The inhibition of the epidermal growth factor (EGF) pathway enhances TGF-beta-induced apoptosis in rat hepatoma cells through inducing oxidative stress coincident with a change in the expression pattern of the NADPH oxidases (NOX) isoforms

Biochim Biophys Acta. 2009 Feb;1793(2):253-63. doi: 10.1016/j.bbamcr.2008.09.003. Epub 2008 Sep 24.


Transforming growth factor-beta (TGF-beta) induces apoptosis in hepatocytes, through a mechanism mediated by reactive oxygen species (ROS) production. Numerous tumoral cells develop mechanisms to escape from the TGF-beta-induced tumor suppressor effects. In this work we show that in FaO rat hepatoma cells inhibition of the epidermal growth factor receptor (EGFR) with the tyrphostin AG1478 enhances TGF-beta-induced cell death, coincident with an elevated increase in ROS production and GSH depletion. These events correlate with down-regulation of genes involved in the maintenance of redox homeostasis, such as gamma-GCS and MnSOD, and elevated mitochondrial ROS. Nonetheless, not all the ROS proceed from the mitochondria. Emerging evidences indicate that ROS production by TGF-beta is also mediated by the NADPH oxidase (NOX) system. TGF-beta-treated FaO cells induce nox1 expression. However, the treatment with TGF-beta and AG1478 greatly enhanced the expression of another family member: nox4. NOX1 and NOX4 targeted knock-down by siRNA experiments suggest that they play opposite roles, because NOX1 knockdown increases caspase-3 activity and cell death, whilst NOX4 knock-down attenuates the apoptotic process. This attenuation correlates with maintenance of GSH and antioxidant enzymes levels. In summary, EGFR inhibition enhances apoptosis induced by TGF-beta in FaO rat hepatoma cells through an increased oxidative stress coincident with a change in the expression pattern of NOX enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / metabolism
  • Apoptosis / drug effects*
  • Carcinoma, Hepatocellular / enzymology*
  • Carcinoma, Hepatocellular / genetics
  • Carcinoma, Hepatocellular / pathology
  • Epidermal Growth Factor / metabolism*
  • ErbB Receptors / antagonists & inhibitors
  • Gene Expression Regulation, Neoplastic / drug effects
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Liver Neoplasms / enzymology*
  • Liver Neoplasms / genetics
  • Liver Neoplasms / pathology
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • NADH, NADPH Oxidoreductases / genetics
  • NADH, NADPH Oxidoreductases / metabolism
  • NADPH Oxidase 1
  • NADPH Oxidase 4
  • NADPH Oxidases / genetics
  • NADPH Oxidases / metabolism*
  • Oxidative Stress / drug effects*
  • Protein Kinase Inhibitors / pharmacology
  • Quinazolines
  • RNA, Small Interfering / metabolism
  • Rats
  • Reactive Oxygen Species / metabolism
  • Transforming Growth Factor beta / pharmacology*
  • Tyrphostins / pharmacology


  • Antioxidants
  • Isoenzymes
  • Protein Kinase Inhibitors
  • Quinazolines
  • RNA, Small Interfering
  • Reactive Oxygen Species
  • Transforming Growth Factor beta
  • Tyrphostins
  • RTKI cpd
  • Epidermal Growth Factor
  • NADH, NADPH Oxidoreductases
  • NADPH Oxidase 1
  • NADPH Oxidase 4
  • NADPH Oxidases
  • NOX1 protein, rat
  • Nox4 protein, rat
  • ErbB Receptors