title: Nuclear EGFR renders cells radio-resistant by binding mRNA species and triggering a metabolic switch to increase lactate production.
abstract: OBJECTIVE
  EGFR is translocated into the cell nucleus in response to irradiation, where it is involved in regulation of radio-sensitivity. The aim of this study is to elucidate the functional role of nuclear EGFR.
  
  
  METHODS
  To identify EGFR-bound nuclear proteins and mRNAs, Maldi-TOF analysis and mRNA gene arrays were used. Complex formation of proteins was shown by confocal microscopy, immunoprecipitation and Western blotting. The effect of EGFR binding to mRNAs was exhibited by quantitative RT-PCR. Cellular endpoints were shown by Western blotting, mitochondrial mass quantification, lactate quantification and clonogenic survival assays.
  
  
  RESULTS
  Maldi-TOF analysis of proteins bound to nuclear EGFR in response to irradiation showed colocalization with Lamin A and heterogeneous nuclear ribonucleoproteins. Confocal microscopy and Western blotting confirmed this colocalization. Both Lamin A and heterogeneous nuclear ribonucleoproteins are involved in mRNA processing. To support a role of nEGFR in this context after irradiation, we isolated EGFR-bound mRNA and observed an EGFR kinase-dependent mRNA stabilizing effect. With the help of DNA microarrays, we identified mRNAs associated with the Warburg effect that were bound to nuclear EGFR. In this context, we observed radiation-induced HIF1α expression, which triggers inhibition of pyruvate dehydrogenase and blocks the tricarboxylic acid cycle. Consequently, we detected mitophagy and increased lactate production, which is associated with increased treatment resistance. Reduction of nEGFR decreased radiation-induced expression of Hif1α and lactate production.
  
  
  CONCLUSIONS
  We showed that nuclear EGFR selectively binds and stabilizes mRNA involved in the Warburg effect in response to irradiation. As a consequence, cells switch from aerobic to anaerobic glucose metabolism, which can be prevented by HIF1α inhibitor BAY87-2243, Dasatinib, Erlotinib or EGFR siRNA.
authors: Division of Radiobiology and Molecular Environmental Research, Department of Radiation Oncology, University of Tuebingen, Germany. Electronic address: klaus.dittmann@uni-tuebingen.de.
authors: Klaus
authors: K
authors: Dittmann
authors: Division of Radiobiology and Molecular Environmental Research, Department of Radiation Oncology, University of Tuebingen, Germany.
authors: Claus
authors: C
authors: Mayer
authors: Division of Radiobiology and Molecular Environmental Research, Department of Radiation Oncology, University of Tuebingen, Germany.
authors: Angela
authors: A
authors: Paasch
authors: Laboratory for Experimental Radiooncology, Department of Radiation Oncology, University of Tuebingen, Germany.
authors: Stephan
authors: S
authors: Huber
authors: Department of Dermatology, University of Tuebingen, Germany.
authors: Birgit
authors: B
authors: Fehrenbacher
authors: Department of Dermatology, University of Tuebingen, Germany.
authors: Martin
authors: M
authors: Schaller
authors: Division of Radiobiology and Molecular Environmental Research, Department of Radiation Oncology, University of Tuebingen, Germany.
authors: H Peter
authors: HP
authors: Rodemann
mesh_terms: D015153:Blotting, Western; D001984:Bronchial Neoplasms / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D000069439:Dasatinib / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000502:physiology* / Q000528:radiation effects; D000069347:Erlotinib Hydrochloride / Q000494:pharmacology; D015870:Gene Expression; D006258:Head and Neck Neoplasms / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis*; D009687:Nuclear Proteins / Q000378:metabolism; D010069:Oxadiazoles / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism*; D011836:Radiation Tolerance / Q000187:drug effects
chemical_list: C000591541:1-cyclopropyl-4-(4-((5-methyl-3-(3-(4-(trifluoromethoxy)phenyl)-1,2,4-oxadiazol-5-yl)-1H-pyrazol-1-yl)methyl)pyridin-2-yl)piperazine; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D010069:Oxadiazoles; D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; D012333:RNA, Messenger; D019344:Lactic Acid; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D000069439:Dasatinib
keywords: Hif1α; PDH; Warburg effect; mRNA; nEGFR