title: Requirement of hypoxia-inducible factor-1alpha down-regulation in mediating the antitumor activity of the anti-epidermal growth factor receptor monoclonal antibody cetuximab.
abstract: We tested our novel hypothesis that down-regulation of hypoxia-inducible factor-1alpha (HIF-1alpha), the regulated subunit of HIF-1 transcription factor that controls gene expression involved in key functional properties of cancer cells (including metabolism, survival, proliferation, invasion, angiogenesis, and metastasis), contributes to a major antitumor mechanism of cetuximab, an approved therapeutic monoclonal antibody that blocks activation of the epidermal growth factor receptor. We showed that cetuximab treatment down-regulates HIF-1alpha levels by inhibiting synthesis of HIF-1alpha rather than by enhancing degradation of the protein. Inhibition of HIF-1alpha protein synthesis was dependent on effective inhibition of the phosphoinositide-3 kinase (PI3K)/Akt pathway by cetuximab, because the inhibition was prevented in cells transfected with a constitutively active PI3K or a constitutively active Akt but not in cells with a constitutively active MEK. Overexpression of HIF-1alpha conferred cellular resistance to cetuximab-induced apoptosis and inhibition of vascular endothelial growth factor production in sensitive cancer cell models, and expression knockdown of HIF-1alpha by RNA interference substantially restored cellular sensitivity to the cetuximab-mediated antitumor activities in experimental resistant cell models created by transfection of an oncogenic Ras gene (G12V) or by concurrent treatment of the cells with insulin-like growth factor-I. In summary, our data show that cetuximab decreases HIF-1alpha protein synthesis through inhibition of a PI3K-dependent pathway and that an effective down-regulation of HIF-1alpha is required for maximal therapeutic effects of cetuximab in cancer cells.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Unit 036, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
authors.forename: Xinqun
authors.initials: X
authors.lastname: Li
authors.forename: Yang
authors.initials: Y
authors.lastname: Lu
authors.forename: Ke
authors.initials: K
authors.lastname: Liang
authors.forename: Tianhong
authors.initials: T
authors.lastname: Pan
authors.forename: John
authors.initials: J
authors.lastname: Mendelsohn
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*; D045744:Cell Line, Tumor; D000068818:Cetuximab; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000276:immunology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D051058:Oncogene Protein v-akt / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051058:Oncogene Protein v-akt; D000068818:Cetuximab