Minicircle-IFNgamma induces antiproliferative and antitumoral effects in human nasopharyngeal carcinoma

Evaluation of BMP-2 Minicircle DNA for Enhanced Bone Engineering and Regeneration

BACKGROUND

To date, the significant osteoinductive potential of bone morphogenetic protein 2 (BMP-2) non-viral gene therapy cannot be fully exploited therapeutically. This is mainly due to weak gene delivery and brief expression peaks restricting the therapeutic effect.

OBJECTIVE

Our objective was to test the application of minicircle DNA, allowing prolonged expression potential. It offers notable advantages over conventional plasmid DNA. The lack of bacterial sequences and the resulting reduction in size, enables safe usage and improved performance for tissue regeneration.

METHODS

We inserted an optimized BMP-2 gene cassette with minicircle plasmid technology. BMP-2 minicircle plasmids were produced in E. coli yielding plasmids lacking bacterial backbone elements. Comparative studies of these BMP-2 minicircles and conventional BMP-2 plasmids were performed in vitro in cell systems, including bone marrow derived stem cells. Tests performed included gene expression profiles and cell differentiation assays.

RESULTS

A C2C12 cell line transfected with the BMP-2-Advanced minicircle showed significantly elevated expression of osteocalcin, alkaline phosphatase (ALP) activity, and BMP-2 protein amount when compared to cells transfected with conventional BMP-2-Advanced plasmid. Furthermore, the plasmids show suitability for stem cell approaches by showing significantly higher levels of ALP activity and mineralization when introduced into human bone marrow stem cells (BMSCs).

CONCLUSION

We have designed a highly bioactive BMP-2 minicircle plasmid with the potential to fulfil clinical requirements for non-viral gene therapy in the field of bone regeneration.

Repair of Retinal Degeneration following Ex Vivo Minicircle DNA Gene Therapy and Transplantation of Corrected Photoreceptor Progenitors

The authors describe retinal reconstruction and restoration of visual function in heritably blind mice missing the rhodopsin gene using a novel method of ex vivo gene therapy and cell transplantation. Photoreceptor precursors with the same chromosomal genetic mutation were treated ex vivo using minicircle DNA, a non-viral technique that does not present the packaging limitations of adeno-associated virus (AAV) vectors. Following transplantation, genetically modified cells reconstructed a functional retina and supported vision in blind mice harboring the same founder gene mutation. Gene delivery by minicircles showed comparable long-term efficiency to AAV in delivering the missing gene, representing the first non-viral system for robust treatment of photoreceptors. This important proof-of-concept finding provides an innovative convergence of cell and gene therapies for the treatment of hereditary neurodegenerative disease and may be applied in future studies toward ex vivo correction of patient-specific cells to provide an autologous source of tissue to replace lost photoreceptors in inherited retinal blindness. This is the first report using minicircles in photoreceptor progenitors and the first to transplant corrected photoreceptor precursors to restore vision in blind animals.

Pushing the Right Buttons: Improving Efficacy of Therapeutic DNA Vectors

Gene therapy represents a potent therapeutical application for regenerative medicine. So far, viral and nonviral approaches suffer from major drawbacks hindering efficient gene therapeutic applicability: the immunogenicity of viral systems on the one hand, and the low gene transfer efficiency of nonviral systems on the other hand. Therefore, there is a high demand for improvements of therapeutical systems at several levels. This review summarizes different DNA vector modifications to enhance biological efficacy and efficiency of therapeutical vectors, aiming for low toxicity, high specificity, and biological efficacy-the cornerstones for successful translation of gene therapy into the clinic. We aim to provide a step-by-step instruction to optimize their vectors to achieve the desired outcome of gene therapy. Our review provides the means to either construct a potent gene therapeutic vector de novo or to specifically address a bottleneck in the chain of events mandatory for therapeutic success. Although most of the introduced techniques can be translated into different areas, this review primarily addresses improvements for applications in transient gene therapy in the field of tissue engineering.

Advances in Non-Viral DNA Vectors for Gene Therapy

Uses of viral vectors have thus far eclipsed uses of non-viral vectors for gene therapy delivery in the clinic. Viral vectors, however, have certain issues involving genome integration, the inability to be delivered repeatedly, and possible host rejection. Fortunately, development of non-viral DNA vectors has progressed steadily, especially in plasmid vector length reduction, now allowing these tools to fill in specifically where viral or other non-viral vectors may not be the best options. In this review, we examine the improvements made to non-viral DNA gene therapy vectors, highlight opportunities for their further development, address therapeutic needs for which their use is the logical choice, and discuss their future expansion into the clinic.

