Oxidative stress enhances Axl-mediated cell migration through an Akt1/Rac1-dependent mechanism

Free Radic Biol Med. 2013 Dec;65:1246-1256. doi: 10.1016/j.freeradbiomed.2013.09.011. Epub 2013 Sep 21.

Abstract

Persistent oxidative stress is common in cancer cells because of abnormal generation of reactive oxygen species (ROS) and has been associated with malignant phenotypes, such as chemotherapy resistance and metastasis. Both overexpression of Axl and abnormal ROS elevation have been linked to cell transformation and increased cell migration. However, the relationship between Axl and ROS in malignant cell migration has not been previously evaluated. Using an in vitro human lung cancer model, we examined the redox state of lung adenocarcinoma cell lines of low metastatic (CL1-0) and high metastatic (CL1-5) potentials. Here we report that Axl activation elicits ROS accumulation through the oxidase-coupled small GTPase Rac1. We also observed that oxidative stress could activate Axl phosphorylation to synergistically enhance cell migration. Further, Axl signaling activated by H2O2 treatment results in enhancement of cell migration via a PI3K/Akt-dependent pathway. The kinase activity of Axl is required for the Axl-mediated cell migration and prolongs the half-life of phospho-Akt under oxidative stress. Finally, downregulation of Akt1, but not Akt2, by RNAi in Axl-overexpressing cells inhibits the amount of activated Rac1 and the ability to migrate induced by H2O2 treatment. Together, these results show that a novel Axl-signaling cascade induced by H2O2 treatment triggers cell migration through the PI3K/Akt1/Rac1 pathway. Elucidation of redox regulation in Axl-related malignant migration may provide new molecular insights into the mechanisms underlying tumor progression.

Keywords: 2′,7′-dichlorodihydrofluorescein diacetate; Akt1; Axl; DCF-DA; Free radicals; Gas6; NSCLC; Oxidative stress; ROS; RTK; Rac1; SOD; growth-arrest-specific 6; non-small-cell lung cancer; reactive oxygen species; receptor tyrosine kinase; superoxide dismutase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / pathology
  • Adenocarcinoma of Lung
  • Cell Line, Tumor
  • Cell Movement / genetics*
  • Cell Transformation, Neoplastic / pathology
  • Enzyme Activation
  • Humans
  • Hydrogen Peroxide / pharmacology
  • Lung Neoplasms / pathology
  • Oxidation-Reduction
  • Oxidative Stress / physiology*
  • Phosphatidylinositol 3-Kinases
  • Phosphorylation
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism*
  • RNA Interference
  • RNA, Small Interfering
  • Receptor Protein-Tyrosine Kinases / metabolism*
  • Signal Transduction
  • rac1 GTP-Binding Protein / antagonists & inhibitors
  • rac1 GTP-Binding Protein / metabolism*

Substances

  • Proto-Oncogene Proteins
  • RAC1 protein, human
  • RNA, Small Interfering
  • Hydrogen Peroxide
  • Phosphatidylinositol 3-Kinases
  • Receptor Protein-Tyrosine Kinases
  • axl receptor tyrosine kinase
  • AKT1 protein, human
  • AKT2 protein, human
  • Proto-Oncogene Proteins c-akt
  • rac1 GTP-Binding Protein