In vivo inhibition of tumor angiogenesis by a soluble VEGFR-2 fragment

Antiangiogenic AAV2 gene therapy with a truncated form of soluble VEGFR-2 reduces the growth of choroidal neovascularization in mice after intravitreal injection

Pathological angiogenesis related to neovascularization in the eye is mediated through vascular endothelial growth factors (VEGFs) and their receptors. Ocular neovascular-related diseases are mainly treated with anti-VEGF agents. In this study we evaluated the efficacy and safety of novel gene therapy using adeno associated virus 2 vector expressing a truncated form of soluble VEGF receptor-2 fused to the Fc-part of human IgG1 (AAV2-sVEGFR-2-Fc) to inhibit ocular neovascularization in laser induced choroidal neovascularization (CNV) in mice. The biological activity of sVEGFR-2-Fc was determined in vitro. It was shown that sVEGFR-2-Fc secreted from ARPE-19 cells was able to bind to VEGF-A₁₆₅ and reduce VEGF-A₁₆₅ induced cell growth and survival. A single intravitreal injection (IVT) of AAV2-sVEGFR-2-Fc (1 μl, 4.7 × 10¹² vg/ml) one-month prior laser photocoagulation did not cause any changes in the retinal morphology and significantly suppressed fluorescein leakage at 7, 14, 21 and 28 days post-lasering compared to controls. Macrophage infiltration was observed after the injection of both AAV2-sVEGFR-2-Fc and PBS. Our findings indicate that AAV2 mediated gene delivery of the sVEGFR-2-Fc efficiently reduces formation of CNV and could be developed to a therapeutic tool for the treatment of retinal diseases associated with neovascularization.

Biomembrane-based nanostructures for cancer targeting and therapy: From synthetic liposomes to natural biomembranes and membrane-vesicles

The translational success of liposomes in chemotherapeutics has already demonstrated the great potential of biomembrane-based nanostructure in effective drug delivery. Meanwhile, increasing efforts are being dedicated to the application of naturally derived lipid membranes, including cellular membranes and extracellular vesicles in anti-cancer therapies. While synthetic liposomes support superior multifunctional flexibility, natural biomembrane materials possess interesting biomimetic properties and can also be further engineered for intelligent design. Despite being remarkably different from each other in production and composition, the phospholipid bilayer structure in common allows liposomes, cell membrane-derived nanomaterials, and extracellular vesicles to be modified, functionalized, and exploited in many similar manners against challenges posed by tumor-targeted drug delivery. This review will summarize the recent advancements in engineering the membrane-derived nanostructures with "intelligent" modules to respond, regulate, and target tumor cells and the microenvironment to fight against malignancy. We will also discuss perspectives of combining engineered functionalities with naturally occurring activity for enhanced cancer therapy.

The Role of VEGF Receptors as Molecular Target in Nuclear Medicine for Cancer Diagnosis and Combination Therapy

Simple Summary

The rapid development of diagnostic and therapeutic methods of the cancer treatment causes that these diseases are becoming better known and the fight against them is more and more effective. Substantial contribution in this development has nuclear medicine that enables very early cancer diagnosis and early start of the so-called targeted therapy. This therapeutic concept compared to the currently used chemotherapy, causes much fewer undesirable side effects, due to targeting a specific lesion in the body. This review article discusses the possible applications of radionuclide-labelled tracers (peptides, antibodies or synthetic organic molecules) that can visualise cancer cells through pathological blood vessel system in close tumour microenvironment. Hence, at a very early step of oncological disease, targeted therapy can involve in tumour formation and growth.

Abstract

One approach to anticancer treatment is targeted anti-angiogenic therapy (AAT) based on prevention of blood vessel formation around the developing cancer cells. It is known that vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptors (VEGFRs) play a pivotal role in angiogenesis process; hence, application of angiogenesis inhibitors can be an effective approach in anticancer combination therapeutic strategies. Currently, several types of molecules have been utilised in targeted VEGF/VEGFR anticancer therapy, including human VEGF ligands themselves and their derivatives, anti-VEGF or anti-VEGFR monoclonal antibodies, VEGF binding peptides and small molecular inhibitors of VEGFR tyrosine kinases. These molecules labelled with diagnostic or therapeutic radionuclides can become, respectively, diagnostic or therapeutic receptor radiopharmaceuticals. In targeted anti-angiogenic therapy, diagnostic radioagents play a unique role, allowing the determination of the emerging tumour, to monitor the course of treatment, to predict the treatment outcomes and, first of all, to refer patients for AAT. This review provides an overview of design, synthesis and study of radiolabelled VEGF/VEGFR targeting and imaging agents to date. Additionally, we will briefly discuss their physicochemical properties and possible application in combination targeted radionuclide tumour therapy.

Gene polymorphisms of VEGF and VEGFR2 are associated with the severity of Hashimoto's disease and the intractability of Graves' disease, respectively

Vascular endothelial growth factor (VEGF) is one of main regulators of angiogenesis that functions by binding to its receptors, including VEGF receptor (VEGFR) 2. There are few data available regarding the association between VEGF and VEGFR polymorphisms and the susceptibility to and prognosis of autoimmune thyroid diseases (AITDs). To elucidate this association, we genotyped four functional VEGF and two VEGFR2 polymorphisms and measured serum VEGF levels. In the four functional VEGF polymorphisms, the frequencies of the I carrier and I allele of VEGF -2549 I/D, which has lower activity, were higher in patients with severe HD than in those with mild HD. In the two functional VEGFR2 polymorphisms, the frequency of the rs2071559 CC genotype, which has higher activity, was higher in patients with intractable GD than in controls, and the proportion of GD patients with larger goiters was higher in those with the CC genotype. Moreover, the frequency of the rs1870377 TT genotype with higher activity was higher in patients with intractable GD than in those with GD in remission. Combinations of VEGF and VEGFR2 polymorphisms with stronger interactions were associated with the intractability of GD. Serum VEGF levels were higher in HD and AITD patients than those in controls. In conclusion, VEGF polymorphisms with lower activity were associated with the severity of HD, while VEGFR2 polymorphisms and the combinations of VEGF and VEGFR2 polymorphisms, which have stronger interactions, were associated with the intractability of GD. VEGF and VEGFR2 polymorphisms were associated with HD severity and GD intractability, respectively.

