Systemic gene expression after intravenous DNA delivery into adult mice

Dual Induction of the Epo-Egr-TNF-α Plasmid in Hypoxic Human Colon Adenocarcinoma Produces Tumor Growth Delay

Gene therapy is a modality for the treatment of solid tumors that involves the introduction of a suicide gene into the tumor cells. Genetic radiotherapy involves the placement of a radiation-sensitive promoter upstream from a suicide gene. Because of their irregular vasculature some solid tumors are chronically hypoxic and hence are resistant to conventional treatment with chemotherapy and ionizing radiation (IR). The purpose of this study was to demonstrate that regional tumor hypoxia could be exploited to improve local tumor control. The cDNA coding the erythropoietin hypoxia-responsive element (EPO) was placed upstream from the Egr-TNF-α construct. WIDR human colon adenocarcinoma cells were injected into the right hind limb of nude mice and treated with Epo-Egr-TNF-α plasmid with or without IR. Tumor volumes were measured by calipers and tumor necrosis factor (TNF)-α content of the tumor was determined by enzyme-linked immunosorbent assay. Treatment with the combined regimen of Epo-Egr-TNF-α plasmid + IR resulted in significant tumor growth delay. Tumor TNF-α content was increased by 30 per cent in the combined treatment group compared with each treatment alone. Regional tumor hypoxia can be exploited successfully to induce tumor growth delay, enhance local control, and enhance the therapeutic ratio.

Free cationic liposomes inhibit the inflammatory response to cationic lipid-DNA complex injected intravenously and enhance its transfection efficiency

In this report, we show that intravenous (i.v.) injection into mice of a complex made of the cationic lipid diC14-amidine and the luciferase reporter plasmid (pCMV-luc) results in efficient gene expression in several organs but elicits an inflammatory response characterized by a release of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) into the serum of treated animals. A single preinjection of free diC14-amidine liposomes improves the i.v. transfection efficiency of the diC14-amidine/protamine/pCMV-luc complex as much as 40 times. This improvement is correlated with the ability of free liposomes to inhibit TNF-alpha but not IFN-gamma production resulting from complex injection. TNF-alpha-rich serum obtained from mice injected with diC14-amidine/protamine/pCMV-luc complex inhibits luciferase expression in transfected mouse lung endothelial (MLE) cells cultured in vitro, whereas IFN-gamma has no effect. This inhibitory effect can be partly abolished by treating the mouse serum with a specific anti-TNF-alpha antibody. These data point out that cationic lipids are potent inhibitors of the inflammatory response to the CpG motifs in plasmid DNA. This property is shown to enhance the in vivo transfection efficiency.

Modified microplex vector enhances transfection of cells in culture while maintaining tumour-selective gene delivery in-vivo

A non-commercial liposome (dimethyl dioctadecyl ammonium bromide:dioleoyl phosphatidylethanolamine) was compared with a commercial variety (Lipofectamine) for transfection of cultured rat adenocarcinoma cells and in an in-vivo kidney tumour model. Transfection of the cells in culture and in tumours in-vivo was variable with both types of liposomes. A high-dose microplex (lipoplex-microsphere) vector enhanced liposome-mediated transfection of cells in culture. When these high-dose microplexes were tested in-vivo, they were better than both microspherical and liposomal delivery modes in terms of transgene expression levels and the tumour-to-normal tissue ratio of gene delivery. Microplexes have been demonstrated to be capable of not only selective delivery of plasmids to solid tumours, but also of increasing transfection in cell culture, a finding that may be used in ex-vivo transfection studies. It is hypothesized that microspheres anchored the combination vector closer to the cultured cells, allowing attached liposomes to gain easier access into cells. In-vivo, microspheres permitted the microplexes to selectively deliver their genetic payload within the tumour tissue, from where the action of cationic liposomes on cellular membranes facilitated increased access of plasmids into the cytosol of target cells.

