NF-kappaB protects rat ARL-6 hepatocellular carcinoma cells against hydrogen peroxide-induced apoptosis

Cancer Biol Ther. 2005 Nov;4(11):1195-202. doi: 10.4161/cbt.4.11.2078. Epub 2005 Nov 3.


Background/aims: Refractoriness of some tumours to apoptosis has been related to over-expression of NF-kappaB, while NF-kappaB inhibition can promote apoptosis in several cell types. We compared NF-kappaB activation profiles between normal rat hepatocytes and ARL-6 rat hepatocellular carcinoma (HCC) cells exposed to hydrogen peroxide (H2O2), and examined whether NF-kappaB activation could explain the observed resistance to apoptosis of ARL-6 cells. We then infected ARL-6 cells with recombinant adenovirus containing mutant (non-degradable) IkBa (Adv-mIkappaBalpha), and examined whether this rendered ARL-6 cells more sensitive to oxidative stress-induced apoptosis.

Methods: Cultured primary rat hepatocytes and ARL-6 cells were treated with graded doses of H2O2. To block NF-kappaB, ARL-6 cells were incubated with Adv-mIkappaBalpha for 24 h. Cytotoxicity, NF-kappaB activation, cell proliferation, and apoptosis were determined.

Results: H2O2 induced more apoptosis in primary hepatocytes than ARL-6 cells, and the relative resistance of ARL-6 cells to H2O2-induced apoptosis was associated with more pronounced NF-kappaB activity. In ARL-6 cells, nuclear translocation of NF-kappaB took place within 2 h of administering H2O2 and remained prominent at 36 h. Adv-mIkappaBalpha sensitized ARL-6 cells to H2O2-induced apoptosis, but cell proliferation was minimally suppressed.

Conclusions: Compared with normal hepatocytes, ARL-6 cells are refractory to apoptosis after exposure to H2O2, and this is associated with NF-kappaB activation. Conversely, NF-kappaB inhibition sensitises ARL-6 cells to H2O2-induced apoptosis. Sustained NF-kappaB activation in these HCC cells may protect them against apoptosis produced by oxidative stress.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Carcinoma, Hepatocellular / pathology*
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cells, Cultured
  • Cytoprotection*
  • Dose-Response Relationship, Drug
  • Hepatocytes / drug effects*
  • Hepatocytes / ultrastructure
  • Hydrogen Peroxide / pharmacology*
  • Liver Neoplasms / pathology*
  • Male
  • NF-kappa B / genetics
  • NF-kappa B / metabolism*
  • Oxidants / pharmacology
  • Rats
  • Rats, Wistar
  • Time Factors


  • NF-kappa B
  • Oxidants
  • Hydrogen Peroxide