Gene transfer to hepatocellular carcinoma: transduction efficacy and transgene expression kinetics by using retroviral and lentiviral vectors

Design, Simulation, and Evaluation of Polymer-Based Microfluidic Devices via Computational Fluid Dynamics and Cell Culture "On-Chip"

Organ-on-a-chip (OoC) technology has experienced exponential growth driven by the need for a better understanding of in-organ processes and the development of novel approaches. This paper investigates and compares the flow behavior and filling characteristics of two microfluidic liver-on-a-chip devices using Computational Fluid Dynamics (CFD) analysis and experimental cell culture growth based on the Huh7 cell line. The conducted computational analyses for the two chips showed that the elliptical chamber chip proposed herein offers improved flow and filling characteristics in comparison with the previously presented circular chamber chip. Huh7 hepatoma cells were cultured in the microfluidic devices for 24 h under static fluidic conditions and for 24 h with a flow rate of 3 μL·min^-1. Biocompatibility, continuous flow, and biomarker studies showed cell attachment in the chips, confirming the cell viability and their consistent cell growth. The study successfully analyzed the fluid flow behavior, filling characteristics, and biocompatibility of liver-on-a-chip prototype devices, providing valuable insights to improve design and performance and advance alternative methods of in vitro testing.

Pseudotyped lentiviral vectors: Ready for translation into targeted cancer gene therapy?

Gene therapy holds great promise for curing cancer by editing the deleterious genes of tumor cells, but the lack of vector systems for efficient delivery of genetic material into specific tumor sites in vivo has limited its full therapeutic potential in cancer gene therapy. Over the past two decades, increasing studies have shown that lentiviral vectors (LVs) modified with different glycoproteins from a donating virus, a process referred to as pseudotyping, have altered tropism and display cell-type specificity in transduction, leading to selective tumor cell killing. This feature of LVs together with their ability to enable high efficient gene delivery in dividing and non-dividing mammalian cells in vivo make them to be attractive tools in future cancer gene therapy. This review is intended to summarize the status quo of some typical pseudotypings of LVs and their applications in basic anti-cancer studies across many malignancies. The opportunities of translating pseudotyped LVs into clinic use in cancer therapy have also been discussed.

Development of a Hybrid Polymer-Based Microfluidic Platform for Culturing Hepatocytes towards Liver-on-a-Chip Applications

The drug development process can greatly benefit from liver-on-a-chip platforms aiming to recapitulate the physiology, mechanisms, and functionalities of liver cells in an in vitro environment. The liver is the most important organ in drug metabolism investigation. Here, we report the development of a hybrid cyclic olefin copolymer (COC) and polydimethylsiloxane (PDMS) microfluidic (HCP) platform to culture a Huh7 hepatoma cell line in dynamic conditions towards the development of a liver-on-a-chip system. The microfluidic platform is comprised of a COC bottom layer with a microchannel and PDMS-based flat top layer sandwiched together. The HCP device was applied for culturing Huh7 cells grown on a collagen-coated microchannel. A computational fluid dynamics modeling study was conducted for the HCP device design revealing the presence of air volume fraction in the chamber and methods for optimizing experimental handling of the device. The functionality and metabolic activity of perfusion culture were assessed by the secretion rates of albumin, urea, and cell viability visualization. The HCP device hepatic culture remained functional and intact for 24 h, as assessed by resulting levels of biomarkers similar to published studies on other in vitro and 2D cell models. The present results provide a proof-of-concept demonstration of the hybrid COC–PDMS microfluidic chip for successfully culturing a Huh7 hepatoma cell line, thus paving the path towards developing a liver-on-a-chip platform.

Searching for Promoters to Drive Stable and Long-Term Transgene Expression in Fibroblasts for Syngeneic Mouse Tumor Models

Tumor is a complex system of interactions between cancer cells and other cells of the tumor microenvironment. The cancer-associated fibroblasts (CAFs) of the tumor microenvironment remain in close contact with the cancer cells and play an important role in cancer progression. Genetically, CAFs are more stable than cancer cells, making them an attractive target for genetic modification in gene therapy. However, the efficiency of various promoters for transgene expression in fibroblasts is scarcely studied. We performed a comparative analysis of transgene long-term expression under the control of strong cytomegalovirus promoter (pCMV), constitutive cell promoter of the PCNA gene (pPCNA), and the potentially fibroblast-specific promoter of the IGFBP2 gene (pIGFBP2). In vitro expression of the transgene under the control of pCMV in fibroblasts was decreased soon after transduction, whereas the expression was more stable under the control of pIGFBP2 and pPCNA. The efficiency of transgene expression was higher under pPCNA than that under pIGFBP2. Additionally, in a mouse model, pPCNA provided more stable and increased transgene expression in fibroblasts as compared to that under pCMV. We conclude that PCNA promoter is the most efficient for long-term expression of transgenes in fibroblasts both in vitro and in vivo.

Adeno-Associated Virus Vectors and Stem Cells: Friends or Foes?