Towards effective non-viral gene delivery vector

Despite very good safety records, clinical trials using plasmid DNA failed due to low transfection efficiency and brief transgene expression. Although this failure is both due to poor plasmid design and to inefficient delivery methods, here we will focus on the former. The DNA elements like CpG motifs, selection markers, origins of replication, cryptic eukaryotic signals or nuclease-susceptible regions and inverted repeats showed detrimental effects on plasmids' performance as biopharmaceuticals. On the other hand, careful selection of promoter, polyadenylation signal, codon optimization and/or insertion of introns or nuclear-targeting sequences for therapeutic protein expression can enhance the clinical efficacy. Minimal vectors, which are devoid of the bacterial backbone and consist exclusively of the eukaryotic expression cassette, demonstrate better performance in terms of expression levels, bioavailability, transfection rates and increased therapeutic effects. Although the results are promising, minimal vectors have not taken over the conventional plasmids in clinical trials due to challenging manufacturing issues.

Minicircle-oriP-miR-31 as a Novel EBNA1-Specific miRNA Therapy Approach for Nasopharyngeal Carcinoma

MicroRNAs (miRNAs) are important post-transcriptional regulators that control cancer development and progression. However, the application of miRNA therapy in cancer has been hampered by a lack of an efficient and targeted delivery system. In our previous studies, an oriP promoter-based minicircle system successfully mediated targeted foreign gene expression in EBNA1-positive nasopharyngeal carcinoma (NPC). However, it remains to be evaluated whether this system can be applied for tumor miRNA therapy. miR-31-5p, a tumor suppressive miRNA involved in the tumorigenesis of EBV-positive NPC, was selected as the therapeutic miRNA to be transferred. In this work, we constructed a novel EBNA1-specific miRNA expression system, minicircle-oriP-miR-31. The results indicated that mc-oriP-miR-31 mediated selective miR-31-5p expression in EBNA1-positive NPC cells. Both the proliferation and migration of EBNA1-positive NPC cell lines were inhibited by mc-oriP-miR-31 treatment in vitro. Furthermore, mc-oriP-miR-31 treatment inhibited xenograft growth and lung metastasis in vivo. We also identified WDR5 as a novel miR-31-5p target. Knockdown of WDR5 inhibited NPC cell proliferation and migration and was associated with downregulation of Notch1. Reintroduction of WDR5 partially abrogated the suppressive effects induced by miR-31-5p. In conclusion, we demonstrate for the first time that targeted expression of miR-31-5p using a nonviral minicircle vector can serve as a novel approach for tumor miRNA therapy. Moreover, WDR5 may be a promising therapeutic target for NPC treatment.

E10A, an adenovirus carrying human endostatin gene, in combination with docetaxel treatment inhibits prostate cancer growth and metastases

E10A, a replication-defective adenovirus carrying human endostatin gene, has finished Phase I clinical trials for solid cancers. We assessed whether the combination of E10A with docetaxel would enhance antiangiogenic activities and inhibit prostate cancer growth and metastases. Combination use of conditioned medium from prostate cancer cells infected by E10A and docetaxel exerted synergistic inhibition of HUVECs proliferation, migration and tube formation, compared with either agent alone. In prostate cancer s.c. xenograft models, combined therapy resulted in significant tumor growth inhibition and survival improvement. The antitumoral effect was tightly correlated with a remarkable decrease in tumor cell proliferation, microvessel, especially immature vasculature and significant increase in apoptosis induction. Systemic administration of E10A and docetaxel also effectively inhibited orthotopic growth and metastases of prostate cancer and achieved better in vivo antiangiogenic effects than either agent alone. Our data indicate that E10A in combination with docetaxel exert enhanced antiangiogenic activities and inhibit prostate cancer growth and metastases. Therefore, this approach may be an effective treatment for advanced prostate cancer and deserves more extensive investigation.

Minicircle DNA vectors for gene therapy: advances and applications

INTRODUCTION

Nucleic-acid-based biopharmaceuticals enclose a remarkable potential for treating debilitating or life-threatening diseases that currently remain incurable. This promising area of research envisages the creation of state-of-the-art DNA vaccines, pluripotent cells or gene-based therapies, which can be used to overcome current issues. To achieve this goal, DNA minicircles are emerging as ideal nonviral vectors due to their safety and persistent transgene expression in either quiescent or actively dividing cells.

AREAS COVERED

This review focuses on the characteristics of minicircle DNA (mcDNA) technology and the current advances in their production. The possible modifications to further improve minicircle efficacy are also emphasized and discussed in light of recent advances. As a final point, the main therapeutic applications of mcDNA are summarized, with a special focus on pluripotent stem cells production and cancer therapy.

EXPERT OPINION

Achieving in-target and persistent transgene expression is a challenging issue that is of critical importance for a successful therapeutic outcome. The use of miniaturized mcDNA cassettes with additional modifications that increase and prolong expression may contribute to an improved generation of biopharmaceuticals. The unique features of mcDNA render it an attractive alternative to overcome current technical issues and to bridge the significant gap that exists between basic research and clinical applications.