Endostatin gene therapy on murine lung metastases model utilizing cationic vector-mediated intravenous gene delivery

Tumors require ongoing angiogenesis to support their growth. Inhibition of angiogenesis by production of antiangiogenic factors should be a viable approach for cancer gene therapy. In this study, we investigated whether intravenous administration of endostatin gene complexed with a cationic vector (GL67/DOPE or PEI22K) could inhibit the development of lung tumors in mice injected i.v. with NFSa Y83 fibrosarcoma cells (5 x 10(5)) which frequently form lung metastasis. mRNA and protein of the transfected gene were produced in the lung and other organs of the transfected mice as assessed by immunohistochemistry, Western blotting and reverse transcription-polymerase chain reaction. Single intravenous injection of the endostatin gene (60 microg) complexed with either GL67/DOPE or PEI22K on day 3 or day 7 after fibrosarcoma cell inoculation significantly inhibited tumor formation in the lung as evidenced by the reduced number of lung tumors and lung weight, and prolonged survival of the endostatin gene-transfected mice compared with control mice. These findings suggested that the endostatin gene therapy, using cationic vector-mediated intravenous gene transfer, might be a feasible strategy for organ-targeted prevention and regulation of possible disseminated cancers.

Barriers to and new approaches for gene therapy and gene delivery in cystic fibrosis

Clinical trials of gene therapy for cystic fibrosis suggest that current levels of gene transfer efficiency are probably too low to result in clinical benefit, largely as a result of the barriers faced by gene transfer vectors within the airways. The respiratory epithelium has evolved a complex series of extracellular barriers (mucus, lack of receptors, immune surveillance, etc.) aimed at preventing penetration of lumenally delivered materials, including gene therapy vectors. In addition, once in the cell, further hurdles have to be overcome, including DNA degradation, nuclear import and the ability to maintain long-term transgene expression. Strategies to overcome these barriers will be addressed in this review and include the use of: (i) clinically relevant adjuncts to overcome the extra- and intracellular barriers; (ii) less-conventional delivery routes, such as intravenous or in utero administration; (iii) more efficient non-viral vectors and 'stealth' viruses which can be re-administered; and (iv) new approaches to prolong transgene expression by means of alternative promoters or integrating vectors. These advances have the potential to improve the efficiency of gene delivery to the airway epithelium, thus making gene therapy a more realistic option for cystic fibrosis.

Liposomal delivery of nucleic acids in vivo

Optimization of cationic liposomal complexes for in vivo applications and therapeutics is complex involving many distinct components. These components include nucleic acid purification, plasmid design, formulation of the delivery vehicle, administration route and schedule, dosing, detection of gene expression, and others. This review will focus on optimization of these components for use in a variety of in vivo applications. Use of improved liposome formulations for delivery in vivo is valuable for gene therapy and would avoid several problems associated with viral delivery. Delivery of nucleic acids using liposomes is promising as a safe and non-immunogenic approach to gene therapy. Furthermore, gene therapeutics composed of artificial reagents can be standardized and regulated as drugs rather than as biologics. Optimizing all components of the delivery system will allow broad use of liposomal complexes to treat or cure human diseases or disorders.

Enhanced gene expression in breast cancer cells in vitro and tumors in vivo

Gene therapy clinical trials for cancer frequently produce inconsistent results. Some of this variability could result from differences in transcriptional regulation that limit expression of therapeutic genes in specific cancers. Systemic liposomal delivery of a nonviral plasmid DNA showed efficacy in animal models for several cancers. However, we observed large differences in the levels of gene expression from a CMV promoter-enhancer between lung and breast cancers. To optimize gene expression in breast cancer cells in vitro and in vivo, we created a new promoter-enhancer chimera to regulate gene expression. Serial analyses of gene expression data from a panel of breast carcinomas and normal breast cells predicted that the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter is highly active in breast cancers. Furthermore, GAPDH is up-regulated by hypoxia, which is common in tumors. We added the GAPDH promoter, including the hypoxia enhancer sequences, to our in vivo gene expression plasmid. The novel CMV-GAPDH promoter-enhancer showed up to 70-fold increased gene expression in breast tumors compared to the optimized CMV promoter-enhancer alone. No significant increase in gene expression was observed in other tissues. These data demonstrate tissue-specific effects on gene expression after nonviral delivery and suggest that gene delivery systems may require plasmid modifications for the treatment of different tumor types. Furthermore, expression profiling can facilitate the design of optimal expression plasmids for use in specific cancers.

