An Ex Vivo Human Tumor Assay Shows Distinct Patterns of EGFR Trafficking in Squamous Cell Carcinoma Correlating to Therapeutic Outcomes

EGFR overexpression is associated with squamous cell carcinoma development. Altered endocytosis and polarization of receptor tyrosine kinases, including EGFR, affect migration and invasion in three-dimensional culture. These studies have been completed via genetic sequencing, cell line, or three-dimensional in vitro and in vivo murine models. Here, we describe an imaging method that allows ex vivo examination of ligand-induced endocytosis of EGFR in non-dissociated human tumors. We analyzed sets of tumor samples from advanced cutaneous squamous cell carcinoma and head and neck squamous cell carcinoma, actinic keratosis, intraepidermal carcinoma, and cutaneous squamous cell carcinoma. We show that EGFR endocytosis is dysregulated in advanced SCC and correlates with anti-EGFR monoclonal antibody therapy outcomes. In actinic keratosis, intraepidermal carcinoma, and well-differentiated cutaneous squamous cell carcinoma, different patterns of epidermal growth factor ligand uptake and binding were observed at the leading edge of different dysplastic lesions, suggesting that these differences in EGFR endocytosis might influence the metastatic potential of dysplastic squamous epithelium. These studies in live ex vivo human tumors confirm that endocytosis dysregulation is a physiological event in human tumors and has therapeutic implications.