Sustained expression from DNA vectors

DNA vectors have the potential to become powerful medical tools for treatment of human disease. The human body has, however, developed a range of defensive strategies to detect and silence foreign or misplaced DNA, which is more typically encountered during infection or chromosomal damage. A clinically relevant human gene therapy vector must overcome or avoid these protections whilst delivering sustained levels of therapeutic gene product without compromising the vitality of the recipient host. Many non-viral DNA vectors trigger these defense mechanisms and are subsequently destroyed or rendered silent. Thus, without modification or considered design, the clinical utility of a typical DNA vector is fundamentally limited due to the transient nature of its transgene expression. The development of safe and persistently expressing DNA vectors is a crucial prerequisite for its successful clinical application and subsequently remains, therefore, one of the main strategic tasks of non-viral gene therapy research. In this chapter we will describe our current understanding of the mechanisms that can destroy or silence DNA vectors and discuss strategies, which have been utilized to improve their sustenance and the level and duration of their transgene expression.

Functional expression of chloride channels and their roles in the cell cycle and cell proliferation in highly differentiated nasopharyngeal carcinoma cells

We previously demonstrated that the growth of the poorly differentiated nasopharyngeal carcinoma cells (CNE‐2Z) was more dependent on the activities of volume‐activated chloride channels than that of the normal nasopharyngeal epithelial cells (NP69‐SV40T). However, the activities and roles of such volume‐activated chloride channels in highly differentiated nasopharyngeal carcinoma cells (CNE‐1) are not clarified. In this study, it was found that a volume‐activated chloride current and a regulatory volume decrease (RVD) were induced by 47% hypotonic challenges. The current density and the capacity of RVD in the highly differentiated CNE‐1 cells were lower than those in the poorly differentiated CNE‐2Z cells, and higher than those in the normal cells (NP69‐SV40T). The chloride channel blockers, 5‐nitro‐2‐(3‐phenylpropylamino) benzoic acid (NPPB) and tamoxifen inhibited the current and RVD. Depletion of intracellular Cl⁻ abolished the RVD. The chloride channel blockers reversibly inhibited cell proliferation in a concentration‐ and time‐dependent manner, and arrested cells at the G0/G1 phases, but did not change cell viability. The sensitivity of the three cell lines to the chloride channel blockers was different, with the highest in poorly differentiated cells (CNE‐2Z) and the lowest in the normal cells (NP69‐SV40T). ClC‐3 proteins were expressed in the three cells and distributed inside the cells as well as on the cell membrane. In conclusion, the highly differentiated nasopharyngeal carcinoma CNE‐1 cells functionally expressed the volume‐activated chloride channels, which may play important roles in controlling cell proliferation through modulating the cell cycle, and may be associated with cell differentiation. Chloride channels may be a potential target of anticancer therapy.

In this paper, we demonstrated that the volume‐activated chloride channels were involved in regulating CNE‐1 cells proliferation and cell cycle progress. Thus, volume‐activated chloride channels may be a potential target of anticancer therapy.

Applying horizontal gene transfer phenomena to enhance non-viral gene therapy

Horizontal gene transfer (HGT) is widespread amongst prokaryotes, but eukaryotes tend to be far less promiscuous with their genetic information. However, several examples of HGT from pathogens into eukaryotic cells have been discovered and mimicked to improve non-viral gene delivery techniques. For example, several viral proteins and DNA sequences have been used to significantly increase cytoplasmic and nuclear gene delivery. Plant genetic engineering is routinely performed with the pathogenic bacterium Agrobacterium tumefaciens and similar pathogens (e.g. Bartonella henselae) may also be able to transform human cells. Intracellular parasites like Trypanosoma cruzi may also provide new insights into overcoming cellular barriers to gene delivery. Finally, intercellular nucleic acid transfer between host cells will also be briefly discussed. This article will review the unique characteristics of several different viruses and microbes and discuss how their traits have been successfully applied to improve non-viral gene delivery techniques. Consequently, pathogenic traits that originally caused diseases may eventually be used to treat many genetic diseases.

