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Abstract The present study deals with the computational design and analysis of a novel fusion protein based on a single chain variable fragment that binds to the extracellular domain of human epidermal growth factor receptor 2 (HER2) in breast cancer cells. Alpha luffin, a small ribosome inactivating protein (RIP), was attached to the anti-HER2 antibody fragment. I-TASSER modeling provided the full-length structure of the fusion protein. Molecular docking evaluated the molecular interactions of the complementarity-determining regions of designed fusion protein to HER2. Energy minimization and molecular dynamics simulations were conducted to refine the complexes. RMSD plot revealed reasonable stability of the fusion protein during the simulation. The free binding energy profile of complexes affirmed a favorable binding affinity of proteins in complex with HER2 using molecular mechanics Poisson-Boltzmann surface area (G-MMPBSA) algorithm. In general, this approach looks promising in the development of new fusion proteins in terms of immunotoxins with appropriate cytotoxicity.
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@#The purpose of this experiment is to achieve the soluble expression of immunotoxins in Escherichia coli and avoid the complicated operation caused by the formation of inclusion bodies. An anti-mesothelin monoclonal antibody SS1 and it′s derivative SS1P which composing of SS1 and a truncated pseudomonas exotoxin PE38KDEL were used as the passenger protein. We took advantages of solubility promoting fusion tags and the self-cleaving split intein in recombinant antibody fragment and immunotoxin expression and purification. We constructed solubilizing tags-NpuCD118G fusion tags, and recombinant SS1/SS1P were fused at the C-terminal of the fusion tags. The constructs were expressed in E. coli(SHuffle T7)cytoplasm in soluble form at low temperature. Dextrin Beads 6FF column and Nickel column was used to purify the fusion protein. The self-cleavage of the fusion protein was achieved by adding the NpuN fragment. The released solubilizing tag and unreacted precursor were removed by Nickel column and the cleaved antibody fragment and immunotoxinwere further captured by Capto L. The dissociation constant of the obtained Fv and immunotoxin were determined by Fortebio. In summary, the current method could enhance the solubility of antibody fragment and immunotoxin in E. coli, and could improve the purification process. This method provides a reference for the development of a method for soluble expression and purification of immunotoxin-type pharmaceutical recombinant proteins based on the Escherichia coli expression system.
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Objective:To construct anti-B7-H4-scFv-PE38KDEL,a recombinant toxin based on anti-B7-H4 single chain antibody (scFv),to detect anti-tumor effect of toxin protein.Methods:The anti-B7-H4-scFv gene was ligated with the toxin PE38KDEL gene by overlapping extension PCR(SOE-PCR).The recombinant gene was cloned into prokaryotic expression vector pET28a(+),and the protein was renatured and purified by chromatography (Ni-NTA),and was identified by Western blot.Indirect ELISA and flow analysis technology were used for specific identification.The inhibitory effects of toxins on tumor cells were detected by MTT assay and subcutaneous xenograft model in vitro and in vivo.HE staining and immunohistochemical analysis were performed on tumor tissues.Results:The recombinant expression vector pET28a-anti-B7-H4-scFv-PE38KDEL was obtained by restriction endonuclease di-gestion.The purified toxin protein was inoculated on the tumor cells.The tumor growth was inhibited in the tumor model.Conclusion:The recombinant toxin expression system based on anti-B7-H4 single chain antibody was successfully constructed.The recombinant toxin protein had good biological activity and anti-tumor activity.
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Objective:To prepare nanobody-based immunotoxin BI7D12-PE38KDEL targeting EGFR and to examine its cytotoxicity against EGFR positive tumor cells.Methods:By using molecular cloning strategy,prokaryotic expression construct of pET28a-BI7D12-PE38KDEL was generated which consisted of nanobody 7D12 targeting EGFR in the form of a divalent fused with PE38KDEL,a truncated form of pseudomonas exotoxin A via a flexible peptide(G4S)4,and then transformed into E.coli BL21(DE3).Protein expression was induced by adding IPTG,purified by Ni-affinity column chromatography,and verified by Western blot.The binding capacity of the resulted immunotoxin to EGFR-positive cells A549,HT29,MCF-7 and EGFR-negative cells CEM,Jurkat were determined by flow cytometry assay,and its cytotoxicity against the target cells was examined.Briefly,tumor cells were treated with different dosage of the immunotoxin,and the killing efficacy of BI7D12-PE38KDEL on these cells were assessed by WST-1 assay after 72 hours.Results:The SDS-PAGE and Western blot results showed the recombinant immunotoxin BI7D12-PE38KDEL was successfully prepared,and majority of them was expressed in soluble form.BI7D12-PE38KDEL could selectively bind to EGFR-positive cells of A549,HT29,and MCF-7.More importantly,the immunotoxin exhibited much more significant killing effect on these EGFR positive cells compared to the negative control group of CEM and Jurkat cells(P<0.01).Conclusion:In the current study,the nanobody-based immunotoxin BI7D12-PE38KDEL targeting EGFR was successfully prepared and exhibited a superior inhibition effect for the growth of EGFR-positive cells.
