Overexpression of biologically active VEGF121 fusion proteins in Escherichia coli

Evaluation of recombinant human vascular endothelial growth factor VEGF121-loaded poly-l-lactide microparticles as a controlled release delivery system

Vascular endothelial growth factor A (VEGF-A) is an important growth factor that plays a major role in angiogenesis. With different isoforms distributed in various tissues, the shortest isoform of VEGF-A is VEGF121, one of the physiologically functional variants next to VEGF165. It is well known that VEGF has a shorter half-life, and the stability of the protein must be considered in therapeutic aspects. Poly-l-lactide (PLA) microparticles can release the encapsulated protein in a sustained release mode. In this study, the VEGF121 gene was cloned and expressed in a prokaryotic expression system (Escherichia coli). The recombinant VEGF121 was encapsulated with PLA microparticles and studied in vitro  and ex ovo  for the sustained release mechanism. The PLA-VEGF microparticles and the recombinant VEGF121 were explored for their bioactivity in human umbilical vein endothelial cells (HUVEC). VEGF released in vitro  from PLA microparticles on days 1, 20, and 30 showed remarkable biological activity compared to PBS-loaded PLA microparticles such as the ability of the cells to proliferate, migrate, and form tubes similar to recombinant VEGF121. Besides, PLA-VEGF microparticles and the recombinant VEGF121 were also tested for their proangiogenic action in embryonated eggs by chicken chorioallantoic membrane assay (CAM), and the effect was observed in both forms. This study suggests that PLA-loaded VEGF microparticles in a sustainable release format can be effectively used in proangiogenic therapy and reduce the adverse effects caused due to multiple dosages.

Expression, purification and functionality of bioactive recombinant human vascular endothelial growth factor VEGF165 in E. coli

Vascular endothelial growth factor (VEGF) is associated with tumour growth and metastasis. Because VEGF is the major player in both angiogenesis and vascular permeability and the most explored factor in angio-inhibitory therapies, many expression procedures have been developed to produce functional VEGF₁₆₅ in convenient yield. In this study, recombinant human VEGF₁₆₅ was cloned and expressed in Escherichia coli (BL21)-DE3 cells and large scale production was performed by fermentation. A high yield of active soluble protein was obtained after protein extraction employing both lysozyme and sonication treatment. Inclusion bodies were also isolated from the cell lysate and subjected to a simple protocol of solubilisation and refolding. Single-step purification was performed using nickel affinity chromatography and the purified proteins were able to recognize monoclonal Anti-poly-His antibody. The biological activity of the VEGF₁₆₅ was successfully tested using the Chicken chorioallantoic membrane assay, wound-healing migration and proliferation assay on human umbilical vein endothelial cells (HUVEC).

Recombinant expression and purification of functional vascular endothelial growth factor-121 in the baculovirus expression system

OBJECTIVE

To express human vascular endothelial growth factor121 (VEGF121) in insect cells.

METHODS

A gene construct containing VEGF was cloned in the pFastBac-HTA vector, followed by transformation in DH10BAC. The recombinant bacmid was then extracted, and transfected into Sf9 insect cells. The transfected cells were harvested, and then VEGF expression was confirmed by western blotting using specific antibodies. The tube formation assay was used for functional assessment of VEGF.

RESULTS

Our results showed that VEGF could be successfully expressed in the baculovirus system. Purified VEGF was able to stimulate in vitro tube formation of human endothelial cells.

CONCLUSIONS

Results from this study demonstrated that the recombinantly-produced VEGF can be considered as a promising candidate for therapeutic purposes.