Intratracheal adenovirus-mediated gene transfer is optimal in experimental lung transplantation

OBJECTIVE

Gene transfer to experimental lung grafts has been shown to reduce ischemia-reperfusion injury and acute rejection. The optimal delivery route should produce high lung expression with no inflammation and minimal systemic expression. The goal of this study was to determine the optimal gene transfer route for use in experimental lung transplantation.

METHODS

F344 rats were injected with 2.9 x 10(10) plaque-forming units of adenovirus vector encoding beta-galactosidase through intratracheal, intravenous, intraperitoneal, or intramuscular delivery routes and killed 48 hours later. Gene expression was measured by means of enzyme-linked immunosorbent assay.

RESULTS

Intratracheal delivery produces significantly greater gene expression in the lung (75,350 +/- 47,288 pg/100 microg of protein, P <.001 vs intravenous, intraperitoneal, and intramuscular routes) and minimal systemic expression (nonsignificant in serum, kidney, liver, spleen, and muscle vs that seen in control animals, P =.016 for heart). Immunohistochemistry staining showed beta-galactosidase expression in the bronchial epithelium of lungs transfected through the intratracheal route with mild inflammation.

CONCLUSIONS

Intratracheal gene transfer provides significant expression in the lung with mild to no inflammation and minimal systemic expression. This delivery strategy has tremendous potential in experimental lung transplant models to reduce ischemia-reperfusion injury and acute allograft rejection and should be investigated further.

Novel gene therapy approach for nasopharyngeal carcinoma

This article will provide an overview on the status of cancer gene therapy, focussed specifically on its potential application in nasopharyngeal carcinoma (NPC). The concepts and strategies behind the design of therapeutic targets such as p53, p16, and death genes will be described. One of the major challenges in cancer gene therapy is tumor-specific expression of therapeutic genes, and a transcriptional targeting approach will be reviewed, in reference to NPC. Specifically, the ability to exploit the presence of Epstein-Barr virus (EBV) will be emphasized. The currently available preclinical data on genetic therapeutic approaches for NPC will be reviewed, and an outline for its future role in management of NPC, in conjunction with existing cytotoxic modalities of ionizing radiation and chemotherapy will be provided.

In vivo characteristics of cationic liposomes as delivery vectors for gene therapy

After a decade of clinical trials, gene therapy seems to have found its place between excessive ambitions and feasible aims, with encouraging results obtained in recent years. Intracellular delivery of genetic material is the key step in gene therapy. Optimization of delivery vectors is of major importance for turning gene therapy into a successful therapeutic method. Nonviral gene delivery relies mainly on the complexes formed from cationic liposomes (or cationic polymers) and DNA, i.e., lipoplexes (or polyplexes). Many lipoplex formulations have been studied, but in vivo activity is generally low compared to that of viral systems. This review gives a concise overview of studies on the application of cationic liposomes in vivo in animal models of diseases and in clinical studies. The transfection efficiency, the pharmacokinetic and pharmacodynamic properties of the lipid-DNA complexes, and potentially relevant applications for cationic liposomes are discussed. Furthermore, the toxicity of, and the induction of an inflammatory response in association with the administration of lipoplexes are described. Increasing understanding of lipoplex behavior and gene transfer capacities in vivo offers new possibilities to enhance their efficiency and paves the path to more extensive clinical applications in the future.

