title: Signaling via ErbB2 and ErbB3 associates with resistance and epidermal growth factor receptor (EGFR) amplification with sensitivity to EGFR inhibitor gefitinib in head and neck squamous cell carcinoma cells.
abstract: OBJECTIVE
  The epidermal growth factor receptor (EGFR) inhibitor gefitinib (Iressa) has shown antitumor activity in clinical trials against cancers, such as non-small cell lung cancer and head and neck squamous cell carcinoma (HNSCC). Research on non-small cell lung cancer has elucidated factors that may predict response to gefitinib. Less is known about molecular markers that may predict response to gefitinib in HNSCC patients.
  
  
  METHODS
  We analyzed possible associations of responsiveness to gefitinib with molecular markers of the EGFR/ErbB receptor family signaling pathway using 10 established HNSCC lines in vitro. IC50 of gefitinib sensitivity was determined using clonogenic survival assays. ErbB signaling was assessed by Western and real-time reverse transcription-PCR analyses of EGFR, ErbB2, ErbB3, and ErbB4 expression levels as well as by phosphorylation analysis of pEGFR, pErbB2, pErbB3, pAkt, and pErk. EGFR sequences encoding kinase domain and EGFR gene copy numbers were determined by cDNA sequencing and real-time PCR, respectively. Finally, responsiveness to gefitinib was compared with responsiveness to the anti-EGFR antibody cetuximab (Erbitux).
  
  
  RESULTS
  Expression levels of pErbB2 (P = 0.02) and total ErbB3 protein (P = 0.02) associated with resistance to gefitinib. Combining gefitinib with pertuzumab (Omnitarg), an antibody targeting ErbB2 heterodimerization, provided additional growth-inhibitory effect over gefitinib alone on relatively gefitinib-resistant HNSCC cell lines. The same markers did not predict resistance to cetuximab. In contrast, a similar trend suggesting association between EGFR gene copy number and drug sensitivity was observed for both gefitinib (P = 0.0498) and cetuximab (P = 0.053). No activating EGFR mutations were identified.
  
  
  CONCLUSIONS
  EGFR amplification may predict sensitivity to gefitinib in HNSCC. However, other EGFR/ErbB receptor family members than EGFR may contribute to resistance to gefitinib. ErbB2 and ErbB3 may have potential as predictive markers and as therapeutic targets for combination therapy in treatment of HNSCC with gefitinib.
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Turku University Central Hospital, Finland.
authors.forename: Kaisa
authors.initials: K
authors.lastname: Erjala
authors.forename: Maria
authors.initials: M
authors.lastname: Sundvall
authors.forename: Teemu T
authors.initials: TT
authors.lastname: Junttila
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.forename: Mika
authors.initials: M
authors.lastname: Savisalo
authors.forename: Pekka
authors.initials: P
authors.lastname: Mali
authors.forename: Jarmo
authors.initials: J
authors.lastname: Kulmala
authors.forename: Jaakko
authors.initials: J
authors.lastname: Pulkkinen
authors.forename: Reidar
authors.initials: R
authors.lastname: Grenman
authors.forename: Klaus
authors.initials: K
authors.lastname: Elenius
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000235:genetics*; D045744:Cell Line, Tumor; D000068818:Cetuximab; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics; D000077156:Gefitinib; D005784:Gene Amplification; D020869:Gene Expression Profiling; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000235:genetics*; D006801:Humans; D008297:Male; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020893:Receptor, ErbB-3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D000068818:Cetuximab; D066246:ErbB Receptors; D000077156:Gefitinib; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; C508053:ERBB2 protein, human; C485206:pertuzumab