Fluorescently-Labeled Cetuximab-IRDye800 for Guided Surgical Excision of Ameloblastoma: A Proof of Principle Study

Abstract Purpose Fluorescently labeled epidermal growth factor receptor (EGFR) antibodies can successfully identify microscopic tumors in multiple in vivo models of human cancers with limited toxicity. This study demonstrates the ability of fluorescently labeled anti-EGFR, cetuximab-IRDye800, to localize to ameloblastoma tumor cells in vitro and in vivo. Material and Methods EGFR expression in ameloblastoma cells was confirmed by qRT-PCR and immunohistochemistry. Primary ameloblastoma cells were labeled in vitro with cetuximab-IRDye800 or non-specific IgG-IRDye800. An in vivo patient-derived xenograft model of ameloblastoma was developed: tumor tissue from three patients was implanted subcutaneously into immunocompromised mice, animals received intravenous injection of cetuximab-IRDye800 or IgG-IRDye800, and were imaged to detect infrared fluorescence using a LI-COR Pearl imaging system. Following overlying skin resection, tumor to background ratios (TBR) were calculated and statistically analyzed by paired t-test. Results EGFR expression was seen in all ameloblastoma samples. Tumor-specific labeling was achieved, as evidenced by positive fluorescence signal from cetuximab-IRDye800 binding to ameloblastoma cells, with little staining seen in the negative controls treated with IgG-IRDye800. In the animal PDX model, imaging revealed the tumor-to-background ratios (TBRs) produced by cetuximab were significantly higher than those produced by IgG on days 7-14 for AB-20 tumors. Following skin flap removal to simulate a pre-resection state, TBRs increased with cetuximab and were significantly higher than the IgG control for PDX tumors derived from three ameloblastoma patients. Excised tissues were paraffin-embedded to confirm the presence of tumor. Conclusions Fluorescently labeled anti-EGFR demonstrates specificity for ameloblastoma cells and PDX tumors. This study is the first report of tumor-specific, antibody-based imaging of odontogenic tumors, of which ameloblastoma is one of the most clinically aggressive. We expect this technology will ultimately assist surgeons treating ameloblastomas by helping them to accurately assess tumor margins during surgery, leading to improved long-term local tumor control and less surgical morbidity.