Construction of retroviral vector carrying HSV tk gene under control of human AFP enhancer core sequence and human pgk promotor *

AIM Tenstruct retroviral vector bringing HSV tk gene under control by human AFP enhancer core sequence and human pgk promotor.

Construction of retroviral vectors to induce a strong expression of human class Ⅰ interferon gene in human hepatocellular carcinoma cells in vitro

AIM To establish the hepatoma cell specific expression of human interferon gene mediated by retroviral vectors. METHODS Human interferon α and interforon β complementary DNA (IFNs cDNA) were cloned into polylinker site of pMNSM retroviral vector to construct recombinant retroviral vector pMNSIFNA and pMNSIFNB, where the transcription of IFN gene was driven by SV40 early region promoter, and pMNAIFNA, pAMNSIFNA and pMNAIFNB, where the transcription of IFN gene was driven by SV40 early region promoter regulated by α fetoprotein enhancer. The retroviral constructs were respectively introduced into retroviral amphotropic packaging cells by means of lipofectamine mediated gene transfer procedure. The plasmids transfection rate was (4～40)×10 3 colonies/μg DNA/10 6 PA317 cells. The retrovirus infection rate was (5～500)×10 4 colony forming units (CFU)/ml. The recombinant retroviruses were used to infect human hepatoma cells, renal carcinoma cells and melanoma cell lines in the presence of 4mg/L polybrene. RESULTS Northern and Dot hybridization of total RNA from the neomycin resistant colonies and interferon expression assay indicated that human α fetoprotein enhancer induced efficient and apecific transcription and expression of IFNs gene driven by the promoter of different origin in human hepatoma cells by which α fetoprotein was highly produced. CONCLUSION Cis active element of α fetoprotein gene can drive specific expression of IFNs gene in human hepatoma cells, which provides some valuable data for the hepatoma specific immune gene therapy.

Killing effect of TNF-related apoptosis inducing ligand regulated by tetracycline on gastric cancer cell line NCI-N87

AIM: To clone the cDNA fragment of human TRAIL (TNF-related apoptosis inducing ligand) into a tetracycline-regulated gene expression system, the RevTet-On system, transduce expression vectors into a gastric carcinoma cell line-NCI-N87 and examine the effects of controlled expression of TRAIL in vitro on the gastric carcinoma cells. METHODS: The full-length cDNA of TRAIL was inserted into a vector under the control of the tetracycline-responsive element (TRE) to obtain the plasmid pRevTRE-TRAIL, which was transfected into a packaging cell line PT67. In addition, vector pRev-Tet On and pRevTRE were also transfected into PT67 separately. After hygromycin and G418 selection, the viral titer was determined. The medium containing retroviral vectors was collected and used to transduce a gastric carcinoma cell line NCI-N87. The resulting cell line NCI-N87-Tet On TRE-TRAIL and a control cell line, NCI-N87 Tet On-TRE, were established. TRAIL expression in the cell line was induced by incubating cells with doxycycline (Dox), which is a tetracycline analogue. The killing effect on gastric carcinoma cells was analyzed after induction. RESULTS: The recombinant plasmid pRev-TRE-TRAIL was constructed. After hygromycin or G418 selection, the producer cell lines PT67-TRE, PT67-TRE-TRAIL and PT67-Tet On were obtained,with titers of about 10(8)CFU.L(-1). By transducing NCI-N87 cells with retroviral vectors from these cell lines, stable cell lines NCI-N87-Tet-On TRE-TRAIL (NN3T) and control cell line NCI-N87-Tet-On-TRE (NN2T) were established. The growth curves of the selected cell lines were the same with the wild type NCI-N87. When Dox was added, cell death was obvious in the test groups (29%-77%), whereas no difference was observed in control and wild type cell lines. With the addition of a medium from the test group, human leukemia cell line Jurkat was activated till death (83%), indicating the secretion of active TRAIL proteins from the test cells to the medium. CONCLUSION: With the use of the RevTet-On system, a regulated expression system for TRAIL was constructed. Using this system, the selected killing effect of TRAIL on gastric carcinoma cell line NCI-N87 could be observed.