The infusion of healthy stem cells into a patient-termed "stem-cell therapy"-has shown great promise for the treatment of genetic and non-genetic diseases, including mucopolysaccharidosis type 1, Parkinson's disease, multiple sclerosis, numerous immunodeficiency disorders, and aplastic anemia. Stem cells for cell therapy can be collected from the patient (autologous) or collected from another "healthy" individual (allogeneic). The use of allogenic stem cells is accompanied with the potentially fatal risk that the transplanted donor T cells will reject the patient's cells-a process termed "graft-versus-host disease." Therefore, the use of autologous stem cells is preferred, at least from the immunological perspective. However, an obvious drawback is that inherently as "self," they contain the disease mutation. As such, autologous cells for use in cell therapies often require genetic "correction" (i.e., gene addition or editing) prior to cell infusion and therefore the requirement for some form of nucleic acid delivery, which sets the stage for the AAV controversy discussed herein. Despite being the most clinically applied gene delivery context to date, unlike other more concerning integrating and non-integrating vectors such as retroviruses and adenovirus, those based on adeno-associated virus (AAV) have not been employed in the clinic. Furthermore, published data regarding AAV vector transduction of stem cells are inconsistent in regards to vector transduction efficiency, while the pendulum swings far in the other direction with demonstrations of AAV vector-induced toxicity in undifferentiated cells. The variation present in the literature examining the transduction efficiency of AAV vectors in stem cells may be due to numerous factors, including inconsistencies in stem-cell collection, cell culture, vector preparation, and/or transduction conditions. This review summarizes the controversy surrounding AAV vector transduction of stem cells, hopefully setting the stage for future elucidation and eventual therapeutic applications.

Orthotopic hepatic cancer: radiofrequency hyperthermia-enhanced intratumoral herpes simplex virus-thymidine kinase gene therapy

Purpose

To validate the feasibility of using interventional radiofrequency hyperthermia(RFH) to enhance herpes simplex virus-thymidine kinase (HSV-TK)/ganciclovir (GCV) gene therapy of rat orthotopic hepatic cancer.

Material and Methods

Rat hepatocellular carcinoma cells (MCA-RH-7777) were transduced with lentivirus/luciferase gene for optical imaging. In-vitro experiments with the luciferase cells and in-vivo experiments on rats with orthotopic hepatic tumors were divided into four treatment groups: (i) HSV-TK/GCV-mediated gene therapy combined with RFH; (ii) gene therapy alone; (iii) RFH alone; and (iv) phosphate buffered saline (PBS). Cell viability was evaluated by MTS assay and confocal microscopy, and HSV-TK gene expression in cells and tumors was quantified by western blotting. Bioluminescent optical imaging and ultrasound imaging were used to monitor and compare the photon signal and tumor size changes among different treatment groups overtime, respectively. The imaging findings were correlated with histology.

Results

For in-vitro experiments, the combination therapy group (gene therapy + RFH) demonstrated the lowest cell proliferation by MTS assay, compared to the gene therapy alone, RFH alone, and PBS (26.1±3.2% vs 50.4±4.6% vs 82.9±6.3% vs 100%, p<0.01). The combination therapy group also showed fewer survived cells by the confocal microscopy and the lowest bioluminescent signal by the optical imaging. For in-vivo experiments, the combination therapy group demonstrated a significantly decreased signal intensity on the bioluminescent optical imaging (0.57±0.09, 1.06±0.10 vs 3.43±0.27 vs 3.85±0.12, p<0.05) and smallest tumor volume by ultrasound imaging (0.28±0.11 vs 1.28±0.23vs 4.64±0.35 vs 6.37±0.36, p<0.05), compared to the other three groups. Additionally, these imaging findings correlated well with the histological confirmation.

Conclusion

It is feasible to use RFH to enhance HSV-TK/GCV gene therapy of hepatic tumors in in-vitro and in-vivo settings, as assessed by molecular imaging. This technical development may provide a novel opportunity for effective treatment of liver malignancies by employing simultaneous integration of radiofrequency technology, interventional oncology, and direct intratumoral gene therapy.

Visualization of the Biological Behavior of Tumor-Associated Macrophages in Living Mice with Colon Cancer Using Multimodal Optical Reporter Gene Imaging

We sought to visualize the migration of tumor-associated macrophages (TAMs) to tumor lesions and to evaluate the effects of anti-inflammatory drugs on TAM-modulated tumor progression in mice with colon cancer using a multimodal optical reporter gene system. Murine macrophage Raw264.7 cells expressing an enhanced firefly luciferase (Raw/effluc) and murine colon cancer CT26 cells coexpressing Rluc and mCherry (CT26/Rluc-mCherry, CT26/RM) were established. CT26/RM tumor-bearing mice received Raw/effluc via their tail veins, and combination of bioluminescence imaging (BLI) and fluorescence imaging (FLI) was conducted for in vivo imaging of TAMs migration and tumor progression. Dexamethasone (DEX), a potent anti-inflammatory drug, was administered intraperitoneally to tumor-bearing mice following the intravenous transfer of Raw/effluc cells. The migration of TAMs and tumor growth was monitored by serial FLI and BLI. The migration of Raw/effluc cells to tumor lesions was observed at day 1, and BLI signals were still distinct at tumor lesions on day 4. Localization of BLI signals from migrated Raw/effluc cells corresponded to that of FLI signals from CT26/RM tumors. In vivo FLI of tumors demonstrated enhanced tumor growth associated with macrophage migration to tumor lesions. Treatment with DEX inhibited the influx of Raw/effluc cells to tumor lesions and abolished the enhanced tumor growth associated with macrophage migration. These findings suggest that molecular imaging approach for TAM tracking is a valuable tool for evaluating the role of TAMs in the tumor microenvironment as well as for the development of new drugs to control TAM involvement in the modulation of tumor progression.

Expression of CHODL in hepatocellular carcinoma affects invasion and migration of liver cancer cells

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-associated death. Due to rapid progression and metastasis, the long-term survival remains poor for most patients. Thus, it is important to discover and develop novel preventive strategies and therapeutic approaches for HCC. Recent data show that chondrolectin (CHODL) is commonly overexpressed in the majority of lung cancers, indicating a possible correlation between CHODL and metastasis of lung cancer cells. Our investigation shows that the expression of CHODL is significantly decreased in HCC clinical samples and in HCC cell lines. Overexpression of CHODL in SMMC7721 cells with a lentiviral vector increased SMMC7721 cell migration and invasion. Our findings establish for the first time an association between human CHODL and HCC metastasis.

