title: Activating mutations in β-catenin in colon cancer cells alter their interaction with macrophages; the role of snail.
abstract: BACKGROUND
  Tumor cells become addicted to both activated oncogenes and to proliferative and pro-survival signals provided by the abnormal tumor microenvironment. Although numerous soluble factors have been identified that shape the crosstalk between tumor cells and stroma, it has not been established how oncogenic mutations in the tumor cells alter their interaction with normal cells in the tumor microenvironment.
  
  
  RESULTS
  We showed that the isogenic HCT116 and Hke-3 cells, which differ only by the presence of the mutant kRas allele, both stimulate macrophages to produce IL1β. In turn, macrophages enhanced Wnt signaling, proliferation and survival in both HCT116 and Hke-3 cells, demonstrating that signaling by oncogenic kRas in tumor cells does not impact their interaction with macrophages. HCT116 cells are heterozygous for β-catenin (HCT116(WT/MT)), harboring one wild type (WT) and one mutant (MT) allele, but isogenic lines that carry only the WT (HCT116(WT)) or MT β-catenin allele (HCT116(MT)) have been generated. We showed that macrophages promoted Wnt signaling in cells that carry the MT β-catenin allele, but not in HCT116(WT) cells. Consistent with this observation, macrophages and IL1β failed to stabilize Snail in HCT116(WT) cells, and to protect these cells from TRAIL-induced apoptosis. Finally, we demonstrated that HCT116 cells expressing dominant negative TCF4 (dnTCF4) or HCT116 cells with silenced Snail failed to stimulate IL1β production in macrophages, demonstrating that tumor cells activate macrophages via a Wnt-dependent factor.
  
  
  CONCLUSIONS
  Our data demonstrate that oncogenic β-catenin mutations in tumor cells, and subsequent activation of Wnt signaling, not only trigger cell-intrinsic alterations, but also have a significant impact on the crosstalk of tumor cells with the tumor associated macrophages.
authors.affiliation: Department of Oncology, Albert Einstein Cancer Center, Montefiore Medical Center, Bronx, NY, USA.
authors.forename: Pawan
authors.initials: P
authors.lastname: Kaler
authors.forename: Leonard
authors.initials: L
authors.lastname: Augenlicht
authors.forename: Lidija
authors.initials: L
authors.lastname: Klampfer
mesh_terms: D000483:Alleles; D017209:Apoptosis; D002450:Cell Communication / Q000235:genetics*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D011905:Genes, ras; D045325:HCT116 Cells; D006801:Humans; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D008954:Models, Biological; D009000:Monocytes / Q000378:metabolism; D009154:Mutation; D015398:Signal Transduction; D000071250:Snail Family Transcription Factors; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D059016:Tumor Microenvironment / Q000235:genetics / Q000276:immunology; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics*
chemical_list: D000071250:Snail Family Transcription Factors; D053221:TNF-Related Apoptosis-Inducing Ligand; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin