title: Conditional disruption of Axin1 leads to development of liver tumors in mice.
abstract: OBJECTIVE
  Mutations in components of the Wnt signaling pathway, including β-catenin and AXIN1, are found in more than 50% of human hepatocellular carcinomas (HCCs). Disruption of Axin1 causes embryonic lethality in mice. We generated mice with conditional disruption of Axin1 to study its function specifically in adult liver.
  
  
  METHODS
  Mice with a LoxP-flanked allele of Axin1 were generated by homologous recombination. Mice homozygous for the Axin1fl/fl allele were crossed with AhCre mice; in offspring, Axin1 was disrupted in liver following injection of β-naphthoflavone (Axin1fl/fl/Cre mice). Liver tissues were collected and analyzed by quantitative real-time polymerase chain reaction and immunoprecipitation, histology, and immunoblot assays.
  
  
  RESULTS
  Deletion of Axin1 from livers of adult mice resulted in an acute and persistent increase in hepatocyte cell volume, proliferation, and transcription of genes that induce the G(2)/M transition in the cell cycle and cytokinesis. A subset of Wnt target genes was activated, including Axin2, c-Myc, and cyclin D1. However, loss of Axin1 did not increase nuclear levels of β-catenin or cause changes in liver zonation that have been associated with loss of the adenomatous polyposis coli (APC) or constitutive activation of β-catenin. After 1 year, 5 of 9 Axin1fl/fl/Cre mice developed liver tumors with histologic features of HCC.
  
  
  CONCLUSIONS
  Hepatocytes from adult mice with conditional disruption of Axin1 in liver have a transcriptional profile that differs from that associated with loss of APC or constitutive activation of β-catenin. It might be similar to a proliferation profile observed in a subset of human HCCs with mutations in AXIN1. Axin1fl/fl mice could be a useful model of AXIN1-associated tumorigenesis and HCC.
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, United Kingdom.
authors.forename: Gui Jie
authors.initials: GJ
authors.lastname: Feng
authors.forename: Welwyn
authors.initials: W
authors.lastname: Cotta
authors.forename: Xiao Qing
authors.initials: XQ
authors.lastname: Wei
authors.forename: Oliver
authors.initials: O
authors.lastname: Poetz
authors.forename: Rebecca
authors.initials: R
authors.lastname: Evans
authors.forename: Thierry
authors.initials: T
authors.lastname: Jardé
authors.forename: Karen
authors.initials: K
authors.lastname: Reed
authors.forename: Valerie
authors.initials: V
authors.lastname: Meniel
authors.forename: Geraint T
authors.initials: GT
authors.lastname: Williams
authors.forename: Alan R
authors.initials: AR
authors.lastname: Clarke
authors.forename: Trevor C
authors.initials: TC
authors.lastname: Dale
mesh_terms: D000483:Alleles; D000818:Animals; D060466:Axin Protein / Q000235:genetics* / Q000502:physiology*; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000503:physiopathology*; D002453:Cell Cycle / Q000502:physiology; D049109:Cell Proliferation; D004195:Disease Models, Animal; D017353:Gene Deletion; D022781:Hepatocytes / Q000473:pathology; D008113:Liver Neoplasms / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D008817:Mice, Mutant Strains; D051153:Wnt Proteins / Q000502:physiology; D051176:beta Catenin / Q000502:physiology
chemical_list: D060466:Axin Protein; C555452:Axin1 protein, mouse; D051153:Wnt Proteins; D051176:beta Catenin