Therapeutic efficacy of a DNA vaccine targeting the endothelial tip cell antigen delta-like ligand 4 in mammary carcinoma

Abstract

The Notch ligand delta-like ligand 4 (DLL4) is an essential component expressed by endothelial tip cells during angiogenic sprouting. We have described a conceptually novel therapeutic strategy for targeting tumor angiogenesis and endothelial tip cells based on DNA vaccination against DLL4. Immunization with DLL4-encoding plasmid DNA by in vivo electroporation severely retarded the growth of orthotopically implanted mammary carcinomas in mice by induction of a nonproductive angiogenic response. Mechanistically, vaccination brought about a break in tolerance against the self-antigen, DLL4, as evidenced by the production of inhibitory and inherently therapeutic antibodies against mouse DLL4. Importantly, no evidence for a delayed wound healing response, or for toxicity associated with pharmacological blockade of DLL4 signaling, was noted in mice immunized with the DLL4 vaccine. We have thus developed a well-tolerated DNA vaccination strategy targeting the endothelial tip cells and the antigen DLL4 with proven therapeutic efficacy in mouse models of mammary carcinoma; a disease that has been reported to dramatically induce the expression of DLL4. Conceivably, induction of immunity toward principal mediators of pathological angiogenesis could provide protection against recurrent malignant disease in the adjuvant setting.

JAG2 Induction in Hypoxic Tumor Cells Alters Notch Signaling and Enhances Endothelial Cell Tube Formation

“…In total, this results in a mechanism in which tip-cells with low Notch-activity drive the branching of new vasculature, whereas stalk-cells with high Notch-activity drive the lengthening of the vessels. This mechanism is supported by multiple studies in which inhibition of Notch signaling during vascular development results in a hyper-branching phenotype (38)(39)(40)(41)43). Considering the known involvement on Notch in the process of angiogenesis, we speculated that hypoxic induction of JAG2 and its influence on Notch signaling could represent a novel mechanism for tumor-induced vasculogenesis.…”

Dll4-Notch signaling as a therapeutic target in tumor angiogenesis

“…Pharmacological targeting of Dll4-Notch signaling in preclinical tumor models has been achieved by several different mechanisms including anti-Dll4 antibodies, DNA vaccination, soluble Dll4-Fc and Notch-Fc decoys, Notch antibodies, and γ-secretase inhibitors [24,28,30,31,37,41,67,68]. Unlike γ-secretase inhibitors that broadly block all Notch signaling, specific targeting of Dll4 with anti-Dll4 antibodies did not induce overt gastrointestinal toxicity and has thus emerged as an attractive target for anti-angiogenic cancer therapy [30,69].…”

Vaccination approach to anti-angiogenic treatment of cancer

“…Haller et al [42] reported on a xenogeneic cDNA vaccine encoding human DLL4, an essential component of tip cell integrity. Mice received 3 intradermal injections followed by in vivo electroporation.…”