Enhanced Mitogenic Activity of Recombinant Human Vascular Endothelial Growth Factor VEGF121 Expressed in E. coli Origami B (DE3) with Molecular Chaperones

We describe the production of a highly-active mutant VEGF variant, α2-PI1-8-VEGF121, which contains a substrate sequence for factor XIIIa at the aminoterminus designed for incorporation into a fibrin gel. The α2-PI1-8-VEGF121 gene was synthesized, cloned into a pET-32a(+) vector and expressed in Escherichia coli Origami B (DE3) host cells. To increase the protein folding and the solubility, the resulting thioredoxin-α2-PI1-8-VEGF121 fusion protein was co-expressed with recombinant molecular chaperones GroES/EL encoded by independent plasmid pGro7. The fusion protein was purified from the soluble fraction of cytoplasmic proteins using affinity chromatography. After cleavage of the thioredoxin fusion part with thrombin, the target protein was purified by a second round of affinity chromatography. The yield of purified α2-PI1-8-VEGF121 was 1.4 mg per liter of the cell culture. The α2-PI1-8-VEGF121 expressed in this work increased the proliferation of endothelial cells 3.9-8.7 times in comparison with commercially-available recombinant VEGF121. This very high mitogenic activity may be caused by co-expression of the growth factor with molecular chaperones not previously used in VEGF production. At the same time, α2-PI1-8-VEGF121 did not elicit considerable inflammatory activation of human endothelial HUVEC cells and human monocyte-like THP-1 cells.

Inhibition of angiogenesis in human endothelial cell using VEGF specific nanobody

Angiogenesis is an important step in tumor development and metastasis. Vascular endothelial growth factor (VEGF) plays an important role in progression of angiogenesis. VEGF121 and VEGF165 are the most relative forms of VEGF family which contain the full biological activity. Nanobodies derived from camelidae are the smallest biding site of antigen. Unique characteristic of nanobodies make them as a useful candidate for research. In this report, we describe the isolation of VEGF specific nanobodies from dromedaries immunized with purified VEGF antigen using phage display. Four clones that showed the highest signal value in ELISA experiment were selected and expressed as a His-tagged fusion protein. Four selected nanobodies were reacted strongly to VEGF in cross-reactivity assay. The binding affinity of selected nanobodies named Nb22, Nb23, Nb35 and Nb42 were differed from 0.1 to 60nM. The nanobodies inhibited endothelial cell proliferation or tube formation in response of VEGF in a dose-dependent manner. These results indicate the potential of nanobodies in inhibition of VEGF and represent a promising candidate for cancer research and therapeutics.

Expression and purification of functional human vascular endothelial growth factor-a121; the most important angiogenesis factor

PURPOSE

Angiogenesis or formation of new blood vessels is an essential process for tumor growth, invasion and metastasis. Vascular Endothelial Growth Factor (VEGF) and its receptors play an important role in angiogenesis-dependent tumors. VEGF-A is the most important factor in angiogenesis process. Human VEGF-A gene consists of eight exons that undergoes alternative exon splicing and produce five different proteins consisting of 121, 145, 165, 189 and 206 amino acids (named VEGF121, VEGF145, VEGF165, VEGF189, and VEGF206).

METHODS

In this study, VEGF121 gene synthesized and cloned into the pET-26b plasmid. The recombinant plasmid was transferred into appropriate expression strain of BL-21. Expression of VEGF121 induced by IPTG (Isopropyl β-D-1-thiogalactopyranoside) and confirmed by SDS-PAGE and Western-Blotting. Recombinant VEGF121 was purified by nickel affinity chromatography. HUVECs (Human Umbilical Vein Endothelia Cells) cells were isolated from umbilical vein and the effect of VEGF121 on tube formation of endothelial cells was investigated.

RESULTS

SDS-PAGE and Western-Blotting results verified the purification of VEGF121. The final yield of recombinant protein was about 5mg per liter. Endothelial cell tube formation assay results showed that VEGF121 leads to tube formation of endothelial cell on matrix and induces angiogenesis in vitro.

CONCLUSION

Recombinant VEGF121 is important factor in tube formation of endothelial cell, so it could be used in different cancer researches and angiogenesis assay.