Carvacrol alters soluble factors in HCT-116 and HT-29 cell lines

Background/aim

Natural products are popular insights for researchers to investigate promising anti-cancer agents since some of these substances have lesser adverse effects restricting the treatment than traditional chemotherapeutic agents. A well-known monoterpene Carvacrol, widely consumed in Mediterranean cuisine and lower risks of cancer, has efficient anticancer effects. However, the mechanism of action is yet to be discovered.

Materials and methods

The investigation aims to illuminate a new perceptive in the role of this substance on colorectal cancer treatment, by the means of differences in a well-defined range of soluble factors. Carvacrol effect on both HT-29 and HCT-116 cell lines was evaluated on proliferation and the IC50 values were calculated by the RTCA xCELLigence device. Then MAGPIX assay was performed to obtain the changes in soluble factors of the cell lines.

Results

The Multiplexing assay suggests some of these factors were altered in favor of surviving and proliferation in aggressive cell line HCT-116 whereas they were altered against these characters in HT-29, were correlated with the increased IC50 concentration of HCT- 116 in carvacrol treatment.

Conclusion

The current study indicates that differences in the levels of these soluble factors could modulate the anticancer effect related to carvacrol.

Modulation of Receptor Tyrosine Kinase Activity through Alternative Splicing of Ligands and Receptors in the VEGF-A/VEGFR Axis

Vascular endothelial growth factor A (VEGF-A) signaling is essential for physiological and pathological angiogenesis. Alternative splicing of the VEGF-A pre-mRNA gives rise to a pro-angiogenic family of isoforms with a differing number of amino acids (VEGF-A_xxxa), as well as a family of isoforms with anti-angiogenic properties (VEGF-A_xxxb). The biological functions of VEGF-A proteins are mediated by a family of cognate protein tyrosine kinase receptors, known as the VEGF receptors (VEGFRs). VEGF-A binds to both VEGFR-1, largely suggested to function as a decoy receptor, and VEGFR-2, the predominant signaling receptor. Both VEGFR-1 and VEGFR-2 can also be alternatively spliced to generate soluble isoforms (sVEGFR-1/sVEGFR-2). The disruption of the splicing of just one of these genes can result in changes to the entire VEGF-A/VEGFR signaling axis, such as the increase in VEGF-A₁₆₅a relative to VEGF-A₁₆₅b resulting in increased VEGFR-2 signaling and aberrant angiogenesis in cancer. Research into this signaling axis has recently focused on manipulating the splicing of these genes as a potential therapeutic avenue in disease. Therefore, further research into understanding the mechanisms by which the splicing of VEGF-A/VEGFR-1/VEGFR-2 is regulated will help in the development of drugs aimed at manipulating splicing or inhibiting specific splice isoforms in a therapeutic manner.

Overweight and obesity versus concentrations of VEGF-A, sVEGFR-1, and sVEGFR-2 in plasma of patients with lower limb chronic ischemia

OBJECTIVE

Being overweight or obese comprises a significant risk factor for atherosclerosis. Fat tissue also generates factors stimulating angiogenesis, the process by which new blood vessels form. The purpose of this paper is to assess concentrations of the vascular endothelial growth factor A (VEGF-A) and its soluble type-1 and type-2 receptors (sVEGFR-1 and sVEGFR-2) in plasma of patients with peripheral arterial disease (PAD) depending on the level of nutrition according to body mass index (BMI).

METHODS

The study group included patients suffering from symptomatic PAD (n=46) in Fontaine classes IIa-IV without any history of neoplastic disease and who have a normal BMI (n=15), are overweight (n=21) or are obese (n=10). The control group (n=30) consisted of healthy non-smoking volunteers who were neither overweight nor obese. Venous blood plasma samples were collected from both groups at rest in the morning to determine plasma concentrations of VEGF-A, sVEGFR-1, and sVEGFR-2 using the enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

The group of patients with PAD co-existent with being overweight or obese tended to have higher mean concentration levels of VEGF-A and sVEGFR-2 when compared with patients suffering from PAD with normal BMI. A statistically significant positive correlation was obtained between BMI and average plasma concentrations of sVEGFR-2 (R=0.37, P=0.0103). However, no significant correlation was noticed between BMI and VEGF-A or sVEGFR-1 concentrations.

CONCLUSIONS

A positive correlation determined between the level of antiangiogenic factor and BMI value may be indicative of the linearly growing prevalence of some antiangiogenic factors in patients with metabolic disorders, which may be one of numerous factors contributing to incomplete efficiency of collateral circulation development in patients with PAD.

Reduction in the mRNA expression of sVEGFR1 and sVEGFR2 is associated with the selection of dominant follicle in cows

The vascular endothelial growth factor (VEGF) is essential for follicular development by promoting follicular angiogenesis, as well as for the proliferation and survival of granulosa cells. The biological effects of VEGF are regulated by two membrane receptors, VEGFR1 and VEGFR2, and two soluble receptors, sVEGFR1 and sVEGFR2, which play an antagonistic role. Thus, the objective of this study was to identify the mRNA expression pattern of total VEGF, VEGFR1, VEGFR2, sVEGFR1 and sVEGFR2 in bovine preselected follicles (PRF) and post-selected follicles (POF). The mRNA expression of these five genes in both granulosa cells (GC) and theca cells (TC) was compared between follicles classified as PRF and POF based on their diameter and on their ratio of estradiol/progesterone (E2/P4). Results showed a lower expression of mRNA of sVEGFR1 and sVEGFR2 in POF than in PRF (p < .05). Regarding the mRNA expression of total VEGF, VEGFR1 and VEGFR2, there was no difference between POF and PRF follicles (p > .05). Our results showed that the mRNA expression of VEGFR2 and sVEGFR1 was more abundant than the expression of VEGFR1 and sVEGFR2, while GC was the main source of mRNA for total VEGF. On the other hand, TC was the follicular compartment where the receptors were most expressed. Our results suggest that non-dominant follicles maintain a greater concentration of the mRNA expression of both membrane and soluble VEGF receptors. On the other hand, follicular dominance is related to a reduction in the mRNA expression of sVEGFR1 and sVEGFR2, which may favour VEGF binding with VEGFR2 and, hence, improve the follicular health and development.

Association between Regular Aspirin Use and Circulating Markers of Inflammation: A Study within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

BACKGROUND

Regular aspirin use may decrease cancer risk by reducing chronic inflammation. However, associations between aspirin use and circulating markers of inflammation have not been well studied.

