title: YAP1 is a potential biomarker for cetuximab resistance in head and neck cancer.
abstract: OBJECTIVE
  Targeted therapy against the epidermal growth factor receptor (EGFR) only variably represents a therapeutic advance in head and neck squamous cell carcinoma (HNSCC). This study addresses the need of biomarkers of treatment response to the EGFR-targeting antibody cetuximab (Erbitux®).
  
  
  METHODS
  The intrinsic cetuximab sensitivity of HNSCC cell lines was assessed by a crystal violet assay. Gene copy number analysis of five resistant and five sensitive cell lines was performed using the Affymetrix SNP 6.0 platform. Quantitative real-time PCR was used for verification of selected copy number alterations and assessment of mRNA expression. The functional importance of the findings on the gene and mRNA level was investigated employing siRNA technology. The data was statistically evaluated using Mann-Whitney U-test and Spearman's correlation test.
  
  
  RESULTS
  Analysis of the intrinsic cetuximab sensitivity of 32 HNSCC cell lines characterized five and nine lines as cetuximab sensitive or resistant, respectively. Gene copy number analysis of five resistant versus five sensitive cell lines identified 39 amplified protein-coding genes, including YAP1, in the genomic regions 11q22.1 or 5p13-15. Assessment using qPCR verified that YAP1 amplification associated with cetuximab resistance. Amplification of YAP1 correlated to higher mRNA levels, and RNA knockdown resulted in increased cetuximab sensitivity. Assessment of several independent clinical data sets in the public domain confirmed YAP1 amplifications in multiple tumor types including HNSCC, along with highly differential expression in a subset of HNSCC patients.
  
  
  CONCLUSIONS
  Taken together, we provide evidence that YAP1 could represent a novel biomarker gene of cetuximab resistance in HNSCC cell lines.
authors.affiliation: Division of Oto-Rhino-Laryngology and Head and Neck Surgery, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Jerhammar
authors.affiliation: Division of Oto-Rhino-Laryngology and Head and Neck Surgery, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden. Electronic address: ann-charlotte.johansson@liu.se.
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Johansson
authors.affiliation: Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Ceder
authors.affiliation: Division of Cell Biology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Welander
authors.affiliation: Division of Oncology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Agneta
authors.initials: A
authors.lastname: Jansson
authors.affiliation: Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Medical Biotechnology, VTT Technical Research Centre of Finland, Turku, Finland.
authors.forename: Roland C
authors.initials: RC
authors.lastname: Grafström
authors.affiliation: Division of Cell Biology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Söderkvist
authors.affiliation: Division of Oto-Rhino-Laryngology and Head and Neck Surgery, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden; Department of ENT-Head and Neck Surgery UHL, County Council of Östergötland, Linköping, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Roberg
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D061067:Antibodies, Monoclonal, Humanized / Q000627:therapeutic use*; D001483:Base Sequence; D015415:Biomarkers / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000378:metabolism*; D045744:Cell Line, Tumor; D000068818:Cetuximab; D017931:DNA Primers; D019008:Drug Resistance, Neoplasm; D020868:Gene Silencing; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D006801:Humans; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D061067:Antibodies, Monoclonal, Humanized; D015415:Biomarkers; D017931:DNA Primers; D010750:Phosphoproteins; D012333:RNA, Messenger; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins; C088374:YAP1 protein, human; D000068818:Cetuximab
keywords: Drug resistance; Gene copy number; Head and neck cancer; Predictive marker; SCCHN; Treatment response; YAP1