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Objective To construct a recombinant immunotoxin expression vector composed of a single-chain Fv fragment of Sehistosorna japomicum and PE38KDEL gene,and identify the binding activity of the purified product with SEA antigen.Methods The V_H and V_L genes were amplified by PCR from the parent monoclonal antibody NP11-4.Then the amplified scFv and PE38KDEL genes were inserted into the expression vector pBAD/gIII A.The fusion protein expressed in E.coli Top10F' induced by L-arabinose.After purification,the activity of the immunotoxin was evaluated by Westem-blot and ELISA.Results The new recombinant immunotoxin expression vector pBAD/gIII A-scfv-PE38KDEL was constructed successfully.The main product was in inclusion bodies.ELISA assay showed that the refolding recombinant immunotoxin remained binding activity with SEA antigen.Conclusion A new recombinant expression plasmid pBAD/gIII A-scfv-PE38KDEL has been constructed and expressed successfully,which is useful in further study of the treatment of schistosomiasis japonica.
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Objective To construct a new recombinant immunotoxin expression vector by using human VEGF165 and a truncated pseudomonas exotoxin A ramification (PE38) gene, and explore the expression of the VEGF165-PE38 fusion protein in HEK293 cells. Methods VEGF165 was cloned by polymerase chain reaction (PCR). PE38 gene was gained from an vector plasmid pRB391 by restriction endonuclease digestion, and then inserted to the eukaryotic expression vector pIRES2-EGFP. After the eukaryotic recombinant vector pIRES2-VEGF165-PE38-EGFP was identified by restriction endonuclease digestion and sequence analysis, the vector was transfected into HEK293 cells by liposome protocol. RT-PCR and ELISA method was used to confirm the expression of the fusion gene in the HEK293 cells. Results Restriction endonuclease digestion and sequence analysis revealed the VEGF165-PE38 fusion gene was cloned into the eukaryotic expression plasmid vector pIRES2-EGFP successfully. The pIRES2-VEGF165-PE38-EGFP fusion gene could express in the HEK293 cells. Conclusion The result provide the basis for search of the targeted cytotoxic activity to tumor vascular endothelial cells and may have some potential value in clinical application.
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objective To observe whether the killing effect on HCC SMMC-7721 cell of the antihepatocellular carcinoma scFv reconstructed by pharmacy was enhanced or not.Methods Prokarycytic expression vector containing PET32a-RC-RNase was induced to express by IPTG.The inclusion body purified and Western-blotting was used.PC.CHOL and CHS was added in chloroform.Dry membrane was formed after chloroform was removed.RC-RNase protein solution was added to dissolute the membrane.Then pass the solution over a Sephadex G-50 column after ultrasound and filtrated to detect the encapsulation efficiency of the liposome.The solution reacted in EDC.SSNHS and MES for 30 minutes.Then add hdscFv to the solution in 4 ℃ over night.MTT method was used to detect the killing effect on HCC cell of immunoliposome RC-RNase,immunotoxin RC-RNase and liposome RC-RNase in vitro.Resuits The killing effect on HCC cell of immunoliposome RC-RNase is the best.but that of Iiposome RC-RNase is the worst.The respective JC50 are:3.28μg/ml,22.44μg/ml and 98.26μg/ml.Conclusion The anti-hepatocellular carcinoma scFv relomtructed by pharmacy can promote the killing effect on HCC cell and may have potential in the treatment of hepatocarcinoma.
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Objective:To prepare a new type of anti-leukemia immunotoxin with killing activity.Methods:The method of cytotoxicity was used to study the activity of the immunotoxin after the induction of IPTG. Results:The expressed fusion proteins were detected mostly as inclusion bodies at high level.The result showed IL3-PE38KDEL had liable activity of toxicity. Conclusion:The fusion protein IL3-PE38KDEL has good biological activity,which paves way for the further study on its treatment of leukemia.