METHODS

Serum levels of 78 inflammatory markers were measured in 1,819 55- to 74-year-old men and women in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Data were combined from three completed case-control studies and reweighted to the PLCO screening arm. Self-reported aspirin and ibuprofen use (number of tablets taken per day/week/month) over the previous 12 months was collected at baseline. Associations between (i) nonregular (<4 tablets/month), (ii) low (1-4 tablets/week), (iii) moderate (1 tablet/day), or (iv) high (2+ tablets/day) regular aspirin or ibuprofen use and marker levels were assessed with weighted logistic regression.

RESULTS

Aspirin use was nominally associated with (Ptrend across categories ≤ 0.05) decreased levels of chemokine C-C motif ligand 15 [CCL15; OR, 0.5; 95% confidence intervals (CI), 0.3-0.8; moderate versus nonregular use]; soluble vascular endothelial growth factor receptor 2 (sVEGFR2; OR, 0.7; 95% CI, 0.4-1.0); soluble tumor necrosis factor receptor 1 (sTNFR1; OR, 0.6; 95% CI, 0.4-0.9) and increased levels of CCL13 (OR, 1.3; 95% CI, 0.8-2.1); CCL17 (OR, 1.1; 95% CI, 0.7-1.9) and interleukin 4 (IL4; OR, 1.6; 95% CI, 0.9-2.8). Trends were not statistically significant following correction for multiple comparisons. Likewise, no statistically significant associations were observed between ibuprofen use and marker levels.

CONCLUSIONS

No significant associations were observed between regular aspirin use and the inflammatory markers assessed.

IMPACT

Additional studies are needed to better understand the relationship between aspirin use, chronic inflammation, and cancer risk.

Expression and characterization of a soluble VEGF receptor 2 protein

Objective

To clone and express a truncated, soluble vascular endothelial growth factor receptor 2 (sVEGFR2) possessing the combined-functional domains 1–3 and 5 in eukaryotic cells and to test the inhibitory effects of full length VEGFR2 in vivo.

Results

pCMV6-trunctated-rVegfr2 (6100 bp) was successfully cloned. The transfection experiments showed that either pCMV6-truncated-rat-Vegfr2 (pCMV6-truncated-rVegfr2) or pCMV6-rVegfr2 inhibited the expression of intracellular green fluorescent protein, which is usually used as an exogenous transfected reporter gene to determine the transfected efficiency. An analysis of the transfected cells revealed that the amount of full-length VEGFR2 protein in the pCMV6-truncated-rVegfr2 transfected cells was 20% lower than that in the negative control (non-transfected HEK 293 cells). The differences in test results between the transfected and negative control groups were greatest from 24–30 h after transfection; this period was therefore chosen as optimal for collecting culture supernatants. This analysis was highly sensitive for detecting the amount of sVEGFR2 protein expressed and secreted by the cells, and the sVEGFR2 protein content was found to increase by approximately 26% in the transfected cells compared to that in the negative control cells (68.2% ± 1.7% vs. 41.9% ± 2.9%, P = 0.000) and by 18% compared to the negative control cells (68.2% ± 1.7% vs. 50.0% ± 0.5%, P = 0.003). Propidium iodide and Hoechst staining indicated no significant change in the number of HEK293 cells undergoing apoptosis 6 days after pCMV6-trucated-Vegfr2 transfection, compared to the negative control. Soluble VEGFR2 produced by pCMV6-truncated-rVegfr2 inhibited full-length VEGFR2 protein expression in the cell membrane.

Conclusions

This study employed a eukaryotic system to express sVEGFR2. The use of transient transfection technology greatly improved transfect efficiency. Recombinant sVEGFR2 inhibited the effect of endogenous full-length VEGFR2 but was not cytotoxic.

The soluble VEGF receptor 1 and 2 expression in cerebral spinal fluid as an indicator for leukemia central nervous system metastasis

Over-expression of vascular endothelial growth factor A (VEGF-A) is correlated with leukemia metastasis. VEGF-A acts by binding to its membrane receptors R1 and R2 present in soluble forms (sVEGFR1, sVEGFR2) with different functions. sVEGFR could inhibit VEGF-A bioactivities, associated with favorable prognosis in solid tumors. However, its role is obscure in central nervous system leukemia (CNSL). The aim of this study was to investigate sVEGFR1, R2 as biomarkers in CNSL. Paired cerebrospinal fluid (CSF) and serum samples were collected from 35 leukemia cases with or without CNS metastasis. Levels of sVEGFR1 and sVEGFR2 in both CSF (sVEGFR1CSF, sVEGFR2CSF) and serum (sVEGFR1Serum, sVEGFR2Serum) were detected by ELISA. Other risk factors related to CNSL prognosis were also analyzed. sVEGFRSerum levels were 2.54-fold (sVEGFR1) and 25.6-fold (sVEGFR2) higher than sVEGFRCSF in both leukemic groups. sVEGFR1CSF in CNSL were 33 % higher than in the non-CNSL, and the levels of sVEGFR2CSF and sVEGFR2Serum had the same trend. Elevated sVEGFR1CSF and sVEGFR2CSF is closely correlated with blood-brain barrier (BBB) values and WBCCSF that is an indicator of CNSL disease burden. Cox regression analysis showed that the sVEGFR2CSF had a positive effect on event-free survival. Our data suggest that sVEGFR2CSF may be more potent than sVEGFR1CSF in predicting the outcome of leukemia patients, the balance between sVEGFR2CSF and VEGF-ACSF levels might be crucial for the progression of CNSL.

Disruption of components of vascular endothelial growth factor angiogenic signalling system in metabolic syndrome. Findings from a study conducted in rural Bangladeshi women

Metabolic syndrome (MetS) is associated with impaired angiogenesis, a process that is chiefly regulated by vascular endothelial growth factor (VEGF) upon binding to its specific receptors, VEGF-R1 and VEGF-R2. The purpose of the present study was to assess trends or patterns in plasma levels of VEGF and its soluble receptors in subjects with (MetS) or without (non-MetS) MetS; and further examine their association with clinical or metabolic parameters using a subpopulation of South Asian country. A total of 1,802 rural Bangladeshi women aged ≥15 years were studied using a population-based cross-sectional survey. Plasma levels of VEGF were found to be significantly increased (MetS vs. non-MetS: 483.9 vs. 386.9, p<0.001), whereas, the soluble forms of VEGF receptors, sVEGF-R1 and sVEGF-R2, were significantly decreased in subjects with Mets (sVEGF-R1, MetS vs. non-MetS: 512.5 vs. 631.3, p<0.001; sVEGF-R2, MetS vs. non-MetS: 9,302.8 vs. 9,787.4, p=0.004). After adjustment for age and all potential variables, multiple regression analysis revealed that plasma levels of VEGF had significant positive association with blood glucose (p = 0.019) and body mass index (p = 0.007). We also found that mean plasma levels of VEGF increased in direct proportion to levels of MetS components. The present study is the first ever to demonstrate a positive association between trends in levels of plasma VEGF and MetS using a large sample size from South Asia. The association between plasma VEGF and MetS needs further investigations in order to clearly decipher the clinical predictive value and accuracy of plasma VEGF in MetS.