Transduction of human hepatocellular carcinoma cells with human γ-interferon gene via retroviral vector

AIM To investigate the therapeutic potential of gamma interferon (IFN γ) gene modified human hepatocellular carcinoma (HCC) cells. METHODS The IFN γ gene was introduced retrovirally into four HCC cell lines. Secreted IFN γ activity was assessed using bioassay. The expression of MHC molecules was detected by FACS. Tumorigenicity was analysed by tumor formation in nude mice. RESULTS Four IFN γ gene transduced HCC cell lines secreted different amounts of IFN γ, as in the same case of five clones derived from one HCC cell line. Transduction with IFN γ caused significant increase in the expression of major histocompatibility complex (MHC) antigens on HCC cells. The expression of HLA class Ⅰ was increased by 2-3 times in terms of mean fluorescence intensities, while for class Ⅱ expression, the percentage of positive cells augmented from <10% to >50%. When equal amount of tumor cells were injected into nude mice, the tumorigenicity of some transduced cells decreased dramatically. CONCLUSION IFN γ gene transduction can convert weakly immunogenic HCC cells to activate antitumor immune response, and further pave the way for the future use of such gene modified tumor cells as a modality for the cancer immunotherapy.

Overexpression of heme oxygenase-1 protects smooth muscle cells against oxidative injury and inhibits cell proliferation

To investigate whether the expression of exogenous heme oxygenase-1 (HO-1) gene within vascular smooth muscle cells (VSMC) could protect the cells from free radical attack and inhibit cell proliferation, we established an in vitro transfection of human HO-1 gene into rat VSMC mediated by a retroviral vector. The results showed that the profound expression of HO-1 protein as well as HO activity was 1.8- and 2.0-fold increased respectively in the transfected cells compared to the non-transfected ones. The treatment of VSMC with different concentrations of H2O2 led to the remarkable cell damage as indicated by survival rate and LDH leakage. However, the resistance of the HO-1 transfected VSMC against H2O2 was significantly raised. This protective effect was dramatically diminished when the transfected VSMC were pretreated with ZnPP-IX, a specific inhibitor of HO, for 24 h. In addition, we found that the growth potential of the transfected cells was significantly inhibited directly by increased activity of HO-1, and this effect might be related to decreased phosphorylation of MAPK. These results suggest that the overexpression of introduced hHO-1 is potentially able to reduce the risk factors of atherosclerosis, partially due to its cellular protection against oxidative injury and to its inhibitory effect on cellular proliferation.

Retrovirus-mediated herpes simplex virus thymidine kinase gene therapy approach for hepatocellular carcinoma

The therapeutic effect of herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system on hepatocellular carcinoma was studied in this experiment. The tk-containing retroviral recombinants were used to infect hepatoma cells (BEL-7402) and the cells were treated with ganciclovir (0-1000 microg/ml). The results showed that HSV-tk gene could be efficiently transferred in vitro into hepatoma cells and stably expressed. The growth potential of the tk-containing cells was significantly inhibited by GCV (P

IL 6 expression in transferred NIH3T3 cells by retrovirus vector

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Anti-tumor effect of human endostatin mediated by retroviral gene transfer in nude mice

OBJECTIVE: To explore the inhibitory effect of human endostatin gene mediated by retroviral vector on the growth of human liver carcinoma. METHODS: A recombinant retroviral plasmid containing human endostatin gene and signal peptide was engineered and transferred into PA317 cells to produce retrovirus. Human liver carcinoma cells (SMMC7721) were infected with the above retrovirus to build a stable endostatin-transfected liver carcinoma cell line (SMMC-endo). The control liver carcinoma cell line (SMMC-pLncx) was developed in a similar way except that the plasmid was replaced by an empty retroviral vector. Immunohistochemistry and Western blot were used to test the expression and secretion of human endostatin. The biological activity of the expressed human endostatin was assessed by endothelial cell proliferation assay. The growth rates of SMMC-endo and control SMMC-pLncx cells in vivo and in vitro were also observed. RESULTS: The expression and secretion of human endostatin by endostatin-transfected SMMC-endo cells were confirmed by immunohistochemistry and Western blot. Compared with the control group, concentrated supernatant of SMMC-endo cells remarkably inhibited the proliferation of human umbilical vein endothelial cells by 48%, significantly higher than the inhibition by the control (10.2%; P

