A three-step purification method of large quantities of human recombinant alpha endothelial cellular growth factor for clinical use.

The endothelial cellular growth factor alpha-ECGF is a candidate drug for the induction of therapeutic neoangiogenesis. Its use in extensive experimental and clinical trials is hampered by the fact that currently published purification procedures allow only small yields, and the absence of pyrogenic impurities is not demonstrated. The rh alpha-ECGF was expressed in E. coli. Isolation of rh alpha-ECGF from E. coli lysates to apparent homogenicity was achieved by a three step purification procedure involving ionic exchange, heparin-sepharose and polymyxin B chromatography. By this method, 200 mg of rh alpha-ECGF was purified from 15 g wet weight E. coli bacteria. The isolated protein of 18 kDa appeared as a single band after SDS gel electrophoresis and subsequent silver-staining. The biological activity was expressed in the chorion-allantois-membrane assay and in the 3H-thymidine proliferation in baby hamster kidney cells. Drug trials with rabbits revealed no increase in body temperature after intravenous injections with 1 mg rh-ECGF.

[Cloning, purification and biological activity of human vascular endothelial growth factor fragment in E. coli].

OBJECTIVE: To observe the effect of human vascular endothelial growth factor (VEGF) fragment (3 approximately 4 exon) in E. coli on anti-angiogenesis. METHODS: Through RT-PCR amplification, endonuclease cut and DNA sequence analysis identification, hVEGF fragment cDNA was inserted into E. coli expression vector pTrcHis2A. The prokaryotic expression plasmid pTrcHis2A/VEGF(3 approximately 4) was constructed and transformed into TOP10F. RESULTS: After 8hr isopropy-beta-D-thiogalactoside (IPTG) induction, VEGF fragment was expressed in 15% of total proteins through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The expressed protein was highly antigenic and specific. The VEGF fragment was further purified by affinity, which could inhibit HUVEC proliferation and neovascularization of the chick chorioallantoic membrane. CONCLUSION: VEGF fragment is anti-angiogenetic, which may potentially be used in oncologico-biological targeting therapy.

Src kinase becomes preferentially associated with the VEGFR, KDR/Flk-1, following VEGF stimulation of vascular endothelial cells.

BACKGROUND: The cytoplasmic tyrosine kinase, Src, has been found to play a crucial role in VEGF (vascular endothelial growth factor) - dependent vascular permeability involved in angiogenesis. The two main VEGFRs present on vascular endothelial cells are KDR/Flk-1 (kinase insert domain-containing receptor/fetal liver kinase-1) and Flt-1 (Fms-like tyrosine kinase-1). However, to date, it has not been determined which VEGF receptor (VEGFR) is involved in binding to and activating Src kinase following VEGF stimulation of the receptors. RESULTS: In this report, we demonstrate that Src preferentially associates with KDR/Flk-1 rather than Flt-1 in human umbilical vein endothelial cells (HUVECs), and that VEGF stimulation resulted in an increase of Src activity associated with activated KDR/Flk-1. These findings were determined through immunoprecipitation-kinase experiments and coimmunoprecipitation studies, and were further confirmed by GST-pull-down assays and Far Western studies. However, Fyn and Yes, unlike Src, were found to associate preferentially with Flt-1. CONCLUSIONS: Thus, Src preferentially associates with KDR/Flk-1, rather than with Flt-1, upon VEGF stimulation in endothelial cells. Our findings further highlight the potential significance of upregulated KDR/Flk-1-associated Src activity in the process of angiogenesis, and help to elucidate more clearly the specific roles and mechanisms involving Src family tyrosine kinase in VEGF-stimulated signal transduction events.

Folding screening assayed by proteolysis: application to various cystine deletion mutants of vascular endothelial growth factor.

