Properdistatin inhibits angiogenesis and improves vascular function in human melanoma xenografts with low thrombospondin-1 expression

The thrombospondin module 1 domain of the matricellular protein CCN3 shows an atypical disulfide pattern and incomplete CWR layers

The members of the CCN (Cyr61/CTGF/Nov) family are a group of matricellular regulatory proteins that are essential to a wide range of functional pathways in cell signalling. Through interacting with extracellular matrix components and growth factors via one of their four domains, the CCN proteins are involved in critical biological processes such as angiogenesis, cell proliferation, bone development, fibrogenesis and tumorigenesis. Here, the crystal structure of the thrombospondin module 1 (TSP1) domain of CCN3 (previously known as Nov) is presented, which shares a similar three-stranded fold with the thrombospondin type 1 repeats of thrombospondin-1 and spondin-1, but with variations in the disulfide connectivity. Moreover, the CCN3 TSP1 domain lacks the typical π-stacked ladder of charged and aromatic residues on one side of the domain that is seen in other TSP1 domains. Using conservation analysis among orthologous domains, it is shown that a charged cluster in the centre of the domain is the most conserved site and this cluster is predicted to be a potential functional epitope for heparan sulfate binding. This variant TSP1 domain has also been used to revise the sequence determinants of TSP1 domains and to derive improved Pfam sequence profiles for the identification of novel TSP1 domains in more than 10 000 proteins across diverse phyla.

Integration of pro- and anti-angiogenic signals by endothelial cells

Angiogenesis or neovascularization is a complex multi-step physiological process that occurs throughout life both in normal tissues and in disease. It is tightly regulated by the balance between pro-angiogenic and anti-angiogenic factors. The angiogenic switch has been identified as the key step during tumor progression in which the balance between pro-angiogenic and anti-angiogenic factors leans toward pro-angiogenic stimuli promoting the progression of tumors from dormancy to dysplasia and ultimately malignancy. This event can be described as either the outcome of a genetic event occurring in cancer cells themselves, or the positive and negative cross-talk between tumor-associated endothelial cells and other cellular components of the tumor microenvironment. In recent years, the mechanisms underlying the angiogenic switch have been extensively investigated in particular to identify therapeutic targets that can lead to development of effective therapies. In this review, we will discuss the current findings on the regulatory pathways in endothelial cells that are involved in the angiogenic switch with an emphasis on the role of anti-angiogenic protein, thrombospondin-1 (TSP-1) and pro-angiogenic factor, vascular endothelial growth factor (VEGF).

Potential role of sirtuin 1 in Müller glial cells in mice choroidal neovascularization

This study investigated the potential role of sirtuin 1 in Müller glial cells in choroidal neovascularization. In the in vitro study, primary Müller glial cells were cultured and treated with resveratrol, a sirtuin 1 activator. Glial fibrillary acidic protein expression and angiogenesis-related gene expression were examined using quantitative polymerase chain reaction and phagocytosis, as a marker of Müller glial cell function; in addition, a latex bead assay was used to analyze cell function. For the in vivo study, choroidal neovascularization was induced in C57BL/6 mice via laser photocoagulation, and resveratrol was administered intravitreally. Eyecup whole mounts were created to measure choroidal neovascularization volumes on day 7. Immunohistochemical analysis with anti-glial fibrillary acidic protein antibody was used to detect Müller glial cell activation in eyes with choroidal neovascularization on day 1, 3, 5, and 7 after laser surgery. Resveratrol significantly promoted glial fibrillary acidic protein, anti-angiogenic factor, pigment epithelium-derived factor, and thrombospondin-1 expression in the cells as well as the phagocytic activities. Treatment of the choroidal neovascularization model with resveratrol resulted in early activation of Müller glial cells near choroidal neovascularization sites. Resveratrol-activated cells but not the controls migrated to the top of choroidal neovascularization sites and into the lesions from day 3. Resveratrol reduced the choroidal neovascularization size relative to controls. In conclusion, sirtuin 1 activation in Müller glial cells suppressed the development of choroidal neovascularization, and therefore, might be a therapeutic option.

Antiangiogenic agents targeting different angiogenic pathways have opposite effects on tumor hypoxia in R-18 human melanoma xenografts

Background

Studies comparing the effect of antiangiogenic agents targeting different angiogenic pathways are sparse. The purpose of this study was to compare the effect of properdistatin and sunitinib treatment in a preclinical model of malignant melanoma. Properdistatin is a small peptide derived from the thrombospondin-1 domain of the plasma protein properdin, and sunitinib is a tyrosine kinase inhibitor targeting several receptors including the vascular endothelial growth factor receptors.

Methods

R-18 human melanoma xenografts growing in dorsal window chambers were treated with properdistatin, sunitinib, or vehicle. Parameters describing the morphology of tumor vasculature were assessed from high-resolution transillumination images, and BST (blood supply time; the time needed for arterial blood to flow from the main supplying artery to downstream microvessels) was assessed from first-pass imaging movies recorded after a bolus of fluorescence-labeled dextran had been administered intravenously. Tumor hypoxia was assessed from immunohistochemical preparations of the imaged tissue by using pimonidazole as a hypoxia marker.