Tumor cell-specific gene transfer with retroviral vectors displaying single-chain antibody

OBJECTIVE: To specifically deliver the therapeutic gene to cancer cells and construct target retroviral vectors by inserting the single-chain variable antibody fragment into the retroviral envelope. METHODS: Single-chain antibody expression vector pET -20bScfv was constructed. Binding activity of the genetically engineered single-chain variable antibody fragment was verified by enzyme-linked immunosorbent assay (ELISA) and Western blot. At the same time, by means of polymerase chain reaction (PCR)-directed mutagenesis, the appropriate cloning site EcoT22/Sal was generated at the N-terminus of receptor-binding SU domain in the MoMLV env polypeptide. Then the single- chain antibody gene, encoding a functional antibody, was inserted into the cloning site. The Scfv-env fusion gene fragment was subcloned into CMV expression vector. The Lac-Z retrovirus that co-displayed the Scfv-env chimeric protein and wild-type env protein was produced by transfection of Psi 2 cells with retroviral plasmid and the fusion gene expressing plasmid.To confirm the specificity of the recombinant retrovirus, infection assays and competitive inhibition assays were performed. RESULTS: The results of ELISA and Western blot showed that the genetically engineered single-chain variable antibody fragment could bind to the SHG44 cells surface membrane antigen. Virus-binding assay, viral infection and competitive inhibition assays confirmed that the harvested virus efficiently bound to and infected SHG44 cancer cells expressing the relative membrane antigen specially via the recognition of the target antigen. CONCLUSION: These results imply that insertion of Scfv into the retroviral envelope can specifically deliver the interested gene into specific antigen-producing cancer cells.

A bicistronic retroviral vector to introduce drug resistance genes into human umbilical cord blood CD34^+ cells to improve combination chemotherapy tolerance

OBJECTIVE: To study whether human umbilical cord blood CD34+ cells transduced with human aldehyde dehydrogenase class-1 (ALDH-1) and multidrug resistance gene (MDR1) have increases resistance to 4-Hydroperoxycyclo-phosphamide (4-HC) and P-glycoprotein effluxed drugs. METHODS: A bicistronic retroviral vector G1Na-ALDH1-IRES-MDR1 was constructed and used to transfect the packaging cell lines GP + E86 and PA317 by LipofectAMINE method, using the medium containing VCR and 4-HC agents for cloning selection and ping-ponging supernatant infection between the ecotropic producer clone and the amphotropic producer clone, we obtained high titer amphotropic PA317 producing cells with high titers up to 5.6 x 10(5) CFU/ml. Cord blood CD34+ cells were transfected repeatedly with supernatant of retrovirus containing human ALDH-1 and MDR1cDNA under the stimulation of hemopoietic growth factors. RESULTS: Bicistronic retroviral vector construction was verified by restriction endonuclease analysis. Polymerase chain reaction (PCR), reverse transcription (RT)-PCR, Southern blot, Northern blot, fluorescenceactivated cell sorting (FACS) method and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analyses showed that dual drug resistance genes have been integrated into the genomic DNA of cord blood CD34+ cells and expressed efficiently. The transgenes recipient cells confered 4-fold stronger resistance to 4-HC and 5.5 to 7.2-fold P-glycoprotein effluxed drug than untransduced cells. CONCLUSION: The bicistronic retroviral vector-mediated transfer of two different types of drug resistance genes into human cord blood CD34+ cells and co-expression provided an experimental foundation for improving combination chemotherapy tolerance in tumor clinical trial.

