Anti-tumor effect of a novel soluble recombinant human endostatin: administered as a single agent or in combination with chemotherapy agents in mouse tumor models.

BACKGROUND: Angiogenesis has become an attractive target in cancer treatment. Endostatin is one of the potent anti-angiogenesis agents. Its recombinant form expressed in the yeast system is currently under clinical trials. Endostatin suppresses tumor formation through the inhibition of blood vessel growth. It is anticipated that combined therapy using endostatin and cytotoxic compounds may exert an additive effect. In the present study, we expressed and purified recombinant human endostatin (rhEndostatin) that contained 3 additional amino acid residues (arginine, glycine, and serine) at the amino-terminus and 6 histidine residues in its carboxyl terminus. The recombinant protein was expressed in E. Coli and refolded into a soluble form in a large scale purification process. The protein exhibited a potent anti-tumor activity in bioassays. Furthermore, rhEndostatin showed an additive effect with chemotherapy agents including cyclophosphamide (CTX) and cisplatin (DDP). METHODS: rhEndostatin cDNA was cloned into PQE vector and expressed in E. Coli. The protein was refolded through dialysis with an optimized protocol. To establish tumor models, nude mice were subcutaneously injected with human cancer cells (lung carcinoma A549, hepatocellular carcinoma QGY-7703, or breast cancer Bcap37). rhEndostatin and/or DDP was administered peritumorally to evaluate the rate of growth inhibition of A549 tumors. For the tumor metastasis model, mice were injected intravenously with mouse melanoma B16 cells. One day after tumor cell injection, a single dose of rhEndostatin, or in combination with CTX, was administered intravenously or at a site close to the tumor. RESULTS: rhEndostatin reduced the growth of A549, QGY-7703, and Bcap37 xenograft tumors in a dose dependent manner. When it was administered peritumorally, rhEndostatin exhibited a more potent inhibitory activity. Furthermore, rhEndostatin displayed an additive effect with CTX or DDP on the inhibition of metastasis of B16 tumors or growth of A549 tumors. CONCLUSION: Soluble rhEndostatin exhibits a potent anti-tumor activity in mouse xenograft models and it also has an additive effect with CTX and DDP, implying possible applications in clinical settings.

Transcription expression and clinical significance of mRNA of vascular endothelial growth factor and endostatin in liquid-based preparation specimens from patients with cervical dysplasia and carcinoma.

OBJECTIVES: The aim of this study was to assess the diagnostic usefulness of vascular endothelial growth factor (VEGF) and endostatin mRNA in cervical specimens of patients with cervical dysplasia and carcinoma. STUDY DESIGN: Transcription levels of VEGF and endostatin were detected by RT-PCR in cervical liquid-based preparation specimens and compared with cytological assessments. RESULTS: VEGF as well as endostatin mRNA expression was significantly associated with either cytological or histological diagnosis (p < 0.05). VEGF mRNA and endostatin mRNA were significantly more likely to be expressed in squamous cell carcinomas (SCC) than in cervical intraepithelial neoplasia (CIN) III (p < 0.01 and p < 0.05), and obviously also more likely to be expressed in CINII than in CINI and in CINIII than in CINII (p < 0.05). Eleven inflammation lesions gave positive results by cytology but negative results by RT-PCR for VEGF and endostatin mRNA. Twenty-four SCC lesions gave false-negative or precancerous lesion results by cytology but positive results by RT-PCR for VEGF and/or endostatin mRNA expression. CONCLUSION: Transcription levels of VEGF and endostatin by RT-PCR may be an adjunct to cytology screening for early detection of cervical carcinomas and may determine the progressive potentiality of individual lesions, especially in high-risk patients.

Molecular cloning, expression and purification of recombinant soluble mouse endostatin as an anti-angiogenic protein in Escherichia coli.

Inhibition of angiogenesis has become a particular interest for treatment of solid tumors. Endostatin, a C-terminal fragment of collagen XVIII, has been reported to exhibit potent inhibitory effect on endothelial cells proliferation, migration and tube formation. In this research, the cDNA library of endostatin was synthesized from mouse liver and inserted into the SacI and SalI enzyme-cutting sites of pUC18 cloning vector. The recombinant vector was transferred into Escherichia coli DH5a and the recombinant clone was selected on LB agar plate plus ampicillin. PCR analysis and DNA sequencing proved the presence of intact endostatin gene in pUC18. The endostatin gene subcloned into pET32a expression vector and the competent bacterial cells of E. coli BL21 were transformed by the vector harboring endostatin gene. In the optimum conditions, expression plasmid was induced with IPTG and recombinant soluble endostatin as a fusion with thioredoxin was purified with Ni-NTA (Ni(2+)-nitrilotriacetate) resin. The results showed that soluble recombinant endostatin as a fusion protein with thioredoxin is a homogenous polypeptide that inhibits angiogenesis (capillary tube formation) in human umbilical vein endothelial cells by 200 ng/ml.

Characterization of a monoPEG20000-Endostar.

In this study, we investigated the PEG attachment site of mono-PEGylated Endostar, a modified recombinant human endostatin approved in China for lung cancer. N-terminal site-directed mono-PEGylation of Endostar was accomplished using mPEG-propionaldehyde derivatives (Mw=20 kDa) under slightly acidic pH conditions (pH 5.5). One-step cation exchange chromatography was used to purify the mono-PEGylated Endostar. Following tryptic digestion, the peptide fragment containing PEG was separated by SDS-PAGE. Barium iodide staining and Western blotting were used to detect the PEG moiety and the N-terminus of Endostar, respectively. The peptide fragment stained by barium iodide showed a positive response to anti-(His) 6 mAb, demonstrating that PEG was located at the N-terminus of Endostar. LC/MS was applied to verify the occurrence of mono-PEGylation at the N-terminus of Endostar.

Immobilized kidney 28-kDa endostatin-related (KES28kDa) fragment promotes endothelial cell survival.

BACKGROUND/OBJECTIVE: Renal ischemia-hypoxia is a leading cause of acute kidney injury (AKI). Ischemia causes extracellular matrix breakdown of the tubular basement membrane. Endostatin (ES) is the C-terminal fragment of collagen XVIII generated by proteolytic cleavage. Recent studies have demonstrated that ES expression is upregulated in ischemic kidneys. The present study aimed to characterize ES from ischemic kidneys. METHODS: Ischemic renal failure was induced via 45 min of occlusion of the left renal artery and vein. After the ischemic period, blood was collected. Kidneys were harvested and used for immunohistochemical testing and protein extraction. Three-step purification was used. Soluble and immobilized purified ES were tested in cell viability and adhesion assays. results: The soluble KES28kDa inhibited endothelial cell proliferation: 25 versus 12.5 microg (p < 0.05); 12.5 versus 3.15 microg (p < 0.05). Immobilization of KES28kDa supports endothelial cell survival over the control (p = 0.021). Human umbilical vein endothelial cells plated on immobilized KES28kDa showed an increase in membrane ruffles and stress fibers. CONCLUSION: These data demonstrate the local synthesis of a 28-kDa ES-related fragment following AKI and suggest its role in endothelium survival.

Bioactivity and stability analysis of endostatin purified from fermentation supernatant of 293 cells transfected with Ad/rhEndo.

Endostatin is a potent angiogenic inhibitor that has been approved for the treatment of cancer. However, endostatin is unstable in vitro and difficult to produce in large quantities. Endostatin gene therapy is an alternative to overcome these difficulties by expressing sustained bioactive endostatin in vivo. We previously developed a recombinant replication-defective adenovirus, E10A, which carries the human endostatin gene. Phase I trial of E10A given as a weekly intratumoral injection in adult patients with solid tumors has been finished. The clinical application of endostatin gene therapy was limited by the high cost of large-scale production. In the current study, we found that there was a high level (100mg/L) of endostatin in the fermentation supernatant of 293 cells transfected with Ad/rhEndo. A protocol was developed to purify recombinant endostatin in the fermentation supernatant to a yield of 24mg/L and 98% purity by the use of SP Sepharose FF cation exchange chromatography, Sepharose-heparin Hi Trap affinity chromatography and gel filtration chromatography. The anti-proliferative activity of 293 cell-expressed endostatin (ArhEndo) is comparable to that of yeast-expressed endostatin (YrhEndo). Cell migration assay indicated that ArhEndo is more effective than YrhEndo. Moreover, ArhEndo is of higher stability than YrhEndo. These results suggested that purification of recombinant endostatin from fermentation supernatant provided an economic and available strategy for Ad/rhEndo production.

Highly-efficient purification of native polyhistidine-tagged proteins by multivalent NTA-modified magnetic nanoparticles.

A new bis-nitrilotriacetic acid (NTA) chelate with catechol anchor was synthesized and immobilized on superparamagnetic iron oxide nanoparticles. When loaded with Ni(II), these bis-NTA-immobilized nanoparticles were shown to bind polyhistidine (His x 6-tagged) fusion proteins in their native, folded conformations that commercial microbeads failed to bind under identical conditions. Control experiments with a mono-NTA chelate immobilized on iron oxide nanoparticles indicate a similarly high affinity for His x 6-tagged native proteins, suggesting that the high density of the mono-NTA chelate presented by the nanoparticles allows the binding of the His x 6-tag to more than one Ni-NTA moiety on the surface. This study shows that the multivalency strategy can be utilized to enhance the binding of His x 6-tagged proteins in their native, folded conformations. We further demonstrated the selective purification of His x 6-tagged proteins from crude cell lysates by using the Ni(II)-loaded iron oxide nanoparticles. The present platform is capable of efficient purification of His x 6-tagged proteins that are expressed at low levels in mammalian cells. This work thus presents a novel nanoparticle-based high-capacity protein purification system with shorter incubation times, proportionally large washes, and significantly smaller elution volumes compared to commercially available microbeads.