The production of recombinant proteins in Escherichia coli often leads to the formation of inclusion bodies. Although this has a number of advantages, a major disadvantage is the need to develop folding protocols for the renaturing of the proteins. However, the systematic screening of folding conditions is often hampered by the lack of convenient assays to detect correctly folded proteins. To address this problem we present a simple protocol, which combines folding screens and limited proteolysis to rapidly assess and optimize folding conditions. The efficacy of this method, termed FSAP (folding screening assayed by proteolysis), is demonstrated by the large-scale folding, purification and crystallization of various cystine deletion mutants of the cystine knot family member: vascular endothelial growth factor (VEGF). These mutants are particularly difficult to fold as the cystine knot is believed to make major contributions to the stability of the protein and this family of proteins lacks extensive hydrophobic core regions.

Primary study of vascular endothelial growth factor immunohistochemical staining in the diagnosis of early acute myocardial ischemia.

The expression of vascular endothelial growth factor (VEGF) in the model of rat early acute myocardial ischemia was studied by Strept-Avidin-Biotin-Peroxidase Complex (SABC) immunohistochemical staining. After ligating the anterior descending branch of the left coronary artery, an initial rapid (30min) positive expression of VEGF in myocardial ischemic areas was observed, the intensity of positive expression of VEGF increased with the continuation of myocardial ischemia. After 5h infarction, the strongly positive myocytes of SABC-VEGF staining were predominantly limited to perimyocardial infarction areas. No positive expression of VEGF was found in the control group. These findings suggested that SABC-VEGF method could give a sensitive, specific, simple and objective morphologic evidence to the diagnosis of sudden cardiac death caused by acute early myocardial ischemia.

A novel role for VEGF in endocardial cushion formation and its potential contribution to congenital heart defects.

Normal cardiovascular development is exquisitely dependent on the correct dosage of the angiogenic growth factor and vascular morphogen vascular endothelial growth factor (VEGF). However, cardiac expression of VEGF is also robustly augmented during hypoxic insults, potentially mediating the well-established teratogenic effects of hypoxia on heart development. We report that during normal heart morphogenesis VEGF is specifically upregulated in the atrioventricular (AV) field of the heart tube soon after the onset of endocardial cushion formation (i.e. the endocardium-derived structures that build the heart septa and valves). To model hypoxia-dependent induction of VEGF in vivo, we conditionally induced VEGF expression in the myocardium using a tetracycline-regulated transgenic system. Premature induction of myocardial VEGF in E9.5 embryos to levels comparable with those induced by hypoxia prevented formation of endocardial cushions. When added to explanted embryonic AV tissue, VEGF fully inhibited endocardial-to-mesenchymal transformation. Transformation was also abrogated in AV explants subjected to experimental hypoxia but fully restored in the presence of an inhibitory soluble VEGF receptor 1 chimeric protein. Together, these results suggest a novel developmental role for VEGF as a negative regulator of endocardial-to-mesenchymal transformation that underlies the formation of endocardial cushions. Moreover, ischemia-induced VEGF may be the molecular link between hypoxia and congenital defects in heart septation.

Distribution of transforming growth factor-beta isoforms TGF-beta 1, TGF-beta 2 and TGF-beta 3 and vascular endothelial growth factor in vulvar lichen sclerosus.

OBJECTIVE: To study the distribution of transforming growth factor beta (TGF-beta) isoforms TGF-beta 1, TGF-beta 2 and TGF-beta 3 and vascular endothelial growth factor (VEGF) in vulvar lichen sclerosus. STUDY DESIGN: Biopsies were obtained from 10 patients with vulvar lichen sclerosus, snap frozen and stained with polyclonal antibodies to TGF-beta 1, TGF-beta 2, TGF-beta 3 and VEGF. Control tissues used were uninvolved thigh tissue from two of the lichen sclerosus patients and normal vulvar tissue obtained from eight patients during gynecologic procedures. Two specimens of morphea were also examined. RESULTS: Weak TGF-beta 1 staining was demonstrated in the epidermis of all the lichen sclerosus, morphea, thigh and five of the eight normal vulvar specimens. Slight increase in TGF-beta 1 staining was seen in the upper and middermis in 6 of the 10 lichen sclerosus specimens and in the morphea specimens as compared to the control tissue, and this staining was localized within cells. TGF-beta 2 staining was present throughout the epidermis in all the normal thigh, normal vulva, lichen sclerosus and morphea specimens. TGF-beta 2 staining was increased within cells in the upper and middermis of the lichen sclerosus and morphea specimens. TGF-beta 3 staining occurred in the basal half of the epidermis of all the control, lichen sclerosus and morphea specimens, and only slight upper dermal staining of a few individual cells was seen in 3 of the 10 lichen sclerosus specimens. VEGF staining was similar in the normal tissues, lichen sclerosus and morphea. CONCLUSION: These results suggest that TGF-beta may.