Folate-targeted, cationic liposome-mediated gene transfer into disseminated peritoneal tumors

A folate-targeted, cationic lipid based transfection complex was developed and found to specifically transfect folate receptor-expressing cells and tumors. These liposomal vectors were comprised of protamine-condensed plasmid DNA, a mixture of cationic and neutral lipids, and a folic acid-cysteine-polyethyleneglycol-phosphatidylethanolamine (FA-Cys-PEG-PE) conjugate. Pre-optimization studies revealed that inclusion of low amounts (0.01 to 0.03%) of FA-Cys-PEG-PE yielded the highest binding activity of dioleoylphosphatidylcholine/cholesterol liposomes to folate receptor-bearing cells. In contrast, higher amounts (>0.5%) of FA-Cys-PEG-PE progressively decreased cellular binding of the liposomes. In vitro studies with cationic lipid/dioleoylphosphatidylethanolamine formulations indicated that as little as 0.01 to 0.3% of FA-Cys-PEG-PE was needed to produce optimal targeted expression of plasmid DNA. Similarly, using a disseminated intraperitoneal L1210A tumor model, maximum in vivo transfection activity occurred with intraperitoneally administered formulations that contained low amounts (0.01 mol%) of the FA-Cys-PEG-PE targeting lipid. Overall, folate-labeled formulations produced an eight- to 10-fold increase in tumor-associated luciferase expression, as compared with the corresponding non-targeted cationic lipid/DNA formulations. These results collectively indicate that transfection of widespread intraperitoneal cancers can be significantly enhanced using folate-targeted techniques.

Possible mechanism of gene transfer into early to mid-gestational mouse fetuses by tail vein injection

Our aim is to develop a simple gene transfer method into egg cylinder and mid-gestational murine embryos. We examined whether plasmid/lipid complexes injected into the tail veins of pregnant transgenic mice can be transferred to fetuses at E 4.5-13.5. When pregnant CETZ-17 mice carrying a transgene consisting of a ubiquitous promoter, floxed EGFP/CAT and the LacZ gene, were injected with a Cre expression vector DNA/lipid complex, Cre-mediated excision of the transgenes, as evaluated by X-gal staining, occurred in 10-50% of fetuses treated at E 11.5-13.5. Although younger embryos remained unstained, PCR analysis revealed low levels of the Cre vector DNA and recombined transgene. To examine the fate of a solution given intravenously, we injected trypan blue or fluorescence-labeled plasmid DNA/lipid complexes into females at E 5.5-11.5 and E 6.5, respectively. Both collected in the visceral endoderm (VE) lineage, but were undetectable in the embryo proper. These findings suggest that substances in maternal blood are delivered to post-implantation embryos via cells of the VE lineage and placenta, but that most are trapped in the VE. If significantly improved, gene transfer to fetuses by injection into the maternal circulation may become a promising tool in fetal gene therapy and embryological studies.

Cationic lipid-DNA complexes-lipoplexes-for gene transfer and therapy

Cationic lipid-mediated gene transfer and delivery still attract great attention of many gene therapy laboratories. From the point of view of the most important characteristics of lipoplex particles, e.g. its charge and size, we reviewed recent studies available. In general, the paper deals with non-viral systems of gene transfer into eukaryotic cell based on various lipids. Having usually less efficiency in gene transfer, lipid-based gene transfer vehicles (lipoplexes/genosomes) are characterized with certain advantages even over viral ones: they are less toxic and immunogenic, could be targetable and are easy for large-scale production, a size of transferred DNA being quite high. Conditions of DNA condensation during interactions with lipids are described. Results of the studies of mechanism of DNA-lipid complex interactions with the cell membrane and their transport into the nucleus are summarized. Dependence of efficiency of gene transfer on lipoplex structure and physical-chemical properties is reviewed. Advantages and disadvantages of different macromolecule complexes from the point of view of transfection efficiency, possibility of use in vivo, cytotoxicity and targeted gene transfer in certain organs and tissues are also discussed. Results of transfection of different cells using neutral, anion and cation liposomes are reviewed. The conclusion reached was that efficiency and specificity of gene transfer may grow considerably when mixed macromolecule lipid systems including polycations and glycolipids are used.

