• John B McIntyre, Pinaki Bose, Alexander C Klimowicz, Nigel T Brockton, Stephanie Petrillo, Wayne Matthews, Jay Easaw, Anthony Magliocco, and Joseph C Dort.
• Department of Pathology and Laboratory Medicine, Tom Baker Cancer Centre, University of Calgary, Calgary, Canada.
• Plos One. 2012 Jan 1; 7 (2): e31723.

BackgroundThe tumor-specific EGFR deletion mutant, EGFRvIII, is characterised by ligand-independent constitutive signalling. Tumors expressing EGFRvIII are resistant to current EGFR-targeted therapy. The frequency of EGFRvIII in head and neck squamous cell carcinoma (HNSCC) is disputed and may vary by specific sub-site. The purpose of this study was to measure the occurrence of EGFRvIII mutations in a specific HNSCC subsite, oral squamous cell carcinoma (OSCC), using a novel real-time PCR assay.MethodologyPre-treatment Formalin Fixed Paraffin Embedded (FFPE) cancer specimens from 50 OSCC patients were evaluated for the presence of EGFRvIII using a novel hydrolysis probe-based real-time PCR assay. EGFR protein expression in tumor samples was quantified using fluorescent immunohistochemistry (IHC) and AQUA® technology.Principal FindingsWe detected EGFRvIII in a single OSCC patient in our cohort (2%). We confirmed the validity of our detection technique in an independent cohort of glioblastoma patients. We also compared the sensitivity and specificity of our novel real-time EGFRvIII detection assay to conventional RT-PCR and direct sequencing. Our assay can specifically detect EGFRvIII and can discriminate against wild-type EGFR in FFPE tumor samples. AQUAnalysis® revealed that the presence of EGFRvIII transcript is associated with very high EGFR protein expression (98(th) percentile). Contrary to previous reports, only 44% of OSCC over-expressed EGFR in our study.Conclusion And SignificanceOur results suggest that the EGFRvIII mutation is rare in OSCC and corroborate previous reports of EGFRvIII expression only in tumors with extreme over-expression of EGFR. We conclude that EGFRvIII-specific therapies may not be ideally suited as first-line treatment in OSCC. Furthermore, highly specific and sensitive methods, such as the real-time RT-PCR assay and AQUAnalysis® described here, will provide accurate assessment of EGFR mutation frequency and EGFR expression, and will facilitate the selection of optimal tailored therapies for OSCC patients.

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