Molecular oncology 2018 03 30() doi 10.1002/1878-0261.12197
The epidermal growth factor receptor (EGFR, HER1) is a therapeutic target in head and neck squamous cell carcinoma (HNSCC). After initial promising results with EGFR-targeted therapies such as cetuximab, therapeutic resistance has become a major clinical problem, and new treatment options are therefore necessary. Moreover, the relationship between HER receptors, anti-EGFR therapies and the human papillomavirus (HPV) status in HNSCC is not fully understood. In contrast to first generation EGFR inhibitors, afatinib irreversibly inhibits multiple HER receptors simultaneously. Therefore, treatment with afatinib might result in a more pronounced therapeutic benefit, even in patients experiencing cetuximab resistance. In this study, the cytotoxic effect of afatinib as single agent and in combination with cisplatin was investigated in cetuximab sensitive, intrinsically and acquired resistant HNSCC cell lines with different HPV status under normoxia and hypoxia. Furthermore, the influence of cetuximab resistance, HPV and hypoxia on the expression of HER receptors was investigated. Our results demonstrated that afatinib was able to establish cytotoxicity in cetuximab sensitive, intrinsically and acquired resistant HNSCC cell lines, independent of the HPV status. However, cross-resistance between cetuximab and afatinib might be possible. Treatment with afatinib caused a G/Gcell cycle arrest as well as induction of apoptotic cell death. Additive to antagonistic interactions between afatinib and cisplatin could be observed. Neither cetuximab resistance nor HPV status significantly influenced the expression of HER receptors in HNSCC cell lines. In contrast, the expression of EGFR, HER2 and HER3 was significantly altered under hypoxia. Oxygen deficiency is a common characteristic of HNSCC tumors and these hypoxic tumor regions often contain cells that are more resistant to treatment. However, we observed that afatinib maintained its cytotoxic effect under hypoxia. In conclusion, our preclinical data support the hypothesis that afatinib might be a promising therapeutic strategy to treat HNSCC patients experiencing intrinsic or acquired cetuximab resistance.