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AIM: To express the DT389-hbFGF (389 amino acid residues of the N-terminus of diphtheria toxin (human basic fibroblast growth factor) fusion protein for potential targeting therapy towards posterior capsule opacification (PCO) after cataract surgery.METHODS: The DNA of inactivated diphtheria bacillus and RNA of 12-week fetal brain cortex were extracted, respectively. The fragments of truncated diphtheria toxin (containing 389 amino acids of N-terminus, DT389) )and full-length human basic fibroblast growth factor(hbFGF) sequence (encoding 18kDa protein) were amplified by PCR. The two fragments were inserted into pGEX-4T-1 prokaryotic expression vector to obtain pGEX-DT389-hbFGF prokaryotic expression plasmid. After sequence analysis, the expressing plasmid was transformed into Escherichia Coli BL21 strain and expression was induced under IPTG. The expressed fusion protein was purified and identified.RESULTS: The gene fragments encoding DT389 and hbFGF were amplified and their gene sequences were confirmed. Hybrid gene expression plasmid pGEX-DT389 (hbFGF was constructed. The fusion protein DT389-hbFGF was expressed and purified.CONCLUSIONS: The successful cloning and expression of DT389-hbFGF immunotoxin provides a foundation for targeting therapy towards posterior capsule opacification.
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Objective: To observe the targeting therapy of the hdsFv-RC-RNase recombinant single chain immunotoxin on the xenograft of the human hepatocellular carcinoma in nude mice and to explore its clinical potentiality. Methods: The prokaryotic expression vector TIG-hdsFv-RC-RNase was transformed into E.coli BL21(DE3)plys to largely express recombinant single chain immunotoxin hdsFv-RC-RNase against hepatocellular carcinoma induced by IPTG. The expressed product was purified via Ni-NTA affinity chromatography under native conditions and mildly refolded. The ELISA was used to analyze its immunological activity of antigen-binding capability. The xenogrft model of the human hepatocellular carcinoma in nude mice was established and the targeting therapy of hdsFv-RC-RNase was evaluated. Results:After induced by IPTG, a new protein band with M_r 41 000 was found in the supernatant of the bacteria and expressed in a soluble form. The expressed product was purified to homogeneity via Ni-NTA affinity chromatography under native conditions. The results of ELISA showed the refolded hdsFv-RC-RNase had the specific antigen-binding capability to the human hepatocellular carcinoma cell, but not to the normal hepatocyte (P
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A tumor-targeting recombinant fusion immunotoxin B-L-SEC2 was constructed by fusing staphylococcal enterotoxin C2 (SEC2) and an anti-HER-2 single-chain Fv B1 through a peptide linker, and expressed in E. coli strain BL21 (DE3) with an improved expression vector pASK75-EX as inclusion body. The denatured inclusion body was purified with Ni-NTA chelate agarose, and then re-natured by dialysis. FACS and MTT assays indicated that the re-natured fusion immunotoxin B-L-SEC2 could target the HER-2 over-expressing breast tumor cell SK-Br-3 in vitro, and inhibit the growth of SK-Br-3.
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The development of immunotoxin DT386-GMCSF, a fusion protein which bears the N-terminal 386 amino acids of diphtheria toxin and human granulocyte-macrophage colony-stimulating factor (GM-CSF) and targets the GM-CSF receptor (GM-CSFR), has provided a promising alternative therapy to the acute myeloid leukemia (AML). However, the poor expression of the protein in E.coli is still a bottleneck which limits the industrial production. To identify the critical down-regulating factors on the expression of DT386-GMCSF, a series of truncated mutants of DT386-GMCSF at the C-terminal of GM-CSF were generated and expressed in E.coli. The results showed that the encoding sequences for the L114 of the GM-CSF dramatically impact the expression of DT386-GMCSF. On this basis, a serial of mutants integrating amino acid substitutes were generated. The results revealed that the expression level of the mutant DF123GVT, which harbors the amino acids 1-123 of GM-CSF whose L114L115V116 was substituted with G114V115T116, was evidently higher than that of the DT386-GMCSF, whereas the specific cytotoxicity to blast recovered from mice injected with HL60, a cell line highly expresses the GM-CSFR, was similar. These results have provided an important basis for the future development of the immunotoxins targeting the GM-CSFR.