In vivo electroporation of minicircle DNA as a novel method of vaccine delivery to enhance HIV-1-specific immune responses

DNA vaccines offer advantage over conventional vaccines, as they are safer to use, easier to produce, and able to induce humoral as well cellular immune responses. Unfortunately, no DNA vaccines have been licensed for human use for the difficulties in developing an efficient and safe in vivo gene delivery system. In vivo electroporation (EP)-based DNA delivery has attracted great attention for its potency to enhance cellular uptake of DNA vaccines and function as an adjuvant. Minicircle DNA (a new form of DNA containing only a gene expression cassette and lacking a backbone of bacterial plasmid DNA) is a powerful candidate of gene delivery in terms of improving the levels and the duration of transgene expression in vivo. In this study, as a novel vaccine delivery system, we combined in vivo EP and the minicircle DNA carrying a codon-optimized HIV-1 gag gene (minicircle-gag) to evaluate the immunogenicity of this system. We found that minicircle-gag conferred persistent and high levels of gag expression in vitro and in vivo. The use of EP delivery further increased minicircle-based gene expression. Moreover, when delivered by EP, minicircle-gag vaccination elicited a 2- to 3-fold increase in cellular immune response and a 1.5- to 3-fold augmentation of humoral immune responses compared with those elicited by a pVAX1-gag positive control. Increased immunogenicity of EP-assisted minicircle-gag may benefit from increasing local antigen expression, upregulating inflammatory genes, and recruiting immune cells. Collectively, in vivo EP of minicircle DNA functions as a novel vaccine platform that can enhance efficacy and immunogenicity of DNA vaccines.

Efficient sleeping beauty DNA transposition from DNA minicircles

DNA transposon-based vectors have emerged as new potential delivery tools in therapeutic gene transfer. Such vectors are now showing promise in hematopoietic stem cells and primary human T cells, and clinical trials with transposon-engineered cells are on the way. However, the use of plasmid DNA as a carrier of the vector raises safety concerns due to the undesirable administration of bacterial sequences. To optimize vectors based on the Sleeping Beauty (SB) DNA transposon for clinical use, we examine here SB transposition from DNA minicircles (MCs) devoid of the bacterial plasmid backbone. Potent DNA transposition, directed by the hyperactive SB100X transposase, is demonstrated from MC donors, and the stable transfection rate is significantly enhanced by expressing the SB100X transposase from MCs. The stable transfection rate is inversely related to the size of circular donor, suggesting that a MC-based SB transposition system benefits primarily from an increased cellular uptake and/or enhanced expression which can be observed with DNA MCs. DNA transposon and transposase MCs are easily produced, are favorable in size, do not carry irrelevant DNA, and are robust substrates for DNA transposition. In accordance, DNA MCs should become a standard source of DNA transposons not only in therapeutic settings but also in the daily use of the SB system.

Adenovirus-mediated delivery of interferon-γ gene inhibits the growth of nasopharyngeal carcinoma

Background

Interferon-γ (IFN-γ) is regarded as a potent antitumor agent, but its clinical application is limited by its short half-life and significant side effects. In this paper, we tried to develop IFN-γ gene therapy by a replication defective adenovirus encoding the human IFN-γ (Ad-IFNγ), and evaluate the antitumoral effects of Ad-IFNγ on nasopharyngeal carcinoma (NPC) cell lines in vitro and in xenografts model.

Methods

The mRNA levels of human IFN-γ in Ad-IFNγ-infected NPC cells were detected by reverse transcription-polymerase chain reaction (RT-PCR), and IFN-γ protein concentrations were measured by enzyme-linked immunosorbent assay (ELISA) in the culture supernatants of NPC cells and tumor tissues and bloods of nude mice treated with Ad-IFNγ. The effects of Ad-IFNγ on NPC cell proliferation was determined using MTT assay, cell cycle distribution was determined by flow cytometry analysis for DNA content, and cells apoptosis were analyzed by Annexin V-FITC/7-AAD binding assay and hoechst 33342/PI double staining. The anti-tumor effects and toxicity of Ad-IFNγ were evaluated in BALB/c nude mice carrying NPC xenografts.

Results

The results demonstrated that Ad-IFNγ efficiently expressed human IFN-γ protein in NPC cell lines in vitro and in vivo. Ad-IFNγ infection resulted in antiproliferative effects on NPC cells by inducing G1 phase arrest and cell apoptosis. Intratumoral administration of Ad-IFNγ significantly inhibited the growth of CNE-2 and C666-1 cell xenografts in nude mice, while no significant toxicity was observed.

Conclusions

These findings indicate IFN-γ gene therapy mediated by replication defective adenoviral vector is likely a promising approach in the treatment of nasopharyngeal carcinoma.