Applications of functionalized fullerenes in tumor theranostics

Functionalized fullerenes with specific physicochemical properties have been developed for cancer diagnosis and therapy. Notably, metallofullerene is a new class of magnetic resonance imaging (MRI) contrast-enhancing agent, and may have promising applications for clinical diagnosis. Polyhydroxylated and carboxyl fullerenes have been applied to photoacoustic imaging. Moreover, in recent years, functionalized fullerenes have shown potential in tumor therapies, such as photodynamic therapy, photothermal treatment, radiotherapy and chemotherapeutics. Their antitumor effects may be associated with the modulation of oxidative stress, anti-angiogenesis, and immunostimulatory activity. While various types of novel nanoparticle agents have been exploited in tumor theranostics, their distribution, metabolism and toxicity in organisms have also been a source of concern among researchers. The present review summarizes the potential of fullerenes as tumor theranostics agents and their possible underlying mechanisms are discussed.

Generation and characterization of a functional Nanobody against the vascular endothelial growth factor receptor-2; angiogenesis cell receptor

Vascular endothelial growth factor receptor-2 (VEGFR2) is an important tumor-associated receptor and blockade of the VEGF receptor signaling can lead to the inhibition of neovascularization and tumor metastasis. Nanobodies are the smallest intact antigen binding fragments derived from heavy chain-only antibodies occurring in camelids. Here, we describe the identification of a VEGFR2-specific Nanobody, named 3VGR19, from dromedaries immunized with a cell line expressing high levels of VEGFR2. We demonstrate by FACS, that 3VGR19 Nanobody specifically binds VEGFR2 on the surface of 293KDR and HUVECs cells. Furthermore, the 3VGR19 Nanobody potently inhibits formation of capillary-like structures. These data show the potential of Nanobodies for the blockade of VEGFR2 signaling and provide a basis for the development of novel cancer therapeutics.

Enhanced antitumor efficacy by blocking activation of the phosphatidylinositol 3-kinase/Akt pathway during anti-angiogenesis therapy

Anti-angiogenesis has been a promising strategy for cancer therapy. However, many signal pathways are activated during anti-angiogenic treatment to counteract the therapeutic efficacy. Among these pathways, evidence has directly pointed to the phosphatidylinositol 3-kinase/Akt (PI3K/Akt) pathway, whose activation resulted in tolerance to the absence of nutrients and oxygen when tumor angiogenesis has been inhibited. In the present study, we investigated the effects of blocking activation of the PI3K/Akt pathway on cell survival in vitro and tumor growth in vivo during anti-angiogenesis therapy. In modeled microenvironments in vitro, we observed that the phosphorylation of Akt in tumor cells was increased gradually in the absence of serum and oxygen in a time-dependent manner. The specific inhibitors of PI3K inhibited the proliferation of tumor cells in a dose-dependent manner in vitro. Moreover, inhibition was enhanced gradually with increased serum deprivation and/or hypoxia. In a mouse tumor model, we found the phosphorylation of Akt obviously increased following anti-angiogenic therapy using plasmids encoding soluble vascular endothelial growth factor receptor-2, but significantly reduced after treatment with LY294002. Consequently, the combinational treatment exhibited better antitumor effects compared with single treatments, presenting larger necrosis-like areas, more apoptotic cells, less microvessel density and less phosphorylated Akt in tumors. These results suggest that blocking activation of the PI3K/Akt pathway during anti-angiogenesis therapy could enhance antitumor efficacy. Thus, targeting the PI3K/Akt pathway might be a promising strategy to reverse tumor resistance to anti-angiogenesis therapy.

Karyopherin alpha 2 (KPNA2) is associated with the natural resistance to Schistosoma japanicum infection in Microtus fortis

Microtus fortis is a naturally vertebrate host resistant to Schistosoma japonicum infection. In order to understand the molecular mechanism and identify the molecules related to the natural resistance to S. japanicum infection of M. fortis, we screened a gene pool named gE76 by expression cloning and proved it to have high anti-schistosomula effects in our previous work. In this study we identified a clone named gE76.44. We found that the conditioned medium of pcDNA1.1-gE76.44 caused 14.0% schistosomula death rate in 96 h, which was significantly higher than that of negative control (P<0.05). The gE76.44 was sequenced and the full-length cDNA was 2008 bp with ORF of 1590bp encoding a polypeptide of 529 amino acid residues. Bioinformatics analysis indicated it was the homologue of karyopherin alpha 2 (KPNA2). To further confirm its anti-schistosome activity, we inserted full length of Mf-KPNA2 (KPNA2 of M. fortis) gene into a retroviral expression vector pLXSN and packaged the recombinant virus with PA317 cells. Mice infected with S. japanicum cercariae were administrated by intravenous injection through tail vein and treated with pLXSN-KPNA2. Adult worms and egg reduction were counted after heart perfusion of mice 42 d after infection. We found that compared with the control, mice injected with Mf-KPNA2 had 39.42% worm burden reduction and 76.50% reduction in LEPG (liver eggs per gram) (P<0.01), indicating its anti-schistosome effect of Mf-KPNA2 in vivo. Taken together, the results suggested Mf-KPNA2 as a novel anti-schistosome molecule in vitro and in vivo.