A model for evaluating selective delivery of plasmid DNA to tumours via the vasculature

A comparative study of plasmid DNA delivery in a newly established rat renal solid tumour model was undertaken. Free plasmid, plasmids bound to microspheres, and plasmids complexed with liposomes were selectively delivered to tumours via arterial catheterisation. Forty-eight hours post delivery, tumour to normal kidney tissue chloramphenicol acetyltransferase expression ratios were as follows: free (1.8:1), microspherical (3.9:1), and liposomal (1.2:1). Microspheres were able to selectively deliver the plasmids to tumours, whereas cationic liposomes distributed the plasmids to both kidney parenchymal and tumour cells. This tumour model has the potential of screening delivery vehicles as well as therapeutic agents for the capacity of selective delivery to tumours via the vasculature.

In vivo transfection of the mouse vas deferens

To explore the possibility that specific characteristics of the epithelium of the male tract can be modified, transfections of the mouse vas deferens have been performed using in vivo injections of cationic DNA/liposome complexes. Gene transfer was done employing the reporter genes pEGFP-C1 encoding Green Fluorescent Protein (GFP) and pCMV-nls-beta encoding the nuclear beta-Galactosidase (beta-Gal). Foreign gene expression reached a maximum of 6.8% in the epithelial cells of the vas after treatment with the nuclear beta-Gal gene construction and of 13.3% after employing the GFP gene construction. Expression of the GFP gene appeared from one week up to three months following injection, and it appeared as patches of modified cells along the epithelium. Results from immunocytochemistry and Western Blotting support the conclusion that transfection of epithelial cells was achieved. We have also transfected the vas using gene constructions that express secretory proteins--specifically, the reporter system pSEAP-control that expresses a secretory form of human placental alkaline phosphatase, and the pGFP-Ctk-37 that expresses a secretion form of GFP. In both cases, the fluids expressed from the transfected vas showed a significant increase of alkaline phosphatase activity after pSEAP transfection and the presence of GFP protein when pGFP-Ctk-37 gene construction was employed. Our results indicate that the vas can be transfected in vivo using liposomes as vectors of foreign genes and that the vas fluid contents can be modified.

Transfer of maternally administered fusogenic liposome-DNA complexes into monkey fetuses in a pregnancy model

BACKGROUND

Materno-fetal transfer of intravenously administered liposome-plasmid DNA complexes has been demonstrated only in mice. Studies on its materno-fetal transfer in the pregnant monkey model is needed because of critical differences in placental structure between primates including humans and rodents.

METHODS

The reporter plasmid pEGFP-C1 was formulated in cationic lipid containing polybrene and vesicular stomatitis virus G protein. The fusogenic liposome-plasmid DNA complexes were intradermally injected into pregnant common marmosets (N=2), a New World monkey, near term. DNA extracted from fetal tissues was subjected to PCR for detection of the egfp gene. Confocal microscopy and immunostaining were performed to determine the sites of transgene expression in the fetal organs.

RESULTS

The egfp gene was detected in fetal blood and major organs (heart, liver, lung). The encoded protein was mainly produced in the endothelial cells of blood vessels in the fetal lungs.

CONCLUSIONS

This is the first report on materno-fetal transfer of intradermally administered fusogenic liposome-plasmid DNA complexes and fetal expression of a transgene in primates.

Cationic liposome-mediated GDNF gene transfer after spinal cord injury

Glial cell line-derived neurotrophic factor (GDNF) has been shown to protect cranial and spinal motoneurons, which suggests potential uses of GDNF in the treatment of spinal cord injury (SCI) and motor neuron disease. We examined neuroprotective effect of cationic liposome-mediated GDNF gene transfer in vivo on axonal regeneration and locomotor function recovery after SCI in adult rats. The mixture of DC-Chol liposomes and recombinant plasmid pEGFP-GDNF cDNA was injected after SCI. RT-PCR confirmed the increased expression of GDNF mRNA in the injected areas at 7 days after injection. The expression of EGFP-GDNF was observed in the cells around the injection locus by fluorescence microscope at least 4 weeks after injection. Four weeks after GDNF gene transfer, regeneration of the corticospinal tracts was assessed using anterograde tract tracing. There are more HRP labeling of corticospinal tract axons across the lesion in GDNF group compared with control group. In GDNF group, the maximum distance these labeled axons extended varied in different animals and ranged from 5 mm to approximately 9 mm from the lesion. In control group, no HRP labeled axons extended caudal to the lesion. The locomotion function of hindlimbs of rats was evaluated using inclined plane test and BBB locomotor scores. The locomotion functional scores in GDNF group were higher than that in control group within 1-4 weeks after SCI (p < 0.05). These data demonstrate that in vivo transfer of GDNF cDNA can promote axonal regeneration and enhance locomotion functional recovery, suggesting that cationic liposome-mediated delivery of GDNF cDNA may be a practical gene transfer method for traumatic SCI treatment.