Early growth response protein-1 promoter-mediated synergistic antitumor effect of hTERTC27 gene therapy and 5-Flurorouracil on nasopharyngeal carcinoma

hTERTC27 is a newly constructed polypeptide that can induce telomere dysfunction. To study the synergistic antitumor effects of the hTERTC27 polypeptide driven by the early growth response protein-1 (Egr-1) promoter and chemotherapeutic 5-flurorouracil (5-FU) on nasopharyngeal carcinoma, a series of in vitro and in vivo experiments were performed. The results showed that hTERTC27 expression was significantly increased up to 7.21-folds by the 5-FU-activated Egr-1 promoter in C666-1 cells. Overexpressed hTERTC27 made the cells more sensitive to 5-FU, and additionally, inhibited cell proliferation about 20.41%. Combinational therapy of overexpressed hTERTC27 driven by the 5-FU-activated Egr-1 promoter and 5-FU synergistically inhibited cell proliferation and promoted apoptosis of C666-1 cells for about 4.75-fold and 1.76-fold in comparison with a sole therapy of hTERTC27 or 5-FU in vitro. In vivo experiments showed that overexpressed hTERTC27 driven by 5-FU-activated Egr-1 promoter and 5-FU synergistically reduced tumor volume, tumor weight, and local infiltration, which may be relative to tumor cell apoptosis. These results suggest that combinational therapy of overexpressed hTERTC27, which is driven by the 5-FU-activated Egr-1 promoter, and 5-FU may provide a novel approach to treat nasopharyngeal cancer.

Mc-hES, a novel plasmid carrying human endostatin gene, inhibits nasopharyngeal carcinoma growth

Conventional plasmids for gene therapy produce low-level and short-term gene expression. Here, we first created minicircle carrying endostatin (mc-hES) for measurement of transfection efficiency. Compared with pcDNA-hES, MC-mediated endostatin gene transfer in vitro resulted in seven-fold greater endostatin expression levels in transfected cells and inhibited the growth of Human umbilical vein endothelial cells (HUVEC) more efficiently. HUVEC cell migration and tube-formation assays suggested that MC-mediated endostatin gene has significant anti-migration and anti-tube-formation capacity than that in pcDNA-hES. In vivo experiments showed that after transfection, mc-hES inhibited the growth of nasopharyngeal carcinoma xenografts. The tumor inhibition rates of mc-hES and pcDNA-hES were 60.8% and 26.9%, respectively (P<0.05). MC-mediated intratumoral endostatin expression in vivo was 2.2-17.9 times higher than pcDNA-hES in xenografted mice and lasted for 20 days. Our results suggest that minicircle DNA vectors might be a promising vector for biotherapy and should be further investigated.

New generation of plasmid backbones devoid of antibiotic resistance marker for gene therapy trials

Since it has been established that the injection of plasmid DNA can lead to an efficient expression of a specific protein in vivo, nonviral gene therapy approaches have been considerably improved, allowing clinical trials. However, the use of antibiotic resistance genes as selection markers for plasmid production raises safety concerns which are often pointed out by the regulatory authorities. Indeed, a horizontal gene transfer to patient's bacteria cannot be excluded, and residual antibiotic in the final product could provoke allergic reactions in sensitive individuals. A new generation of plasmid backbones devoid of antibiotic resistance marker has emerged to increase the safety profile of nonviral gene therapy trials. This article reviews the existing strategies for plasmid maintenance and, in particular, those that do not require the use of antibiotic resistance genes. They are based either on the complementation of auxotrophic strain, toxin-antitoxin systems, operator-repressor titration, RNA markers, or on the overexpression of a growth essential gene. Minicircles that allow removing of the antibiotic resistance gene from the initial vector will also be discussed. Furthermore, reported use of antibiotic-free plasmids in preclinical or clinical studies will be listed to provide a comprehensive view of these innovative technologies.

Minicircle-oriP-IFNγ: a novel targeted gene therapeutic system for EBV positive human nasopharyngeal carcinoma

Background

Nonviral vectors are attractively used for gene therapy owing to their distinctive advantages. Our previous study has demonstrated that transfer of human IFNγ gene into nasopharyngeal carcinoma (NPC) by using a novel nonviral vector, minicircle (mc), under the control of cytomegalovirus (CMV) promoter was effective to inhibit tumor growth. However, therapies based on CMV promoter cannot express the targeted genes in cancer tissues. Previous studies indicated that the development of human NPC was closely associated with Epstein-Barr virus (EBV) and demonstrated the transcriptional enhancer function of oriP when bound by EBV protein. Therefore, the present study is to explore the targeted gene expression and the anti-tumor effect of a novel tumor-specific gene therapeutic system (mc-oriP-IFNγ) in which the transgene expression was under the transcriptional regulation of oriP promoter.

Methodology/Principal Findings

Dual-luciferase reporter assay and ELISA were used to assess the expression of luciferase and IFNγ. WST assay was used to assess the cell proliferation. RT-PCR was used to detect the mRNA level of EBNA1. RNAi was used to knockdown the expression of EBNA1. NPC xenograft models in nude mice were used to investigate the targeted antitumor efficacy of mc-oriP-IFNγ. Immunohistochemistry was used to detect the expression and the activity of the IFNγ in tumor sections. Our results demonstrated that mc-oriP vectors mediated comparable gene expression and anti-proliferative effect in the EBV-positive NPC cell line C666-1 compared to mc-CMV vectors. Furthermore, mc-oriP vectors exhibited much lower killing effects on EBV-negative cell lines compared to mc-CMV vectors. The targeted expression of mc-oriP vectors was inhibited by EBNA1-siRNA in C666-1. This selective expression was corroborated in EBV-positive and -negative tumor models.

