Defucosylated Anti-Epidermal Growth Factor Receptor Monoclonal Antibody Exerted Antitumor Activities in Mouse Xenograft Models of Canine Mammary Gland Tumor.

The epidermal growth factor receptor (EGFR) contributes to tumor malignancy through gene amplification and/or protein overexpression. In our previous study, we developed an anti-human EGFR (hEGFR) monoclonal antibody, clone EMab-134 (mouse IgG1, kappa), which specifically detects both hEGFR and dog EGFR (dEGFR). The defucosylated mouse IgG2a version of EMab-134 (134-mG2a-f) exhibits antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in dEGFR-overexpressed Chinese hamster ovary-K1 (CHO/dEGFR) cells and antitumor activities in mouse xenografts of CHO/dEGFR cells. In this study, the reactivity of 134-mG2a-f against a canine mammary gland tumor cell line (SNP) was examined by flow cytometry and immunocytochemistry. Furthermore, 134-mG2a-f highly exerted ADCC and CDC for SNP. The administration of 134-mG2a-f significantly suppressed the SNP xenograft growth. These results suggest that 134-mG2a-f exerts antitumor effects against dEGFR-expressing canine mammary gland tumors, and could be valuable as part of an antibody treatment regimen for them.