Epidermal growth factor receptor structural alterations in gastric cancer

EGFR overexpression has been described in many human tumours including gastric cancer. In NSCLC patients somatic EGFR mutations, within the kinase domain of the protein, as well as gene amplification were associated with a good clinical response to EGFR inhibitors. In gastric tumours data concerning structural alterations of EGFR remains controversial. Given its possible therapeutic relevance, we aimed to determine the frequency and type of structural alterations of the EGFR gene in a series of primary gastric carcinomas.

Direct sequencing of the kinase domain of the EGFR gene was performed in a series of 77 primary gastric carcinomas. FISH analysis was performed in 30 cases. Association studies between EGFR alterations and the clinical pathological features of the tumours were performed.

Within the 77 primary gastric carcinomas we found two EGFR somatic mutations and several EGFR polymorphisms in exon 20. Six different intronic sequence variants of EGFR were also found. Four gastric carcinomas showed balanced polysomy or EGFR gene amplification. We verified that gastric carcinoma with alterations of EGFR (somatic mutations or copy number variation) showed a significant increase of tumour size (p = 0.0094) in comparison to wild-type EGFR carcinomas.

We demonstrate that EGFR structural alterations are rare in gastric carcinoma, but whenever present, it leads to tumour growth. We considered that searching for EGFR alterations in gastric cancer is likely to be clinically important in order to identify patients susceptible to respond to tyrosine kinase inhibitors.