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Soluble receptor-mediated selective inhibition of VEGFR and PDGFRbeta signaling during physiologic and tumor angiogenesis.

ABSTRACT: The simultaneous targeting of both endothelial cells and pericytes via inhibition of VEGF receptor (VEGFR) and PDGFbeta receptor (PDGFRbeta) signaling, respectively, has been proposed to enhance the efficacy of antiangiogenic tumor therapy. Clinical and preclinical modeling of combined VEGFR and PDGFRbeta signaling inhibition, however, has used small molecule kinase inhibitors with inherently broad substrate specificities, precluding detailed examination of this hypothesis. Here, adenoviral expression of a soluble VEGFR2/Flk1 ectodomain (Ad Flk1-Fc) in combination with a soluble ectodomain of PDGFRbeta (Ad sPDGFRbeta) allowed highly selective inhibition of these pathways. The activity of Ad sPDGFRbeta was validated in vitro against PDGF-BB and in vivo with near-complete blockade of pericyte recruitment in the angiogenic corpus luteum, resulting in prominent hemorrhage, thus demonstrating an essential function for PDGF signaling during ovarian angiogenesis. Combination therapy with Ad PDGFRbeta and submaximal doses of Ad Flk1-Fc produced modest additive antitumor effects; however, no additivity was observed with maximal VEGF inhibition in numerous s.c. models. Notably, VEGF inhibition via Ad Flk1-Fc was sufficient to strongly suppress tumor endothelial and pericyte content as well as intratumoral PDGF-B mRNA, obscuring additive Ad sPDGFRbeta effects on pericytes or tumor volume. These studies using highly specific soluble receptors suggest that additivity between VEGFR and PDGFRbeta inhibition depends on the strength of VEGF blockade and appears minimal under conditions of maximal VEGF antagonism.

SUBMITTER: Kuhnert F

PROVIDER: S-EPMC2474564 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundTumor necrosis factor (TNF) is pathologically elevated in human abdominal aortic aneurysms (AAA). Non-selective TNF inhibition-based therapeutics are approved for human use but have been linked to several side effects. Compounds that target the proinflammatory soluble form of TNF (solTNF) but preserve the immunomodulatory capabilities of the transmembrane form of TNF (tmTNF) may prevent these side effects. We hypothesize that inhibition of solTNF signaling prevents AAA expansion.MethodsThe effect of the selective solTNF inhibitor, XPro1595, and the non-selective TNF inhibitor, Etanercept (ETN) was examined in porcine pancreatic elastase (PPE) induced AAA mice, and findings with XPro1595 was confirmed in angiotensin II (ANGII) induced AAA in hyperlipidemic apolipoprotein E (Apoe) -/- mice.ResultsXPro1595 treatment significantly reduced AAA expansion in both models, and a similar trend (p = 0.06) was observed in PPE-induced AAA in ETN-treated mice. In the PPE aneurysm wall, XPro1595 improved elastin integrity scores. In aneurysms, mean TNFR1 levels reduced non-significantly (p = 0.07) by 50% after TNF inhibition, but the histological location in murine AAAs was unaffected and similar to that in human AAAs. Semi-quantification of infiltrating leucocytes, macrophages, T-cells, and neutrophils in the aneurysm wall were unaffected by TNF inhibition. XPro1595 increased systemic TNF levels, while ETN increased systemic IL-10 levels. In ANGII-induced AAA mice, XPro1595 increased systemic TNF and IL-5 levels. In early AAA development, proteomic analyses revealed that XPro1595 significantly upregulated ontology terms including "platelet aggregation" and "coagulation" related to the fibrinogen complex, from which several proteins were among the top regulated proteins. Downregulated ontology terms were associated with metabolic processes.ConclusionIn conclusion, selective inhibition of solTNF signaling reduced aneurysm expansion in mice, supporting its potential as an attractive treatment option for AAA patients.

