A novel anti-human HB-EGF monoclonal antibody with multiple antitumor mechanisms against ovarian cancer cells.

PURPOSE: Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is a member of the EGF family and plays a pivotal role in tumor progression in ovarian cancer. We developed an anti-HB-EGF monoclonal antibody (mAb) and investigated its antitumor activities in vitro and in vivo to evaluate its potential as a therapeutic antibody against ovarian cancer. EXPERIMENTAL DESIGN: We prepared mAbs from HB-EGF null mice immunized with recombinant human soluble HB-EGF and evaluated their binding and neutralizing activity against HB-EGF. Next, we generated a mouse-human chimeric antibody and examined its in vitro and in vivo antitumor activities. RESULTS: Two murine anti-HB-EGF mAbs were developed, and one of them, KM3566, was revealed to have a high binding reactivity for membrane-anchored HB-EGF (pro-HB-EGF) expressed on the cell surface, as well as neutralizing activity against growth promoting activity of soluble HB-EGF. The mouse-human chimeric counterpart for KM3566 (cKM3566) induced dose-dependent antibody-dependent cellular cytotoxicity (ADCC) against cancer cells expressing HB-EGF in vitro, and significantly inhibited tumor growth in severe combined immunodeficient mice inoculated with MCAS or ES-2 human ovarian cancer cells. CONCLUSIONS: A novel anti-HB-EGF chimeric antibody, cKM3566, with two antitumor mechanisms, neutralization and ADCC, exhibits potent in vivo antitumor activity. These results indicate that cKM3566 is a promising antiovarian cancer therapeutic antibody.

Anti-human HB-EGF monoclonal antibodies inhibiting ectodomain shedding of HB-EGF and diphtheria toxin binding.

HB-EGF is a member of the EGF family of growth factors that bind and activate the EGF receptor. HB-EGF is synthesized as a membrane-anchored protein (proHB-EGF), and then proteolytically cleaved, resulting in the mitogenically active soluble form. ProHB-EGF functions as the receptor for the diphtheria toxin (DT). HB-EGF plays pivotal roles in pathophysiological processes, including cancer. Monoclonal antibodies (mAbs) specific for HB-EGF could be an important tool in HB-EGF research. However, few such mAbs have been established to date. In this study, we newly generated seven clones of hybridoma-derived mAbs by immunizing HB-EGF null mice with recombinant human HB-EGF protein. All mAbs specifically bound to human HB-EGF but not to mouse HB-EGF. Epitope mapping analysis showed that most of the mAbs recognized the EGF-like domain. Although none of the newly isolated mAbs directly inhibited the mitogenic activity of HB-EGF for EGFR-expressing cells, some strongly inhibited DT-binding. Interestingly, some of the mAbs efficiently inhibited ectodomain shedding of proHB-EGF, and consequently prevented the cell growth of the EGFR-expressing cells in a co-culture system with proHB-EGF-expressing cells. Hence, these new anti-HB-EGF mAbs may advance clinical as well as basic research on HB-EGF.