Hepatocyte-specific Bid depletion reduces tumor development by suppressing inflammation-related compensatory proliferation

Cell Death Differ. 2015 Dec;22(12):1985-94. doi: 10.1038/cdd.2015.46. Epub 2015 Apr 24.

Abstract

Liver cancer is a major health-care concern and its oncogenic mechanisms are still largely unclear. Persistent hepatocyte cell death is a common feature among various chronic liver diseases, the blocking of which presents as logical treatment. Therefore, we aimed at investigating tumor development in mice with hepatocyte-specific Bid depletion--a BH3-only Bcl-2 family member that amplifies apoptotic death signals. Hepatocyte-specific conditional Bid-knockout mice (Bid(Δhep)) were injected with 25 mg/kg diethylnitrosamine (DEN) at 14 days of age, and liver tumorigenesis was investigated 9 months later. Additionally, different models of acute liver injury were used including: acute high-dose DEN challenge, 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet and carbon tetrachloride (CCL4) injection. Bid(Δhep) mice developed significantly fewer tumors, showed smaller maximal and average tumor size and reduced tumor incidence. In the acute DEN model, 48 h post injection we observed a significant reduction in liver injury in Bid(Δhep) animals, assessed via serum transaminases and liver histopathology. Furthermore, TNF-α, IL-1ß, cJUN and IL-6 mRNA expression was reduced. These findings were accompanied by reduced compensatory hepatocyte proliferation in Bid(Δhep) mice when compared with controls by immunohistochemistry for Ki67 and proliferating cell nuclear antigen 48 h after DEN injection. In the acute CCL4 model, Bid(Δhep) mice displayed reductions in liver injury and inflammation when compared with controls. No differences in liver injury and serum bilirubin levels were detected in Bid(Δhep) and Bid(flo/flo) mice fed with DDC, which induces bile duct injury and a ductular reaction. Our study demonstrates that in DEN-induced hepatocellular carcinoma, the inhibition of hepatocyte death pathways through Bid deletion protects animals from tumorigenesis. These results suggest that reducing hepatocyte cell death, liver inflammation and compensatory proliferation has a stronger beneficial effect than the potential side effect of enhancing tumor cell survival.

Publication types

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

MeSH terms

  • Animals
  • BH3 Interacting Domain Death Agonist Protein / genetics
  • BH3 Interacting Domain Death Agonist Protein / metabolism*
  • Carbon Tetrachloride / toxicity
  • Cell Proliferation / drug effects
  • Cells, Cultured
  • Chemical and Drug Induced Liver Injury / metabolism
  • Chemical and Drug Induced Liver Injury / pathology
  • Cyclin D1 / genetics
  • Cyclin D1 / metabolism
  • Diethylnitrosamine / toxicity
  • Disease Models, Animal
  • Hepatocytes / cytology
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism
  • Hydrogen Peroxide / toxicity
  • Inflammation* / metabolism
  • Interleukin-6 / genetics
  • Interleukin-6 / metabolism
  • Liver / enzymology
  • Liver / metabolism
  • Liver / pathology
  • Liver Neoplasms / etiology
  • Liver Neoplasms / metabolism
  • Liver Neoplasms / pathology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Transgenic
  • Non-alcoholic Fatty Liver Disease / metabolism
  • Non-alcoholic Fatty Liver Disease / pathology
  • Pyridines / toxicity
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • 3,5-diethoxycarbonyl-1,4-dihydrocollidine
  • BH3 Interacting Domain Death Agonist Protein
  • Bid protein, mouse
  • Interleukin-6
  • Pyridines
  • Tumor Necrosis Factor-alpha
  • Cyclin D1
  • Diethylnitrosamine
  • Hydrogen Peroxide
  • Carbon Tetrachloride