Project description:Tumor necrosis factor (TNF) is elevated in human abdominal aortic aneurysms (AAA). Non-selective TNF inhibition has been linked to several severe side effects. Compounds that target the proinflammatory soluble TNF (solTNF) while preserving the immunomodulatory capabilities of transmembrane TNF (tmTNF) may prevent such side effects. We hypothesize that inhibition of solTNF signaling by XPro1595 is just as effective as non-selective TNF inhibition by etanercept (ETN) in preventing AAA expansion. The effect of XPro1595 and ETN was examined in porcine pancreatic elastase (PPE) induced AAA mice and findings of XPro1595 was confirmed in Angiotensin II (AngII) induced AAA in hyperlipidemic apolipoprotein E (Apoe) -/- mice. XPro1595 treatment significantly reduced AAA expansion in both models, while a similar trend (p=0.06) was observed in ETN-treated mice using the PPE model. In the PPE aneurysm wall, elastin integrity scores were significantly improved in the XPro1595 group. In the aneurysms, mean TNFR1wasreduced no-significantly (p=0.07) by 50% non-significant after TNF inhibition, but the cellular location in murine AAAs were unaffected and like the localization in human AAAs. Systemic TNF levels were elevated in XPro1595-treated mice, while systemic IL-10 levels were significantly increased after ETN-treatment, while in AngII induced AAA mice systemic TNF and IL5 levels were elevated after XPro1595 treatment. In early AAA development, proteomic analyses revealed that components of the fibrinogen complex were elevated while prostaglandin E2 synthase was down regulated by Xpro1595 (unadjusted p-values). David’s ontology analyses revealed that several pathways including cell matrix adhesion, extracellular space, fibrinogen complex, blood microparticles and glycoproteins were elevated by XPro1595 treatment. In conclusion, selective inhibition of solTNF reduces aneurysm expansion. This supports targeting solTNF as an attractive treatment option for AAA patients.

Project description:The fusion protein VEGF(121)/rGel composed of the growth factor VEGF(121) and the plant toxin gelonin targets the tumor neovasculature and exerts impressive anti-vascular effects. We have previously shown that VEGF(121)/rGel is cytotoxic to endothelial cells overexpressing VEGFR-2 but not to endothelial cells overexpressing VEGFR-1. In this study, we examined the basis for the specific toxicity of this construct and assessed its intracellular effects in vitro and in vivo.We investigated the binding, cytotoxicity and internalization profile of VEGF(121)/rGel on endothelial cells expressing VEGFR-1 or VEGFR-2, identified its effects on angiogenesis models in vitro and ex vivo, and explored its intracellular effects on a number of molecular pathways using microarray analysis.Incubation of PAE/VEGFR-2 and PAE/VEGFR-1 cells with (125)I-VEGF(121)/rGel demonstrated binding specificity that was competed with unlabeled VEGF(121)/rGel but not with unlabeled gelonin. Assessment of the effect of VEGF(121)/rGel on blocking tube formation in vitro revealed a 100-fold difference in IC(50) levels between PAE/VEGFR-2 (1 nM) and PAE/VEGFR-1 (100 nM) cells. VEGF(121)/rGel entered PAE/VEGFR-2 cells within one hour of treatment but was not detected in PAE/VEGFR-1 cells up to 24 hours after treatment. In vascularization studies using chicken chorioallantoic membranes, 1 nM VEGF(121)/rGel completely inhibited bFGF-stimulated neovascular growth. The cytotoxic effects of VEGF(121)/rGel were not apoptotic since treated cells were TUNEL-negative with no evidence of PARP cleavage or alteration in the protein levels of select apoptotic markers. Microarray analysis of VEGF(121)/rGel-treated HUVECs revealed the upregulation of a unique "fingerprint" profile of 22 genes that control cell adhesion, apoptosis, transcription regulation, chemotaxis, and inflammatory response.Taken together, these data confirm the selectivity of VEGF(121)/rGel for VEGFR-2-overexpressing endothelial cells and represent the first analysis of genes governing intoxication of mammalian endothelial cells by a gelonin-based targeted therapeutic agent.

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Soluble receptor-mediated selective inhibition of VEGFR and PDGFRbeta signaling during physiologic and tumor angiogenesis.

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