Results

Properdistatin treatment selectively removed small-diameter vessels and reduced BST, whereas sunitinib treatment reduced the density of small- and large-diameter vessel similarly and did not change BST. These observations imply that properdistatin treatment reduced geometric resistance to blood flow and improved vascular function, whereas sunitinib treatment did not affect vascular function. Accordingly, sunitinib-treated tumors showed higher hypoxic fractions than properdistatin-treated tumors.

Conclusions

Properdistatin and sunitinib both inhibited angiogenesis, but had distinctly different effects on vascular morphology, vascular function, and extent of hypoxia in R-18 human melanoma xenografts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3404-4) contains supplementary material, which is available to authorized users.

The Different Effects of VEGFA121 and VEGFA165 on Regulating Angiogenesis Depend on Phosphorylation Sites of VEGFR2

The effects of VEGFA isoforms on the vascular permeability and structure are still unclear. In this study, we found that VEGFA121 and VEGFA165, 2 isoforms of VEGFA, exerted the opposing effects of antiangiogenesis and proangiogenesis on regulating vascular endothelia cells proliferation and tube formation. The 2 isoforms affected the protein expression of Ras-related protein 1-GTPase-activating protein 1 (Rap1GAP) and thrombospondin 1, 2 important signal molecules of Rap1GAP/thrombospondin 1 signal pathway in primary human umbilical vein endothelial cells by regulating 2 different phosphorylating sites of VEGFR2, Tyr(1175) and Tyr(1214). We also found that VEGFA121 and VEGFA165 regulating angiogenesis was related to their regulating VEGFR2 and Rap1GAP/thrombospondin 1 signal pathway with the technology of RNA intervening the gene expression of VEGFR2 and Rap1GAP. Meanwhile, 2 inhibitors of VEGFR2, cabozantinib malate and ZM 323881 HCl (ZM), were used to investigate the relationship among VEGFA(121 and 165), VEGFR2, and angiogenesis. It was demonstrated that cabozantinib malate blocked VEGFA121 and VEGFA165 binding to VEGFR2 and inhibited angiogenesis by specifically binding to VEGFR2 rather than changing VEGFR2 phosphorylation or regulating the expression of VEGFR2. However, ZM antagonized the effect of VEGFA on angiogenesis by specifically reversing the phosphorylation induced by VEGFA121 and VEGFA165. The experiments in vivo also demonstrated that obvious abnormality of VEGFA121 and VEGFA165 presented in the serum of ulcerative colitis (UC) rats compared with that of the normal rats. ZM could promote the repairation of the injuries of the vessels and tissues of colonic mucosa of UC rats and caused mild inflammation in colonic mucosa of normal rats. On the contrary, cabozantinib malate caused injury of vessels and inflammation in the colonic mucosa of normal rats and aggravated the injuries of the vessels and inflammation in the colonic mucosa of UC rats. Hence, our data indicated that the activation of different phosphorylation sites of VEGFR2 leaded to VEGFA121 and VEGFA165 exerting opposing effects on angiogenesis, and it might be an underlying pathogenesis of UC and a potential target for UC treatment.

Expression of Vascular Endothelial Growth Factor in Odontogenic Cysts: Is There Any Impression on Clinical Outcome?

Background:

The recent scientific reports have shown that angiogenesis can affect biological behavior of pathologic lesions.

Objective:

Regarding unique clinical outcome of Odontogenic keratocyst (OKC), the present study was aimed to compare angiogenesis in Odontogenic keratocyst and Dentigerous cyst (DC).

Method:

In this experimental study, tissue sections of 46 samples of OKC and DC were stained through immunohistochemical method using Vascular Endothelial Growth Factor (VEGF) antibody. VEGF expression was evaluated in epithelial cells, fibroblasts and endothelial cells. The average percentage of stained cells in any samples was categorized to 3 groups as follows: SCORE 0: 10% of cells or less are positive. SCORE 1: 10 to 50% of cells are positive. SCORE 2: more than 50% of cells are positive. Mann-U-Whitney, T-test and chi-square was used for statistical analysis.

Result:

The average of VEGF expression in 24 samples of DC was 20.2% and in 22 samples of OKC was 52.6%, respectively. The average of VEGF expression in these two cysts had statistical significant differences. (PV= 0.045). There was significant statistical differences between two cysts in the terms of VEGF SCORE (PV= 0.000). OKC samples had significantly higher SCORE for the purpose of VEGF incidence than DC. Also, there were no differences between VEGF expression in epithelial cells of two cysts (PV= 0.268) there were significant statistical differences between two cysts in terms of endothelial cell staining. The endothelial cell staining was significantly higher in OKC than DC (PV= 0.037%).

Conclusion:

Regarding higher expression of Vascular Endothelial Growth factor in OKC than DC, it seems that angiogenesis may have great impression on clinical outcome of OKC.