Developmental expression of vascular endothelial growth factor in the masseter muscle of rats.

Developmental changes in vascular endothelial growth factor (VEGF) in rat masseter after birth were investigated. VEGF was extracted efficiently and reproducibly from muscle homogenate with low concentrations of non-ionic detergents, such as Triton X-100, Nonidet P-40, and Tween 20. The amount of VEGF measured by enzyme-linked immunosorbent assay (ELISA) increased markedly by approximately 9-fold, from day 8 to 35 after birth. The increase in VEGF was closely correlated with the development of the capillary network, as shown by the capillary to muscle fibre ratio (C/F ratio). Immunoblotting revealed that the predominant molecular species of VEGF concentrated with heparin-sepharose beads was VEGF(188). These results suggest that VEGF plays an important part in the development and maintenance of the capillary network in the rat masseter.

Expression of human vascular endothelial growth factor (VEGF165) in Pichia pastoris and its biological activity.

OBJECTIVE: To express human vascular endothelial growth factor (hVEGF165) cDNA in Pichia pastroris, purify the expressed product and detect the biological activity of it. METHODS: By inserting hVEGF165 cDNA coding 165 amino acid residues into Pichia pastoris expression vector pPIC9K containing AOX1 promoter and the sequences of alpha secreting signal peptides, a recombinant expression plasmid pPIC9K/hVEGF165 was constructed and transformed to yeast host strain KM71, then multiple-copy insert transformants were screened out and cultured in flasks, and hVEGF165 was expressed under the induction of 1% methanol. RESULTS: SDS-PAGE showed that after being induced with 1% methanol for 4 d, the expressed product existed in supernatant in the form of soluble molecule and contained 60% of total protein expressed. Western blot showed good antigenicity and specificity of expressed product. After being purified by Heparin-Sepharose CL6B affinity chromatography, the purity of expressed product reached above 90%. Biological assays proved that the expressed product could stimulate the proliferation of HUVEC. CONCLUSION: hVEGF165 was successfully expressed. The study opened up a wide prospect for the application of VEGF165 in the prevention and treatment of ischemic heart disease and other tissue ischemic diseases such as secondary arterial occlusion in limbs.

Purification and refolding of vascular endothelial growth factor-B.

Vascular endothelial growth factor (VEGF)-A interacts with the receptor tyrosine kinases VEGF-R1 and R2, and the importance of this interaction in endothelial cell (EC) function and blood vessel development has been well documented. Other ligands that interact differentially with these receptors and that are structurally related to VEGF-A include VEGF-B, VEGF-C, VEGF-D, and placenta growth factor (PLGF). Compared with VEGF-A, relatively little is known about the biological role of the VEGF-R1 specific ligand, VEGF-B. Two splice variant isoforms that differ at the COOH-terminus and which retain unique solubility characteristics are widely expressed throughout embryonic and postnatal development. Recent analysis of mice with a targeted deletion of the VEGF-B gene has revealed a defect in heart development and function consistent with an important role in vascularization of the myocardium (Bellomo D et al., 2000, Circ Res 86:E29-E35). To facilitate further characterization of VEGF-B, we have developed a protocol for expression and purification of refolded recombinant protein from Escherichia coli inclusion bodies (IBs). The approach developed resolves a number of significant issues associated with VEGF-B, including the ability to heterodimerize with endogenous VEGF-A when co-expressed in mammalian cells, a complex secondary structure incorporating inter- and intrachain disulfide bonds and hydrophobic characteristics that preclude the use of standard chromatographic resins. The resulting purified disulfide-linked homodimer was demonstrated to bind to VEGF-R1 and to compete with VEGF-A for binding to this receptor.

