High gene copy number of epidermal growth factor receptor by fluorescence in situ hybridization is frequent in head and neck squamous cell carcinomas and associates with worse recurrence-free survival

Abstract

5502 Background: Epidermal growth factor receptor (EGFR) is expressed in 90–95% of head and neck squamous cell carcinoma (HNSCC). High EGFR gene copy number and activating mutations correlate with response and survival in lung cancer upon the treatment with EGFR tyrosine kinase inhibitors, but such findings have not been reported for HNSCC. A better understanding of the EGFR pathway may improve the use of EGFR inhibitors and provide a rationale for combination therapy. Methods: Tumor samples were obtained from 47 patients and analyzed for increased EGFR copy numbers by fluorescence in situ hybridization (FISH) (Vysis/Abbot) (N = 47), by immunohistochemistry (IHC) using antibodies against EGFR, phospho-EGFR (Tyr1173) and phospho-AKT (Ser473) (N = 31), for activating mutations in EGFR exons 18, 19 and 21 (N = 29), and for gene expression using Affymetrix Human 133U Plus 2.0 GeneChip (N = 18). Results from these assessments were tested for associations with patient characteristics and clinical endpoints. Univariate analysis was performed to test for differences in recurrence-free survival (RFS) and overall survival. Results: Twenty-six (63%) of 41 samples with FISH result demonstrated EGFR high polysomy and/or gene amplification (FISH+). The FISH(+) group did not differ from the FISH(−) group with regard to age, sex, race, tumor grade and site, disease stage, total EGFR, phospho-EGFR, or phospho-AKT, although the total EGFR protein score was close to significance (p = 0.10, Chi2-test for trend). The FISH(+) were associated with worse RFS, although this association did not reach significance (p = 0.057, Wilcoxon test). No activating EGFR point mutations were found. Using the FISH results as a supervising parameter, microarray data was interrogated and expression of genes involved in wnt signalling, cell motility, G-protein regulation and epithelial-mesenchymal transition pathways were found to be enhanced in the FISH(+) group (FDR <25%). Conclusions: High gene copy number of EGFR by FISH is frequent in HNSCC and may be a poor prognosticator. This data suggests that FISH(+) may be a marker of clinical benefit upon EGFR inhibition in HNSCC and further investigation is indicated. [Table: see text]