β-Catenin loss in hepatocytes promotes hepatocellular cancer after diethylnitrosamine and phenobarbital administration to mice

PLoS One. 2012;7(6):e39771. doi: 10.1371/journal.pone.0039771. Epub 2012 Jun 25.

Abstract

Hepatocellular Carcinoma (HCC) is the fifth most common cancer worldwide. β-Catenin, the central orchestrator of the canonical Wnt pathway and a known oncogene is paramount in HCC pathogenesis. Administration of phenobarbital (PB) containing water (0.05% w/v) as tumor promoter following initial injected intraperitoneal (IP) diethylnitrosamine (DEN) injection (5 µg/gm body weight) as a tumor inducer is commonly used model to study HCC in mice. Herein, nine fifteen-day male β-catenin knockout mice (KO) and fifteen wild-type littermate controls (WT) underwent DEN/PB treatment and were examined for hepatic tumorigenesis at eight months. Paradoxically, a significantly higher tumor burden was observed in KO (p<0.05). Tumors in KO were β-catenin and glutamine synthetase negative and HGF/Met, EGFR & IGFR signaling was unremarkable. A significant increase in PDGFRα and its ligand PDGF-CC leading to increased phosphotyrosine-720-PDGFRα was observed in tumor-bearing KO mice (p<0.05). Simultaneously, these livers displayed increased cell death, stellate cell activation, hepatic fibrosis and cell proliferation. Further, PDGF-CC significantly induced hepatoma cell proliferation especially following β-catenin suppression. Our studies also demonstrate that the utilized DEN/PB protocol in the WT C57BL/6 mice did not select for β-catenin gene mutations during hepatocarcinogenesis. Thus, DEN/PB enhanced HCC in mice lacking β-catenin in the liver may be due to their ineptness at regulating cell survival, leading to enhanced fibrosis and regeneration through PDGFRα activation. β-Catenin downregulation also made hepatoma cells more sensitive to receptor tyrosine kinases and thus may be exploited for therapeutics.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carcinogens / toxicity*
  • Diethylnitrosamine / toxicity*
  • Hepatocytes / metabolism*
  • Immunohistochemistry
  • Ligands
  • Liver Neoplasms, Experimental / chemically induced*
  • Liver Neoplasms, Experimental / metabolism
  • Liver Neoplasms, Experimental / pathology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Phenobarbital / toxicity*
  • Receptor, Platelet-Derived Growth Factor alpha / metabolism
  • beta Catenin / genetics
  • beta Catenin / physiology*

Substances

  • Carcinogens
  • Ligands
  • beta Catenin
  • Diethylnitrosamine
  • Receptor, Platelet-Derived Growth Factor alpha
  • Phenobarbital