In vitro effect of aspartame in angiogenesis induction

Aspartame (APM) is the most widely used artificial sweetener and is added to a wide variety of foods, beverages, drugs, and hygiene products. In vitro and in vivo tests have reported contradictory data about APM genotoxicity. We evaluated the angiogenic effect of APM in an in vitro model using blood vessel development assay (Angio-Kit), cultured endothelial cells and fibroblasts. The release of IL-6, VEGF-A, and their soluble receptors sIL-R6 and sVEGFR-2 were determined over time in the conditioned medium of the Angio-Kit system, endothelial cells and cell lines with fibroblast properties after APM treatment. Reactive oxygen species (ROS) formation, cell viability, and stimulation of the extracellular signal-regulated kinases (erk1/2) and protein p38 were also evaluated. Exposure to APM induced blood vessel formation. ROS production was observed in endothelial cells after APM treatment, which was associated with a slight cell cytotoxicity. Neither intracellular ROS formation nor cell death was observed in fibroblasts. APM increases the levels of inflammatory mediator IL-6, VEGF and their soluble receptors released from endothelial cells into the medium. APM treatment induces VEGF-pathway activation by erk1/2 and p38 phosphorylation. APM at low doses is an angiogenic agent that induces regenerative cytokine production leading to the activation of MAPKs and resulting in the formation of new blood vessels.

Identification of the resistance of a novel molecule heat shock protein 90alpha (HSP90alpha) in Microtus fortis to Schistosoma japonicum infection

Microtus fortis is a naturally resistant vertebrate host of Schistosoma japonicum by preventing completion of parasite's life cycle. Sera of M. fortis were found to have anti-schistosome effect in vitro and in vivo. In order to identify genes associated with the anti-schistosome effect of M. fortis, we screened a M. fortis marrow cDNA expression library by expression cloning and identified a 331-bp clone gC14.75. It was the homologue of heat shock protein 90alpha (HSP90alpha). Full-length of M. fortis HSP90alpha gene, Mf-HSP90alpha, was amplified according to gC14.75 and Cricetulus griseus HSP90alpha. To test the potential anti-schistosome function of Mf-HSP90alpha, we prepared conditioned medium of Mf-HSP90alpha and added it to schistosomula cultured in vitro. It caused 27.0% schistosomula death rate in 96h, which was considerably higher than that of negative control. We transferred Mf-HSP90alpha by retroviral expression vector pLXSN into mice to investigate its anti-schistosome effect in vivo. Compared with those of DMEM injection control, mice injected with Mf-HSP90alpha recombinant retrovirus had 40.8% worm burden reduction and 57.9% reduction in liver eggs per gram (LEPG) indicating its anti-schistosome effect in vivo. Taken together, our results suggested Mf-HSP90alpha as a novel anti-schistosome molecule in vitro and in vivo.

Soluble forms of VEGF receptor-1 and -2 promote vascular maturation via mural cell recruitment

Two soluble forms of vascular endothelial growth factor (VEGF) receptors, sVEGFR-1 and sVEGFR-2, are physiologically released and overproduced in some pathologies. They are known to act as anti-VEGF agents. Here we report that these soluble receptors contribute to vessel maturation by mediating a dialogue between endothelial cells (ECs) and mural cells that leads to blood vessel stabilization. Through a multidisciplinary approach, we provide evidence that these soluble VEGF receptors promote mural cell migration through a paracrine mechanism involving interplay in ECs between VEGF/VEGFR-2 and sphingosine-1-phosphate type-1 (S1P)/S1P1 pathways that leads to endothelial nitric oxyde synthase (eNOS) activation. This new paradigm is supported by the finding that sVEGFR-1 and -2 perform the following actions: 1) induce an eNOS-dependent outgrowth of a mural cell network in an ex vivo model of angiogenesis, 2) increase the mural cell coverage of neovessels in vitro and in vivo, 3) promote mural cell migration toward ECs, and 4) stimulate endothelial S1P1 overproduction and eNOS activation that promote the migration and the recruitment of neighboring mural cells. These findings provide new insights into mechanisms regulating physiological and pathological angiogenesis and vessel stabilization.

Preparation of extracellular domain 3 of human VEGF receptor-2 and the monitoring of its real-time binding to VEGF by biosensors

Vascular endothelial growth factor receptor-2 (VEGFR-2) plays an important role in stimulating the proliferation of endothelial cells and improving the permeability of blood vessels, which is involved in tumor angiogenesis, a process that is essential for tumor growth and metastasis. In this study, we describe a method for high yield of recombinant extracellular domain 3 (KDR3) of human VEGFR-2 in an Escherichia coli system with further purification by cation exchange chromatography and immobilized metal affinity chromatography (IMAC). The biological activity of recombinant KDR3 was performed by sequestering VEGF in HUVEC proliferation assay. The real-time binding of human VEGF to immobilized KDR3 was monitored by a label-free biosensor, Optical waveguide lightmode spectroscopy (OWLS). Under the given experimental conditions, the association rate constant k(a) was 4.2 x 10(3) M(-1) s(-1) and the dissociation rate k(d) was 5.1 x 10(-3) s(-1). The dissociation constant K(D) was then calculated to be 1.2 x 10(-6) M. The obtained values will serve as baseline parameters for the design of improved versions of recombinant soluble VEGF receptors and the evaluation of developed anti-KDR antibodies. In addition, such a scenario established by the use of OWLS will potentiate the kinetic study of ligand/receptor and antigen/antibody. The receptor discussed here, which block VEGF binding to cell membrane KDR, have potential clinical application in the treatment of cancer and other diseases where pathological angiogenesis is involved.

VEGFR2 expression and relationship between tumor neovascularization and histologic characteristics in oral squamous cell carcinoma

Neovascularization in the stroma of a tumor plays an important role in tumor growth and the establishment of metastases. The present study examined the immunohistochemical expression of vascular endothelial growth factor receptor 2 (VEGFR2) in 34 cases of oral squamous cell carcinoma (OSCC). Moreover, the relationships between parameters of tumor neovascularization (count of VEGFR2-positive [+] cells and total size of vessel lumen [TSVL]) and those of histology (differentiation type and mode of invasion) were analyzed statistically. Immunohistochemical expression of VEGFR2 was localized in stromal cells at the tumor invasive front. The VEGFR2+ cell count around poorly differentiated tumors was significantly higher than that around well differentiated tumors (P = 0.032, one-way ANOVA). The TSVL around the well differentiated type was found to be significantly larger than that around the poorly or moderately differentiated type (P < 0.001, respectively; one-way ANOVA). With regard to the mode of invasion, the TSVL was significantly larger for lower-grade (Grades 1+2) than for higher-grade (Grades 3+4) tumors (P < 0.001, unpaired t-test). On the basis of our results, we suggest that vascular development at the invasive front of OSCC is governed by the following factors: the tumor cells themselves may induce hemangiogenesis in the adjoining stromal tissue; hemangiogenic activity is higher when parenchymal intercellular adhesion is looser and when the parenchymal area exposed to the stroma is greater; and the rate of blood flow is higher when parenchymal intercellular adhesion is tighter and parenchymal nests are larger.

