title: Involvement of tumor necrosis factor-alpha in the upregulation of CXCR4 expression in gastric cancer induced by Helicobacter pylori.
abstract: BACKGROUND
  H. pylori, whose infection increases tumor invasiveness and metastasis, is generally labelled as the strongest risk factor for the development of gastric cancer. It appears not to be a coincidence that there is also an overexpression of CXCR4 and an obvious involvement in gastric cancer metastasis. The aim of this study attempts to investigate and further to establish a link between them. With H. pylori being a potent inducer of TNF-alpha, whether TNF-alpha, a tumor promoter, is involved in the induction of CXCR4 expression by H. pylori was also under research in this study.
  
  
  METHODS
  Expression of CXCR4, TNF-alpha, IL-6 and IL-1 beta mRNA was determined by real-time PCR. CXCR4 protein expression was detected by Western blotting. Concentrations of TNF-alpha, IL-6 and IL-1 beta in cell culture supernatants were measured using the Quantikine Elisa kit. To abrogate TNF-alpha expression in HGC27 cells, TNF-alpha RNAi plasmid was used to transfect them.
  
  
  RESULTS
  Levels of CXCR4 and TNF-alpha mRNA were significantly higher in H. pylori-positive gastric cancers (n = 19) compared to H. pylori-negative ones (n = 15). A subsequently Spearman's rank correlation test showed there was a positive correlation between the level of CXCR4 mRNA and that of TNF-alpha in 34 primary gastric cancers. Other results followed: Expression of CXCR4 and TNF-alpha was upregulated in gastric cancer cell MKN45 and HGC27 after infection with H. pylori 26695 (cag PAI+ ) or Tx30a (cag PAI- ); The induction of CXCR4 expression by H. pylori was inhibited significantly by a neutralizing TNF-alpha antibody, infliximab; CXCR4 expression was upregulated in MKN45 cells after treatment with exogenous TNF-alpha or co-culture with macrophage, and was downregulated in HGC27 cells after transfection with TNF-alpha RNAi plasmid. There was a significant increase in the migration of MKN45 cells treated with H. pylori 26695, and a strong inhibition when AMD 3100, a CXCR4 antagonist, or infliximab, was added.
  
  
  CONCLUSIONS
  Our findings demonstrated that H. pylori upregulates CXCR4 expression in gastric cancer through TNF-alpha.
authors.affiliation: Department of Pathophysiology, College of Basic Medical Science, China Medical University, Shenyang, China. zhaochenghai2005@yahoo.com.cn
authors.forename: Chenghai
authors.initials: C
authors.lastname: Zhao
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Lu
authors.forename: Xianmin
authors.initials: X
authors.lastname: Bu
authors.forename: Ning
authors.initials: N
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D016481:Helicobacter Infections / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D016480:Helicobacter pylori / Q000502:physiology*; D006801:Humans; D007124:Immunoenzyme Techniques; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D019718:Receptors, CXCR4 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000382:microbiology* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D053583:Interleukin-1beta; D015850:Interleukin-6; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019718:Receptors, CXCR4; D014409:Tumor Necrosis Factor-alpha