Antitumor activities of a defucosylated anti-EpCAM monoclonal antibody in colorectal carcinoma xenograft models

Abstract

Epithelial cell adhesion molecule (EpcAM) is a type I transmembrane glycoprotein, which is highly expressed on tumor cells. As EpcAM plays a crucial role in cell adhe- sion, survival, proliferation, stemness, and tumorigenesis, it has been considered as a promising target for tumor diagnosis and therapy. Anti-EpcAM monoclonal antibodies (mAbs) have been developed and have previously demonstrated promising outcomes in several clinical trials. An anti-EpcAM mAb, EpMab-37 (mouse IgG1, kappa) was previously devel- oped by the authors, using the cell-based immunization and screening method. In the present study, a defucosylated version of anti-EpcAM mAb (EpMab-37-mG2a-f) was generated to evaluate the antitumor activity against EpcAM-positive cells. EpMab-37-mG2a-f recognized EpcAM-overexpressing cHO-K1(cHO/EpCAM)cellswithamoderatebinding-affinity [dissociation constant (Kd)=2.2x10-8 M] using flow cytometry. EpMab-37-mG2a-fexhibitedpotentantibody-dependentcellular cytotoxicity (Adcc) and complement-dependent cytotoxicity (cdc) for cHO/EpcAM cells by murine splenocytes and complements, respectively. Furthermore, the administration of EpMab-37-mG2a-f significantly suppressed CHO/EpcAM xenograft tumor development compared with the control mouse IgG. EpMab-37-mG2a-f also exhibited a moderate binding-affinity (Kd=1.5x10-8 M) and high Adcc and cdc activities for a colorectal cancer cell line (caco-2 cells). The administration of EpMab-37-mG2a-f to caco-2 tumor-bearing mice significantly suppressed tumor development compared with the control. By contrast, EpMab-37-mG2a-f never suppressed the xenograft tumor growth of caco-2 cells in which EpcAM was knocked out. On the whole, these results indicate that EpMab-37-mG2a-f may exert antitumor activities against EpcAM-positive cancers and may thus be a promising therapeutic regimen for colorectal cancer.