Promoter optimisation of lentiviral vectors for efficient insulin gene expression in canine mesenchymal stromal cells: potential surrogate beta cells

BACKGROUND

The lack of an ideal cell type that can be easily acquired, modified to produce insulin, and re-implanted has been a limitation for ex vivo insulin gene therapy. Canine diabetes is currently treated with human insulin and is a good model for human diabetes. Mesenchymal stromal cells (MSCs) are a promising candidate cell type for gene therapy. In the present study, we optimised insulin production using lentiviral transduced canine MSCs (cMSCs), aiming to evaluate their ability for use as surrogate beta cells.

METHODS

Canine MSCs were derived from bone marrow and validated by measuring the expression of MSC lineage specific markers. Lentivirus vectors encoding the proinsulin gene (with or without a Kozak sequence) under the control of spleen focus forming virus, cytomegalovirus, elongation factor 1α and simian virus 40 promotors were generated and used to transduce primary cMSCs and a hepatocyte cell line. The insulin-producing capacity of transduced primary cMSCs was assessed by measuring the concentration of C-peptide produced.

RESULTS

Primary cMSC could be readily expanded in culture and efficiently transduced using lentiviral vectors encoding proinsulin. Increasing the multiplicity of infection from 3 to 20 led to an increase in C-peptide secretion (from 1700 to 4000 pmol/l). The spleen focus forming virus promoter conferred the strongest transcriptional ability.

CONCLUSIONS

The results of the present study suggest that optimised lentiviral transduction of the insulin gene into primary cMSCs renders these cells capable of secreting insulin over both the short- and long-term, in sufficient quantities in vitro to support their potential use in insulin gene therapy.

Safe and Efficient Gene Therapy for Pyruvate Kinase Deficiency

Pyruvate kinase deficiency (PKD) is a monogenic metabolic disease caused by mutations in the PKLR gene that leads to hemolytic anemia of variable symptomatology and that can be fatal during the neonatal period. PKD recessive inheritance trait and its curative treatment by allogeneic bone marrow transplantation provide an ideal scenario for developing gene therapy approaches. Here, we provide a preclinical gene therapy for PKD based on a lentiviral vector harboring the hPGK eukaryotic promoter that drives the expression of the PKLR cDNA. This therapeutic vector was used to transduce mouse PKD hematopoietic stem cells (HSCs) that were subsequently transplanted into myeloablated PKD mice. Ectopic RPK expression normalized the erythroid compartment correcting the hematological phenotype and reverting organ pathology. Metabolomic studies demonstrated functional correction of the glycolytic pathway in RBCs derived from genetically corrected PKD HSCs, with no metabolic disturbances in leukocytes. The analysis of the lentiviral insertion sites in the genome of transplanted hematopoietic cells demonstrated no evidence of genotoxicity in any of the transplanted animals. Overall, our results underscore the therapeutic potential of the hPGK-coRPK lentiviral vector and provide high expectations toward the gene therapy of PKD and other erythroid metabolic genetic disorders.

Gene therapy to treat cardiac arrhythmias

Gene therapy to treat electrical dysfunction of the heart is an appealing strategy because of the limited therapeutic options available to manage the most-severe cardiac arrhythmias, such as ventricular tachycardia, ventricular fibrillation, and asystole. However, cardiac genetic manipulation is challenging, given the complex mechanisms underlying arrhythmias. Nevertheless, the growing understanding of the molecular basis of these diseases, and the development of sophisticated vectors and delivery strategies, are providing researchers with adequate means to target specific genes and pathways involved in disorders of heart rhythm. Data from preclinical studies have demonstrated that gene therapy can be successfully used to modify the arrhythmogenic substrate and prevent life-threatening arrhythmias. Therefore, gene therapy might plausibly become a treatment option for patients with difficult-to-manage acquired arrhythmias and for those with inherited arrhythmias. In this Review, we summarize the preclinical studies into gene therapy for acquired and inherited arrhythmias of the atria or ventricles. We also provide an overview of the technical advances in the design of constructs and viral vectors to increase the efficiency and safety of gene therapy and to improve selective delivery to target organs.

Adeno-associated virus vectors as therapeutic and investigational tools in the cardiovascular system

The use of vectors based on the small parvovirus adeno-associated virus has gained significant momentum during the past decade. Their high efficiency of transduction of postmitotic tissues in vivo, such as heart, brain, and retina, renders these vectors extremely attractive for several gene therapy applications affecting these organs. Besides functional correction of different monogenic diseases, the possibility to drive efficient and persistent transgene expression in the heart offers the possibility to develop innovative therapies for prevalent conditions, such as ischemic cardiomyopathy and heart failure. Therapeutic genes are not only restricted to protein-coding complementary DNAs but also include short hairpin RNAs and microRNA genes, thus broadening the spectrum of possible applications. In addition, several spontaneous or engineered variants in the virus capsid have recently improved vector efficiency and expanded their tropism. Apart from their therapeutic potential, adeno-associated virus vectors also represent outstanding investigational tools to explore the function of individual genes or gene combinations in vivo, thus providing information that is conceptually similar to that obtained from genetically modified animals. Finally, their single-stranded DNA genome can drive homology-directed gene repair at high efficiency. Here, we review the main molecular characteristics of adeno-associated virus vectors, with a particular view to their applications in the cardiovascular field.