Pigment epithelium-derived factor maintains retinal pigment epithelium function by inhibiting vascular endothelial growth factor-R2 signaling through gamma-secretase

Wet age-related macular degeneration (AMD) attacks the integrity of the retinal pigment epithelium (RPE) barrier system. The pathogenic process was hypothesized to be mediated by vascular endothelial growth factor (VEGF) and antagonized by pigment epithelium-derived factor (PEDF). To dissect these functional interactions, monolayer cultures of RPE cells were established, and changes in transepithelial resistance were evaluated after administration of PEDF, placenta growth factor (VEGF-R1 agonist), and VEGF-E (VEGF-R2 agonist). A recently described mechanism of VEGF inhibition in endothelia required the release of VEGF-R1 intracellular domain by gamma-secretase. To evaluate this pathway in the RPE, cells were pretreated with inhibitors DAPT or LY411575. Processing of VEGF receptors was assessed by Western blot analysis. Administration of VEGF-E rapidly increased RPE permeability, and PEDF inhibited the VEGF-E response dose-dependently. Both gamma-secretase antagonists prevented the inhibitory effects of PEDF. The co-administration of PEDF and VEGF-E depleted the amount of VEGF-R2 in the membrane and increased the amount of VEGF-R2 ectodomain in the media. Therefore, the inhibitory effect of PEDF appears to be mediated via the processing of VEGF-R2 by gamma-secretase. gamma-Secretase generates the amyloid-beta (Abeta) peptide of Alzheimer disease from its precursor (amyloid precursor protein). This peptide is also a component of drusen in dry AMD. The results support the hypothesis that misregulation of gamma-secretase may not only lead to Abeta deposits in dry AMD but can also be damaging to RPE function by blocking the protective effects of PEDF to prevent VEGF from driving the dry to wet AMD transition.

VEGF-A splicing: the key to anti-angiogenic therapeutics?

The physiology of microvessels limits the growth and development of tumours. Tumours gain nutrients and excrete waste through growth-associated microvessels. New anticancer therapies target this microvasculature by inhibiting vascular endothelial growth factor A (VEGF-A) splice isoforms that promote microvessel growth. However, certain VEGF-A splice isoforms in normal tissues inhibit growth of microvessels. Thus, it is the VEGF-A isoform balance, which is controlled by mRNA splicing, that orchestrates angiogenesis. Here, we highlight the functional differences between the pro-angiogenic and the anti-angiogenic VEGF-A isoform families and the potential to harness the synthetic capacity of cancer cells to produce factors that inhibit, rather than aid, cancer growth.

Inhibition of corneal neovascularization by recombinant adenovirus-mediated sFlk-1 expression

The interaction of vascular endothelial growth factor (VEGF) and its receptors (Flt-1, Flk-1/KDR) is correlated with neovascularization in the eyes. Therefore, blocking the binding of VEGF and the corresponding receptor has become critical for inhibiting corneal neovascularization. In this study, we have expressed the cDNA for sFlk-1 under the control of cytomegalovirus immediate-early promoter (CMV) from an E1/partial E3 deleted replication defective recombinant adenovirus, and Ad.sflk-1 expression was determined by Western blotting. We have shown that conditioned media from Ad.sflk-1-infected ARPE-19 cells significantly reduced VEGF-induced human umbilical vein endothelial cells (HUVEC) and murine endothelial cells (SVEC) proliferation in vitro compared with the control vector. In vivo, adenoviral vectors expressing green fluorescent protein alone (Ad.GFP) were utilized to monitor gene transfer to the cornea. Moreover, in the models of corneal neovascularization, the injection of Ad.sflk-1 (10(8)PFU) into the anterior chamber could significantly inhibit angiogenic changes compared with Ad.null-injected and vehicle-injected models. Immunohistochemical analysis showed that corneal endothelial cells and corneal stroma of cauterized rat eyes were efficiently transduced and expressed sFlk-1. These results not only support that adenoviral vectors are capable of high-level transgene expression but also demonstrate that Ad.sflk-1 gene therapy might be a feasible approach for inhibiting the development of corneal neovascularization.

Differential expression of growth-, angiogenesis- and invasion-related factors in the development of placenta accreta

Placenta accreta is the major cause of maternal death complicated by massive peripartum hemorrhage. Its development is traditionally considered to be related to a decidual defect caused by previous cesarean deliveries or uterine curettages. Usually, placental villi firmly adhere to the superficial myometrium and deeply invade, or even penetrate, the uterine wall. Abnormal uteroplacental neovascularization is another characteristic. Therefore, we hypothesized that placenta accreta develops as a result of abnormal expressions of growth-, angiogenesis- and invasion-related factors in trophoblast populations. We have found, in pregnancies complicated by placenta accreta: upregulated epidermal growth factor receptor and downregulated c-erbB-2 oncoprotein in syncytiotrophoblasts; downregulated vasculoendothelial growth factor receptor-2 expression in syncytiotrophoblasts and increased vasculoendothelial growth factor in placental lysates; and downregulated Tie-2 expression in syncytiotrophoblasts and enhanced angiopoietin-2 level in placental lysates. However, matrix metalloproteinase expression was not upregulated, so the association of these invasion-related molecules with placenta accreta is less likely. Taken together, these findings imply that complex factors, either alone or in combination, might be responsible for the development of placenta accreta. Further studies are needed to understand the signaling pathways and possible genetic events.

Anti-angiogenic gene therapy of cancer: current status and future prospects

The discovery of endogenous inhibitors of angiogenesis has made it possible to test the hypothesis that blocking the angiogenic switch may keep tumor growth in check, and has added a new investigational arm to the field of cancer gene therapy. Angiogenesis inhibitors are heterogeneous in origin and potency, and their growing list includes proteolysis products of larger molecules with a different function, such as angiostatin, endostatin and vasostatin, modulators of vascular endothelial growth factor activity, such as sFLT-1, and some cytokines/chemokines with marked anti-endothelial activity, such as IL-12, IFN-alpha, and CXCL10. Pre-clinical studies have clearly indicated that these factors are essentially cytostatic and that they need long-term administration in order to obtain prolonged anti-tumor effects, representing a rational basis for their delivery by a gene therapy approach. The experimental approaches attempted to date, reviewed herein, indicate overall that anti-angiogenic gene therapy has efficacy mainly as an early intervention strategy and that a better understanding of the biological mechanisms underlying resistance to angiogenesis inhibition, as well as appropriate combined treatments, are required to generate a conceptual advancement which could drive the field towards successful management of established tumors.

