Targeting EGFR-positive cancer cells with cetuximab-ZZ-PE38: Results of in vitro and in vivo studies.

ABSTRACT

BACKGROUND: Arming antibody with toxins is a new approach in cancer therapy. We evaluated the efficacy of cetuximab-ZZ-PE38 immunocomplex in killing cancer cells in vitro and inhibiting tumor growth in nude mice. METHODS: Several cancer cell lines and human foreskin fibroblasts were tested for epidermal growth factor receptor (EGFR) expression and cetuximab binding using Western blot assay, enzyme-linked immunosorbent assay (ELISA), and flow cytometry. Cell survival in vitro was estimated by XTT assay. Tumor size was measured twice a week. RESULTS: Cetuximab-ZZ-PE38 immunocomplex was significantly more effective in killing head and neck cancer cells than nonspecific IgG-ZZ-PE38 complex or free ZZ-PE38, whereas normal cells were not affected. Tumor treatment with immunocomplex resulted in tumor shrinkage. The immunocomplex was safe to mice at a therapeutic dosage of 0.25 mg/mL, whereas the dosage of 0.50 mg/mL induced liver toxicity. CONCLUSIONS: Cetuximab-ZZ-PE38 immunocomplex is a highly effective agent in killing EGFR-positive cancer cells and in tumor shrinkage.