Epidermal growth factor receptor-targeted immunophotodiagnosis and photoimmunotherapy of oral precancer in vivo

Immunophotodiagnosis uses a fluorescence-labeled monoclonal antibody (MAb) that recognizes a tumor-associated antigen to image the fluorescence emitte d from the fluorophore-bound MAb that has localized in the tissue, It may b e used to diagnose malignant or precancerous lesions, to delineate the marg ins for tumor resection, or as a feedback mechanism to assess response to t reatment. In oral precancer, the epidermal growth factor receptor (EGFR) is overexpressed and could be used as a marker for early detection or as a ta rget for therapy, The goal of this study was to test an anti-EGFR MAb (C225 ) coupled to either the near-infrared fluorescent dye N,N ' -di-carboxypent yl -indodicarbocyanine-5,5 ' -disulfonic acid for detection or a photochemi cally active dye (chlorin(e6)) for therapy of early premalignancy in the ha mster cheek pouch carcinogenesis model, fluorescence levels in the carcinog en-treated tissue correlated with the histological stage of the lesions whe n the C225-N,N ' -di-carboxypentyl-indodicarbocyanine-5,5 '- acid conjugate was used but did not do so with the irrelevant conjugates. Discrete areas of clinically normal mucosa with high fluorescence (hot spots) were subsequ ently shown by histology to contain dysplastic areas. The best contrast bet ween normal and carcinogen-treated cheek pouches vias found at 4-8 days aft er injection, To test the potential of immunophotodiagnosis as a feedback m odality for therapeutic intervention, experiments were conducted with the s ame MAb conjugated to chlorin(e6) followed by illumination to reduce expres sion of the EGFR by a photodynamic effect. Subsequent immunophotodiagnosis showed that this treatment led to a significant reduction in fluorescence i n the carcinogen-treated cheek pouch compared with nonilluminated areas, Th is difference between illuminated and dark areas was not seen in the normal cheek pouch, Taken together, the results demonstrate the potential for dev elopment of immunophotodiagnosis as a diagnostic fool and as a method of mo nitoring response to therapy and that the EGFR may be an appropriate target in head and neck cancer.