title: The inflammatory cytokine TNFα cooperates with Ras in elevating metastasis and turns WT-Ras to a tumor-promoting entity in MCF-7 cells.
abstract: BACKGROUND
  In the present study we determined the relative contribution of two processes to breast cancer progression: (1) Intrinsic events, such as activation of the Ras pathway and down-regulation of p53; (2) The inflammatory cytokines TNFα and IL-1β, shown in our published studies to be highly expressed in tumors of >80% of breast cancer patients with recurrent disease.
  
  
  METHODS
  Using MCF-7 human breast tumor cells originally expressing WT-Ras and WT-p53, we determined the impact of the above-mentioned elements and cooperativity between them on the expression of CXCL8 (ELISA, qRT-PCR), a member of a "cancer-related chemokine cluster" that we have previously identified. Then, we determined the mechanisms involved (Ras-binding-domain assays, Western blot, luciferase), and tested the impact of Ras + TNFα on angiogenicity (chorioallantoic membrane assays) and on tumor growth at the mammary fat pad of mice and on metastasis, in vivo.
  
  
  RESULTS
  Using RasG12V that recapitulates multiple stimulations induced by receptor tyrosine kinases, we found that RasG12V alone induced CXCL8 expression at the mRNA and protein levels, whereas down-regulation of p53 did not. TNFα and IL-1β potently induced CXCL8 expression and synergized with RasG12V, together leading to amplified CXCL8 expression. Testing the impact of WT-Ras, which is the common form in breast cancer patients, we found that WT-Ras was not active in promoting CXCL8; however, TNFα has induced the activation of WT-Ras: joining these two elements has led to cooperative induction of CXCL8 expression, via the activation of MEK, NF-κB and AP-1. Importantly, TNFα has led to increased expression of WT-Ras in an active GTP-bound form, with properties similar to those of RasG12V. Jointly, TNFα + Ras activities have given rise to increased angiogenesis and to elevated tumor cell dissemination to lymph nodes.
  
  
  CONCLUSIONS
  TNFα cooperates with Ras in promoting the metastatic phenotype of MCF-7 breast tumor cells, and turns WT-Ras into a tumor-supporting entity. Thus, in breast cancer patients the cytokine may rescue the pro-cancerous potential of WT-Ras, and together these two elements may lead to a more aggressive disease. These findings have clinical relevance, suggesting that we need to consider new therapeutic regimens that inhibit Ras and TNFα, in breast cancer patients.
authors.forename: Tal
authors.initials: T
authors.lastname: Leibovich-Rivkin
authors.forename: Yulia
authors.initials: Y
authors.lastname: Liubomirski
authors.forename: Tsipi
authors.initials: T
authors.lastname: Meshel
authors.forename: Anastasia
authors.initials: A
authors.lastname: Abashidze
authors.forename: Daphna
authors.initials: D
authors.lastname: Brisker
authors.forename: Hilla
authors.initials: H
authors.lastname: Solomon
authors.forename: Varda
authors.initials: V
authors.lastname: Rotter
authors.forename: Miguel
authors.initials: M
authors.lastname: Weil
authors.affiliation: Department Cell Research and Immunology, George S, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel. aditbb@tauex.tau.ac.il.
authors.forename: Adit
authors.initials: A
authors.lastname: Ben-Baruch
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002642:Chick Embryo; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D053583:Interleukin-1beta; D016209:Interleukin-8 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D061986:MCF-7 Cells; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D016283:Proto-Oncogene Proteins p21(ras) / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D053583:Interleukin-1beta; D016209:Interleukin-8; D016328:NF-kappa B; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D006160:Guanosine Triphosphate; D016283:Proto-Oncogene Proteins p21(ras)