EGFR alterations in pancreatic ductal adenocarcinoma: a chromogenic in situ hybridization analysis based on tissue microarrays

To evaluate epidermal growth factor receptor (EGFR) gene status in pancreatic ductal adenocarcinoma correlating the results to protein expression and clinicopathological features

Using tissue microarray technology (TMArrayer 100), fifty (n = 50) paraffin-embedded tissue samples of histologically-confirmed primary tumors were cored twice at a diameter of 1 mm and re-embedded into the final recipient block. Immunohistochemistry was performed by the use of anti-EGFR monoclonal antibody (31G7). Also, a chromogenic in situ hybridization protocol was applied based on the use of EGFR gene and chromosome 7 centromeric probes, respectively.

EGFR protein overexpression was observed in 29/50 (58%) cases and correlated to stage (p = 0.001) but not to grade (p = 0.206). EGFR gene analysis identified numerical alterations in 6/50 (12%), including 2 cases characterized by low-level gene amplification and 4 by absence of one allele. Gene status was associated to tumor grade (p = 0.023) and stage (p = 0.02). Chromosome 7 analysis detected aneuploidy in 14 (28%) cases.

A subset of pancreatic ductal adenocarcinomas (PDACs) is characterized by EGFR gene numerical alterations including sporadic cases of amplification or absence of one allele (maybe due to gene deletion or intragenic point mutation and allelic silence). Those alternative mechanisms maybe influence the efficacy of novel targeted therapeutic strategies based on monoclonal antibodies or intracellular tyrosine-kinase inhibitors in PDACs.