Conclusions/Significance

This study demonstrates the feasibility of mc-oriP-IFNγ as a safe and highly effective targeted gene therapeutic system for the treatment of EBV positive NPC.

Advancement and prospects of tumor gene therapy

Gene therapy is one of the most attractive fields in tumor therapy. In past decades, significant progress has been achieved. Various approaches, such as viral and non-viral vectors and physical methods, have been developed to make gene delivery safer and more efficient. Several therapeutic strategies have evolved, including gene-based (tumor suppressor genes, suicide genes, antiangiogenic genes, cytokine and oxidative stress-based genes) and RNA-based (antisense oligonucleotides and RNA interference) approaches. In addition, immune response-based strategies (dendritic cell- and T cell-based therapy) are also under investigation in tumor gene therapy. This review highlights the progress and recent developments in gene delivery systems, therapeutic strategies, and possible clinical directions for gene therapy.

Anti-tumor effect of 125I-UdR in combination with Egr-1 promoter-based IFNγ gene therapy in vivo

Although (125)I-UdR treatment of malignant tumors in animal models and patients has achieved a certain effect, the short half-life of (125)I-UdR in vivo and its cellular uptake only in S phase of the cell cycle are limiting factors with regard to tumor eradication, and therefore its combination with other applications is a promising strategy in cancer therapy. In this study, we show that (125)I-UdR radionuclide therapy in combination with Egr-1 promoter-based IFNγ gene therapy is more effective than (125)I-UdR therapy alone in suppressing tumor growth and extending survival duration in mice bearing H22 hepatomas. Combined therapy could significantly inhibit cell proliferation and tumor angiogenesis, induce apoptosis and enhance cytotoxic activities of splenic CTL of the mice. Our results suggest that (125)I-UdR in combination with Egr-1 promoter-based IFNγ gene therapy may provide novel approaches for cancer treatment.

Gene transfer to mouse heart and skeletal muscles using a minicircle expressing human vascular endothelial growth factor

BACKGROUND

: Gene transfer to heart muscle is a promising modality to treat ischemic heart disease. However, current vectors are inefficient and need to be improved. A novel vector system that shows great promise is the minicircle (MC) vector being smaller than conventional plasmid vectors and devoid of bacterial sequences.

AIMS

: To study gene transfer of MC DNA, expressing the human vascular endothelial growth factor (hVEGF), to mouse heart and skeletal muscles and to compare it with one of the efficient plasmids used in cardiovascular trials, the phVEGF165 containing the same expression cassette as the MC.

RESULTS

: The MC and the phVEGF165 plasmid show similar expression patterns both in vitro and in mouse heart and skeletal muscle studies in vivo on molar basis (equal expression in heart 24 hours, 0.9 fold lower expression from MC in heart and 1.9 fold higher in skeletal muscle at 7 days), whereas on weight basis the MC construct was more efficient in skeletal muscle (5.6 fold higher expression, P < 0.05), and at least as efficient in heart (1.6 fold higher expression).

CONCLUSIONS

: The gene expression is similar in the 2 vector systems, so the smaller size and the fact that the MC construct is devoid of bacterial sequences and antibiotics resistance gene make the MC vector an attractive alternative for nonviral gene therapy.

Association of ABCC2 and CDDP-Resistance in Two Sublines Resistant to CDDP Derived from a Human Nasopharyngeal Carcinoma Cell Line

Cisplatin (CDDP) is one of the most active drugs to treat nasopharyngeal carcinoma (NPC) patients. To further understand the mechanisms of CDDP-resistance in NPC, two CDDP-resistant sublines (CNE2-CDDP and CNE2-CDDP-5Fu) derived from parental NPC cell line CNE2 were established. It was found that at the IC50 level, the resistance of CNE2-CDDP and CNE2-CDDP-5Fu against CDDP was 2.63-fold and 5.35-fold stronger than that of parental CNE2, respectively. Of the four ABC transporters (ABCB1, ABCC1, ABCC2 and ABCG2) related to MDR, only ABCC2 was found to be elevated both in CDDP-resistant sublines, with ABCC2 located in nucleus of CNE2-CDDP-5Fu but not in CNE2-CDDP and parental CNE2. Further research showed that compared to untreated CNE2, the intracellular levels of CDDP were decreased by 2.03-fold in CNE2-CDDP and 2.78-fold in CNE2-CDDP-5Fu. After treatment with PSC833, a modulator of MDR associated transporters including ABCC2, the intracellular level of CDDP was increased in CDDP-resistant sublines, and the resistance to CDDP was partially reversed from 2.63-fold to 1.62-fold in CNE2-CDDP and from 5.35-fold to 4.62-fold in CNE2-CDDP-5Fu. These data indicate that ABCC2 may play an important role in NPC resistant to CDDP.