Interleukin-12 inhibits eotaxin secretion of cultured primary lung cells and alleviates airway inflammation in vivo

The mechanisms that cause the inflammation of airway and lung tissue in asthma have been studied extensively. It is noted that type 1T helper cell (Th1)-related cytokines could decrease the accumulation of eosinophils in lung tissue and relieve airway constriction. But the therapeutic mechanisms of Th1 cytokines remain unclear. In this study, interleukin-12 (IL-12) DNA plasmid as a therapeutic reagent was delivered intravenously. Bronchoalveolar lavage (BAL) fluids were collected from IL-12 treated and control mice, and analyzed for cell composition and eotaxin level. The results showed that IL-12 DNA plasmid could effectively inhibit eosinophilia and airway inflammation in vivo. The level of eotaxin in BAL fluid also decreased. To further investigate the effect of Th1-related cytokines such as IL-12 or interferon-gamma (IFN-gamma) on the eotaxin level produced by lung cells, primary lung cell culture was established. The results demonstrated that both IL-12 and IFN-gamma could suppress eotaxin secretion from IL-13 or IL-4 stimulated primary lung cell culture. Moreover, the inhibitory effect of IL-12 could not be reversed by the administration of anti-IFN-gamma antibody. All the evidences suggested that IL-12 could regulate airway inflammation by suppressing the eotaxin secretion of lung tissue through an IFN-gamma independent mechanism.

Biochemical and biophysical characteristics of lipoplexes pertinent to solid tumour gene therapy

Cationic liposomes have become the reagent of choice for transfer of nucleic acids such as plasmids and oligodeoxynucleotides to cells in culture and in vivo. Whilst these reagents have several advantages over other forms of nucleic acid transfer methods, toxicity remains a significant problem, especially in vivo. Recent studies have also highlighted the immunostimulatory nature of these cationic vesicles when complexed to plasmid DNA, a phenomenon that may be harnessed for efficacious usage against tumours. Current research in this dynamic technological field is aimed at the development of cationic lipids that have negligible toxic effects and enhanced transfection capabilities.

Lipoplex-induced hemagglutination: potential involvement in intravenous gene delivery

We report a study aiming to characterize the interaction of blood and blood components with lipoplexes under conditions relevant to in vivo intravenous transfection. In this study we focus on the interaction of lipoplexes with red blood cells (RBC). It was found that no significant hemolysis occurred during several hours' incubation using lipoplex compositions and lipoplex/red blood cell ratios in the range commonly used for in vivo transfection. However, the interaction of RBC with lipoplexes resulted in massive agglutination, which occurs irrespective of the type of cationic lipid or helper lipid. Agglutination was also induced by polyplexes (such as dendrimer/DNA complexes) and lipoplexes in the presence of spermidine or protamine sulfate (the latter induced hemagglutination by itself). DSPE-PEG(2000) inserted into the lipoplexes inhibits hemagglutination somewhat. In order to understand the effect of serum on the agglutination better, plasma was separated into its high molecular weight components (HMWC, >14 kDa) and its low molecular weight components (LMWC, < or = 14 kDa). These fractions were characterized for their level of proteins, primary amino groups, osmotic pressure, and electrical conductivity, and compared with saline (0.15 M NaCl). It was found that both LMWC and HMWC inhibit agglutination by themselves, although whole serum demonstrates better hemagglutination inhibition than each fraction separately. The inhibitory effect of the serum (or plasma) is explained by its effect on the electrostatics of the lipoplexes, reducing their positive charge, as was demonstrated using fluorescein-phosphatidylethanolamine-labeled lipoplexes. The effect of LMWC was related to ionic strength and was equal to the effect of 0.15 M NaCl. The level of agglutination was reduced with increasing lipoplex DNA(-)/cationic lipid(+) (DNA(-)/L(+)) ratio. However, at the low DNA(-)/L(+) ratio needed to achieve significant in vivo transfection after i.v. administration, massive agglutination occurred. These data suggest that i.v. administration of lipoplexes and polyplexes may lead to RBC agglutination, and the agglutinates formed may explain the localization of lipoplexes and expression of their transgenes in the lungs.