Inhibitory effect of retroviral vector containing anti-sense Smad_4 gene on Ito cell line, LI90

Background Transforming growth factor-β1 (TGF-β1) exerts strong fibrogenic potential in culture-activated HSCs Smad 4 is a key intracellular mediator for the transforming growth factor-β (TGF-β) superfamily of growth factors The aim of this study was to assess the effects of the antisense Smad 4 gene on Ito cell line, LI90 Methods The recombinant retroviral vector pLXSN-Smad 4 was constructed by cloning the rat antisense Smad 4 cDNA into the retroviral vector pLXSN Retroviruses with or without the antisense gene were obtained by transfecting pLXSN-Smad 4 and pLXSN vectors into PA317 cells Human hepatic stellate cells (HSCs) LI90 were infected with these retroviruses followed by selection with G418 The expression of Smad 4 was detected by Northern and Western blots Cell biological characteristics, including cell growth curve, 3H-TdR and 3H-proline uptake by HSCs and the production of extracellular matrix were assessed Results mRNA and protein expressions of Smad 4 in LI90 cells transfected with retrovirus containing the antisense Smad 4 gene were much lower than those in LI90 cells transfected with empty vector or parental LI90 cells Cells hypoexpressing the Smad 4 gene exhibited a slower rate of growth, a lower uptake of 3H-TdR and 3H-proline ( P <0 01), and smaller production of th extracellular matrix, compared with parental LI90 cells and cells transfected with empty retrovirus Conclusions The antisense Smad 4 gene can suppress the expression of the Smad 4 gene, reduce endogenous production of Smad 4 mRNA and protein, block TGF-β1 signaling pathway, inhibit activation of Ito cells, obstruct the growth of Ito cells, decrease the production of the extracellular matrix (ECM) Our results may provide a basis for the development of antifibrotic gene therapy

The emerging roles of retromer and sorting nexins in the life cycle of viruses

Retromer and sorting nexins(SNXs)transport cargoes from endosomes to the trans-Golgi network or plasma membrane.Recent studies have unveiled the emerging roles for retromer and SNXs in the life cycle of viruses,including members of Coronaviridae,Flaviviridae and Retroviridae.Key components of retromer/SNXs,such as Vps35,Vps26,SNX5 and SNX27,can affect multiple steps of the viral life cycle,including facilitating the entry of viruses into cells,participating in viral replication,and promoting the assembly of virions.Here we present a comprehensive updated review on the interplay between retromer/SNXs and virus,which will shed mechanistic insights into controlling virus infection.

Changes of phenotype and function of human CD4^(+)CD25^(-) T cells induced by transfection of Foxp3

The aim of this paper is to explore the effects of transfection of Foxp3 gene on the phenotype and function of naive CD4^(+)T cells.The pMSCV-Foxp3 retroviral vec-tor encoding Foxp3 gene was transduced into the PT67 packaging cell line.Virus-containing supernatant was applied to differentiate CD4^(+)CD25^(-) T cells.The resulting cells were sorted with flow cytometry.The expressions of CD25,CD127,CTLA-4 and the proliferation of trans-fected T cells were examined.The effect of transfected CD4^(+)T cells on the proliferation and cytokine production of CD4^(+)CD25^(-) T cells was examined.Foxp3-gene trans-fected CD4^(+)T cells could express Foxp3 and transfection of Foxp3 gene up-regulated the expressions of CD25 and CTLA-4,but down-regulated CD127 expression.After transfection,the proliferation of CD4^(+)T cells was elimi-nated.Transfected T cells inhibited the proliferation of CD4^(+)CD25^(-) T cells.CD4^(+)CD25^(-) T cells acquired a reg-ulatory phenotype and function after it was transduced with the Foxp3 gene.This suggested a key role of Foxp3 in the generation of CD4^(+)CD25^(+) regulatory T cells.