ZD6474 inhibits Src kinase leading to apoptosis of imatinib-resistant K562 cells

ZD6474 is an orally available, small-molecule tyrosine kinase inhibitor. This study explores the effect of ZD6474 on imatinib-resistant K562 cell lines, which show markedly increased SRC family kinases (SFKs) activity. ZD6474 induces growth arrest and apoptosis of imatinib-resistant and parental K562 cells, as well as inhibition of Src activity and its downstream effectors, the anti-apoptotic Bcl-2 family. ZD6474 treatment also inhibits the activity of STAT3 and reactivation of its activity results in suppression of the anti-tumor effects of SFKs inhibitors. A single oral administration of ZD6474 produced dose-dependent inhibition of imatinib-resistant K562 cells xenograft tumors. These results suggest that clinical assessment of ZD6474 against imatinib-resistant CML is warranted.

Dynamic distribution and expression in vivo of the human interferon gamma gene delivered by adenoviral vector

BACKGROUND

We previously found that r-hu-IFNgamma exerts a potent anti-tumor effect on human nasopharyngeal carcinoma xenografts in vivo. Considering the fact that the clinical use of recombinant IFNgamma is limited by its short half-life and systemic side effects, we developed a recombinant adenovirus, Ad-IFNgamma.

METHODS

Dynamic distribution of the adenovirus vector and expression of IFNgamma were evaluated by Q-PCR and ELISA after intratumoral administration of Ad-IFNgamma into CNE-2 xenografts.

RESULTS

Ad-IFNgamma DNA was mainly enriched in tumors where the Ad-IFNgamma DNA was injected (P < 0.05, compared to blood or parenchymal organs), as well as in livers (P < 0.05). Concentrations of Ad-IFNgamma DNA in other organs and blood were very low. Intratumoral Ad-IFNgamma DNA decreased sharply at high concentrations (9 x 10(5) copies/microg tissue DNA), and slowly at lower concentrations (1.7-2.9 x 10(5) copies/microg tissue DNA). IFNgamma was detected in the tumors and parenchymal organs. The concentration of IFNgamma was highest in the tumor (P < 0.05), followed by the liver and kidney (P < 0.05). High-level intratumoral expression of IFNgamma was maintained for at least 7 days, rapidly peaking on day 3 after injection of Ad-IFNgamma DNA.

CONCLUSION

An IFNgamma gene delivered by an adenoviral vector achieved high and consistent intratumoral expression. Disseminated Ad-IFNgamma DNA and the transgene product were mainly enriched in the liver.

Progress and prospects: the design and production of plasmid vectors

Plasmid DNA (pDNA) expression vectors are fundamental to all forms of non-viral gene transfer. In this review, we discuss principles of pDNA design and production including the impact of bacterially derived sequences on transgene expression and minicircle approaches to minimize their effects. The impact of inclusion of DNA elements such as scaffold matrix attachment regions (S/MARs), transcription factor (TF)-binding sites and tissue-specific promoters are described. The benefits of eliminating CG dinucleotides (CpGs) from the pDNA are also considered.

Use of minicircle plasmids for gene therapy

A large number of cancer gene therapy clinical trials are currently being performed that are attempting to evaluate novel approaches to eliminate tumor cells by the introduction of genetic material into patients. One of the most important objectives in gene therapy is the development of highly safe and efficient vector systems for gene transfer in eukaryotic cells. Currently, viral and nonviral vector systems are used, both having their advantages and limitations. Minicircles are novel supercoiled minimal expression cassettes, derived from conventional plasmid DNA by site-specific recombination in vivo in Escherichia coli for the use in nonviral gene therapy and vaccination. Minicircle DNA lacks the bacterial backbone sequence consisting of an antibiotic resistance gene, an origin of replication, and inflammatory sequences intrinsic to bacterial DNA. In addition to their improved safety profile, minicircles have been shown to greatly increase the efficiency oftransgene expression in various in vitro and in vivo studies. In this chapter, we describe the production, purification, and application of minicircle DNA and discuss the rationale of the improved gene transfer efficiencies compared to conventional plasmid DNA.

Minicircle-DNA production by site specific recombination and protein-DNA interaction chromatography

BACKGROUND

Conventional plasmid-DNA (pDNA) used in gene therapy and vaccination can be subdivided into a bacterial backbone and a transcription unit. Bacterial backbone sequences are needed for pDNA production in bacteria. However, for gene transfer application, these sequences are dispensable, reduce the overall efficiency of the DNA agent and, most importantly, represent a biological safety risk. For example, the dissemination of antibiotic resistance genes, as well as the uncontrolled expression of backbone sequences, may have profound detrimental effects and unmethylated CpG motifs have been shown to contribute to silencing of episomal transgene expression. Therefore, an important goal in nonviral vector development is to produce supercoiled pDNA lacking bacterial backbone sequences.