The effect of dexamethasone on lentiviral vector infection is associated with importin α

Importin α (Imα) plays an important role during the shuttling of the HIV-1 preintegration complex (PIC) from the cytoplasm to the nucleus. Imα may bind to the glucocorticoid receptor (GR), which is localized to nucleus following hormone binding. However, it remains unclear whether the binding of dexamethasone (Dex) to GR affects the Imα redistribution and, thus, alters PIC import. In our study, 293T cells were transfected with the lentiviral vector (LV) carrying the luciferase (Luci) gene following Dex or RU486 pretreatment. The Luci activity (LucA) in the Dex or RU486 group was significantly higher compared to that in the control group (P≤0.01). The effects of Dex and RU486 were inhibited by the Imα inhibitor Bimax1 (P≤0.01), although the inhibitory effect of Bimax1 was alleviated by increasing the Dex dose. Furthermore, it was observed that the LucA in the 30-min Dex treatment group was lower compared to that in the 30-min Dex pretreatment group (P≤0.01). These results suggested that Dex may improve PIC import via increasing the cytoplasmic Imα levels. Kunming mice were transfected in vivo with the LV, either 30 min or 15 h following an intraperitoneal injection of Dex. The LucA in the liver of the 30-min group mice was significantly lower compared to that of the 15-h group mice (P≤0.01), suggesting that the effect of Dex on LV infection depends mainly on the suppression of immune and inflammatory responses in vivo. Taken together, our data indicated that the effect of Dex on LV infection may be associated with Imα, constituting a novel signaling pathway mediating the effects of Dex on HIV-1 infection.

Cytomegalovirus colitis following azacitidine therapy

The present report describes the first recognized case of cytomegalovirus (CMV) colitis following azacitidine therapy. A 66-year-old woman with myelodysplastic syndrome developed CMV colitis, which responded to treatment with ganciclovir. Currently, patients receiving azacitidine do not undergo CMV testing, or receive prophylaxis or CMV-free blood products; however, this policy needs to be revised.

3' self-inactivating long terminal repeat inserts for the modulation of transgene expression from lentiviral vectors

Gene transfer for research or gene therapy requires the design of vectors that allow for adequate and safe transgene expression. Current methods to modulate the safety and expression profile of retroviral vectors can involve the insertion of insulators or scaffold/matrix-attachment regions in self-inactivating long terminal repeats (SIN-LTRs). Here, we generated a set of lentiviral vectors (with internal CMV or PGK promoter) in which we inserted (at the level of SIN-LTRs) sequences of avian (i.e., chicken hypersensitive site-4, cHS4), human (i.e., putative insulator and desert sequence), or bacterial origin. We characterized them with respect to viral titer, integration, transduction efficiency and transgene expression levels, in both integrase-proficient and -deficient contexts. We found that the cHS4 insulator enhanced transgene expression by a factor of 1.5 only when cloned in the antisense orientation. On the other hand, cHS4 in the sense orientation as well as all other inserts decreased transgene expression. This attenuation phenomenon persisted over long periods of time and did not correspond to extinction or variegation. Decreased transgene expression was associated with lower mRNA levels, yet RNA stability was not affected. Insertions within the SIN-LTRs may negatively affect transgene transcription in a direct fashion through topological rearrangements. The lentiviral vectors that we generated constitute valuable genetic tools for manipulating the level of transgene expression. Moreover, this study demonstrates that SIN-LTR inserts can decrease transgene expression, a phenomenon that might be overcome by modifying insert orientation, thereby highlighting the importance of careful vector design for gene therapy.

Adeno-associated virus gene transfer in Morquio A disease - effect of promoters and sulfatase-modifying factor 1

Mucopolysaccharidosis (MPS) IVA is an autosomal recessive disorder caused by deficiency of the lysosomal enzyme N-acetylgalatosamine-6-sulfate sulfatase (GALNS), which leads to the accumulation of keratan sulfate and chondroitin 6-sulfate, mainly in bone. To explore the possibility of gene therapy for Morquio A disease, we transduced the GALNS gene into HEK293 cells, human MPS IVA fibroblasts and murine MPS IVA chondrocytes by using adeno-associated virus (AAV)-based vectors, which carry human GALNS cDNA. The effects of the promoter and the cotransduction with the sulfatase-modifying factor 1 gene (SUMF1) on GALNS activity levels was evaluated. Downregulation of the cytomegalovirus (CMV) immediate early enhancer/promoter was not observed for 10 days post-transduction. The eukaryotic promoters induced equal or higher levels of GALNS activity than those induced by the CMV promoter in HEK293 cells. Transduction of human MPS IVA fibroblasts induced GALNS activity levels that were 15-54% of those of normal human fibroblasts, whereas in transduced murine MPS IVA chondrocytes, the enzyme activities increased up to 70% of normal levels. Cotransduction with SUMF1 vector yielded an additional four-fold increase in enzyme activity, although the level of elevation depended on the transduced cell type. These findings suggest the potential application of AAV vectors for the treatment of Morquio A disease, depending on the combined choice of transduced cell type, selection of promoter, and cotransduction of SUMF1.

A versatile viral system for expression and depletion of proteins in mammalian cells

The ability to express or deplete proteins in living cells is crucial for the study of biological processes. Viral vectors are often useful to deliver DNA constructs to cells that are difficult to transfect by other methods. Lentiviruses have the additional advantage of being able to integrate into the genomes of non-dividing mammalian cells. However, existing viral expression systems generally require different vector backbones for expression of cDNA, small hairpin RNA (shRNA) or microRNA (miRNA) and provide limited drug selection markers. Furthermore, viral backbones are often recombinogenic in bacteria, complicating the generation and maintenance of desired clones. Here, we describe a collection of 59 vectors that comprise an integrated system for constitutive or inducible expression of cDNAs, shRNAs or miRNAs, and use a wide variety of drug selection markers. These vectors are based on the Gateway technology (Invitrogen) whereby the cDNA, shRNA or miRNA of interest is cloned into an Entry vector and then recombined into a Destination vector that carries the chosen viral backbone and drug selection marker. This recombination reaction generates the desired product with >95% efficiency and greatly reduces the frequency of unwanted recombination in bacteria. We generated Destination vectors for the production of both retroviruses and lentiviruses. Further, we characterized each vector for its viral titer production as well as its efficiency in expressing or depleting proteins of interest. We also generated multiple types of vectors for the production of fusion proteins and confirmed expression of each. We demonstrated the utility of these vectors in a variety of functional studies. First, we show that the FKBP12 Destabilization Domain system can be used to either express or deplete the protein of interest in mitotically-arrested cells. Also, we generate primary fibroblasts that can be induced to senesce in the presence or absence of DNA damage. Finally, we determined that both isoforms of the AT-Rich Interacting Domain 4B (ARID4B) protein could induce G1 arrest when overexpressed. As new technologies emerge, the vectors in this collection can be easily modified and adapted without the need for extensive recloning.

