Functional Profiling of Head and Neck/Esophageal Squamous Cell Carcinoma to Predict Cetuximab Response.

Background: Cetuximab, an epidermal growth factor receptor (EGFR)-targeting antibody, remains the only Food and Drug Administration-approved targeted therapy for squamous cell carcinoma (SCC) of head and neck/esophagus. However, in clinical trials, cetuximab only benefited a subset of patients and frequently caused toxicity. Predicting which patients respond to cetuximab remains unsolved. The authors sought to identify predictive biomarkers in EGFR signaling and autophagy pathways, which may be impacted by cetuximab under certain treatment conditions. Methods: In vitro responses of SCC cell lines to cetuximab under various nutrient conditions were assessed by WST-8 growth assay. Functional profiles of several EGFR signaling biomarkers were investigated by Luminex-based assays and corroborated with immunoblots. Autophagy markers were analyzed with immunoblots. Results: In vitro growth response assays identified cetuximab responder and nonresponder cell lines. Optimal growth conditions and growth factors enhanced responses, and even reversed nonresponsiveness in some cell lines. Strong correlation was found between response in growth assays (reference assay) and dynamic changes in p-Erk1/2 and LC3-II (index assays). Conclusions: This study indicates that nutrient modification may enhance cetuximab response in SCC patients. Biomarker results strengthen the hypothesis that dynamic biomarkers can be used to predict patient response to cetuximab. Future studies are warranted to test in more complex samples including patient-derived tumor tissues.