title: Responses of cancer cells with wild-type or tyrosine kinase domain-mutated epidermal growth factor receptor (EGFR) to EGFR-targeted therapy are linked to downregulation of hypoxia-inducible factor-1alpha.
abstract: BACKGROUND
  Searching for novel molecular markers that dependably predict or indicate responses of human cancer cells to epidermal growth factor receptor (EGFR)-targeted therapy is strongly warranted. The purpose of the current study was to evaluate hypoxia-inducible factor-1alpha (HIF-1alpha) as a novel response marker compared with previously explored markers following treatment with an EGFR-blocking monoclonal antibody (cetuximab) and a small-molecule EGFR tyrosine kinase inhibitor (gefitinib) in a group of cancer cell lines containing wild-type or tyrosine kinase domain-mutated EGFR.
  
  
  RESULTS
  We found that, compared with previously studied response markers, including EGFR per se and three EGFR downstream signal molecules (ERK, Akt, and STAT3), which showed variable post-treatment changes in levels of phosphorylation and no consistent link of the changes to therapeutic responses, HIF-1alpha showed a selective decrease in protein levels only in responsive cell lines. To demonstrate a critical role of HIF-1alpha downregulation by EGFR-targeted treatment, we introduced a constitutively expressed HIF-1alpha mutant (HIF-1alpha/DeltaODD) that is resistant to cetuximab-induced downregulation in a cetuximab-responsive cell line (A431); we found that the HIF-1alpha/DeltaODD-transfected cells remained sensitive to cetuximab-induced inhibition of Akt and ERK phosphorylation but were remarkably less responsive to cetuximab-induced growth inhibition compared with corresponding control cells.
  
  
  CONCLUSIONS
  Our data indicates that downregulation of HIF-1alpha is associated with positive therapeutic responses of cancer cells to EGFR-targeted therapy and suggest further investigation using HIF-1alpha as an indicator of tumor response to EGFR-targeted therapy in preclinical studies and in the clinical setting.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas M, D, Anderson Cancer Center, Houston, Texas 77030, USA. ylu@mdanderson.org
authors.forename: Yang
authors.initials: Y
authors.lastname: Lu
authors.forename: Ke
authors.initials: K
authors.lastname: Liang
authors.forename: Xinqun
authors.initials: X
authors.lastname: Li
authors.forename: Zhen
authors.initials: Z
authors.lastname: Fan
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung; D045744:Cell Line, Tumor; D000068818:Cetuximab; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D066246:ErbB Receptors / Q000187:drug effects / Q000235:genetics*; D000077156:Gefitinib; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics*; D007700:Kinetics; D008175:Lung Neoplasms; D009154:Mutation; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology*; D020794:Receptor Protein-Tyrosine Kinases / Q000187:drug effects / Q000235:genetics*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases; D000068818:Cetuximab; D000077156:Gefitinib