New methodologies to characterize the effectiveness of the gene transfer mediated by DNA-chitosan nanoparticles

In this work three DNA-chitosan nanoparticle formulations (Np), differing in the molecular weight (MW; 150 kDa, 400 kDa, and 600 kDa) of the polysaccharide, were prepared and administered by two different administration routes: the hydrodynamics-based procedure and the intraduodenal injection. After the hydrodynamic injection, DNA-chitosan nanoparticles were predominantly accumulated in the liver, where the transgene was expressed during at least 105 days. No significant influence of MW was observed on the levels of luciferase expression. The curves of bioluminescence versus time obtained using the charge-coupled device (CCD) camera were described and divided in three phases: (i) the initial phase, (ii) the sustained release step and (iii) the decline phase (promotor inactivation, immunological and physiological processes). From these curves, which describe the transgene expression profile, the behavior of the different formulations as gene delivery systems was characterized. Therefore, the following parameters such as C_max (maximum level of detected bioluminescence), AUC (area under the bioluminescence-time curve) and MET (mean time of the transgene expression) were calculated. This approach offers the possibility of studying and comparing transgene expression kinetics among a wide variety of gene delivery systems. Finally, the intraduodenal administration of naked DNA permitted the gene transfer in a dose dependent manner quantifiable with the CCD camera within 3 days. Nevertheless, the same administration procedure of the three formulations did not improve the levels of transgene expression obtained with naked DNA. This fact could be explained by the rapid physiological turn-over of enterocytes and by the ability of chitosan nanoparticles to control the DNA release.

An efficient and safe herpes simplex virus type 1 amplicon vector for transcriptionally targeted therapy of human hepatocellular carcinomas

Our previous studies have shown that transgene expression could be targeted to proliferating cells when cell cycle transcriptional regulatory elements were incorporated into herpes simplex virus type 1 (HSV-1) amplicon backbone vectors. In the study reported here, we further demonstrated the transcriptional activation of transgene expression in association with the onset of cellular proliferation using the mouse partial hepatectomy model. Moreover, transcriptional regulation could be rendered specific to human hepatocellular carcinoma (HCC) cells by inserting the chimeric gene Gal4/NF-YA under the regulation of the HCC-specific hybrid promoter. The hybrid promoter, which consists of four copies of the apolipoprotein E (ApoE) enhancer element inserted upstream of the human alpha1-antitrypsin(hAAT) promoter, induced an higher level of transcription than other liver-specific promoters such as alpha-fetoprotein (AFP) and albumin (Alb) promoter. As a consequence, the enhancement of tissue-specific expression in the context of Gal4/NF-YA fusion proteins enabled the monitoring of transgene expression using a bioluminescence imaging system. Furthermore, these vectors have been shown to be non-toxic and exhibited potent infectivity for proliferating primary HCC cells and HCC cell lines. Together, these results demonstrated that the new hybrid vectors could provide options for the design of safe and efficient systemic gene therapeutic strategies for human HCC.

Collagen alpha1(I) gene (COL1A1) is repressed by RFX family

Collagen type I is composed of three polypeptide chains transcribed from two separate genes (COL1A1 and COL1A2) with different promoters requiring coordinate regulation. Our recent publications, centering on COL1A2 regulation, demonstrate that methylation in the first exon of COL1A2 at a regulatory factor for X box (RFX) site (at -1 to +20) occurs in human cancer cells and correlates with increased RFX1 binding and decreased collagen transcription (Sengupta, P. K., Erhlich, M., and Smith, B. D. (1999) J. Biol. Chem. 274, 36649-36655; Sengupta, S., Smith, E. M., Kim, K., Murnane, M. J., and Smith, B. D. (2003) Cancer Res. 63, 1789-1797). In normal cells, RFX5 complex along with major histocompatibility class II transactivator (CIITA) is induced by interferon-gamma to occupy this site and repress collagen transcription (Xu, Y., Wang, L., Buttice, G., Sengupta, P. K., and Smith, B. D. (2004) J. Biol. Chem. 279, 41319-41332). In this paper, we demonstrate that COL1A1 has an RFX consensus binding site surrounding the transcription start site (-11 to +10) that contains three methylation sites rather than one in the COL1A2 gene RFX binding site. RFX1 interacts weakly with the unmethylated COL1A1 site, and binds with higher affinity to the methylated site. RFX1 represses the unmethylated COL1A1 less efficiently than COL1A2. COL1A1 promoter activity is sensitive to DNA methylation and the COL1A1 gene is methylated in human cancer cells with coordinately decreased collagen expression. The DNA methylation inhibitor, 5-aza-2'-deoxycytidine (aza-dC) increases collagen gene expression with time in human cancer cells. On the other hand, RFX5 interacts with both collagen type I genes with a similar binding affinity and represses both promoters equally in transient transfections. Two dominant negative forms of RFX5 activate both collagen genes coordinately. Finally, CIITA RNA interference experiments indicate that CIITA induction is required for interferon gamma-mediated repression of both collagen type I genes.

