title: Inhibition of STAT-3 results in greater cetuximab sensitivity in head and neck squamous cell carcinoma.
abstract: OBJECTIVE
  The inhibition of epidermal growth factor receptor (EGFr) with the monoclonal antibody cetuximab reduces cell proliferation and survival which correlates with increased DNA damage. Since the signal transducer and activator of transcription-3 (STAT-3) is involved in the EGFr-induced signaling pathway, we hypothesized that depletion of STAT-3 may augment cetuximab-induced processes in human head and neck cancer cells.
  
  
  METHODS
  Human head and neck squamous carcinoma cells (UM-SCC-5) were transfected with short hairpin RNA (shRNA) against STAT-3 (STAT3-2.4 and 2.9 cells). A mutated form of this shRNA was transfected for a control (NEG4.17 cells). Radiosensitivity was assessed by a standard colony formation assay. Proliferation was assessed by daily cell counts following treatment and apoptosis was assessed by an annexin V-FITC assay. The alkaline comet assay was used to assess DNA damage.
  
  
  RESULTS
  The STAT-3 knockdown cells (STAT3-2.4 and STAT3-2.9 cells) demonstrated enhanced radiosensitivity compared to control NEG4.17 cells, which correlated with increased apoptosis. Also, the STAT-3 knockdown cells demonstrated decreased proliferation with cetuximab treatments compared to control cells (NEG4.17). The increased cetuximab sensitivity of the STAT-3 knockdown cells correlated with increased apoptosis and DNA damage compared to control cells (NEG4.17).
  
  
  CONCLUSIONS
  These studies revealed that the greater anti-proliferative effects and increased cytotoxicity of cetuximab in the STAT3-2.4 and STAT3-2.9 cells compared to control NEG4.17 cells, may be a result of STAT3-mediated effects on cellular apoptosis and DNA damage.
authors.affiliation: Department of Radiation Oncology, The University of Alabama at Birmingham, USA. jabonner@uabmc.edu
authors.forename: James A
authors.initials: JA
authors.lastname: Bonner
authors.forename: Eddy S
authors.initials: ES
authors.lastname: Yang
authors.forename: Hoa Q
authors.initials: HQ
authors.lastname: Trummell
authors.forename: Somaira
authors.initials: S
authors.lastname: Nowsheen
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Willey
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Raisch
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D000068818:Cetuximab; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D006258:Head and Neck Neoplasms / Q000188:drug therapy*; D006801:Humans; D015151:Immunoblotting; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors*; D015398:Signal Transduction; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D011838:Radiation-Sensitizing Agents; D050796:STAT3 Transcription Factor; D000068818:Cetuximab