Abstract 1212: Co-targeting epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase overcomes EGFR inhibitor resistance in head and neck squamous cell carcinoma patient-derived models

Abstract

Abstract Background: HNSCC is the sixth most common cancer worldwide. EGFR is overexpressed in up to 90% of HNSCC and associated with poor outcome. An EGFR monoclonal antibody is the only approved molecular targeted therapy for HNSCC, however, resistance eventually occurs in all patients. Methods: Functional screens including a small-molecule kinase inhibitor panel and an RNAi screen panel were used to identify agents that synergized with EGFR inhibitors in reducing cell viability in HNSCC patient-derived tumor cells. Effective combination therapies were validated in scale-up experiments in 2D and 3D, and their true targets were evaluated using siRNAs to rule out off-target effects of the drugs. Cell viability, cell number and cell colony formation ability were tested upon siRNA treatment. qRT-PCR and immunofluorescent staining was used to test ALK expression in tumor cells before and after anti-EGFR treatment. Results: Two ALK inhibitors on the drug screen panel showed synergistic effects with EGFR inhibitors in 6/8 HNSCC patients’ tumor cells, despite ineffectiveness of single drug. Scale-up dose-response experiments confirmed patient cell sensitivity to 4 different ALK inhibitors in combination with the EGFR inhibitor Gefitinib. siRNA targeting ALK synergized with Gefitinib in reducing cell viability in the patient cells that responded to EGFR/ALK inhibitor combinations, indicating specificity to ALK. Scale-up RNAi experiments confirmed synergy between siRNAs targeting ALK and EGFR in reducing cell viability, cell number, and colony formation ability. Inhibition of EGFR by siRNA or Gefitinib each increased ALK expression at the mRNA level and protein level, suggesting induction of ALK as a novel mechanism of EGFR inhibitor resistance in HNSCC. Conclusion: We identified EGFR/ALK inhibitor combinations as a potential strategy for treating EGFR inhibitor resistant HNSCC. Citation Format: Xiaoming Ouyang, Ashley Barling, Aletha Lesch, Jeffrey Tyner, Sophia Jeng, Christina Zheng, Sara A. Courtneidge, Shannon McWeeney, Molly Kulesz-Martin. Co-targeting epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase overcomes EGFR inhibitor resistance in head and neck squamous cell carcinoma patient-derived models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1212. doi:10.1158/1538-7445.AM2017-1212