Transduction of human glial and neuronal tumor cells with different lentivirus vector pseudotypes

Lentiviral vectors have proven to be valuable tools for in vitro and in vivo gene delivery because they can transduce dividing and non-dividing cells efficiently, and mediate long-term gene expression. Pseudotyping of lentiviral vectors with envelope proteins other than VSV-G has resulted in enhanced transduction of certain cell types and tissues. In order to improve lentiviral vector-based gene therapy for peripheral neuroectodermal and brain tumors, we compared the efficiency of eight different lentivirus pseudotypes in transducing neuronal and glial tumor cell lines. Here, lentiviral vectors pseudotyped with the envelopes from human foamy virus, rabies, Mokola or amphotropic murine leukemia virus displayed the highest transduction efficiency in neuroblastomas, whereas pseudotyping with the lymphocytic choriomeningitis virus glycoprotein from strain Armstrong 53b resulted in the highest transduction efficiency in gliomas.

Demethylation using the epigenetic modifier, 5-azacytidine, increases the efficiency of transient transfection of macrophages

This study was aimed at developing a method for high-efficiency transient transfection of macrophages. Seven methods were evaluated for transient transfection of murine macrophage RAW 264.7 cells. The highest transfection efficiency was achieved with DEAE-dextran, although the proportion of cells expressing the reporter gene did not exceed 20%. It was subsequently found that the cytomegalovirus plasmid promoter in these cells becomes methylated. When cells were treated with the methylation inhibitor 5-azacytidine, methylation of the plasmid promoter was abolished and a dose-dependent stimulation of reporter gene expression was observed with expression achieved in more than 80% of cells. Treatment of cells with 5-azacytidine also caused increased efficiency of transfection of macrophages with plasmids driven by RSV, SV40, and EF-1alpha promoters and transient transfection of human HepG2 cells. Inhibition of methylation also increased the amount and activity of sterol 27-hydroxylase (CYP27A1) detected in RAW 264.7 cells transfected with a CYP27A1 expression plasmid. Treatment of cells with 5-azacytidine alone did not affect either cholesterol efflux from nontransfected cells or expression of ABCA1 and CYP27A1. However, transfection with CYP27A1 led to a 2- to 4-fold increase of cholesterol efflux. We conclude that treatment with 5-azacytidine can be used for high-efficiency transient transfection of macrophages.

Transduction of terminally differentiated neurons by avian sarcoma virus

Recent studies have demonstrated that avian sarcoma virus (ASV) can transduce cycle-arrested cells. Here, we have assessed quantitatively the transduction efficiency of an ASV vector in naturally arrested mouse hippocampal neurons. This efficiency was determined by comparing the number of transduced cells after infection of differentiated neurons versus dividing progenitor cells. The results indicate that ASV is able to transduce these differentiated neurons efficiently and that this activity is not the result of infection of residual dividing cells. The transduction efficiency of the ASV vector was found to be intermediate between the relatively high and low efficiencies obtained with human immunodeficiency virus type 1 and murine leukemia virus vectors, respectively.

Expression of a model gene in prostate cancer cells lentivirally transduced in vitro and in vivo

In a preclinical model for prostate cancer gene therapy, we have tested lentiviral vectors as a practical possibility for the transfer and long-term expression of the EGFP gene both in vitro and in vivo. The human prostate cancer cell lines DU145 and PC3 were transduced using experimental conditions which permitted analysis of the expression from a single proviral vector per cell. The transduced cells stably expressed the EGFP transgene for 4 months. After injection of the transduced cell populations into Nod-SCID mice a decrease in EGFP was only observed in a minority of cases, while the majority of tumors maintained transgene expression at in vitro levels. In vivo injection of viral vector preparations directly into pre-established subcutaneous or orthotopic tumor masses, obtained by implantation of untransduced PC3 and DU145 cells led to a high transduction efficiency. While the efficiency of direct intratumoral transduction was proportional to the dose of virus injected, the results indicated some technical limitations inherent in these approaches to prostate cancer gene therapy.

CMV enhancer/human PDGF-beta promoter for neuron-specific transgene expression

Using cell-type-specific promoters to restrict expression of therapeutic genes to particular cells is an attractive approach for gene therapy, but often hindered by inefficient transcriptional activities of the promoters. Knowing the enhancer for the human cytomegalovirus (CMV) immediate-early gene improves activities of several cell-type- or tissue-type-specific promoters, we set out to investigate whether it improves neuronal transgene expression driven by a neuron-specific promoter, the platelet-derived growth factor B-chain (PDGF-beta) promoter. A hybrid promoter was constructed by appending a 380-bp fragment of the CMV enhancer 5' to the PDGF-beta promoter. The plasmid containing the promoter was complexed with polyethylenimine for in vitro and in vivo gene transfer. In cultured cells, the plasmid with the hybrid promoter significantly augmented expression of a luciferase reporter gene, providing expression levels 8- to 90-fold and 7- to 178-fold higher than those from two baseline constructs containing the PDGF-beta promoter alone and the CMV enhancer alone, respectively. In particular, the activities of the hybrid promoter in two neural cell lines were close to or higher than that of the CMV immediate-early gene enhancer/promoter, a transcriptional control element that has been considered to be the most robust one identified thus far. After stereotaxic injection into the hippocampus and striatum in rats, the hybrid promoter displayed a neuronal specificity, driving gene expression almost exclusively in neurons. Transgene expression in the brain driven by the hybrid promoter was detectable 24 h after injection, being 10-fold higher than that driven by the PDGF-beta promoter alone. The expression peaked around 5 days at 1.5 x 10(5) relative light units per brain and lasted for at least 4 weeks. This differed strikingly from the expression driven by the PDGF-beta promoter, which was no longer detectable on day 3. The new gene regulatory construct reported in this study will be useful to improve neuronal transgene expression required for gene therapy of neurological disorders and functional studies of the nervous system.