Binding of phosphorothioate oligonucleotides to zwitterionic liposomes

Although double-stranded DNA (dsDNA) has been shown to bind to zwitterionic lipids, it has been reported that this association is stronger for disordered (L(alpha)) phase lipids than for well-ordered (L(beta)) lipids. In this work, the interaction of single-strand phosphorothioate oligonucleotides (ONs) with unilamellar liposomes of saturated and unsaturated zwitterionic phosphocholines (PCs) and phosphoroethylamine (PE) was investigated. It is shown that the association of phosphorothioate ONs to diacyl glycerophosphocholines is strong, but only for L(beta) phase or otherwise ordered bilayers. There is no measurable affinity for PE lipids. The apparent affinity of three different phosphorothioate ONs for L(beta) phase 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) has been measured and the dissociation constants were on the order of 10(-7) M. Purine-rich ON sequences had stronger binding to DPPC liposomes than did pyrimidine-rich sequences, but there were other sequence-dependent factors. This exceptionally high affinity could be an important consideration in ON uptake, delivery, and biodistribution.

Liver- and lobe-selective gene transfection following the instillation of plasmid DNA to the liver surface in mice

The present study has undertaken the liver- and lobe-selective gene transfections following the instillation of plasmid DNA (pDNA) to the liver surface in mice. The luciferase levels produced in the applied (left) liver lobe at 6 h after liver surface instillation of pDNA were significantly higher than those produced in the other tissues assayed, and ranged from 8.5-fold higher in other liver lobes to 320-fold higher in other tissues. After small intestine surface instillation of pDNA, the gene expression was a little detected in the tissues assayed. Following liver surface instillation of pDNA at a time from 2 to 48 h or at a volume from 15 to 120 microl, the gene expressions of the applied liver lobe were always significantly higher than those of other liver lobes and other tissues. We demonstrated the novel liver- and lobe-selective gene transfection utilizing the instillation to the liver surface.

