Souka E, Alexiadis E, Theohari I, Giannopoulou I, Papadimitriou C & Nakopoulou L
(2012) Histopathology 61, 644–651
Exon 8 amplification of epidermal growth factor receptor (EGFR) in invasive breast carcinomas
Aims: The rate of EGFR amplification in breast cancer ranges between 0% and 15%. Recent studies have focused on the amplification status of cytosine–adenine (CA) repeats in intron 1 of the gene and correlated it with increased EGFR protein. The aim of this study was to investigate, for the first time, the significance of coding exon 8 amplification of EGFR in invasive breast cancer.
Methods and results: We investigated, by means of real-time polymerase chain reaction (PCR), the amplification status of exon 8 of the EGFR gene in 148 paraffin-embedded tissue sections, 115 with invasive breast carcinoma and 33 controls. Immunohistochemistry was utilized to detect EGFR and human epidermal growth factor receptor 2 (HER2) expression. Univariate and multivariate statistical analyses were performed for the evaluation of our results. EGFR amplification was observed in 7.8% of the patients, and EGFR was immunodetected in 9.6%. EGFR amplification was correlated positively with EGFR expression (P < 0.0001), HER2 expression (P = 0.023), coexpression of EGFR/HER2 (P < 0.0001) and nuclear grade (P = 0.047), and inversely with ER protein expression (P = 0.047).
Conclusions: It appears that amplification of the coding sequence exon 8 exhibits similar biological behaviour to amplification of the regulatory sequence in intron 1, leading to elevated levels of EGFR protein.