Near Infrared Imaging of EGFR of Oral Squamous Cell Carcinoma in Mice Administered Arsenic Trioxide

Background: The effectiveness of near-infrared imaging (NIR) interrogation of epidermal growth factor receptor (EGFR) expression as a sensitive biomarker of oral squamous cell carcinoma (OSCC) response to arsenic trioxide therapy was studied in mice. Material and Methods: A431 OSCC in vitro were exposed to 0 μM, 0.5 μM, 2.5 μM, or 5 μM of As₂O₃ for 0 h, 24 h, 48 h and 72 h. Confocal microscopy and flow cytometry confirmed EGFR expression and demonstrated a sensitivity dose-related signal decline with As₂O₃ treatment. Next, mice with pharynx-implanted A431 cells received As₂O₃ i.p. every 48 h at 0.0, 0.5, 2.5, or 5 mg/kg/day (n = 6/group) from day 0 to 10. An intravenous NIR probe, EGF-Cy5.5, was injected at baseline and on days 4, 8, and 12 for dynamic NIR imaging. Tumor volume and body weights were measured three times weekly. Results: In vitro, A431 EGFR expression was well appreciated in the controls and decreased (p<0.05) with increasing As₂O₃ dose and treatment duration. In vivo EGFR NIR tumor signal intensity decreased (p<0.05) in As₂O₃ treated groups versus controls from days 4 to 12, consistent with increasing dosage. Tumor volume diminished in a dose-related manner while body weight was unaffected. Immunohistochemical staining of excised tumors confirmed that EGFR expression was reduced by As₂O₃ treatment in a dose responsive pattern. Conclusion: This study demonstrates for the first time that OSCC can be interrogated in vivo by NIR molecular imaging of the EGFR and that this biomarker is effective for the longitudinal assessment of OSCC response to As₂O₃ treatment.