Epidermal growth factor receptor (EGFR) expression and mutations in the EGFR signaling pathway in correlation with anti-EGFR therapy in head and neck squamous cell carcinomas

Abstract

Epidermal growth factor receptor (EGFR) is an important therapeutic target and a poor prognosis factor in head and neck squamous cell carcinoma (HNSCC). The aim of the study was to analyze EGFR expression and KRAS and EGFR mutational status and to correlate it with treatment response to anti-EGFR therapy combined with radiotherapy in 29 patients with advanced head and neck squamous cell carcinomas (HNSCC). EGFR gene expression normalized to GAPDH and EGFR variant type III (EGFRvIII) was detected in tumor tissue using real time reverse transcription -PCR. The mutational status of the EGFR and KRAS genes was investigated by real time PCR with sequence specific primers. Gene expression median values were 3.1x108 GAPDH gene copies per μg of RNA, and 8x106 EGFR gene copies per μg of RNA. The median EGFR/GADPH ratio reached 0.14. Patients, who achieved complete response after Cetuximab combined with radiotherapy, had significantly higher expression of the EGFR gene in tumors than patients with partial remission or patient without treatment response. An EGFRvIII mutation was found in 20.7 % of patients and no association was found between this mutation and treatment response. 27 patients (93.1 %) had an EGFR gene wild type tumor, and deletion in exon 19 was found in two patients with a poor clinical outcome. Most of the patients (82.8%) had a KRAS wild type tumor; a p.Gly12Cys was found in three patients and a p.Gly12Val mutation in one. Presence of a p.Gly12Val mutation in the KRAS gene was associated with an absence of response to treatment. Conclusion: Our data suggest that KRAS mutation (p.Gly12Val) and somatic EGFR mutation located in exon 19 may contribute to the limited clinical response to therapy with cetuximab + radiotherapy. Higher EGFR gene expression serves as an independent indicator of good clinical response to EGFR-targeted therapy + radiotherapy.