Matrix metalloproteinase-9 triggers the angiogenic switch during carcinogenesis.

During carcinogenesis of pancreatic islets in transgenic mice, an angiogenic switch activates the quiescent vasculature. Paradoxically, vascular endothelial growth factor (VEGF) and its receptors are expressed constitutively. Nevertheless, a synthetic inhibitor (SU5416) of VEGF signalling impairs angiogenic switching and tumour growth. Two metalloproteinases, MMP-2/gelatinase-A and MMP-9/gelatinase-B, are upregulated in angiogenic lesions. MMP-9 can render normal islets angiogenic, releasing VEGF. MMP inhibitors reduce angiogenic switching, and tumour number and growth, as does genetic ablation of MMP-9. Absence of MMP-2 does not impair induction of angiogenesis, but retards tumour growth, whereas lack of urokinase has no effect. Our results show that MMP-9 is a component of the angiogenic switch.

VEGF-C and VEGF-D expression in neuroendocrine cells and their receptor, VEGFR-3, in fenestrated blood vessels in human tissues.

Recently, vascular endothelial growth factor receptor 3 (VEGFR-3) has been shown to provide a specific marker for lymphatic endothelia in certain human tissues. In this study, we have investigated the expression of VEGFR-3 and its ligands VEGF-C and VEGF-D in fetal and adult tissues. VEGFR-3 was consistently detected in the endothelium of lymphatic vessels such as the thoracic duct, but fenestrated capillaries of several organs including the bone marrow, splenic and hepatic sinusoids, kidney glomeruli and endocrine glands also expressed this receptor. VEGF-C and VEGF-D, which bind both VEGFR-2 and VEGFR-3 were expressed in vascular smooth muscle cells. In addition, intense cytoplasmic staining for VEGF-C was observed in neuroendocrine cells such as the alpha cells of the islets of Langerhans, prolactin secreting cells of the anterior pituitary, adrenal medullary cells, and dispersed neuroendocrine cells of the gastrointestinal tract. VEGF-D was observed in the innermost zone of the adrenal cortex and in certain dispersed neuroendocrine cells. These results suggest that VEGF-C and VEGF-D have a paracrine function and perhaps a role in peptide release from secretory granules of certain neuroendocrine cells to surrounding capillaries.

The N-myc oncogene in human neuroblastoma cells: down-regulation of an angiogenesis inhibitor identified as activin A.

Angiogenesis, the formation of new blood vessels, is seen during embryonic development and tumor progression, but the mechanisms have remained unclear. Recent data indicate that developmental and tumor angiogenesis can be induced by cellular oncogenes, leading to the enhanced activity of molecules stimulating angiogenesis. However, activated oncogenes might also facilitate angiogenesis by down-regulating endogenous inhibitors of angiogenesis. We report here that enhanced expression of the N-myc oncogene in human neuroblastoma cells down-regulates an inhibitor of endothelial cell proliferation, identified by amino acid sequencing as being identical with activin A, a developmentally regulated protein. Down-regulation appears to involve interaction of the N-Myc protein with the activin A promoter. In addition, activin A inhibits both endothelial cell proliferation in vitro and angiogenesis in vivo, and it induces hemorrhage in vivo. We suggest that the N-myc-induced down-regulation of activin A could contribute to developmental and tumor angiogenesis.

EORTC Receptor and Biomarker Study Group Report: a sandwich enzyme-linked immunosorbent assay for vascular endothelial growth factor in blood and tumor tissue extracts.

A four-antibody sandwich enzyme-linked immunosorbent assay (ELISA) for vascular endothelial growth factor (VEGF) for application in blood (serum and plasma) and tumor tissue extracts was set up within the framework of the EORTC Receptor and Biomarker Study Group (RBSG). Polyclonal antibodies against VEGF165 were raised in chickens and rabbits, and used in a previously described assay format. The assay was validated and characterized for use in serum, plasma and tumor tissue extracts. The resulting VEGF ELISA was found to be specific for VEGF165 and VEGF121, the main isoforms of VEGF. The assay showed good precision and parallelism in serial dilutions of samples. The assay was not susceptible to interference by heterophilic antibodies because avian antibodies (duck anti-chicken and chicken anti-VEGF) were used in the pre-analyte stage and mammalian antibodies (rabbit anti-VEGF and goat anti-rabbit) in the post-analyte stage. In conclusion, a sensitive, robust and specific VEGF ELISA has been developed. Research into the prognostic value of VEGF employing this assay is currently underway.