[Fusion expression and identification of angiostatin and endostatin in E. coli BL21(DE3)].

Angiostatin(AS) and endostatin(ES) are both potent endogenous angiogenesis inhibitors, and the combination of AS and ES has been shown to have synergistic antiangiogenic effects. Here we report the fusion protein AS-ES expressed in E. coli which has antiangiogenic effects. At first, AS and ES genes were cloned respectively through RT-PCR, then fusion gene was made through gene splicing ,finally pET-42 (b)/AS-ES expression plasmid was constructed and transduced in E. coli BL21 (DE3). Target protein was in form of inclusion body,the rate of expression was about 14%, and MW about 65KD. Western blotting assay showed expressed protein had specific immune reaction to both the antibodies of AS and ES. The expressed protein which was refolded and purified through heparin affinity chromatography had antiangiogenic effect to vessels on chicken embryo chorioallantoic membrane. The results show that fusion protein AS-ES was expressed successfully in E. coli, and the expressed protein,which was renatured and purified, had immuno-reactivity to anti-AS and anti-ES in Western blotting and angiogenesis inhibition activity.

[Two incompatible plasmids coexpress the human endostatin and predigested human plasminogen kringle 5 in E. coli].

OBJECTIVE: To construct the recombinant plasmid pET28a/hES and coexpress the human endostatin (hES) and predigested human plasminogen kringle 5 (predhPK-5) in E. coli. METHODS: The mRNA was extracted from human liver tissue, and the endostatin gene was amplified by RT-PCR, which then was cloned into pET-28a(+). Under screening pressure by ampicillin and kanamycin simultaneously, E. coli BL21 (DE3) was cotransformed with pET28a/hES and pGEX-1lambdaT/predhPK-5 and induced with IPTG to express the recombinant proteins. The stability of cotransformants existing in E. coli was measured through two aspects in the serial culture time and passage number of bacterium. RESULTS: The two incompatible plasmids could be coexisted under the pressure of two antibiotics (ampicillin and kanamycin). After induced with IPTG, both human endostation and predhPK-5 gene were coexpressed, and the recombinant proteins comprised about 20% and 21% of total cell proteins, respectively. The two incompatible plasmids could still be maintained in over 75% E. coli cells for at least 16 hours or after 120 passages under the pressure of two antibiotics. CONCLUSION: The two incompatible plasmids pET28a/hES and pGEX-1lambda T/predhPK-5 may coexpress the recombinant proteins in E. coli. A new method for coexpression of proteins in E. coli containing two incompatible plasmids is proved to be feasible.

Expression and purification of human endostatin from Hansenula polymorpha A16.

Endostatin (EDN), an endogenous angiogenesis inhibitor of 20 kDa, was originally isolated from the supernatant of culture murine hemangioendothelioma cell line. Interest in EDN arises from its therapeutic potential as anti-tumor and anti-angiogenesis agents. However, it is difficult to obtain sufficient quantities of native EDN from its natural resources. We report here the construction of a pMIRH-type vector pLRG29 by introducing the 25s rDNA of Hansenua wingei and the Km(R) gene into the YIp vector pSML12 and the EDN expression vector pLRG-EDN by cloning the human EDN cDNA into pLRG29. Human EDN was expressed in Hansenula polymorpha (H.p.) A16 (pLRG-EDN) as a secreted soluble protein. The yield of the secreted EDN was 65 mg/L in shake flask. The secreted EDN was purified to a purity of 98 % by the use of SP Sepharose FF ion-exchange chromatography and Sepharose-heparin Hi Trap affinity chromatography. The MTT and chicken embryo chorioallantoic membrane assay demonstrated that the human EDN produced from H. polymorpha inhibited in vitro the proliferation of human umbilical vein endothelial cells and in vivo the neovascularization induced by bFGF.

[Cloning, expression, purification and characterization of human endostatin gene].

OBJECTIVE: To procure biologically active human endostatin. METHODS: Human endostatin gene was acquired by means of reverse transcriptase (RT)-PCR and cloned into PGEM-T vector with subsequent sequence identification. The gene fragment was inserted into the prokaryotic expression vector pBV220 and transformed into E.coli DH5alpha strain. Endostatin expression in the E.coli was identified and the inclusion body isolated, purified and its activity analyzed. RESULTS: The obtained gene fragment 552 bp in length was identified as the functional section of human endostatin gene by sequence analysis, and SDS-PAGE analysis showed that the expressed product was the target protein with biological activity. CONCLUSION: Human endostatin gene was expressed in E.coli and the protein obtained can inhibit the proliferation of ECV 304 cells.