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We evaluated the effect of a basic fibroblast growth factor (bFGF) and saporin conjugate (bFGF-SAP) on proliferation, migration and tubule formation in bovine choriocapillary endothelial cells (BCECs). Cell proliferation and MTS assays were done with 0.01, 0.1, 1, 10, and 100 nM bFGF-SAP, and an equimolar concentration of bFGF and saporin. TUNEL assay was performed to confirm apoptosis. Cells were treated with 1, 10, and 100 nM bFGF-SAP and migration assay and tubule formation assay were done. Results were evaluated with image analysis. All experiments were performed in triplicate and repeated three times. Viable cells (ID50 = 0.62) and cell proliferation by MTS assay (ID50 = 0.75 nM) were inhibited. Saporin caused cytotoxicity and inhibition of proliferation at high concentration. DNA fragmentation was identified by TUNEL assay. Migration and tubule formation were also inhibited. All mechanisms responsible for neovascularization were inhibited, and this could be applied in the management of subretinal choroidal neovascularization (SRN).
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Animals , Cattle , Apoptosis/drug effects , Cell Count , Cell Movement/drug effects , Cell Proliferation/drug effects , Cells, Cultured , Comparative Study , Cytotoxins/pharmacology , Endothelium, Vascular/drug effects , Fibroblast Growth Factor 2/pharmacology , In Situ Nick-End Labeling , Neovascularization, Physiologic/drug effects , Plant Proteins/pharmacology , Recombinant Fusion Proteins/pharmacologyABSTRACT
OBJECTIVE: Immunotoxin therapy is a novel approach for the treatment of tumor, and it has been successfully used in the central nervous system. The purpose of this study is to evaluate the cytotoxicity of OKT9 ScFv-Diphtheria toxin fusion immunotoxin on various human brain tumor cell lines. METHODS: Immunotoxin which was composed of OKT9 ScFv and Diphtheria toxin was made. Its cytotoxicity on glioblastoma cell lines(U87MG, U118MG) and medulloblastoma cell line(TE671) was tested and compared with anti-cancer chemotherapeutic agents. And we also examined the relationship between its cytotoxicity and transferrin receptor expression. RESULTS: It showed most cytotoxicity on U87MG cell line and nearly no effect on U118MG cell line, moderate cytotoxicity on TE671 cell line in sixteen hours exposure experiment. In continuous exposure experiment, it showed moderate cytotoxicity on U118MG cell line, but showed strong cytotoxicity on other cell lines comparable or higher than anti-cancer chemotherapeutic agents. The relationship between its cytotoxicity and transferrin receptor expression was tested using flow cytometry, but no direct relationship could be found. CONCLUSION: Collectively, the result shows the cytotoxic effects of OKT9 ScFv-Diphtheria toxin fusion immunotoxin against various human brain tumor cell lines in continuous exposure experiment. Therefore, we suggest that this immunotoxin could be developed as a potential immunotherapeutic agent in the treatment of various human brain tumor clinically.
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Humans , Brain Neoplasms , Brain , Cell Line , Central Nervous System , Diphtheria Toxin , Flow Cytometry , Glioblastoma , Immunotoxins , Medulloblastoma , Receptors, TransferrinABSTRACT
Objective To construct a single chain Fv immunotoxin HAb25(scFv)-PE40 and explore its targeting effects on human hepatocellular carcinoma(HCC) cells.Methods First,the HAb25(scFv) gene was ligated with PE40,a truncated form of pseudomonas exotoxin on the the plasmid vector ply5 to form the HAb25(scFv)-PE40 gene.Then the HAb25(scFv)-PE40 gene was subcloned into the pBV220 E.Coli expression vector for production of the recombinant immunotoxin.SDS-PAGE was used to identify the expression of objective protein.The specificity of HAb25(scFv)-PE40 binding to HCC cells was tested by indirect immunofluorescent staining,and the in vitro targeting cytotoxic assay was employed to observe the selective cytotoxic activity of the objective protein.Results Enzyme digestion and sequencing analysis proved the construction of HAb25(scFv)-PE40 gene in ply5 vector.HAb25(scFv)-PE40 gene was highly expressed in pBV220 vector(up to 43.3% of total cellular proteins).Indirect immunofluorescent staining showed HAb25(scFv)-PE40 could specifically bind to HCC cells as its parent antibody HAb25.The protein was verified to have selective cytotoxic activity when cocultured with HCC cells.Conclusion A single chain Fv immunotoxin HAb25(scFv)-PE40 was successfully constructed.The immunotoxin has selective cytotoxic activity against HCC,which found a basis for further study on its basic and clinical application.