Herpes simplex virus thymidine kinase-mediated suicide gene therapy for hepatocellular carcinoma using HIV-1-derived lentiviral vectors

BACKGROUND/AIMS

Gene therapy is a promising approach for treatment of hepatocellular carcinoma (HCC). However, transduction of non-tumoral hepatocytes may lead to severe hepatitis when using suicide gene therapy approaches. The aim of our study was to evaluate the gene transfer efficiency into HCC cells and normal hepatocytes using human immunodeficiency virus (HIV)-derived lentiviral vectors in vitro and in vivo.

METHODS

Lentiviral vectors encoding for the LacZ gene or the fusion gene HSV-Tk/GFP were tested in vitro in human HCC cells and human hepatocytes in primary culture and in vivo in a chemically induced rat model of HCC.

RESULTS

We show that HIV-1-derived lentiviral vectors are efficient in transducing HCC cells in vitro and in vivo. No significant transduction of non-tumorous hepatocytes was observed in vivo whatever the route of administration used. Measurement of tumor growth following direct intratumoral injection of a lentiviral vector containing the HSV-Tk gene and GCV treatment showed a strong antitumoral efficacy in the absence of normal liver toxicity.

CONCLUSIONS

These observations suggest that lentiviral vectors allow an antitumoral effect with low liver toxicity when using suicide gene therapy approach and could be efficient tools for HCC gene therapy.

Morphological Analysis and Lentiviral Transduction of Fetal Monkey Bone Marrow-Derived Mesenchymal Stem Cells

We explored the transduction kinetics of HIV-1-derived lentiviral vectors containing the CMV, EF1alpha, or PGK promoter expressing EGFP in fetal rhesus monkey bone marrow-derived mesenchymal stem cells (rhMSC). Studies included the effects of transduction (MOI 0-100) on growth, cell cycle, and differentiation toward an osteogenic lineage. Flow cytometric analysis indicated an approximate 8- to 10-fold greater quantity of EGFP-expressing rhMSC when cells were transduced with the CMV or EF1alpha promoter compared to PGK, although quantitative PCR revealed no differences at the DNA level. The CMV promoter initially expressed 10- to 100-fold higher levels of EGFP compared to EF1alpha or PGK, respectively, at increasing MOI, although a significant decline in transgene expression was observed posttransduction and with advancing passage (P < 0.01), whereas a significant increase in the level of expression was observed over time with the EF1alpha promoter. At an MOI of 100, a transient arrest at the S phase of the cell cycle was observed for both vector constructs. Transduced rhMSC differentiated toward an osteogenic lineage comparable to untransduced rhMSC and showed equivalent levels of alkaline phosphatase activity. These findings suggest that the SIN HIV-1-derived lentiviral vectors used in these studies can efficiently transduce rhMSC in vitro (CMV > EF1alpha > PGK) without inhibiting differentiation potential, although the cell cycle was transiently altered at high MOI

Gene therapy of hepatocarcinoma: a long way from the concept to the therapeutical impact

Hepatocellular carcinoma (HCC), the most prevalent histological form of primary liver cancer is one of the most frequent cancer worldwide. This pathology still requires the development of new therapeutical approaches. Gene therapy strategies focusing on the genetic manipulation of accessory cells involved in the immune reaction against cancer cells, or on the direct transduction of tumor cells with transgenes able to "suicide" cancer cells have been largely developed for more than ten years.

Hepatoma cell-specific ganciclovir-mediated toxicity of a lentivirally transduced HSV-TkEGFP fusion protein gene placed under the control of rat alpha-fetoprotein gene regulatory sequences

Suicide gene therapy combining herpes simplex virus thymidine kinase gene transfer and ganciclovir administration can be envisioned as a powerful therapeutical approach in the treatment of hepatocellular carcinoma; however, safety issues regarding transgene expression in parenchyma cells have to be addressed. In this study, we constructed LATKW, a lentiviral vector expressing the HSV-TkEGFP gene placed under the control of the promoter elements that control the expression of the rat alpha-fetoprotein, and assayed its specific expression in vitro in hepatocarcinoma and nonhepatocarcinoma human cell lines, and in epidermal growth factor stimulated human primary hepatocytes. Using LATKW, a strong expression of the transgene was found in transduced hepatocarcinoma cells compared to a very low expression in nonhepatocarcinoma human cell lines, as assessed by Northern blot, RT-PCR, FACS analysis and ganciclovir-mediated toxicity assay, and no expression was found in lentivirally transduced normal human hepatocytes. Altogether, these results demonstrate the possibility to use a lentivirally transduced expression unit containing the rat alpha-fetoprotein promoter to restrict the HSV-TK-mediated induced GCV sensitivity to human hepatocarcinoma cells.

Adeno-associated virus (AAV) vectors achieve prolonged transgene expression in mouse myocardium and arteries in vivo: a comparative study with adenovirus vectors

