Abstract

Abstract Ovarian cancer in a major cause cancer related death in women and this disease is often characterized by resistance to chemotherapy and tumor recurrence. Cancer stem cells (CSCs) have been shown to be relatively insensitive to chemotherapeutic agents. Several lines of evidence indicate that aberrant Notch signaling plays a major role in ovarian cancer progression and resistance to standard therapies. DLL4 is a key ligand that activates the Notch pathway and has been shown to regulate both CSC function and tumor angiogenesis. DLL4 expression in tumor and endothelial cells has also been associated with resistance to bevacizumab treatment. In these studies, we investigated the role of anti-DLL4 in a panel of patient-derived ovarian cancer xenograft models. We utilized anti-human DLL4 (OMP-21M18) and anti-murine DLL4 to block Notch signaling in both the tumor and stromal/vascular cells in the xenografts. We found that anti-DLL4 treatment was broadly efficacious in these ovarian cancer models, significantly inhibiting tumor growth both as a single agent and in combination with paclitaxel. We carried out serial transplantation studies to investigate the effect on cancer stem cells and found that anti-DLL4 in combination with paclitaxel profoundly reduced the tumor initiating cell frequency. In contrast, treatment with paclitaxel alone had the opposite effect and increased ovarian CSC frequency. These data suggest that anti-DLL4 treatment sensitizes chemoresistant ovarian tumorigenic cells to therapy and provide compelling evidence that anti-DLL4 (demcizumab) is a promising strategy for the clinical treatment of ovarian cancer. Citation Format: Wan-Ching Yen, Marcus M. Fischer, Jalpa Shah, Jie Wei, Jennifer Cain, Pete Yeung, Lucia Beviglia, Belinda Cancilla, Ann Kapoun, John Lewicki, Austin Gurney, Timothy Hoey. Anti-DLL4 (demcizumab) inhibits tumor growth and reduces cancer stem cell frequency in patient-derived ovarian cancer xenografts. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3725. doi:10.1158/1538-7445.AM2013-3725

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