Alternative splicing in angiogenesis: the vascular endothelial growth factor paradigm

Alternative splicing, first discovered in the 1970s, has emerged as one of the key generators of proteomic diversity. Not surprisingly, alternative splicing is increasingly linked to the etiology of cancer. This is illustrated by vascular endothelial growth factor (VEGF), the dominant angiogenic factor. Recently, an antiangiogenic family of VEGF isoforms was discovered, and termed VEGF(xxx)b. VEGF(xxx)b isoforms arise from an alternative 3' splice site in exon 8, and differ by a mere six amino acids at the C-terminus. These alternative six amino acids radically change the functional properties of VEGF. VEGF(xxx)b isoform expression is regulated in human tissues and development, and disregulated in many pathological states including cancer. Understanding what regulates VEGF(xxx)b alternative splicing, and therefore the balance of pro- and antiangiogenic isoforms is of great importance and will be explored in detail over the next few years.

Anti-angiogenic inhibition of tumor growth by systemic delivery of PEI-g-PEG-RGD/pCMV-sFlt-1 complexes in tumor-bearing mice

Vascular endothelial growth factor (VEGF) is an endogenous mediator of tumor angiogenesis. Blocking associations of the VEGF with its corresponding receptors (Flt-1, KDR/flk-1) have become critical for anti-tumor angiogenesis therapy. Previously, we synthesized PEI-g-PEG-RGD conjugate and evaluated as an angiogenic endothelial polymeric gene carrier. In this study, PEI-g-PEG-RGD/pCMV-sFlt-1 complexes are evaluated in terms of tumor growth inhibition in vivo. Complexes were repeatedly injected systemically via tail vein into subcutaneous tumor-bearing mice. As a result, tumor growth was inhibited in the PEI-g-PEG-RGD/pCMV-sFlt-1 injected group. However, this effect was not identified in PEI-g-PEG/pCMV-sFlt-1 or PEI-g-PEG-RGD/pCMV-GFP control groups. Moreover, the survival rate increased in the PEI-g-PEG-RGD/pCMV-sFlt-1 group compared with the controls group. These results suggest that delivery of pCMV-sFlt-1 using PEG-g-PEG-RGD may be effective for anti-angiogenic gene therapy.

Hypoxia increases VEGF-A production by prostate cancer and bone marrow stromal cells and initiates paracrine activation of bone marrow endothelial cells

Hypoxia develops at sites of rapid cancer growth near sites of poorly organized vasculature. Heparin binding growth factors (HBGFs) support neoangiogenesis of tumors. We examined the effect of culturing bone-targeted, metastatic C4-2B prostate cancer cells and bone stromal derived HS27a cells under hypoxic conditions on expression of vascular endothelial growth factor (VEGF) family members. A sealed chamber infused with 1% (hypoxic) or 20% (normoxic) O(2) was used. Both cell lines produced VEGF-A in normoxia, but little or no HB-EGF, another HBGF. HS27a cells produced low levels of FGF-2 and HGF, but little or none was secreted by C4-2B cells. Levels of VEGF-A in conditioned medium (CM) from both cell lines doubled when cultured in hypoxia. Similar changes in VEGF-A mRNA levels were seen. Receptor expression was unchanged by hypoxia. Changes in VEGF-A expression during hypoxia were preceded by nuclear accumulation of hypoxia inducible factor-1alpha (HIF-1alpha). Bone marrow endothelial (BME) cells express high levels of VEGFR2/flk-1, and are targets of VEGF-A induced neovascularization. BME cells proliferated in response to treatment with HS27a CM, but not C4-2B CM. BME cells formed tube-like angiogenic structures on growth factor reduced Matrigel in response to CM from HS27a or C4-2B cells. This response was greater when CM was produced under hypoxia, and was reduced by VEGF-A or FGF-2 neutralizing antibodies. We conclude that hypoxia triggers a physiologically relevant increase in VEGF-A by prostate cancer and bone marrow stromal cells which involves a paracrine loop that recruits and activates BME to support tumor neovascularization-related processes.

Angiogenic factors are elevated in overweight and obese individuals

BACKGROUND

Adipose tissue produces both vascular growth factors and inhibitors. Since obesity is associated with expansion of the capillary bed in regional adipose depots the balance between these factors may favor angiogenesis.

OBJECTIVE

To investigate the relationship between body mass index and serum concentrations of vascular growth factors in human subjects.

METHODS

Vascular endothelial growth factor (VEGF), VEGF-C, VEGF-D, soluble VEGF receptor-2 (sVEGFr2), hepatocyte growth factor (HGF), angiopoietin-2, angiogenin and endostatin concentrations were measured in serum collected from 58 lean (24 males, 34 female, mean BMI, 22.2+/-0.3) and 42 overweight and obese (16 males and 26 females, mean BMI, 33.5+/-1.2) subjects after an overnight fast.

RESULTS

Sexual dimorphism was apparent in the serum concentrations of VEGF-C, VEFG-D and angiopoietin-2 with significantly higher levels in female compared to male subject. VEGF, VEGF-C, VEGF-D, soluble VEGF receptor-2, angiopoietin-2, angiogenin and endostatin but not HGF were significantly elevated in overweight and obese subjects. Positive correlations between BMI and the serum concentrations of VEGF-C, VEGF-D, sVEGF-R2, angiopoietin-2, angiogenin and endostatin were observed even after adjustment for gender and age.

CONCLUSIONS

Increased levels of vascular growth factors as well as the angiogenesis inhibitor endostatin are present in overweight and obese subjects and may contribute to previously documented increased risk of metastatic disease in obese subjects with cancer.

