Abstract

Background: Anti-EGFR antibody therapy is still one of the clinical choices in head and neck squamous cell carcinoma (HNSCC) patients, but the emergence of cetuximab resistance questioned its effectiveness and reduced its applicability. Although several possible reasons of resistance against the antibody treatment and alternative therapeutic proposals have been described (EGFR alterations, activation of other signaling pathways), there is no method to predict the effectiveness of anti-EGFR antibody treatments and to suggest novel therapeutics. Our study investigated the effect of EGFR R521K alteration on efficiency of cetuximab therapy of HNSCC cell lines and tried to find alternative therapeutic approaches against the resistant cells. Methods: After genetic characterization of HNSCC cells, we chose one wild type and one R521K+ cell line for in vitro proliferation and apoptosis tests, and in vivo animal models using different therapeutic agents. Results: Although the cetuximab treatment affected EGFR signalization in both cells, it did not alter in vitro cell proliferation or apoptosis. In vivo cetuximab therapy was also ineffective on R521K harboring tumor xenografts, while blocked the tumor growth of EGFR-wild type xenografts. Interestingly, the cetuximab-resistant R521K tumors were successfully treated with c-MET tyrosine kinase inhibitor SU11274. Conclusion: Our results suggest that HNSCC cell line expressing the R521K mutant form of EGFR does not respond well to cetuximab treatment in vitro or in vivo, but hopefully might be targeted by c-MET tyrosine kinase inhibitor treatment.

Highlights

  • Over 600,000 head and neck squamous cell carcinoma (HNSCC) patients are diagnosed annually worldwide [1]

  • In the current experimental study, we have investigated the effect of different epidermal growth factor receptor (EGFR) inhibitors, the specific mesenchymal epithelial transition factor (c-MET) TK inhibitor SU11274 and the RAS protein specific inhibitor zoledronic acid on proliferation and apoptosis of human squamous cell carcinoma cells in vitro as well as on the growth and metastasis of HNSCC xenografts in vivo, alone and in combination as well

  • The two cell lines were found to be negative for the EGFRvIII isoform and for the mutations of the TK domain, and did not contain any alterations in the hot point regions of Kirsten rat sarcoma viral oncogene homolog (KRAS) and NRAS, either

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Summary

Introduction

Over 600,000 head and neck squamous cell carcinoma (HNSCC) patients are diagnosed annually worldwide [1]. As in many epithelial tumor types, EGFR protein is overexpressed in HNSCC, and increased EGFR gene copy number is frequently described in this region as well [6,7,8,9]. Anti-EGFR antibody therapy is still one of the clinical choices in head and neck squamous cell carcinoma (HNSCC) patients, but the emergence of cetuximab resistance questioned its effectiveness and reduced its applicability. Our study investigated the effect of EGFR R521K alteration on efficiency of cetuximab therapy of HNSCC cell lines and tried to find alternative therapeutic approaches against the resistant cells

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