Abstract 2519: U3-1565, a fully human anti-HB-EGF monoclonal antibody, inhibits oncogenic signaling and tumor cell growth in vitro and in vivo
Authors: Pfeil Ines , aus dem Siepen Patricia , Wagner Tanja , Schramm Julia , Riffner Yvonne , Hettmann Thore , Zwick-Wallasch Esther 
Published: August 2012

Abstract
Background: U3-1565 is a fully human monoclonal antibody directed against human heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the EGF family of ligands that bind to and activate the EGFR and HER4. HB-EGF-mediated activation of its target receptors results in oncogenic signaling. Methods: To determine inhibition of basal EGFR phosphorylation, human tumor cell lines were treated with U3-1565 or IgG2 and pEGFR levels were analyzed by ELISA. Inhibition of in vivo angiogenesis was analyzed by implanting HUVEC-based spheroids under the skin of SCID mice, which were treated with U3-1565, bevacizumab or PBS and analyzed for human neovasculature. To determine in vivo efficacy, SCID mice bearing EFO27-CL58 ovarian cancer xenografts were treated weekly with U3-1565, Cisplatin or with a combination of U3-1565 and Cisplatin. To perform xenograft analysis tumor-bearing mice were treated with U3-1565, cetuximab and erlotinib and primary xenograft tissue was collected, lyzed and pEGFR and pERK levels were analyzed by Western blotting. To determine expression of HB-EGF and pEGFR in human tumor tissue, Immunohistochemistry (IHC) stainings of human carcinoma samples were performed. Results: Inhibition of basal pEGFR levels by U3-1565 in comparison to control IgG2 treatment was demonstrated in various cancer cell lines. U3-1565 showed dose-dependent inhibition of HB-EGF-stimulated pHER4 and pERK activation in vitro (data not shown). Using a HUVEC-based spheroid in vivo system, inhibition of human endothelial cell sprouting by U3-1565 was shown. In a HB-EGF overexpressing ovarian cancer xenograft model U3-1565 demonstrated in vivo tumor cell growth inhibition as a single agent. Combination treatment of U3-1565 with Cisplatin resulted in tumor regression during the treatment phase and prevented re-growth of xenograft tumors after treatment stop. Analysis of EFO27-CL58 tumor xenograft tissue demonstrated strong reduction of pEGFR and partially reduced pERK levels after U3-1565 in vivo treatments. IHC staining of fresh human tumor samples revealed an overlapping expression pattern of HB-EGF and pEGFR. Conclusions: Our results demonstrate that U3-1565 inhibits basal activation of EGFR activation in vitro and reduces neo-vasculature formation (angiogenesis) in vivo. In a tumor xenograft model U3-1565 demonstrated tumor cell growth arrest as a single agent or in combination with Cisplatin or erlotinib. Analysis of xenograft material after in vivo exposure to U3-1565 strongly suggest that U3-1565's anti-tumor activity is based on inhibition of EGFR activation and prevention of oncogenic MAPK signaling. These data together with the evidence that human HB-EGF and activated EGFR are coexpressed in human tumor samples provide preclinical rational to develop U3-1565 as a clinical mAb candidate to treat cancer in human patients.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2519. doi:1538-7445.AM2012-2519