VEGF-binding aptides and the inhibition of choroidal and retinal neovascularization

Age-related macular degeneration and diabetic retinopathy are leading causes of blindness. Vascular endothelial growth factor (VEGF) is known to be the main factor that induces pathological angiogenesis in these diseases. In this study, we investigate the therapeutic potential and safety profiles of high-affinity peptides targeting VEGF which are identified using an 'aptide' technology. We show that two VEGF-binding aptides, APTVEGF1 and APTVEGF2, demonstrate high binding affinity and specificity to VEGF. Furthermore, they suppress VEGF-induced activation of VEGF receptor-2, in vitro angiogenesis, and in vivo pathological choroidal and retinal neovascularization. Despite potent anti-angiogenic effects, both VEGF-binding aptides do not induce any definite toxicity at the level of cellular viability, histological integrity, and gene expression. Our data show the therapeutic potential of VEGF-binding peptides for the treatment of choroidal and retinal neovascularization.

Noninvasive monitoring of orthotopic glioblastoma therapy response using RGD-conjugated iron oxide nanoparticles

Noninvasive imaging techniques have been considered important strategies in the clinic to monitor tumor early response to therapy. In the present study, we applied RGD peptides conjugated to iron oxide nanoparticles (IONP-RGD) as contrast agents in magnetic resonance imaging (MRI) to noninvasively monitor the response of a vascular disrupting agent VEGF(121)/rGel in an orthotopic glioblastoma model. RGD peptides were firstly coupled to IONPs coated with a crosslinked PEGylated amphiphilic triblock copolymer. In vitro binding assays confirmed that cellular uptake of particles was mainly dependent on the interaction between RGD and integrin α(v)β(3) of human umbilical vein endothelial cells (HUVEC). The tumor targeting of IONP-RGD was observed in an orthotopic U87 glioblastoma model. Finally, noninvasive monitoring of the tumor response to VEGF(121)/rGel therapy at early stages of treatment was successfully accomplished using IONP-RGD as a contrast agent for MRI, a superior method over common anatomical approaches which are based on tumor size measurements. This preclinical study can accelerate anticancer drug development and promote clinical translation of nanoprobes.

Ribosome-inactivating proteins: from plant defense to tumor attack

Ribosome-inactivating proteins (RIPs) are EC3.2.32.22 N-glycosidases that recognize a universally conserved stem-loop structure in 23S/25S/28S rRNA, depurinating a single adenine (A4324 in rat) and irreversibly blocking protein translation, leading finally to cell death of intoxicated mammalian cells. Ricin, the plant RIP prototype that comprises a catalytic A subunit linked to a galactose-binding lectin B subunit to allow cell surface binding and toxin entry in most mammalian cells, shows a potency in the picomolar range. The most promising way to exploit plant RIPs as weapons against cancer cells is either by designing molecules in which the toxic domains are linked to selective tumor targeting domains or directly delivered as suicide genes for cancer gene therapy. Here, we will provide a comprehensive picture of plant RIPs and discuss successful designs and features of chimeric molecules having therapeutic potential.

Improved expression of a soluble single chain antibody fusion protein containing tumor necrosis factor in Escherichia coli

The immunocytokine scFvMEL/TNF is a fusion protein composed of tumor necrosis factor (TNF-alpha) and a single-chain Fv antibody scFvMEL targeting the melanoma-associated gp240 antigen. The fusion protein containing thioredoxin and a hexa-histidine tag was expressed in two Escherichia coli host cells, AD494 (DE3) pLysS and T7 Express I (q). The cell growth and expression level of target protein, His-tagged scFvMEL/TNF, were highly dependent on the induction temperature, inducer types and host strains. The ratio of insoluble to soluble target proteins was found to be controllable and could be minimized using cold shock conditions at less than 18 degrees C. The total productivity of soluble target protein was further improved by high cell density cultivation using a DO-STAT feeding strategy. The scFvMEL/TNF purified under their conditions was specifically cytotoxic to gp240-antigen positive melanoma A375-M cells as previously described.