Construction of Recombinant Retroviral Vector Containing HIV-1 Tat Gene and Functional Detection of Expressed Tat in Target Cells

Objective: To construct recombinant retroviral vector containing HIV-1 Tatgene and evaluate the junction of the expressed Tat in target cells. Methods: HIV-1 Tat_(101) genewas recovered from pEV plasmid by Hind Ⅲ digestion and cloned into expression plasmid LZESpBMN-Z toconstruct recombinant retroviral expression plasmid named LZRS-Tat_(101). Using the method ofcalcium phosphate, the construct of LZRS-Tat_(101) was then transfected into packaging cell linesPhoenix (ΦNX) which contained env and gal genes encoding structural proteins and pol gene codingfor 3 enzymes ( reverse transcriptase, protease and integrate) essential for retroviral integrationand replication . The stable transfected cell lines was obtained using puromycin to screen for morethan 3 days. Then, immunohistochemical (IHC ) staining was carried out to detect the expressionlevel of Tat_(101) protein in both transiently and stably trancfected ΦNX, respectively. Thesupematants containing recombinant virus collected from transient and stable transfected cells wereemployed to infect 293 cells, respectively, and the expressed Tat in 293 cells was tested by Westernblot. Meantime, the supematants of infected 293 cells was further added to HL3T1 cells which wereHela cell lines containing an HIV-1-LTR/CAT reporter construct to establish a co-culture system.After co-culture for 72 hours, the protein was extracted from HL3T1 cells and used for CAT activityassay. Results: After LZRS- Tat_(101) was transfected into ΦNX, the amount of expressed Tat intransient transfection cells was significantly higher than that in stable transfection cells; Tatcould be detected not only in 293 cells but also in the supematants from 293 cells culture, and Tatin the supematants could activate HIV-1 LTR promoter in HL3T1, resulting in high 'expression of CATlocated at the downstream of LTR. Conclusion: The construct of recombinant retrovirus LZRS-Tat_(101) could express Tat protein in target cells and the expressed Tat was functionally activeand can really exhibit the ability to activate transcription.

Construction of pINC-lacZ Retroviral Vector and its Expression in Mouse Embryonic Stem Cells

A retroviral vector pINC-lacZ containing an E coli β-galactosidase(β-gal)gene was constructed and introduced into the MESPU-13 cells by electroporation.Four G418-resistant colonies were obtained from 1×107,electroporated MESPU-13 cells. Histochemical staining for β-gal activity showed that lacZ gene was expressed in at least three of the four colonies.Southern analysis proved that one copy of foreign gene was integrated in the chromosome of one of the transformed lines(MC15).These results showed that the expression of lacZ gene driven by SiCMVIE promoter can be detected in the transformed MESPU-13 cells.

CONSTRUCTION AND IDENTIFICATION OF RETROVIRAL VECTOR EXPRESSING HUMAN INTERLEUKIN-17 GENE

Human interleukin 17(IL17) is a newly found cytokine secreted by activated T lymphocytes. Many of its characteristics remain unknown. To provide a way for understanding its role in immunology and hematology further, we constructed a recombinant retroviral vector pL17SN containing the human IL17 gene about 1.3kb with the coding region. The constructed retroviral vector packaged in CRIP cells could infect human primary fibroblasts, and could stimulate the primary fibroblasts secreting human GMCSF and IL6. The retroviral vector containing the human IL17 gene we constructed may present an efficient way to understand the biological functions of human IL17 and to investigate applications of IL17 in cancer gene therapy.

Expression of the Capsid Precursor Protein gene of Foot-and-mouth Disease Virus and Green Fluorescent Protein Gene in BHK-21 Cells Mediated by Retroviral Vector

We have constructed a retroviral vector mediated mammalian cell expression system of the capsid precursor protein of foot-and-mouth disease virus(FMDV).The recombinant retroviral vector pBABEpuro-P1-2A-EGFP was constructed by sequentially inserting capsid precursor protein gene(P1) of FMDV and enhanced green fluorescent protein gene(EGFP) into pBABEpuro.The recombinant retroviral vector and the pVSV-G plasmid were co-transfected into packaging cells(GP2-293) by liposomemediated transduction to produce the pseudovirus.The pseudovirus was used to infect BHK-21 cells and resistant cells were screened with puromycin.Green fluorescent proteins were observed by fluorescence microscopy and expression of the capsid precursor protein gene of FMDV was detected by indirect immunofluorescence.The recombinant retroviral vector pBABEpuro-P1-2A-EGFP was constructed successfully.The capsid precursor protein of FMDV and green fluorescent protein were expressed in BHK-21 cells.The mammalian cell expression system for the capsid precursor protein of FMDV has been constructed successfully,which lays the foundation of development of a FMDV subunit vaccine.

THE ENHANCED GREEN FLUORESCENT PROTEIN AS A MARKER FOR HUMAN TUMOR CELLS LABELLED BY RETROVIRAL TRANSDUCTION

Objective: To investigate the feasibility of marking the human tumor cells with enhanced green fluorescent protein (EGFP) in vitro. Methods: The retroviral vector LGSN encoding EGFP was constructed and three human tumor cell lines were infected with LGSN amphotropic virus. Tumor cell lines that stably express EGFP were selected with G418. The integration and expression of EGFP gene were analyzed by polymerase chain reaction, and flow cytometry (FCM). Results: After gene transfection and ping-pong transduction, amphotropic producer line Am12/LGSN was generated with a stable green fluorescence signal readily detectable by FCM in up to 97% of examined cells. The viral titer in the supernatants was up to 8.2×105CFU/ml. After transduction and selection, G418-resistant leukemia K562, mammary carcinoma MCF-7, and bladder cancer 5637 cells were developed, in which the integration of both EGFP and neomycin resistance gene was confirmed by DNA amplification. In comparison with uninfected cells, FCM analysis revealed EGFP expression in up to 90% (range 85.5%–90.0%) of tumor cells containing LGSN provirus. Conclusion: The retroviral vector LGSN can effectively mark the human tumor cells with a stably EGFP expression which may be in studying tumor growth, metastasis and angiogenesis.

Inhibition of pancreatic carcinoma cell growth in vitro by DPC4 gene transfection

AIM: To detect the expression of DPC4 in malignant and non-malignant specimens of human pancreas,and observe the inhibition of retroviral pLXSN containing DPC4 on pancreatic carcinoma cells in vitro.METHODS: The expression of DPC4 was determined in 40 pancreatic adenocarcinoma and 36 non-malignant pancreatic specimens by reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohisto-chemistry.Furthermore,we constructed retroviral vectors containing DPC4,which then infected the pancreatic carcinoma cell line BxPC-3.Cell growth in vitro after being infected was observed,and the vascular endothelial growth factor (VEGF) mRNA level in the daughter cells was determined by semi-quantitative PCR assay.RESULTS: The RT-PCR assay showed a positive rate of DPC4 mRNA in 100% (36/36) of normal specimens,compared to 40% (16/40) in adenocarcinoma specimens.The regional and intense positive cases of DPC4 expression in adenocarcinoma detected by immunohistochemistry were 10 and four,whereas it was all positive expression in normal tissues.There was a significant difference of DPC4 expression between them.The stable expression of DPC4 in the pancreatic carcinoma cells BxPC-3 could be resumed by retroviral vector pLXSN transfection,and could inhibit cell growth in vitro.Rather,DPC4 could decrease VEGF mRNA transcription levels.CONCLUSION: The deletion of DPC4 expression in pancreatic carcinoma suggests that loss of DPC4 may be involved in the development of pancreatic carcinoma.The retroviral vector pLXSN containing DPC4 can inhibit the proliferation of pancreatic carcinoma cells,and down-regulate the level of VEGF.

Expression of Major Antigen Domains of E2 Gene of CSFV and Analysis of its Immunological Activity

E2 is an envelope glycoprotein of Classical swine fever virus (CSFV) and contains sequential neutralizing epitopes to induce virus-neutralizing antibodies and mount protective immunity in the natural host. In this study, four antigen domains (ABCD) of the E2 gene was cloned from CSFV Shimen strain into the retroviral vector pBABE puro and expressed in eukaryotic cell (PK15) by an retroviral gene expression system, and the activity of recombinant E2 protein to induce immune responses was evaluated in rabbits. The results indicated that recombinant E2 protein can be recognized by fluorescence antibodies of CSFV and CSFV positive serum (Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China) using Western blot, indirect immunofluorescence antibody test (IFAT) and ELISA, Furthermore, anti-CSFV specific antibodies and lymphocyte proliferation were elicited and increased by recombinant protein after vaccination. In the challenge test, all of rabbits vaccinated with recombinant protein and Chinese vaccine strain (C-strain) were fully protected from a rabbit spleen virus challenge. These results indicated that a retroviral-based epitope-vaccine carrying the major antigen domains of E2 is able to induce high level of epitope-specific antibodies and exhibits similar protective capability with that induced by the C-strain, and encourages further work towards the development of a vaccine against CSFV infection.

Construction and packaging of pseudotype retrovirus containing human N-ras cDNA antisense sequence and its biological effects on human hepatoma cells

N-ros is one of the transforming genes in human hepatic cancer cells. It has been found that N-ras was overexpressed at the mENA and protein level in hepatoma cells. In order to explore the biological roles of N-ras in human hepatic oaroinogenesis and the potential application in control of cancer cell growth, a pseudotype retrovirus containing antisense sequence of human N-ras was constructed and packaged. A recombinant rebrovirus vector containing antisense or sense sequences of N-ras oDNA was constructed by pZIP-NeoSV(X)1. The pseudotype virus was packaged and rescued by transfeotion and infection in PA317 and ψ2 helper cells. It has been demonstrated that the pseudotype retrovirus containing antisense N-ras sequence did inhibit the growth of human PLC/PEF/5 hepatoma cells accompanied with inhibition of p21 expression, while the retrovirus containing sense sequence had none. The pseudotype virus had no effect on human diploid fibroblasts.

Retrovirus-mediated transfer of the fusion gene encoding EGFP-BMP_2 in mesenchymal stem cells

Objective To develop retrovirus-mediated transfer of the fusion gene encoding EGFP-BMP_2 in mesenchymal stem cells.Methods Mesenchymal stem cells from New Zealand white rabbits were transduced with retroviral pLEGFP-BMP_2 vector by the optimized retroviral transduction protocol.Fluorescent microscopy's examination was to evaluate the results of the transduction,flow cytometer's analysis was to evaluate the transduction efficiency and the Fluorescence-activated cell sorting method was to sort the transduced cells.Bioactivity test from C_2C_12K_4 cells was to show the expression and bio-activity of the fusion gene.Results Fluorescent microscopy showed the success of the transduction.By flow cytometer's analysis,the mean efficiency of the transduction with EGFP was(42.8±6.1)% SD.Transduced cells were sorted efficiently by the fluorescence-activated cell sorting method and after sorting,almost of those showed the expression of BMP_2.Fluorescently and strongly bioactivity test for C_2C_12K_4 cells demonstrated that fluorescent materials were located the surface of cells and the activity of luciferase increased compared with the control.Analysis of long-term expression showed there was no difference between 2 week-time point and 3 month-time point of culture post-sorting.Conclusion Mesenchymal stem cells can be transduced efficiently by retrovirus-mediated transfer of the fusion gene encoding EGFP-BMP_2,the highly pure transduced cells are obtained by the fluorescence-activated cell sorting technique,the expressed chimeric protein embraced the double bioactivity of EGFP and BMP_2,and moreover,the expression had not attenuated over time.

HE TREATMENT OF HEPATIC CARCINOMA WITH HERPES SIMPLEX THYMIDINE KINASE GENE/ACYCLOVIR SYSTEM

A retroviral vector(LNHcTL)containing the herpes simplex virus type 1 thymldine kinase(HSVI-tk)gene was constructed and used for transduction of the gene into human hepatocellular carcinoma cells(SMMC-7721).Xenografted tumor on nude mice was produced with the injection of the transduced cells(SMMC- 7721/LN HcTL) inoculated subcutaneously and showed regression when treated with Acyclovir.The mean weight of the residual tumors was six times less than that of the controls'tumors. Patients with liver carcinoma were given an intratumoral injection of ampbotropic packing cells(PA317/LNHcTL)producing HSV1-tk recombinant retroviral particles,and then treated with Acyclovir intravenously, which showed a marked regression of the tumor.Our preliminary data suggest that HSV1-tk gene/Acyclovir system might be a useful therapeutic approach for the treatment of hepatic carcinoma in humans.

EFFECTS OF ANTISENSE EPIDERMAL GROWTH FACTOR AND ITSRECEPTOR RETROVIRAL EXPRESSION VECTORS ON CELLGROWTH OF HUMAN PANCREATIC CARCINOMA CELL LINE

A 150 bp epidermal growth factor (EGF) cDNA fragment and a 1024 bp epidermal growth factor receptor (EGFR) cDNA fragment were inserted into 5.05 kb pBabe-puro retroviral vectors between BamH I and EcoR I sites in 3'-5' and / or 5'-3' orientation. The vectors were ligated with EGF and EGFR fragments by T-4 Ligase. The recombinant retroviral vectors were then packaged with packaging cell line PA317 through calcium phosphate mediated transfection. The viral supernatant of transfected PA317 cell lines were used to infect the human pancreatic carcinoma cell line PC-7. The resultant transformant cell lines: PC-7 / AS-EGF, PC-7 / S-EGFR, PC-7 / AS-EGFR and PC-7 / pBabe were tested for their endogenous EGF and EGFR mRNA expressions, cell growth rate, 3H-TdR incorporation rate, soft agar colony formation and tumorigenicity in nude mice. The results showed that there were noticeable inhibitions of cell growth, 3H-TdR incorporation rate, soft agar colony formation and tumorigenicity in nude mice in PC-7 / AS-EGF and PC-7 / AS-EGFR transformant cell lines. The endogenous EGF mRNA expression was blocked in PC-7 / AS-EGF cell line and the endogenous EGFR mRNA was significantly down-regulated in PC-7 / AS-EGFR cell line.

Antitumor Effects of the Fibroblasts Transfected TNF-α Gene and its Mutants

To compare the anti-tumor effects of transmembrane TNF-α(TM-TNF)and secreted TNF-α(S-TNF)in vivo,mouse fibroblasts NIH3T3 were transfected separately with three types of retrovirus containing wild type TNF-α(Wt-TNF),TM-TNF mutant(TM-TNFm),S-TNF mutant(S-TNFm).Southern blot,RT-PCR,FACS and bioassay were used to investigate TNF-αgene integration,expression and its biological activity.It was found that both fixed cells and supernatant of NIH3T3/Wt-TNF,the fixed cells of NIH3T3/TM-TNFm and the supernatant of NIH3T3/S-TNFm could express high level of TNF-αor its mutants and effectively kill H22 in vitro.The transfected NIH3T3 were separately injected into the mice at the sites of H22 tumor cell inoculation according to a ratio of 5∶1 or 1∶1(effector/target cells,E/T)after the third day of H22 challenge,respectively.At the E/T=5∶1,the NIH3T3/TM-TNFm induced the highest tumor regression,while NIH3T3/S-TNFm exerted the strongest tumor depressing effect at the E/T=1∶1 in vivo.No obvious side effects were noted throughout the course of treatment.The results suggest that both TM-TNF and S-TNF could cause tumor regression.The anti-tumor effect of TM-TNF would be more powerful and safe than that of S-TNF at the proper E/T ratio.

RETROVIRUS-MEDIATED TNF-α GENE TRANSFER INTO TCA8113 CELLS

Objective To investigate whether TNF-α gene-modified Tca8113 cells (Tca8113/TNF-α) canbe used as vaccine for oral squamous cell carcinoma. Methods TNF-α gene was transduced into Tca8113 cellsin vitro with retroviral vector carring genes for both TNF-α and NeoR. After that, presence and expression of exoge-nous gene in the transgenic cells, expression of HLA antigen on the cells, expression of TNF-α and survival rate ofthe cells after irradiation and cryopreservation, and mutagenic activity of the cells were analyzed by PCR technique,EL1SA technique, FACS technique, 60Co irradiation inactivation test, cryopreservation test, and Ames test, respec-tively. Results The presence of both TNF-a and NeoR gene and expression of TNF-α gene were demonstrated intransgenic cells. The levels of the HLA-A, B, C, DR expressed by Tca8113/TNF-α were higher than by the parentalcells. Tca8113/TNF-α continued to secrete TNF-α for 14 d, there was a secretion peak time from d4 to d6;and, allthe cells died by dl4 after irradiation. The Level of TNF-α secreted by Tca8113/TNF-α cryopreserved for 48 h wasno different from that cryopreserved for 1 week after irradiation, the level of TNF-α secreted by the cryopreservedcells was just a little lower than that secreted by the noncryopreserved cells. Both DNA and supernatant of the cellshave no mutagenic activity. Conclusion TNF-α gene can be transduced into Tca8113 cells with retroviral vec-tor, and the cells can express TNF-α. Expression of HLA 1,11 antigens on Tca8113 cells can be increased by TNF-αgene transduction. Irradiation is a reliable inactivation method, and cryopreservation is a feasible conservationmethod for Tca8113/TNF-α. Ames test result indicate that Tca8113/TNF-α has no mutagenic activity.

Hybrid retroviral vector with MCK enhancers inserted in LTR for stable and specific expression of human factor IX in skeletal muscle

Background Retroviral vectors have been widely used to introduce foreign into various target cells in vitro,thus showing relatively high systemic delivery efficiency of various transgene products. The authors investigated the stability and efficiency of skeletal muscle-specific hybrid retroviral vectors in expression of human factor IX (FIX) in vitro and iv vivo. Methods FIX cDNA in LIXSN vector was replaced with a FIX minigene containing splicing donor and splicing acceptor sequence of first intron of human FIX gene. Two copies of muscle creatine kinase enhancer (MCK,Me2) were inserted in forward or reverse orientation at NheI site of 3’ long terminal repeat (LTR),resulting in two hybrid vectors,which were designated as LMe2IXm_2SN(F) and LMe2IXm_2SN(R),respectively. The vectors were tested in vitro and in vivo for stability and muscle-specificity of factor IX expression with SCID mice. Results Muscle cells carrying vector with Me2 expressed significantly higher levels of FIX (up to 1800 ng/106.24h) than those without Me2, thus suggesting that Me2 could specifically increase expression level of FIX in muscle cells. Myoblasts transduced with LMe2IXm_2SN(R) produced much less FIX in vivo in SCID mice than LMe2IXm_2SN(F). One or two copies of Me2 sequence were deleted in myoblasts transduced with LMe2IXm2SN(R) without changing the orientation of Me2. Conclusions LTR inserted with MCK enhancers can specifically increase human FIX expression in skeletal muscle cells in vitro and in vivo,and MCK enhancer should be positioned in the same orientation as that of LTR promoter.

High level expression of human Factor Ⅷ in mammalian cells after retroviral-mediated gene transfer

Abstract:Objective To develop a retroviral-mediated high efficient expression system of human coagulation factor Ⅷ. Methods The LNC-FⅧBD retroviral vector was generated by cloning a human B-domain-deleted (760aa～1639aa) Factor Ⅷ (FⅧ) cDNA (FⅧ cDNA BD) into the retroviral vector pLNCX. Several mammalian cell lines, including NIH3T3, CHO, Cos-7 and human hepatic cell line, L-02, were transduced with viral supernatant from the highest virus-producing PA317 clone. Antigen and coagulant activity of human FⅧ in cell culture medium were measured by ELISA and a one-stage method, respectively. RT-PCR was performed for the detection of FⅧBD mRNA. Results Human FⅧ was expressed in all four target cells, with the highest FⅧ expression observed in NIH3T3. The coagulant activity of secreted FⅧ was up to 1.6U/106 cells*24?hrs-1, and the FⅧ antigen was 500?ng/106 cells*24?hrs-1. FⅧ coagulant activity and antigen expressed by transduced CHO cells were 0.12?U/106 cells*24?hrs-1 and 62.4?ng/106 cells*24?hrs-1, respectively. Human FⅧ expression was relatively low in Cos-7 and L-02 cells. RT-PCR results demonstrated transcription of FⅧcDNA BD in the target cells.Conclusions The constructed retroviral vector was able to direct high level expression of human FⅧ in various mammalian cell lines. It has potential utility in the future gene therapy for Hemophilia A.

Retroviral vector containing human p16 gene and its inhibitory effect on Bcap-37 breast cancer cells

Objective To study the effects of the p16 gene on tumor cell growth inhibition and cell cycle arrest. Methods The recombinant retroviral vector pLp16SN was constructed by cloning the human p16 cDNA into the retroviral vector pLXSN. Retroviruses with or without the p16 gene were obtained by transfecting pLp16SN and pLXSN vectors into PA317 cells. Bcap-37 human breast cancer cells were infected with these retroviruses followed by selection with G418. The expression of p16 was detected by Northern and Westem blots. Cell biological characteristics, including cell growth rate, cell cycle and tumorigenesis in nude mice were assessed.Results Both mRNA and protein expression of p16 in Bcap-37 cells transfected with retroviral vector containing the p16 gene were much higher than that in Bcap-37 cells transfected with empty vector or parental Bcap-37 cells. Cell overexpressing the p16 gene exhibited a slower rate of growth, a higher percentage of cells in the G1 phase, and smaller tumors in nude mice, compared with parental Bcap-37 cells and cells transfected with empty vector.Conclusion Overexpression of the p16 gene could suppress the growth of Bcap-37 breast cancer cells by arresting the cell cvcle at the G1 to S-phase.

Effects of recombinant retroviral vector mediated human insulin like growth factor-1 gene transfection on skeletal muscle growth in rat

Background This study transferred a recombinant gene encoding human insulin like growth factor-1 （hIGF-1） into modified primary skeletal myoblasts with a retroviral vector （pLgXSN） and determined whether the hIGF-1 promoted growth of skeletal muscle in rat.Methods hlGF-lcDNA was amplified in vitro from normal human liver cells by using RT-PCR and cloned into plasmid vector pLgXSN. The recombinant vector pLghIGF-1SN and control vector pLgGFPSN were transfected into packaging cell PT67 and G418 was used to select positive colony. Myoblasts were infected with a high titre viral supernatant and transduction efficiency was evaluated as GFP expression. The expression of hIGF-1 mRNA in myoblasts was investigated by immunocytochernistry and RT-PCR. MTT assays detected the growth of myoblasts in vitro. Myoblasts transduced with pLghlGF-1SN were injected into hind limb muscles of 10-12 week male SD rats. Formed tissues were harvested 4 weeks later. Myocyte diameter, mean weight of hind limb and body were measured to evaluate the skeletal muscle growth. Results Recombinant retroviral plasmid vector pLghlGF-1SN was constructed successfully. The titre of the packaged recombinant retrovirus was 1 × 106 cfu/ml. The transfection rate of PT67 cells reached 100% after G418 screening, hIGF-1 expression was positive in myoblast-IGF-1. The proliferation rate of myoblast-IGF-1 in vitro was higher than GFP-myoblast or myoblast （P〈 0.05）. The mean weights of hind limb and body of rats injected myoblast-IGF-1 were higher than those of the rats injected with myoblast-GFP or myoblast （P〈 0.05）. Myocyte diameter had a significant increase in IGF-1 group compared to GFP group and myobiast group （P〈 0.05）. Conclusions The transfection of the human IGF- 1 gene mediated by a retroviral vector can promote the growth of skeletal muscle in rats. Genetically modified primary skeletal myoblasts provide a possibly effective approach to treat some skeletal muscle diseases.

Anti-tumor effect of recombinant retroviral vector-mediated human ANGPTL4 gene transfection

Background This study was designed to obtain a recombinant retroviral vector containing the human hepatocellular carcinoma-related gene ANGPTL4 (angiopoietin-like 4) cDNA and to evaluate the anti-tumor effect of recombinant retroviral vector-mediated human ANGPTL4 gene transfection.Methods ANGPTL4 cDNA was cloned in vitro from normal human liver cells HL-7702 by using RT-PCR, and then subcloned into the plasmid vector pMSCV and sequenced. The retroviral plasmid vectors pMSCV-ANGPTL4, pVSV, and pGAG-POL were co-transfected into the packaging cell line 293 EBNA under mediation of lipofectamine. A high-titer retrovirus was obtained as a result, and HepG 2 cells were infected with this retrovirus in vitro. Flow cytometry and fluorescence microscopy were used to detect expression of green fluorescence protein (GFP). The expression of ANGPTL4 mRNA in HepG 2-ANGPTL4 cells was investigated using RT-PCR. The formation of tumors in nude mice and MTT assays were used to detect the growth of HepG 2-ANGPTL4 cells in vivo and in vitro, respectively.Results The cDNA sequence of the cloned ANGPTL4 gene was consistent with the recently reported sequence. Thus, the recombinant retroviral vector pMSCV-ANGPTL4 was constructed successfully. The titer of the packaged recombinant retrovirus was 1.4×106 infective viral grains/ml, and the rate of HepG 2-ANGPTL4 cells expressing GFP was 68.45%, with an average intensity of fluorescence 31.67 times greater in HepG 2-ANGPTL4 cells than in HepG 2 cells. The expression of ANGPTL4 mRNA in HepG 2-ANGPTL4 cells was higher than in HepG 2-pMSCV cells (154% higher) or HepG 2 cells (161% higher). The proliferation rate of HepG 2-ANGPTL4 cells in vitro was obviously lower than those of HepG 2-pMSCV cells and HepG 2 cells (P<0.01). The mean volume and weight of tumors seeded from HepG 2-ANGPTL4 cells were obviously lower than the mean volume or weight of tumors seeded from HepG 2 cells and HepG 2-pMSCV cells (P<0.01).Conclusion A stable ANGPTL4-transfected human liver cancer cell line HepG 2-ANGPTL4 has been created. The transfer of the human ANGPTL4 gene mediated by a retroviral vector is a possibly effective approach for liver cancer therapy.

Mesenchymal stem cells transduced by PLEGFP-N1 retroviral vector maintain their biological features and differentiation

Background Enhanced green fluorescent protein （EGFP） has been an important reporter gene for gene therapy. Human mesenchymal stem cells （hMSCs） are ideal target cells in cell transplantation and tissue engineering. We investigated their biological characteristics and differentiation mediated by PLEGFP-N1 retroviral transduction.Methods hMSCs were isolated from human bone marrow by density gradient fractionation and adherence to plastic flasks. Individual colonies were selected and cultured in tissue dishes. Packaging cells PT67 were transfected by PLEGFP-N1 retroviral vector , and hMSCs were transduced by viral supernatant infection. Meanwhile, hMSCs-EGFP were identified by immune phenotypes and whether it could differentiate into osteoblasts or adipocytes under conditioned media was investigated.Results The rate of stably transduced hMSCs-EGFP was up to 96% after being screened by G418. hMSCs-EGFP exhibited fibroblast-like morphological features. Flow cytometric analyses showed that hMSCs-EGFP were positive for CD73, CD105, CD166, CD90 and CD44, but negative for CD34 and CD45. In addition, it could functionally be induced into osteocytes or adipocytes under conditioned media. These biological features of hMSCs-EGFP were consistent with those of hMSCs.Conclusions hMSCs transduced by PLEGFP-N1 retroviral vector can be used in vivo securely because they can maintain their biological characteristics and differentiation. It is a simple and reliable way to trace the changes of hMSCs in vivo by EGFP during cell transplantation and gene therapy.

Membrane immunoglobulin expressed by retroviral vector gene transfer mimics partial function of the B-cell receptor in vivo

Activation of B-cells is initiated by the ligation of B-cell receptors by its cognate antigen, inducing a series of signal cascades. Understanding the molecular mechanisms of these important events is a crucial goal for immunologists. Chimeric B cell re- ceptors provide a powerful tool for analysis of B-cell signal function. However, this method can only be used in tool cells, but cannot be used for in vivo study. Here, we constructed a retroviral vector to encode both heavy chains and light chains of a membrane immunoglobulin, and expressed them in primary B-cells using retroviral gene transfer. Our results demonstrate that the membrane immunoglobulin expressed by retroviral vectors transfer can initiate B-cell receptor-mediated signaling, result- ing in the phosphorylation of Syk and Erkl/2 proteins. The results showed that B-cells expressing membrane immunoglobulin can make proliferative responses to cognate antigen both in vitro and in vivo. Therefore, we provide a methodology for rapidly analyzing the downstream signals of B-cell receptors both in vitro and in vivo, which could expedite the identification of proteins involved in B-cell function.