title: Synergistic effects of erlotinib and everolimus on bronchial carcinoids and large-cell neuroendocrine carcinomas with activated EGFR/AKT/mTOR pathway.
abstract: BACKGROUND
  Epidermal growth factor receptor (EGFR) and mammalian target of rapamycin (mTOR) are crucial targets in cancer therapy. Combined inhibition of both targets yielded synergistic effects in vitro and in vivo in several cancer entities. However, the impact of EGFR and mTOR expression and combined inhibition in neuroendocrine lung tumors other than small-cell lung cancer remains unclear.
  
  
  METHODS
  Expression and activation of EGFR/AKT/mTOR pathway constituents were investigated in typical and atypical bronchial carcinoid (AC) tumors and large-cell neuroendocrine lung carcinomas (LCNEC) by immunohistochemistry in 110 tumor samples, and correlated with clinicopathological parameters and patient survival. Cytotoxicity of mTOR inhibitor everolimus and EGFR inhibitor erlotinib alone and in combination was assessed using growth inhibition assay in NCI-H720 AC and SHP-77 LCNEC cells. Cell cycle phase distribution was determined by FACS. Apoptosis-associated activation of caspase-3/7 was measured by Caspase-Glo® assay. Activity status of EGFR and mTOR pathway components was analyzed by immunoblotting.
  
  
  RESULTS
  Activation of the EGFR/AKT/mTOR axis could be demonstrated in all entities and was significantly increased in higher grade tumors. Neoadjuvant chemotherapy correlated significantly with p-AKT expression and p-ERK loss. Erlotinib combined with everolimus exerted synergistic combination effects in AC and LCNEC cells by induction of apoptosis, while cell cycle phase distribution remained unaffected. These effects could be explained by synergistic downregulation of phospho-mTOR, phospho-p70S6 kinase and phospho-AKT expression by everolimus and erlotinib.
  
  
  CONCLUSIONS
  Our study indicates that EGFR and mTOR are clinically important targets in bronchial neuroendocrine tumors, and further in vivo and clinical exploration of combined inhibition is warranted.
authors.affiliation: Clinical Institute of Pathology, Medical University of Vienna, Vienna, Austria.
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Bago-Horvath
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sieghart
authors.forename: Michael
authors.initials: M
authors.lastname: Grusch
authors.forename: Andreas
authors.initials: A
authors.lastname: Lackner
authors.forename: Hubert
authors.initials: H
authors.lastname: Hayden
authors.forename: Christine
authors.initials: C
authors.lastname: Pirker
authors.forename: Oxana
authors.initials: O
authors.lastname: Komina
authors.forename: Józefa
authors.initials: J
authors.lastname: Węsierska-Gądek
authors.forename: Andrea
authors.initials: A
authors.lastname: Haitel
authors.forename: Martin
authors.initials: M
authors.lastname: Filipits
authors.forename: Walter
authors.initials: W
authors.lastname: Berger
authors.forename: Katharina
authors.initials: K
authors.lastname: Schmid
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000494:pharmacology; D002283:Carcinoma, Bronchogenic / Q000378:metabolism* / Q000473:pathology; D018278:Carcinoma, Neuroendocrine / Q000378:metabolism* / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002648:Child; D066246:ErbB Receptors / Q000378:metabolism; D000069347:Erlotinib Hydrochloride; D000068338:Everolimus; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D055815:Young Adult
chemical_list: D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D000068338:Everolimus; D000069347:Erlotinib Hydrochloride; C546842:MTOR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus