Updates on current advances in gene therapy / Actualizaciones acerca de los adelantos presentes en terapia genética

Gene therapy is the attempt to treat diseases by means of genetic manipulation. Numerous challenges remain to be overcome before it becomes available as a safe and effective treatment option. Retroviruses and adenoviruses are among the most commonly used viral vectors in trials. The retrovirus introduces the gene it carries into the target cell genome while the adenovirus introduces the gene into the target cell nucleus without incorporating it into the target cell genome. Other viral vectors such as adenoassociated viruses, pseudotyped viruses and herpes simplex viruses, are also gaining popularity. Proposed nonviral methods for gene transfer include physical methods and the employment of chemical vectors (lipoplexes, polyplexes and inorganic nanoparticles). Recent studies have investigated potential applications of gene therapy in correcting genetic diseases, treating malignant disorders and for treatment of other diseases. Trials on gene therapy for SCID and Leber's congenital amaurosis have achieved considerable success, but the widely publicized adverse reaction in Xlinked SCID patient receiving gene therapy raised concerns for safety profile of gene therapy. For that, several methods of improving safety and efficacy of gene therapy have been proposed. At present, the three main gene therapy strategies for treatment of cancer are application to oncolytic viruses, suicidegene therapy and genebased immunotherapy. Gendicine, the first approved anticancer drugs based on the use of gene therapy principle, is based on the use of oncolytic viruses. More evidence for wider clinical applications of gene therapy are expected as more gene therapy studies progress from the preclinical phase to clinical trial.

La terapia genética es el intento de tratar enfermedades por medio de la manipulación genética. Quedan aún numerosos retos que superar antes de que esté tipo de tratamiento se encuentre disponible como una opción segura y eficaz. Los retrovirus y los adenovirus se hallan entre los vectores virales más comúnmente utilizados en ensayos: el retrovirus introduce el gen - del cual es portador - en el genoma de la célula de destino, mientras el adenovirus introduce el gen en el núcleo de la célula de destino sin incorporarlo al genoma de la célula de destino. Otros vectores virales tales como los virus adenoasociados, los virus pseudotipados, y los virus del herpe simple, también están ganando popularidad. Los métodos no virales propuestos para la transferencia de genes incluyen tanto métodos físicos como el empleo de vectores químicos (lipoplexes, polisomas y nanopartículas inorgánicas). Estudios recientes han investigado las aplicaciones potenciales de la terapia genética en la corrección de las enfermedades genéticas, el tratamiento de los trastornos malignos y para el tratamiento de otras enfermedades. Los ensayos de terapia genética para SCID y la amaurosis congénita de Leber han logrado un éxito considerable, pero la reacción adversa ampliamente divulgada en el caso de los pacientes con SCID ligada al cromosoma, que recibían terapia génica, causó preocupación en cuanto al perfil de seguridad de la terapia génica. Por esa razón, se han propuesto varios métodos para mejorar la seguridad y la eficacia de la terapia génica. En la actualidad, las tres estrategias principales de terapia de genes para el tratamiento del cáncer son la aplicación de virus oncolíticos, la terapia con gen suicida, y la inmunoterapia genética. La gendicina, el primer medicamento anticancerígeno aprobado, basado en el uso del principio de la terapia génica, se basa en el uso de virus oncolíticos. Se esperan más evidencias a favor de aplicaciones clínicas más amplias de la terapia génica, a medida que más estudios de terapia génica progresan de la fase preclínica a la fase de ensayo clínico.

Effect of suicide gene therapy in combination with immunotherapy on antitumour immune response & tumour regression in a xenograft mouse model for head & neck squamous cell carcinoma.

Background & objectives: Prodrug activation strategy as well as immunotherapy have been widely used for cancer gene therapy. In the present study, using a head and neck squamous cell carcinoma (HNSCC) xenograft nude mouse model, we have investigated whether the two therapies in combination could improve tumour cell kill. We also investigated induction of immune effector cells viz., NK (DX5+) and DC (CD11c+) in vivo, post-combination gene therapy. Methods: A retroviral vector producing cell line (PLTK47.1 VPC) carrying Herpes simplex virus thymidine kinase gene (HSVtk) was used for intratumoural injection into NT8e xenograft tumours followed by the prodrug ganciclovir (GCV). IL-2 plasmid DNA was injected intramuscularly. Immune cells were analyzed by flow-cytometry. Non parametric ANOVA was performed with Kruskal Wallis test. Results: IL-2 could induce proliferation of both NK cells (DX5+) and dendritic cells (CD11c+) in vivo. Apoptosis was higher in combination therapy group as compared to HSVtk/GCV alone or IL-2 alone and was mediated through caspase-3 dependent pathway. Significant reduction in tumour volume was seen in all 3 treatment arms as compared to controls. Interpretation & conclusions: Combination of suicide gene therapy and immunotherapy leads to successful tumour regression in a HNSCC xenograft mouse model. Immunotherapy could help in a systemic long lived anti-tumour immune response which would prove powerful for the treatment of metastatic cancers, and also for minimal residual disease. The results of this study may form the basis for Phase 1 clinical trials.

Current progress in bystander effect of suicide gene therapy / 国际外科学杂志

Nowadays, tumor is one of the most challenging human health diseases, which oblige human tirelessly to studied for the tumor.Gene therapy is a promising treatment in oncotherapies. Suicide gene therapy is the most widely researched among gene therapies. At the same time, bystander effect take important role in the mechanism of suicide gene therapy. Therefore, more researchers devote themselves to studyinghow enhance the bystander effect in order to improve the effect of suicide gene therapy. This article reviewed in short how to augment bystander effect of suicide gene therapy against cancer.

Inhibitory effect of mutant cytosine deaminase D314A against human colon cancer cells / 中国肿瘤生物治疗杂志

Objective:To construct a mutant D314A of Escherichia coli cytosine deaminase (EC-CD, substitution of an alanine (A) for the aspartic acid (D) at position 314 of cytosine deaminase) and investigate its antitumor effect. Methods: Eukaryotic expression plasmid containing EC-CD gene (pcDNA3.1-CD~(wt)) was constructed, and the mutant pcDNA3.1-CD~(D314A) plasmid, with aspartic acid (D) at position 314 of EC-CD gene substituted by alanine (A) (EC-CD~(D314A)), was established by site-directed mutation. EC-CD~(wt) and EC-CD~(D314A) were transfected into human colon cancer cell line LoVo via Lipofectamine~(tm) 2000, and positive LoVo-CD~(wt) and LoVo-CD~(D314A) cells stably expressing corresponding genes were selected by G418. The cytotoxicity and bystander effects of EC-CD and EC-CD~(D314A) genes on LoVo cells were e-valuated by MTT assay. Results: The mutant D314A was confirmed by sequence analysis. EC-CD and EC-CD~(D314A) mRNA were expressed after transfected into LoVo cells. The IC_(50) of Lovo-CD~(D314A) cells was (85.13±0.60) mmol/L, which was significantly lower than that of LoVo-CD~(wt) cells ([689.76±0.45] μmol/L, P=0.000). Bystander effect assay showed that, when at the ratio of 30%, the survival rates of LoVo-CD~(wt) cells and Lovo-CD~(D314A) cells were (48.5±0.49)% and (17.3±0.40) % (P = 0.000), respectively. Conclusion: Mutatant EC-CD gene (EC-CD~(D314A)) has a significantly in-creased antitumor effect on LoVo cells compared with wild type EG-CD gene, and it may become a new candidate gene for tumor gene therapy.

Suicide Gene Therapy for Bladder Cancer Using a Recombinant Adenovirus Expressing Escherichia Coli Cytosine Deaminase / 대한비뇨기과학회지

PURPOSE: The poor prognosis of advanced bladder cancer requires the investigation of novel treatment modalities. In this study, we investigated the suicide gene therapy for bladder cancer, using the adenovirus-mediated expression of Escherichia coli cytosine deaminase (CD) in conjunction with the prodrug 5-fluorocytosine (5-FC). MATERIALS AND METHODS: A replication-deficient recombinant adenovirus, which contains the Rous sarcoma virus (RSV) promoter driving the expression of CD, (Ad-RSV-CD) was constructed. In vitro cell-killing assay, using Ad-RSV-CD (20 MOI) plus 5-FC (500muM), was performed in bladder cancer cell lines, HT-1376, UM-UC-3 and NBT-II. The CD enzymatic activity was measured in the Ad-RSV-CD (20 MOI) infected cells, and the concentrations of 5-fluorouracil (5-FU) yielding an IC50 were calculated for those cells. RESULTS: 5-FU dose response curve showed that IC50 of NBT-II was 0.8muM, HT-1376 1.0muM and UM-UC-3 5.1muM at day 6. The CD enzymatic activities of the Ad-RSV-CD infected UM-UC-3, HT-1376 and NBT-II cells were 5696, 4655, 1766 pmole/1x10(6) cells, respectively. Whereas the administration of 5-FC (500muM) or Ad-RSV-CD (20 MOI) alone demonstrated no cytotoxicity to cells, Ad-RSV-CD/5-FC exhibited a significant cytotoxic effect in the cells, especially the UM-UC-3 and HT-1376. CONCLUSIONS: Ad-RSV-CD/5-FC suicide gene therapy is effective for bladder cancer cells in cell cultures, suggesting this approach may have potential as a strategy for the treatment of bladder cancer.

Antitunor effect of carcinoma cells transduced with herpes simplex virus - thymidine kinase by gancyclovir and radiation

BACKGROUND: Many types of cancer become resistant to current chemotherapeutic and radiotherapeutic intervention. To overcome this situation application of gene therapy by the introduction of suicide genes followed by their prodrugs may be promising. A viral enzyme, Herpes simplex thymidine kinase (HSV-tk), which converts ganciclovir from an inactive prodrug to a cytotoxic agent by phosphorylation, are being actively investigated for use in gene therapy for cancer. The purpose of this study was to determine whether combining prodrug-activating gene therapy and irradiation might result in enhanced antitumor effects. METHODS: The HSV-tk gene was cloned into the retroviral vector, pLXSN and established the clones producing retroviruses carrying the HSV-tk gene. The carcinoma cell line, HCT116 and Huh-7 were transduced with high-titer recombinant retroviruses. These cell lines were treated with ganciclovir before or after irradiation for the defining combinational effect of suicide gene therapy and radiotherapy. RESULTS: The titers of cloned PA3 17 amphotropic retroviruses ranged from 4 to 6 X 10(6) CFU/ml . After selectional periods, the expression of HSV-tk was confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR). The growth of cells expressing HSV-tk was inhibited as increase of GCV dose after 48 hr and the growth inhibitory effect of GCV was much higher after 72 hr. When the cells transduced with HSV-tk gene were exposed to radiation, the growth inhibitory effect of GCV was significantly increased, as compared with non-transduced parental cells. CONCLUSIONS: The result s suggest that the addition of HSV-tk gene therapy to standard radiation therapy may improve the effectiveness of treatment for solid tumors.

Adenovirus-mediated Suicide Gene Therapy for Experimental Prostate Cancers with in Vivo Tumor Transduction Using the Herpes Simplex Virus Thymidine Kinase Gene/Acyclovir System / 대한비뇨기과학회지

PURPOSE: The goal of this in vivo study is to determine the feasibility and efficacy of suicide gene therapy using adenovirus-mediated herpes simplex virus thymidine kinase (HSV-TK) and the prodrug acyclovir (ACV) system in animal model of human prostate cancer. MATERIALS AND METHODS: We used a replication-defective adenoviral vector containing the beta-galactosidase gene (Ad-CMV-beta-gal) as a control and Adenovirus-Cytomegalovirus-Thymidine Kinase (Ad-CMV-TK) as the therapeutic vector under the trascriptional control of the CMV promoter. Transduction efficiency was assessed in vitro by infection of LNCaP and PC-3 human prostate cancer cells with Ad-CMV-beta-gal utilizing X-gal staining. TK activity in LNCaP and PC-3 cells infected with Ad-CMV-TK was determined by measuring the TK-mediated [3H]-Ganciclovir (GCV) phosphorylation. Sensitivity of LNCaP and PC-3 cells to Ad-CMV-TK in vitro was determined after infection of therapeutic vector with or without ACV. Subcutaneous tumors were established in athymic nude(nu/nu) mice with PC-3 cells, and Ad-CMV-TK/ACV sucide gene therapeutic system-induced inhibition of tumor growth in vivo was determined in separate and controlled experiments. RESULTS: The mean TK activity was significantly higher in Ad-CMV-TK-infected LNCaP and PC-3 cells than in cells infected with Ad-CMV-beta-gal that was used as a control(P<0.05). The growth of human prostate cancer cells with Ad-CMV-TK was significantly inhibited by the addition of GCV in vitro(p<0.05). In vivo experiments using PC-3 human prostate cancer animal model demonstrated that tumor volume and growth at the conclusion of experiment was significantly attenuated in the suicide toxic gene therapy (Ad-CMV-TK / ACV) group compared with Ad-CMV-TK, ACV and no treatment control groups(p<0.05). CONCLUSIONS: Adenovirus-mediated suicide gene therapy using HSV-TK / ACV system provides an effective therapy in an experimental human prostate cancer animal model by significantly inhibiting tumor growth.

VP22 Enhanced Intercellular Trafficking of HSV Thymidine Kinase Promoted an Effective Cell Killing Effect at Lower Concentration of Ganciclovir / 中国肿瘤生物治疗杂志

Objective: To explore the enhanced cell killing effect of HSV tk using VP22 intercellular traffciking. Methods: The chimeric genes were constructed by fusing a marker gene for the green fluorescent protein (GFP) or a prodrug enzyme gene for the Herpes simplex virus thymidine kinase (HSV tk) with that of VP22. After being sequenced, the fusion genes were transferred into 293T or COS7 cells. The transfection efficiency and intercellular trafficking were certified using Western blot and immunofluorescence.The cell proliferation was detected through MTT method in the different concentration of GCV and under indicated between transfected cells and untransfected cells. The supernatant of transfected cells was used to culture the untransfected cells to test whether the bystander effect could transferred by media. Results: The gene insertion was proved correct using PCR and DNA sequencing. When the fusion genes were transferred into 293T or COS7 cells at transfection efficiency of 25%～30%, fusion proteins were expressed and efficient intercellular trafficking was demonstrated.The VP22 HSV tk, as a prodrug enzyme fused with VP22, showed an amplified cell killing effect in the presence of GCV as low as 0.1 ?g/ml. Further quantification of the bystander effect showed that cell killing increased with higher proportion of VP22 HSV tk expressing cells. The bystander effect could not be transferred through media. Conclusion: These results clearly indicate that VP22 enhanced intercellular trafficking promotes tumor cell killing effect of HSV tk/GCV.

The relationship of gap junction with the bystander effect in the HSV-TK/GCV treatment / 中国药理学通报

The bystander effect(BE) plays an important role in the gene therapy of cancer by the herpes thymidine kinase/ganciclovir(HSV-TK/GCV) system.It enhances the therapeutic efficacy of this system.Up to now,the exact underlying mechanism of the bystander effect remains unclear.A large body of evidence has indicated a close correlation of the connexin expression and gap junction in the targeted cells to the bystander effect.Here the publications concerning the relationship of gap junction with the bystander effect in the HSV-TK/GCV treatment have been reviewed.The possible cell death signals that can be transferred through gap junction to induce the bystander effect are also discussed.

The synergistic effect of Danshen injection combining with suicide gene tk/GCV system / 中国药理学通报

Aim To investigate the curative effect of Danshen injection combining with HSV-tk/GCV system on rats′ hepatocarcinoma cells and murine transplanted hepatocarcinoma.Methods ① Rats′ hepatocarcinoma cell line CBRH7919(tk~-),CBRH7919/tk(tk~+) and the 5% tk~+ mixed cells were treated with diverse concentrations of Danshen injection,GCV separately,and Danshen injection plus GCV(n=3).The survival rate of each groups was examined using MTT Assay and was analyzed using paired comparison.Q-value analysis method was used to estimate the synergistic effect of Chinese herbal on the suicide gene system.Q-value is a ratio of the actural effect of combination treatment to its theoretical effect.It is thought to be an additive effect when 0.85≤Q