DLL4-Notch Signaling Mediates Tumor Resistance to Anti-VEGF Therapy In Vivo

Abstract

Resistance to VEGF inhibitors is emerging as a major clinical problem. Notch signaling has been implicated in tumor angiogenesis. Therefore, to investigate mechanisms of resistance to angiogenesis inhibitors, we transduced human glioblastoma cells with retroviruses encoding Notch delta-like ligand 4 (DLL4), grew them as tumor xenografts and then treated the murine hosts with the VEGF-A inhibitor bevacizumab. We found that DLL4-mediated tumor resistance to bevacizumab in vivo. The large vessels induced by DLL4-Notch signaling increased tumor blood supply and were insensitive to bevacizumab. However, blockade of Notch signaling by dibenzazepine, a g-secretase inhibitor, disrupted the large vessels and abolished the tumor resistance. Multiple molecular mechanisms of resistance were shown, including decreased levels of hypoxiainduced VEGF and increased levels of the VEGF receptor VEGFR1 in the tumor stroma, decreased levels of VEGFR2 in large blood vessels, and reduced levels of VEGFR3 overall. DLL4-expressing tumors were also resistant to a VEGFR targeting multikinase inhibitor. We also observed activation of other pathways of tumor resistance driven by DLL4-Notch signaling, including the FGF2-FGFR and EphB4-EprinB2 pathways, the inhibition of which reversed tumor resistance partially. Taken together, our findings show the importance of classifying mechanisms involved in angiogenesis in tumors, and how combination therapy to block DLL4-Notch signaling may enhance the efficacy of VEGF inhibitors, particularly in DLL4-upregulated tumors, and thus provide a rational base for the development of novel strategies to overcome antiangiogenic resistance in the clinic. Cancer Res; 71(18); 6073-83. Ó2011 AACR.

Dll4-Fc, an Inhibitor of Dll4-Notch Signaling, Suppresses Liver Metastasis of Small Cell Lung Cancer Cells through the Downregulation of the NF-κB Activity

“…A previous report showed that Dll4 expressed in tumor cells regulated cancer growth and differentiation (26), and improved tumor vascular function and promoted tumor growth (27,28). Moreover, Zhang and colleagues showed that Dll1-Notch signaling in cancer cells regulates invasion and metastasis in vitro and in vivo (29).…”

Recent molecular discoveries in angiogenesis and antiangiogenic therapies in cancer

“…Tumor ECs engineered to overexpress DLL4 develop enlarged mature vessels that are resistant against VEGF blockade, while inhibition of Notch signaling restores the sensitivity to antiangiogenic drugs in a xenograft model (83). Resistance can result from activation of FGF2-FGFR and EphB4-Ephrin-B2 pathways or from decreased levels of VEGFR2 (83). Several proangiogenic molecules become upregulated under selective pressure by VEGFIs/ VEGFRIs (79, 84).…”

The Longitudinal Transcriptional Response to Neoadjuvant Chemotherapy with and without Bevacizumab in Breast Cancer

“…Vascular Endothelial Growth Factor (VEGF) stimulates angiogenesis by influencing vessel formation through regulation of proliferation, migration and survival of endothelial cells (1)(2)(3). Blocking VEGF by bevacizumab, a monoclonal antibody, has been proposed to cause inhibition of neovascularization, regression of existing immature micro-vessels, and normalization of abnormal vasculature (4,5); this has consequences for the flux of oxygen, nutrients, metabolites and therapeutic agents, ultimately preventing tumor growth and resulting in tumor shrinkage.…”