title: Erlotinib-induced autophagy in epidermal growth factor receptor mutated non-small cell lung cancer.
abstract: OBJECTIVE
  Erlotinib is a commonly used tyrosine kinase inhibitor (TKI) in non-small cell lung cancer (NSCLC). Autophagy is a catabolic process in response to stress and deprivation of nutrients. This study aims to investigate whether autophagy confers acquired resistance to erlotinib treatment in NSCLC.
  
  
  METHODS
  Four NSCLC cell lines (HCC827, HCC4006, H358 and H1975) with different epidermal growth factor receptor (EGFR) mutation status (exon 19 deletion, exon 19 deletion, wild-type and L858R/T790M respectively) were selected. MTT assay, crystal violet staining and Annexin-V assay were performed to determine cell viability and apoptosis. Autophagic proteins were detected by Western blot. Acidic vesicular organelle (AVO) formation was determined by acridine orange staining. Autophagy inhibitor (chloroquine) and RNA interference were used to demonstrate the biological effect of erlotinib-induced autophagy.
  
  
  RESULTS
  In line with EGFR mutation status, it was shown that both HCC827 and HCC4006 cells were sensitive to erlotinib, while H358 and H1975 cell lines were resistant. Erlotinib treatment at clinically relevant concentrations induced autophagy (increased LC3II expression, Atg-5/Atg12 conjugation, formation of AVO and p62 degradation) in sensitive NSCLC cell lines, via p53 nuclear translocation, AMPK activation and mTOR suppression. Addition of chloroquine, as an autophagy inhibitor, enhanced erlotinib sensitivity in sensitive cells. Similarly, silencing of Atg5 or Beclin-1 significantly increased sensitivity to erlotinib in both sensitive cell lines. In contrast, there was no induction of autophagy in resistant H358 and H1975 cell lines upon erlotinib exposure.
  
  
  CONCLUSIONS
  Erlotinib can induce both apoptosis and autophagy in sensitive NSCLC cell lines with activating EGFR mutation (exon 19 del). Inhibition of autophagy can further enhance sensitivity to erlotinib in EGFR-mutated NSCLC, suggesting that autophagy may serve as a protective mechanism.
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong Special Administrative Region.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Li
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong Special Administrative Region.
authors.forename: Sze-Kwan
authors.initials: SK
authors.lastname: Lam
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong Special Administrative Region.
authors.forename: Judith Choi-Wo
authors.initials: JC
authors.lastname: Mak
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong Special Administrative Region.
authors.forename: Chun-Yan
authors.initials: CY
authors.lastname: Zheng
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong Special Administrative Region. Electronic address: jhocm@hku.hk.
authors.forename: James Chung-Man
authors.initials: JC
authors.lastname: Ho
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics*; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics*; D000069347:Erlotinib Hydrochloride; D055785:Gene Knockdown Techniques; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000235:genetics; D009154:Mutation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use; D015398:Signal Transduction
chemical_list: C502778:ATG5 protein, human; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D000071187:Autophagy-Related Protein 5; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors
keywords: 5′ adenosine monophosphate-activated protein kinase; AMPK; Atg; Autophagy; Epidermal growth factor receptor; Erlotinib; LC3; Lung cancer; NFκB; PARP; Resistance; autophagy-related protein; mTOR; mammalian target of rapamycin; microtubule-associated protein light chain 3; nuclear factor kappa beta; poly (ADP-ribose) polymerase