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Objective To induce islet grafting tolerance by intravenous injection of anti-CD4,anti-CD8 immunotoxins and donor soluble antigen.Methods 14 days or 7 days prior to transplantation,the immunotoxon 200 μg respectively,and donor soluble antigen 500 μg were injected intravenously into the recipients, then 500 donor islets were translanted under the left renal subcapsular space of diabetes reciPients (SD rats).Results The islet grafting survival time that pretreated with immunotoxon and dono soluble antigen was over 60 days(P<0.01).The immunotoxins or donor soluble antigen treatment alone only slightly prolonged the graft survival.Conclusion The anti-CD4,anti-CD8 immunotoxins combined with donor soluble antigen can induce donor specific immune tolerance.
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Gastric cancer cells express large amounts of galectin-3 on the cell surface. This fact may provide the possibility to use galectin-3 protein as a surface target for delivering cytotoxic anticancer agents. To investigate the possibility of application of galectin-3 protein as a target protein in delivering cytotoxic anticancer agents, we synthesized doxorubicin immunoconjugate by using maleimidocaproic acid and conjugated doxorubicin immunoconjugate to anti-galectin-3 mAb. The anticancer effect of immunotoxin was assayed on NIH3T3, AGS and KATO III cell lines. The anticancer effect of immunotoxin on AGS cell line is highest and that of KATO III is higher than that of NIH3T3. This results relate to that of flow cytometry analysis previously shown and indicate that galectin-3 protein can be used as a target protein on the surface of gastric cancer cell for delivering cytotoxic anticancer agents.
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Antineoplastic Agents , Cell Line , Doxorubicin , Flow Cytometry , Galectin 3 , Galectins , Immunoconjugates , Immunotoxins , Staphylococcal Protein A , Stomach NeoplasmsABSTRACT
Objective: Immunotoxin rRTA:DS27, which was prepared by conjugating DS27 with recombinanl ricin a chain, was compared with ricin:DS27 as immunotoxins. Methods: System analysis were performed regard to their cell-specific cytotoxicity, inhibition on the proliferation of hemoapeutic potential cells, immunogold-labelled intracellular routing and effect of NH_(4)Cl on the cytotoxicity. Results: Results showed that rRTA: DS27 got a more specific cytotoxicity and a weaker inhibition on the proliferation of hemoapeutic potential cells than ricin:DS27, NH_(4)Cl could obsolutelyy enhence the cytotoxicity of rRTA:DS27. Conclusion: rRTA:DS27 had more advantages than ricin: DS27 as immunotoxins.
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Bone marrow transplantation was considered effective treatment for leukemias and other haematological diseases. Acute graft v-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation. The T lymphocytes were specially depleted by anti-CD5, CD2, CD8, CD27 monoclonal antibody-ricin immunotoxins. Inhibition of the protein synthesis and T-cell functions in the target cells was observed in vitro. At 10 9mol / L of the immunotoxin, 3 logs (99.9%) of target cells were killed, but no cytotoxicity on nontarget cells. At the same concentration, the anti T cell immunotoxin had no any influence on the proliferating rate of CFU-GM and BFU E. None of the ten patients who received T cell depleted bone marrow developed grade III or IV acute GVHD.
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Eight saporin peaks were obtained from the purification of seed extracts of Saponaria officinalis L. Saporin peak No. 6 (SAP-6) showed the highest activity in the inhibition of protein synthesis (98%) in an in vitro translation study. An immunotoxin (IT) was prepared from SAP-6 conjugated to a monoclonal anti-CEA antibody 26/5/1 (mab B) using N-succinimidyl pyridyl dithiopropionate (SPDP) and 2-iminothiolane as a cross linker. Under thermal stability study by a DSC (differential scanning calorimetry), the IT showed a denature temperature of 75 degrees C. In in vitro translation studies, the purified IT showed the same activity as SAP-6 at 10(-7) M and 10(-9) M protein concentration at 0, 30 and 60-min incubation effects with mab B and SAP-6 not conjugated at 24-hr incubation periods on human promyelocytic cell line HL 60 and on human colon adenocarcinoma cell lines which were SW 403, LoVo and LS 174 T. SAP-6, mab B and IT had no cytotoxic effect on HL-60. The IT showed a higher cytotoxic effect than SAP-6 in CEA-positive cell lines. The IT demonstrated the highest cytotoxic effect of 51% inhibition of control at 10(-7) M on the LS 174 T.