Identification and characterization of novel endogenous proteolytic forms of the human angiogenesis inhibitors restin and endostatin.

Restin and endostatin are C-terminal fragments of the noncollagenous domains of collagen XV and collagen XVIII exhibiting high sequence homology. Both polypeptides are distinguished by strong anti-angiogenic activity in vivo restricting the growth of solid tumors and metastasis. They are therefore currently being tested in clinical trials as anti-cancer drugs. We present the identification of new endogenous variants of both angiogenesis inhibitors isolated from a human hemofiltrate peptide library. Using an immunological screening approach with time-resolved rare earth metal fluorometry, immunoreactive compounds were purified chromatographically and characterized by mass spectrometry. We discovered four novel proteolytic products of restin as well as four variants of endostatin. Two endostatin products were characterized as short internal fragments (R176-L215 and R176-S219) of the entire molecule containing the recently identified beta1 integrin receptor binding site, which plays a major role in endothelial cell migration and angiogenesis. Two additional forms contain mucin-type O-glycosylations. The O-glycosylated variants possess an oligosaccharide unit consisting of one N-acetylgalactosamine (GalNAc), one N-acetylneuraminic acid (NANA) and two galactose residues (Gal) occurring as sialo-(V117-S311-GalNAc-Gal2-NANA) and asialoglycopeptides (V117-S311-GalNAc-Gal2). The four restin variants (R(I)-R(IV)) were identified with identical C- but different N-termini and no posttranslational modification (R(I): P66-A254, R(II): P75-A254, R(III): Y81-A254 and R(IV): A89-A254). Following a differential peptide mass fingerprint approach by reflector mode MALDI-TOFMS, the disulfide patterns of these circulating restins were determined as Cys1-Cys4 and Cys2-Cys3. These endogenous circulating collagen fragments will help to understand the physiological processing of the therapeutic proteins.

[Expression of recombinant human endostatin in Pichia pastoris and its inhibitory effects on the growth of human lungadenocarcinoma Astc-a-1 cells].

OBJECTIVE: To achieve expression of recombinant human endostatin (rhES) in a highly efficient foreign gene expression system, the yeast strain Pichia pastoris, and to evaluate the inhibitory effect of rhES on the growth of nude mouse pulmonary adenocarcinoma cells. METHODS AND RESULTS: The rhES gene was efficiently expressed in the yeast strain, and heparin affinity chromatography yielded highly purified endostatin identified by Western blotting, which proved to significantly inhibit the growth of the ECV-304 cells in vitro and also the growth of the lung adenocarcinoma Astc-a-1 in nude mice. CONCLUSIONS: The rhES gene can be expressed in Pichia pastoris, and has the ability to restrain the growth of ECV-304 cells and lung adenocarcinoma Astc-a-1 in nude mice, showing important potentials for future clinical applications.

Endostatin capture from Pichia pastoris culture in a fluidized bed. From on-chip process optimization to application.

One of the characteristics of the methylothrophic yeast Pichia pastoris is its ability to grow to a very high cell density. Biomass concentrations of 300-400 g wet mass/l are common. It is therefore obvious that the recovery processes of extracellular proteins from this microorganism should take into account the effect of high biomass content. Separation by filtration and/or centrifugation is possible but these steps are cumbersome and can affect the protein recovery. The use of fluidized beds is attractive proteins capture option since it eliminates the biomass while capturing the desired protein. Zirconia-based resins possess unique properties which make them appropriate for processing high biomass concentrations in an expanded bed mode. The beads are particularly heavy (density is 3.2 g/ml) and small (75 microm) and therefore can accommodate high fluidization velocity and high mass transport. Specific operating conditions for effective capture of expressed protein have to be determined. This determination is generally time consuming and requires relatively large amount of feedstock for the lab trials. To avoid multiple chromatographic trials in columns, optimal conditions of adsorption and elution were determined by ProteinChip technology coupled with mass spectrometry. This technology involves flat chip surfaces functionalized as chromatographic beads where it is possible to adsorb and desorb proteins. Four different functional groups (strong anion-exchange, weak cation-exchange, hydrophobic and metal chelate) were tested and the retained proteins were analyzed directly by mass spectrometry. The weak cation-exchange group was chosen for further work. The Zirconia-based weak cation-exchange sorbent (CM HyperZ) was evaluated for binding capacity in a packed column and then for capturing endostatin from crude feed stock. Based on the previously determined conditions; 45 l of culture containing approximately 15 kg of biomass (wet mass) and 3 g endostatin were applied on an expanded bed at a flow-rate of 535 cm/h, yielding 80% of the endostatin and removing approximately 80% of foreign proteins.