Growth suppressing factor for endothelial cells exhibits tumor regressing activity.

Endothelium growth suppressing and tumor-regressing activities were copurified from the conditioned medium of P388D1 culture in the presence of 100 microg/ml carboxymethylated curdlan by a procedure including ammonium sulfate fractionation and six column chromatographies of Ceramic hydroxyapatite, Q-Sepharose, Sephacryl S-300 HR, Matrex PBA-30, PBE94, and anti-bovine serum albumin (anti-BSA) agarose. The intravenous administration of the purified growth suppressing factor for endothelial cells to sarcoma 180-bearing mouse caused a rapid decrease in the number of viable tumor cells in tumor lumps within 16 h. Immunohistochemical study showed that the intravenous injection of the purified factor to sarcoma 180-bearing mouse resulted in hemorrhagic disorder all over the tissue in the tumor lamp. Thus, the purified factor exhibited not only growth suppressing activity for endothelial cells but also tumor regressing activity at a concentration as low as about 15 ng/mouse. The purified factor significantly inhibited in vitro tubulogenesis of bovine artery, human umbilical vein, and adult human darmal microvascular endothelial cells on collagen gel at a concentration of about 5 ng/ml. After the tube formation of endothelial cells was completed on a collagen gel, the purified factor disrupted the tubes at a concentration of about 5 ng/ml within 48 h. These findings demonstrate that endothelium growth suppressing factor is a potent inhibitor of angiogenesis as well as the growth of endothelial cells, and may bring about the regression of a solid tumor by inhibiting angiogenesis.

A novel regulatory function of proteolytically cleaved VEGF-2 for vascular endothelial and smooth muscle cells.

By high throughput sequencing, we have identified a cDNA encoding a polypeptide related to vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) in the VEGF/PDGF gene family. It is designated vascular endothelial growth factor 2 (VEGF-2). Similar to VEGF, expression of VEGF-2 mRNA is abundant in vascular smooth muscle cells and several highly vascularized tissues. VEGF-2 protein is expressed as a secreted 52 kDa precursor as well as the 30 kDa amino-terminal and 27 kDa carboxy-terminal cleavage products. The latter two cleavage products are linked via a disulfide bridge (or bridges) and can be copurified. Using copurified 30 and 27 kDa proteins, the effect of VEGF-2 on growth of several cell types, including vascular endothelial and smooth muscle cells, was determined. Our results demonstrate that VEGF-2 protein stimulates the growth of human vascular endothelial cells but inhibits growth of human aortic smooth muscle cells induced by platelet-derived growth factor. These studies establish VEGF-2 as a novel regulator for growth of vascular endothelial and smooth muscle cells.

Synthesis and physiological activity of heterodimers comprising different splice forms of vascular endothelial growth factor and placenta growth factor.

Vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) are members of a dimeric-growth-factor family with angiogenic properties. VEGF is a highly potent and specific mitogen for endothelial cells, playing a vital role in angiogenesis in vivo. The role of PIGF is less clear. We expressed the monomeric splice forms VEGF-165, VEGF-121, PIGF-1 and PIGF-2 as unfused genes in Escherichia coli using the pCYTEXP expression system. In vitro dimerization experiments revealed that both homo- and hetero-dimers can be formed from these monomeric proteins. The dimers were tested for their ability to promote capillary growth in vivo and stimulate DNA synthesis in cultured human vascular endothelial cells. Heterodimers comprising different VEGF splice forms, or combinations of VEGF/PIGF splice forms, showed mitogenic activity. The results demonstrate that four different heterodimeric growth factors are likely to have as yet uncharacterized functions in vivo.