:adverse effects*; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis; D009062:Mouth Neoplasms / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000235:genetics / Q000378:metabolism; D009532:Nickel / Q000494:pharmacology*; D011485:Protein Binding; D021381:Protein Transport / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: D016209:Interleukin-8; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D051197:Toll-Like Receptor 4; C022838:nickel chloride; D009532:Nickel