Blockade of Dll4 inhibits tumour growth by promoting non-productive angiogenesis

Abstract

Tumour growth requires accompanying expansion of the host vasculature, with tumour progression often correlated with vascular density. Vascular endothelial growth factor (VEGF) is the best-characterized inducer of tumour angiogenesis. We report that VEGF dynamically regulates tumour endothelial expression of Delta-like ligand 4 (Dll4), which was previously shown to be absolutely required for normal embryonic vascular development. To define Dll4 function in tumour angiogenesis, we manipulated this pathway in murine tumour models using several approaches. Here we show that blockade resulted in markedly increased tumour vascularity, associated with enhanced angiogenic sprouting and branching. Paradoxically, this increased vascularity was non-productive-as shown by poor perfusion and increased hypoxia, and most importantly, by decreased tumour growth-even for tumours resistant to anti-VEGF therapy. Thus, VEGF-induced Dll4 acts as a negative regulator of tumour angiogenesis; its blockade results in a striking uncoupling of tumour growth from vessel density, presenting a novel therapeutic approach even for tumours resistant to anti-VEGF therapies.

Delta-like ligand 4 (Dll4) is induced by VEGF as a negative regulator of angiogenic sprouting

“…Similarly, it is likely that Dll4 is involved in the modulation of diverse forms of pathological angiogenesis. For example, VEGF also induces Dll4 as a negative feedback regulator of vascular sprouting during tumor angiogenesis (22). Here, blockade of Dll4/Notch signaling was found to retard tumor growth by enhancing the chaotic, nonproductive vascular sprouting characteristic of tumor angiogenesis.…”

“…To confirm that the increased angiogenic sprouting observed during postnatal retinal development in Dll4 ϩ/lacZ mice was directly attributable to a local, intraretinal deficiency in Dll4/Notch signaling, and not secondary to an undetected systemic abnormality, we injected a soluble version of Dll4 [termed Dll4-Fc (22)] that acts as a blocker of Dll4/Notch interactions, or a neutralizing antibody specific for the extracellular domain of Dll4, into the vitreous of wild-type mice. Three days after intraocular administration of either Dll4 blocker, the retinal vessels exhibited morphologic changes that closely resembled those found in Dll4 ϩ/lacZ mice ( Fig.…”

“…Dll4-Fc was expressed in CHO cells and affinity-purified by protein A chromatography. Dll4-Fc was shown to inhibit Notch signaling in vitro (22). Anti-Dll4 antibody was produced by immunization of rabbits with recombinant mDll4-hFc.…”

Therapeutic efficacy of combined vaccination against tumor pericyte-associated antigens DLK1 and DLK2 in mice

“…37 Notch signaling also plays a role in tumor neovascularization, as suppression of the DLL4-Notch1 interaction leads to the formation of excessive immature blood vessel branches as a result of uncontrolled endothelial proliferation. [38][39][40] Both DLK1 and DLK2 block downstream Notch1 receptor signaling by interacting with the EGF-like repeat 12 of the receptor, 17 known to be the binding site for canonical ligands. 41,42 Thus, DLK1 and DLK2 impede Notch signaling by blocking receptor activation and by competing with ligands for binding sites.…”

CCM1 and the second life of proteins in adhesion complexes

“…DLL4-Notch can inhibit endothelial sprouting by inhibition of excessive tip-cell formation and is shown to inhibit sprouting in culture cells, animal embryos, and during tumor angiogenesis. [88][89][90][91] Interestingly, loss of CCM1, CCM3, or ICAP1 impairs DLL4-Notch signaling, resulting in excessive angiogenesis. [92][93][94] Furthermore, induction of DLL4-NOTCH signaling by CCM1 results in increased PKB signaling and inhibition of ERK.…”