title: Short-course treatment with gefitinib enhances curative potential of radiation therapy in a mouse model of human non-small cell lung cancer.
abstract: OBJECTIVE
  To evaluate the combination of radiation and an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) in preclinical models of human non-small cell lung cancer.
  
  
  METHODS
  Sensitivity to an EGFR TKI (gefitinib) or radiation was assessed using proliferation assays and clonogenic survival assays. Effects on receptor signal transduction pathways (pEGFR, pAKT, pMAPK) and apoptosis (percentage of cleaved PARP Poly (ADP-ribose) polymerase (PARP)) were assessed by Western blotting. Radiation-induced DNA damage was assessed by γH2AX immunofluorescence. Established (≥ 100 mm(3)) EGFR-mutated (HCC287) or EGFR wild-type (A549) subcutaneous xenografts were treated with radiation (10 Gy, day 1) or gefitinib (50 mg/kg, orally, on days 1-3) or both.
  
  
  RESULTS
  In non-small cell lung cancer (NSCLC) cell lines with activating EGFR mutations (PC9 or HCC827), gefitinib treatment markedly reduced pEGFR, pAKT, and pMAPK levels and was associated with an increase in cleaved PARP but not in γH2AX foci. Radiation treatment increased the mean number of γH2AX foci per cell but did not significantly affect EGFR signaling. In contrast, NSCLC cell lines with EGFR T790M (H1975) or wild-type EGFR (A549) were insensitive to gefitinib treatment. The combination of gefitinib and radiation treatment in cell culture produced additive cell killing with no evidence of synergy. In xenograft models, a short course of gefitinib (3 days) did not significantly increase the activity of radiation treatment in wild-type EGFR (A549) tumors (P=.27), whereas this combination markedly increased the activity of radiation (P<.001) or gefitinib alone (P=.002) in EGFR-mutated HCC827 tumors, producing sustained tumor regressions.
  
  
  CONCLUSIONS
  Gefitinib treatment increases clonogenic cell killing by radiation but only in cell lines sensitive to gefitinib alone. Our data suggest additive rather than synergistic interactions between gefitinib and radiation and that a combination of short-course gefitinib and high-dose/-fraction radiation may have the greatest potential against the subsets of lung cancers harboring activating mutations in the EGFR gene.
authors.affiliation: Department of Oncology, Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, United Kingdom.
authors.forename: Sivan M
authors.initials: SM
authors.lastname: Bokobza
authors.affiliation: Department of Oncology, Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, United Kingdom.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Oncology, Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, United Kingdom.
authors.forename: Anika M
authors.initials: AM
authors.lastname: Weber
authors.affiliation: Department of Oncology, Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, United Kingdom.
authors.forename: Aoife M
authors.initials: AM
authors.lastname: Devery
authors.affiliation: Department of Oncology, Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, United Kingdom. Electronic address: anderson.ryan@oncology.ox.ac.uk.
authors.forename: Anderson J
authors.initials: AJ
authors.lastname: Ryan
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy / Q000379:methods; D004195:Disease Models, Animal; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D000077156:Gefitinib; D018773:Genes, erbB-1; D064593:Heterografts; D006657:Histones / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000532:radiotherapy*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000627:therapeutic use*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; C468783:H2AX protein, human; D006657:Histones; D011799:Quinazolines; D011065:Poly(ADP-ribose) Polymerases; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases; D000077156:Gefitinib