METHODS

A method is described to provide circular, supercoiled minimal expression cassettes (minicircle-DNA) based on two processes: (i) an inducible, sequence specific, in vivo recombination process that is almost 100% efficient and (2) a novel affinity-based chromatographic purification approach for the isolation of the minicircle-DNA.

RESULTS

Quantitative real-time polymerase chain reaction analysis, capillary gel electrophoresis and restriction analysis of the recombination products, and the minicircle-DNA revealed a recombination efficiency greater than 99.5% and a purity of the isolated minicircle-DNA of more than 98.5%.

CONCLUSIONS

The results obtained in the present study demonstrate that the described technology facilitates the production of highly pure minicircle-DNA for direct application in gene therapy and vaccination. The process described is efficient, stable and suitable for further scale-up in industrial large-scale manufacturing.

Gene expression profiling for the prediction of lymph node metastasis in patients with cervical cancer

We investigated whether gene expression profiling of primary cervical tumor tissue could be used to predict lymph node (LN) metastasis and compared this with conventional magnetic resonance imaging. We obtained 43 primary cervical cancer samples (16 with LN metastasis and 27 without LN metastasis) for microarray analysis. A prediction model for LN metastasis from the training set was developed by support vector machine methods using a 10-fold cross-validation. The 'LN prediction model' derived from the signature of 156 distinctive genes (P < 0.01) had a prediction accuracy of 77%. Correlation between mRNA expressions measured by microarray and semiquantitative reverse transcription-polymerase chain reaction was ascertained in four (RBM8A, SDHB, SERPINB13, and gamma-interferon) out of 10 genes. Magnetic resonance imaging showed accuracy (69%) for the prediction of LN metastasis. These results suggest that gene expression profiling allows reliable prediction of LN metastasis in cervical cancer.

Induction of cell cycle arrest and apoptosis in human nasopharyngeal carcinoma cells by ZD6474, an inhibitor of VEGFR tyrosine kinase with additional activity against EGFR tyrosine kinase

ZD6474 is a vascular endothelial growth factor receptor (VEGFR) and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor. The present study was undertaken to investigate the direct antiproliferative effect of ZD6474 on human nasopharyngeal carcinoma (NPC) in vitro and the antitumor activity on NPC xenografts in vivo. Results indicated that ZD6474 treatment inhibited EGFR phosphorylation and led to a dose- and time-dependent decrease in NPC cell (CNE-1, CNE-2 and C666-1) proliferation. Further investigation demonstrated G0/G1 cell cycle arrest in all 3 cell lines, which was associated with an upregulation of p21 and/or p27, and downregulation of CDK4, CDK6 and CDK2. ZD6474 treatment also induced apoptosis in CNE-1 and CNE-2 cells. The apoptosis mechanisms involved reduction of Bcl-2 and/or Bcl-XL, induction of Bak and/or Bax, and activation of caspases-3, -9 and/or -8. The in vivo antitumor activity was evaluated in CNE-2 and C666-1 xenografted nude mice. Administration of ZD6474 (25-100 mg/kg/day, once-daily, p.o.) produced a dose-dependent inhibition of tumor growth and prolonged survival in both models. This study suggests that ZD6474 exerts direct antiproliferative effects on NPC cell lines in vitro by inducing G0/G1 arrest and apoptosis, and potent antitumor effects on NPC xenografts in vivo. It indicates that ZD6474 may offer a new and effective treatment for human NPC.

Adenovirus-mediated delivery of human IFNγ gene inhibits prostate cancer growth

Interferon gamma (IFNgamma) is regarded as a potent antitumor agent, but therapy with IFNgamma is hampered by its short half-life and significant side effects. We developed a replication defective adenovirus carrying the human IFNgamma gene and evaluated the effects of adenovirus-mediated IFNgamma (Ad-IFNgamma) gene transfer on human prostate cancer cell lines in vitro and on xenografts in vivo. Our results showed infection of prostate cancer cells with Ad-IFNgamma led to production of an active cytokine and resulted in an antiproliferative effect on the prostate cancer cells. Intratumoral injection of Ad-IFNgamma significantly inhibited the growth of DU-145 cell xenografts in vivo, while no significant toxicity effect was observed. RT-PCR analysis indicated transgene expression mainly enriched in tumors in vivo, and slightly distributed in livers. These findings suggest adenovirus-mediated IFNgamma gene transfer is a promising approach in the treatment of advanced prostate cancer.