title: Endothelial-specific Notch blockade inhibits vascular function and tumor growth through an eNOS-dependent mechanism.
abstract: Notch signaling is important for tumor angiogenesis induced by vascular endothelial growth factor A. Blockade of the Notch ligand Dll4 inhibits tumor growth in a paradoxical way. Dll4 inhibition increases endothelial cell sprouting, but vessels show reduced perfusion. The reason for this lack of perfusion is not currently understood. Here we report that inhibition of Notch signaling in endothelial cell using an inducible binary transgenic system limits VEGFA-driven tumor growth and causes endothelial dysfunction. Neither excessive endothelial cell sprouting nor defects of pericyte abundance accompanied the inhibition of tumor growth and functional vasculature. However, biochemical and functional analysis revealed that endothelial nitric oxide production is decreased by Notch inhibition. Treatment with the soluble guanylate cyclase activator BAY41-2272, a vasorelaxing agent that acts downstream of endothelial nitric oxide synthase (eNOS) by directly activating its soluble guanylyl cyclase receptor, rescued blood vessel function and tumor growth. We show that reduction in nitric oxide signaling is an early alteration induced by Notch inhibition and suggest that lack of functional vessels observed with Notch inhibition is secondary to inhibition of nitric oxide signaling. Coculture and tumor growth assays reveal that Notch-mediated nitric oxide production in endothelial cell requires VEGFA signaling. Together, our data support that eNOS inhibition is responsible for the tumor growth and vascular function defects induced by endothelial Notch inhibition. This study uncovers a novel mechanism of nitric oxide production in endothelial cells in tumors, with implications for understanding the peculiar character of tumor blood vessels.
authors.affiliation: Authors' Affiliations: Genome Sciences Centre; Integrative Oncology Program; Department of Pathology and Laboratory Medicine, British Columbia Cancer Agency; and Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Patenaude
authors.forename: Megan
authors.initials: M
authors.lastname: Fuller
authors.forename: Linda
authors.initials: L
authors.lastname: Chang
authors.forename: Fred
authors.initials: F
authors.lastname: Wong
authors.forename: Grigorios
authors.initials: G
authors.lastname: Paliouras
authors.forename: Rebecca
authors.initials: R
authors.lastname: Shaw
authors.forename: Alastair H
authors.initials: AH
authors.lastname: Kyle
authors.forename: Patricia
authors.initials: P
authors.lastname: Umlandt
authors.forename: Jennifer H E
authors.initials: JH
authors.lastname: Baker
authors.forename: Erika
authors.initials: E
authors.lastname: Diaz
authors.forename: Jade
authors.initials: J
authors.lastname: Tong
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Minchinton
authors.forename: Aly
authors.initials: A
authors.lastname: Karsan
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism; D008546:Melanoma, Experimental / Q000098:blood supply / Q000201:enzymology* / Q000473:pathology; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D055806:Microvessels / Q000187:drug effects / Q000473:pathology; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic / Q000201:enzymology*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000502:physiology*; D020286:Pericytes / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D047368:Tumor Burden / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
chemical_list: C423582:3-(4-Amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo(3,4-b)pyridine; D020533:Angiogenesis Inhibitors; D011720:Pyrazoles; D011725:Pyridines; D051880:Receptors, Notch; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D040301:Vascular Endothelial Growth Factor Receptor-2; D006162:Guanylate Cyclase