Differential expression of vascular endothelial growth factor, placenta growth factor and their receptors in placentae from pregnancies complicated by placenta accreta

Placenta accreta is a pregnancy complication characterized by the presence of life-threatening uteroplacental neovascularization. The factors involving its development are unknown. Vascular endothelial growth factor (VEGF), placenta growth factor (PlGF) and their receptors (VEGFR) have important roles in vascular remodeling. We have investigated the differential expression of these proteins in placentae from placenta accreta (cases) and normal placentation (controls). Immunohistochemically, the expression of VEGFR-2 in the syncytiotrophoblast was significantly lower in cases than in controls during both the second and third trimesters (P = 0.005 and 0.002, respectively). However, VEGFR-2 expression in the cytotrophoblastic and extravillous trophoblastic cells and VEGFR-1, -3 and Ki-67 in the trophoblast populations were not significantly different between controls and cases (P > 0.05). Ki-67 immunostaining also showed that endothelial cells of the larger vessels were stained weaker in normal placenta than in placenta accreta. The majority of VEGFR-2 expression, as demonstrated by Western blot or reverse transcription polymerase chain reaction, was consistent with the immunohistochemical findings in the syncytiotrophoblast. Furthermore, enzyme-linked immunosorbent assay in the placental lysates showed that the women with placenta accreta demonstrated significantly higher VEGF (P = 0.001) and lower soluble VEGFR-2 (P = 0.015) concentrations than did women with normal pregnancy. PlGF and soluble VEGFR-1 levels did not show any significance in study groups (P > 0.05). These observations suggest that the participation of up-regulated VEGF and down-regulated VEGFR-2 (both membrane-bound and soluble forms) may be associated with the development of placenta accreta.

Antiangiogenic peptides and proteins: from experimental tools to clinical drugs

The formation of a 'tumor-associated vasculature', a process referred to as tumor angiogenesis, is a stromal reaction essential for tumor progression. Inhibition of tumor angiogenesis suppresses tumor growth in many experimental models, thereby indicating that tumor-associated vasculature may be a relevant target to inhibit tumor progression. Among the antiangiogenic molecules reported to date many are peptides and proteins. They include cytokines, chemokines, antibodies to vascular growth factors and growth factor receptors, soluble receptors, fragments derived from extracellular matrix proteins and small synthetic peptides. The polypeptide tumor necrosis factor (TNF, Beromun) was the first drug registered for the regional treatment of human cancer, whose mechanisms of action involved selective disruption of the tumor vasculature. More recently, bevacizumab (Avastin), an antibody against vascular endothelial growth factor (VEGF)-A, was approved as the first systemic antiangiogenic drug that had a significant impact on the survival of patients with advanced colorectal cancer, in combination with chemotherapy. Several additional peptides and antibodies with antiangiogenic activity are currently tested in clinical trials for their therapeutic efficacy. Thus, peptides, polypeptides and antibodies are emerging as leading molecules among the plethora of compounds with antiangiogenic activity. In this article, we will review some of these molecules and discuss their mechanism of action and their potential therapeutic use as anticancer agents in humans.

Combinatorial antiangiogenic gene therapy by nonviral gene transfer using the sleeping beauty transposon causes tumor regression and improves survival in mice bearing intracranial human glioblastoma

Glioblastoma is a fatal brain tumor that becomes highly vascularized by secreting proangiogenic factors and depends on continued angiogenesis to increase in size. Consequently, a successful antiangiogenic therapy should provide long-term inhibition of tumor-induced angiogenesis, suggesting long-term gene transfer as a therapeutic strategy. In this study a soluble vascular endothelial growth factor receptor (sFlt-1) and an angiostatin-endostatin fusion gene (statin-AE) were codelivered to human glioblastoma xenografts by nonviral gene transfer using the Sleeping Beauty (SB) transposon. In subcutaneously implanted xenografts, co-injection of both transgenes showed marked anti-tumor activity as demonstrated by reduction of tumor vessel density, inhibition or abolition of glioma growth, and increase in animal survival (P = 0.003). Using luciferase-stable engrafted intracranial gliomas, the anti-tumor effect of convection-enhanced delivery of plasmid DNA into the tumor was assessed by luciferase in vivo imaging. Sustained tumor regression of intracranial gliomas was achieved only when statin-AE and sFlt-1 transposons were coadministered with SB-transposase-encoding DNA to facilitate long-term expression. We show that SB can be used to increase animal survival significantly (P = 0.008) by combinatorial antiangiogenic gene transfer in an intracranial glioma model.

Therapeutic potential of inhibitory VEGF splice variants

Antiangiogenesis by inhibition of vascular endothelial growth factor (VEGF) has recently been demonstrated to be an effective therapeutic mode in human cancer alongside surgery, radiotherapy and chemotherapy. The authors have recently discovered a family of inhibitory VEGF splice variants, which has led to the possibility of using these isoforms as antiangiogenic agents. The discovery, mechanism of action, preclinical evaluation, and the potential uses of these isoforms in future cancer therapy will be discussed herein.

The effects of growth hormone status on circulating levels of vascular growth factors

BACKGROUND

Vascular growth factors are important not only in angiogenesis but also for the maintenance of normal endothelial integrity and function. Elevated levels of vascular endothelial growth factor (VEGF), angiopoietin-2, hepatocyte growth factor (HGF), endostatin and angiogenin have been associated with endothelial dysfunction and atherosclerosis. Both acromegaly and growth hormone deficiency (GHD) are associated with endothelial dysfunction and changes in blood vessel morphology.

AIM

To investigate the effect of GH status on the circulating levels of angiogenic factors.

DESIGN

We measured the levels of six endothelial growth modulators, four angiogenic growth factors and two inhibitors of angiogenesis in 35 untreated acromegalics, 36 untreated GH-deficient subjects and 101 normal control subjects. Fifteen GH-deficient subjects were also studied before and 1 year after treatment with GH.

RESULTS

Mean angiogenin concentrations were increased in acromegaly and decreased in GH-deficient subjects compared to control subjects. Endostatin levels showed a similar pattern although the elevated levels in acromegalic subjects did not achieve statistical significance. Angiogenin and endostatin levels both correlated significantly with IGF-I levels (R = 0.61, P < 0.001 and R = 0.22, P < 0.01, respectively). The relationship between angiogenin and IGF-I levels remained significant even after correction for gender, age, body mass index (BMI) and insulin resistance. There were no significant differences in the levels of HGF, VEGF, VEGF-C or angiopoietin-2 between the three groups. VEGF-D levels were elevated in both acromegalic and GH-deficient male subjects. A similar pattern was apparent in female subjects. After GH treatment, a significant reduction in VEGF-D levels and a significant rise in endostatin levels were observed in GH-deficient subjects. A nonsignificant increase in angiogenin levels was also observed.

CONCLUSION

These data indicate that significant perturbations in the levels of vascular growth modulators are present in both acromegaly and GHD. While changes in endostatin and angiogenin levels appear to correlate with IGF-I levels, VEGF-D levels show similar perturbations in both acromegaly and GHD. Further studies are required to determine the relationship of the perturbations to endothelial dysfunction in these conditions.