EGFR tyrosine kinase inhibitors activate autophagy as a cytoprotective response in human lung cancer cells

PLoS One. 2011;6(6):e18691. doi: 10.1371/journal.pone.0018691. Epub 2011 Jun 2.

Abstract

Epidermal growth factor receptor tyrosine kinase inhibitors gefitinib and erlotinib have been widely used in patients with non-small-cell lung cancer. Unfortunately, the efficacy of EGFR-TKIs is limited because of natural and acquired resistance. As a novel cytoprotective mechanism for tumor cell to survive under unfavorable conditions, autophagy has been proposed to play a role in drug resistance of tumor cells. Whether autophagy can be activated by gefitinib or erlotinib and thereby impair the sensitivity of targeted therapy to lung cancer cells remains unknown. Here, we first report that gefitinib or erlotinib can induce a high level of autophagy, which was accompanied by the inhibition of the PI3K/Akt/mTOR signaling pathway. Moreover, cytotoxicity induced by gefitinib or erlotinib was greatly enhanced after autophagy inhibition by the pharmacological inhibitor chloroquine (CQ) and siRNAs targeting ATG5 and ATG7, the most important components for the formation of autophagosome. Interestingly, EGFR-TKIs can still induce cell autophagy even after EGFR expression was reduced by EGFR specific siRNAs. In conclusion, we found that autophagy can be activated by EGFR-TKIs in lung cancer cells and inhibition of autophagy augmented the growth inhibitory effect of EGFR-TKIs. Autophagy inhibition thus represents a promising approach to improve the efficacy of EGFR-TKIs in the treatment of patients with advanced non-small-cell lung cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autophagy / drug effects*
  • Autophagy-Related Protein 5
  • Autophagy-Related Protein 7
  • Blotting, Western
  • Carcinoma, Non-Small-Cell Lung / genetics
  • Carcinoma, Non-Small-Cell Lung / metabolism
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Dose-Response Relationship, Drug
  • ErbB Receptors / antagonists & inhibitors*
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism
  • Erlotinib Hydrochloride
  • Gefitinib
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Lysosomes / ultrastructure
  • Microscopy, Confocal
  • Microscopy, Electron
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Phagosomes / drug effects
  • Phagosomes / metabolism
  • Phagosomes / ultrastructure
  • Protein Kinase Inhibitors / pharmacology
  • Proto-Oncogene Proteins c-akt / metabolism
  • Quinazolines / pharmacology*
  • RNA Interference
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Signal Transduction / drug effects
  • TOR Serine-Threonine Kinases / metabolism
  • Time Factors
  • Ubiquitin-Activating Enzymes / genetics
  • Ubiquitin-Activating Enzymes / metabolism

Substances

  • ATG5 protein, human
  • Autophagy-Related Protein 5
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • Protein Kinase Inhibitors
  • Quinazolines
  • Erlotinib Hydrochloride
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • ErbB Receptors
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Atg7 protein, human
  • Autophagy-Related Protein 7
  • Ubiquitin-Activating Enzymes
  • Gefitinib