title: 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 γ-secretase inhibitor, disrupted the large vessels and abolished the tumor resistance. Multiple molecular mechanisms of resistance were shown, including decreased levels of hypoxia-induced 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.
authors.affiliation: Molecular Oncology Laboratories, Department of Oncology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, United Kingdom. ji-liang.li@imm.ox.ac.uk
authors.forename: Ji-Liang
authors.initials: JL
authors.lastname: Li
authors.forename: Richard C A
authors.initials: RC
authors.lastname: Sainson
authors.forename: Chern Ein
authors.initials: CE
authors.lastname: Oon
authors.forename: Helen
authors.initials: H
authors.lastname: Turley
authors.forename: Russell
authors.initials: R
authors.lastname: Leek
authors.forename: Helen
authors.initials: H
authors.lastname: Sheldon
authors.forename: Esther
authors.initials: E
authors.lastname: Bridges
authors.forename: Wen
authors.initials: W
authors.lastname: Shi
authors.forename: Cameron
authors.initials: C
authors.lastname: Snell
authors.forename: Emma T
authors.initials: ET
authors.lastname: Bowden
authors.forename: Herren
authors.initials: H
authors.lastname: Wu
authors.forename: Partha S
authors.initials: PS
authors.lastname: Chowdhury
authors.forename: Angela J
authors.initials: AJ
authors.lastname: Russell
authors.forename: Craig P
authors.initials: CP
authors.lastname: Montgomery
authors.forename: Richard
authors.initials: R
authors.lastname: Poulsom
authors.forename: Adrian L
authors.initials: AL
authors.lastname: Harris
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology; D000068258:Bevacizumab; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D003984:Dibenzazepines / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005260:Female; D005354:Fibrosarcoma / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism; D005909:Glioblastoma / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D014183:Transplantation, Heterologous; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000096:biosynthesis
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; D003984:Dibenzazepines; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; D042461:Vascular Endothelial Growth Factor A; C064045:delta protein; D000068258:Bevacizumab; C527817:dibenzazepine