Plasmid DNA and adenovirus vectors currently used in cardiovascular gene therapy trials are limited by low efficiency and short-lived transgene expression, respectively. Recombinant adeno-associated virus (AAV) has recently emerged as an attractive vector for cardiovascular gene therapy. In the present study, we have compared AAV and adenovirus vectors with respect to gene transfer efficiency and the duration of transgene expression in mouse hearts and arteries in vivo. AAV vectors (titer: 5 x 10(8) transducing units (TU)/ml) and adenovirus vectors (1.2 x 10(10) TU/ml) expressing a green fluorescent protein (EGFP) gene were injected either intramyocardially (n=32) or intrapericardially (n=3) in CD-1 mice. Hearts were harvested at varying time intervals (3 days to 1 year) after gene delivery. After intramyocardial injection of 5 microl virus stock solution, cardiomyocyte transduction rates with AAV vectors were 4-fold lower than with adenovirus vectors (1.5% (range: 0.5-2.6%) vs. 6.2% (range: 2.7-13.7%); P<0.05), but similar to titer-matched adenovirus vectors (0.7%; range: 0.2-1.2%). AAV-mediated EGFP expression lasted for at least 1 year. AAV vectors instilled into the pericardial space transduced epicardial myocytes. Arterial gene transfer was studied in mouse carotids (n=26). Both vectors selectively transduced endothelial cells after luminal instillation. Transduction rates with AAV vectors were 8-fold lower than with adenovirus vectors (2.0% (range: 0-3.2%) vs. 16.2% (range: 8.5-20.2%); P<0.05). Prolonged EGFP expression was observed after AAV but not adenovirus-mediated gene transfer. In conclusion, AAV vectors deliver and express genes for extended periods of time in the myocardium and arterial endothelium in vivo. AAV vectors may be useful for gene therapy approaches to chronic cardiovascular diseases.

Gene Therapy Applications to Cancer Treatment

Over the past ten years significant advances have been made in the fields of gene therapy and tumour immunology, such that there now exists a considerable body of evidence validating the proof in the principle of gene therapy based cancer vaccines. While clinical benefit has so far been marginal, data from preclinical and early clinical trials of gene therapy combined with standard therapies are strongly suggestive of additional benefit. Many reasons have been proposed to explain the paucity of clinical responses to single agent vaccination strategies including the poor antigenicity of tumour cells and the development of tolerance through down-regulation of MHC, costimulatory, signal transduction, and other molecules essential for the generation of strong immune responses. In addition, there is now evidence from animal models that the growing tumour may actively inhibit the host immune response. Removal of the primary tumour prior to T cell transfer from the spleen of cancer bearing animals, led to effective tumour cell line specific immunity in the recipient mouse suggesting that there is an ongoing tumour-host interaction. This model also illustrates the potential difficulties of clinical vaccine trials in patients with advanced stage disease.

Lentiviral vectors for gene delivery into cells

Human immunodeficiency virus type I (HIV) is the etiologic agent of acquired immunodeficiency syndrome or AIDS. Vectors based upon HIV have been in use for over a decade. Beginning in 1996, with the demonstration of improved pseudotyping using vesicular stomatitis virus (VSV) G protein along with transduction of resting mammalian cells, a series of improvements have been made in these vectors, making them both safer and more efficacious. Taking a cue from vector development of murine leukemia virus (MLV), split coding and self-inactivating HIV vectors now appear quite suitable for phase I clinical trials. In parallel, a number of pre-clinical efficacy studies in animals have demonstrated the utility of these vectors for various diseases processes, especially neurodegenerative and hematopoietic illnesses. These vectors are also appropriate for the study of other viruses (specifically of viral entry) and investigation of the HIV replicative cycle, along with straightforward transgene delivery to target cells of interest. Vectors based upon other lentiviruses have shown similar abilities and promise. Although concerns remain, particularly with regards to detection and propagation of replication-competent lentivirus, it is almost certain that these vectors will be introduced into the clinic within the next 3-5 years.

Durability of transgene expression and vector integration: recombinant SV40-derived gene therapy vectors

Many applications of gene delivery require long-term transgene expression. In dividing cells, this result necessitates vector genome persistence, usually by integrating into cellular DNA. Since recombinant gene delivery vectors derived from tag-deleted, replication-incompetent simian virus-40 (SV40) provide for long-term transgene expression in resting and dividing cells, we tested whether such enduring transgene expression reflected integration into cellular genomes. Several lines of evidence suggested this likelihood. After transduction in vitro, continuously dividing cell lines and continuously stimulated primary cells uniformly showed transgene expression for many months. Mice whose livers were transduced in vivo, partially resected, and allowed to regenerate showed comparable levels of transgene expression in regenerated and preoperative livers. Thus, replicationincompetent SV40 vectors (rSV40) persist in vitro and in vivo despite extensive cell division. We tested the possibility that this persistence reflected integration directly. Southern blot analyses of genomic DNA from transduced 293 cells showed that vector genome incorporation into cell DNA happened within days of transduction. Episomal vector DNA was barely detectable 96 hours post-transduction. Inverted PCR, used to characterize vector integration points, showed vector DNA integrated randomly into the cell genome. The circular rSV40 genome opened at different points in each integrand. A significant proportion of the integrands did not contain the entire vector sequence, but rather only portions thereof. Quantitative Southern blot analysis showed approximately 3.05 transgene copies per cell. Therefore, recombinant SV40 gene delivery vectors integrate into the cellular DNA of both resting and dividing cells, and do so randomly and within days of transduction. This integration may explain long-term transgene expression.

Differential effects of Rad52p overexpression on gene targeting and extrachromosomal homologous recombination in a human cell line

Overexpression of the RAD52 epistasis group of gene products is a convenient way to investigate their in vivo roles in homologous recombination (HR) and DNA repair. Overexpression has the further attraction that any associated stimulation of HR may facilitate gene-targeting applications. Rad51p or Rad52p overexpression in mammalian cells have previously been shown to enhance some forms of HR and resistance to ionising radiation, but the effects of Rad52p overexpression on gene targeting have not been tested. Here we show that Rad52p overexpression inhibits gene targeting while stimulating extrachromosomal HR. We also find that Rad52p overexpression affects cell-cycle distribution, impairs cell survival and is lost during extensive passaging. Therefore, we suggest that excess Rad52p can inhibit the essential RAD51-dependent pathways of HR most likely to be responsible for gene targeting, while at the same time stimulating the RAD51-independent pathway thought to be responsible for extrachromosomal HR. The data also argue against Rad52p overexpression as a means of promoting gene targeting, and highlight the limitations of using a single HR assay to assess the overall status of HR.