title: Reversal of Warburg Effect and Reactivation of Oxidative Phosphorylation by Differential Inhibition of EGFR Signaling Pathways in Non-Small Cell Lung Cancer.
abstract: OBJECTIVE
  One of the hallmarks of cancer cells is the excessive conversion of glucose to lactate under normoxic conditions, also known as the Warburg effect. Here, we tested whether the targeted inhibition of EGFR may revert this effect and reactivate mitochondrial oxidative phosphorylation in non-small cell lung cancer (NSCLC).
  
  
  METHODS
  Sensitive (HCC827) and resistant (H1975 and H1993) NSCLC cells were treated with a panel of EGFR or MET inhibitors, and then tested for changes of EGFR signaling, glycolytic cascade, and mitochondrial function. Silencing of key glycolytic enzymes was then performed with targeted siRNAs. Furthermore, tumor-bearing nude mice treated with EGFR inhibitors were evaluated with (18)F-FDG PET/CT and tumors were analyzed for glycolytic and mitochondrial proteins.
  
  
  RESULTS
  Effective inhibition of EGFR signaling in NSCLC cells induced a dramatic reduction of hexokinase II (HKII) and phospho-pyruvate kinase M2 (p-PKM2, Tyr105) levels as well as an upregulation of mitochondrial complexes subunits (OXPHOS). Accordingly, a decreased lactate secretion and increased intracellular ATP levels were also observed in response to EGFR inhibitors. Downregulation of HKII and PKM2 by targeted siRNA transfection did not cause upregulation of OXPHOS but enhanced the effects of EGFR TKIs. Conversely, selective inhibition of AKT and ERK1/2 caused OXPHOS upregulation and glycolysis inhibition, respectively. Similar findings were obtained in tumors from animals treated with appropriate EGFR inhibitors.
  
  
  CONCLUSIONS
  Our findings indicate that EGFR inhibitors may reactivate oxidative phosphorylation of cancer cells and provide a mechanistic clue for the rational combination of agents targeting EGFR-dependent proliferation and glucose metabolism in cancer therapy.
authors.affiliation: Institute of Biostructures and Bioimages, National Research Council, Naples, Italy.
authors.forename: Viviana
authors.initials: V
authors.lastname: De Rosa
authors.affiliation: Institute of Biostructures and Bioimages, National Research Council, Naples, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Iommelli
authors.affiliation: Department of Advanced Biomedical Sciences, University of Naples Federico II, Naples, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Monti
authors.affiliation: Institute of Biostructures and Bioimages, National Research Council, Naples, Italy.
authors.forename: Rosa
authors.initials: R
authors.lastname: Fonti
authors.affiliation: Institute of Genetics and Biophysics, National Research Council, Naples, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Votta
authors.affiliation: Institute of Genetics and Biophysics, National Research Council, Naples, Italy.
authors.forename: Maria Patrizia
authors.initials: MP
authors.lastname: Stoppelli
authors.affiliation: Institute of Biostructures and Bioimages, National Research Council, Naples, Italy. Department of Advanced Biomedical Sciences, University of Naples Federico II, Naples, Italy. delvecc@unina.it.
authors.forename: Silvana
authors.initials: S
authors.lastname: Del Vecchio
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010085:Oxidative Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage*; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D047428:Protein Kinase Inhibitors; D019344:Lactic Acid; C512478:EGFR protein, human; D066246:ErbB Receptors; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met; D005947:Glucose