Molecular mechanisms of epidermal growth factor receptor overexpression in patients with cervical cancer

The epidermal growth factor receptor is overexpressed in 70-90% of cervical cancers. Previously, we have shown that epidermal growth factor receptor overexpression independently predicts poor prognosis in cervical cancer patients, which makes it a potential therapeutic target. The aim of this study was to systematically analyze the molecular mechanism leading to epidermal growth factor receptor overexpression in cervical cancer. All experiments were performed on archival paraffin-embedded material. In 166 cervical cancer patients, cytoplasmic, membrane and phosphorylated epidermal growth factor receptor protein expression were studied in association with patient survival. Membrane epidermal growth factor receptor overexpression was associated with poor disease-specific survival (P=0.027). This association was particularly present in human papillomavirus 16-positive patients (P=0.029). We analyzed whether epidermal growth factor receptor overexpression was caused by gene amplification using fluorescence in situ hybridization. Epidermal growth factor receptor gene copy number was linked to chromosome 7 ploidy, as no gene amplification could be detected when corrected for chromosome 7 centromeric signals. Chromosome 7 aneuploidy was associated with membrane epidermal growth factor receptor overexpression (P=0.013). Additional mutation analysis was performed by sequencing pure, flow-sorted tumor cells, but no mutations were detected. Furthermore, human papillomavirus 16 E5 and E6 oncogene mRNA expression was measured, using quantitative real-time polymerase chain reaction, to determine the association between the human papillomavirus and epidermal growth factor receptor overexpression. High human papillomavirus 16 E5 and E6 mRNA expression were associated with decreased survival (P=0.045 and 0.047, respectively). High human papillomavirus 16 E6 mRNA expression was associated with membrane epidermal growth factor receptor overexpression (P=0.013). This is the first study performed on cancer patient material showing that chromosome 7 aneuploidy and high human papillomavirus 16 E6 mRNA expression lead to membrane epidermal growth factor receptor overexpression in cervical cancer.