EGFR and K-RAS gene status evaluation in anal canal squamous cell carcinoma

Abstract

15569 Background: Mutations affecting the epidermal growth factor receptor (EGFR) gene and the K-RAS gene have been identified in a variety of human solid tumours and have been validated as promising therapeutic targets. Approximately 85% of non small-cell lung cancer patients, who responded to gefinitib or erlotinib, have somatic mutations in the EGFR gene (exons 18–21) and for metastatic colorectal cancer patients, wild-type K-RAS is required for responsiveness to panitumumab. In squamous cell carcinoma of the anal canal however, the EGFR and K-RAS gene status has not systematically been investigated. Patients and Methods: In this study, 30 primary squamous cell carcinomas of the anal canal were investigated. The panel consisted of twenty men and 10 women with a median age of 60.5 years (range: 34–86 years). The formalin-fixed paraffin embedded tissues were immunohistochemically (ICH) examined for EGFR expression (Zymed Laboratories) and analysed by fluorescence in situ hybridisation (FISH) for EGFR gene copy numbers. Furthermore, EGFR and K-RAS mutation analysis was performed on DNA isolated from formalin-fixed paraffin embedded tissues. EGFR mutation analysis was carried out using exons 18 through 21 specific primers. For K-RAS, exon 2 was analysed for the presence of mutations. Results: EGFR immunoreactivity was detected in 27 of 29 (93%) tumours. One tumour yielded no conclusive results. Nineteen (65%) cases exhibited a moderate (2+) or strong (3+) staining intensity. FISH results were not interpretable in 18 (60%) cases. Of the remaining 12 cases, none showed EGFR gene amplification. Mutation analysis was performed on 20 samples, but no mutations could be identified in the kinase domain of the EGFR gene nor in the K-RAS gene. Conclusion: In our panel of squamous cell carcinoma of the anal canal, all samples showed a strong EGFR protein expression as evaluated by IHC. However, no EGFR gene amplification nor EGFR and K-RAS mutation could be identified. No significant financial relationships to disclose.