Stabilized plasmid-lipid particles: a systemic gene therapy vector

The ability of a systemically administered gene therapy vector to exhibit extended circulation lifetimes, accumulate at a distal tumor site, and enable transgene expression is unique to SPLP. The flexibility and low toxicity of SPLP as a platform technology for systemic gene therapy allows for further optimization of tumor transfection properties following systemic administration. For example, the PEG coating of SPLP is necessary to engender the long circulation lifetimes required to achieve tumor delivery. However, PEG coatings have also been shown to inhibit cell association and uptake required for transfection. The dissociation rate of the PEG coating from SPLP can be modulated by varying the acyl chain length of the ceramide anchor, suggesting the possibility of developing PEG-Cer molecules that remain associated with SPLP long enough to promote tumor delivery, but which dissociate quickly enough to allow transfection. Alternatively, improvements may be expected from inclusion of cell-specific targeting ligands in SPLP to promote cell association and uptake. Finally, the nontoxic properties of SPLP allow the possibility of higher doses. A dose of 100 micrograms plasmid DNA per mouse corresponds to a dose of approximately 5 mg plasmid DNA per kg body weight. This compares well to small molecules used for cancer therapy, which typically are used at dose levels of 10 to 50 mg per kg body weight. In summary, SPLP consist of plasmid encapsulated in a lipid vesicle that, in contrast to naked plasmid or complexes, exhibit extended circulation lifetimes following intravenous injection, resulting in accumulation and transgene expression at a distal tumor site in a murine model. The pharmacokinetics, biodistribution, and tumor transfection properties of SPLP are highly sensitive to the nature of the ceramide anchor employed to attach the PEG to the SPLP surface. The SPLP-CerC20 system in which the PEG-Cer does not readily dissociate exhibits good serum stability, long circulation lifetimes, and high levels of tumor accumulation and mediates marker gene expression at the tumor site. The flexibility of the SPLP system offers the potential of further optimization to achieve therapeutically effective levels of gene transfer and clearly has considerable potential as a nontoxic systemic gene therapy vehicle with general applicability. These features of SPLP contrast favorably with previous plasmid encapsulation procedures. Plasmid DNA has been encapsulated by a variety of methods, including reverse phase evaporation, ether injection, detergent dialysis in the absence of PEG stabilization, lipid hydration and dehydration-rehydration techniques, and sonication, among others. The characteristics of these protocols are summarized in Table I. None of these procedures yields small, serum-stable particles at high plasmid concentrations and plasmid-to-lipid ratios in combination with high plasmid-encapsulation efficiencies. Trapping efficiencies comparable with the SPLP procedure can be achieved employing methods relying on sonication. However, sonication is a harsh technique that can shear nucleic acids. Size ranges of 100 mm diameter or less can be achieved by reverse-phase techniques; however, this requires an extrusion step through filters with 100 nm or smaller pore size which can often lead to significant loss of plasmid. Finally, it may be noted that the plasmid DNA-to-lipid ratios that can be achieved for SPLP are significantly higher than those achievable by any other encapsulation procedure.

Kidney-targeted naked DNA transfer by retrograde renal vein injection in rats

Kidney-targeted gene transfer is expected to revolutionize the treatment of renal diseases. Previous gene transfer methods using nonviral vectors administered via renal arterial, pelvic, or ureteric routes into the glomerulus, tubules, or interstitial fibroblasts have resulted in low-level expression for <1 month. The peritubular capillaries (PTC) network is one of the main targets of kidney transplant rejection and of progressive tubulointerstitial fibrosis, which typifies all progressive renal diseases. To access the PTC, we retrogradely injected a lacZ expression plasmid in Ringer's solution into the renal vein of rats. We detected lacZ expression exclusively in the interstitial fibroblasts near the PTC of the injected kidney by immunoelectron microscopic analysis. Nephrotoxicity attributable to gene transfer was not apparent. We then used a rat erythropoietin (Epo) expression plasmid vector, pCAGGS-Epo, in a reporter assay. We obtained maximal Epo expression when the DNA solution was injected within 5 sec, and with a volume of 1.0 ml. We observed a dose-response relationship between serum Epo levels and the amount of injected DNA up to 100 microg. We detected the transgene-derived Epo mRNA by reverse transcription polymerase chain reaction only in the kidneys injected with pCAGGS-Epo. After an injection of 100 microg of pCAGGS-Epo, the serum Epo levels peaked at 208.3 +/- 71.8 mU/ml at week 5, and gradually decreased to 116.2 +/- 38.7 mU/ml at week 24. A similar pattern was obtained using smaller doses of plasmid, 2 microg or 30 microg of pCAGGS-Epo. Transgene-derived Epo secretion resulted in significant erythropoiesis. This novel technique is simple and safe, allowing high-level and long-term stable gene expression specific to the fibroblasts near the PTC, and should have therapeutic value for future applications in humans.

Proteolipidic vectors for gene transfer to the lung

In order to develop improved synthetic gene transfer vectors, we have synthesized bifunctional peptides composed of a DNA binding peptide (P2) and ligand peptides selected by the phage display technique on tracheal epithelial cells. We have evaluated the capacity of these peptides to enhance the gene transfer efficiency of the cationic lipid DOTAP to the mouse lung. To optimize the in vivo transfection efficiency, we first compared the efficiency of DOTAP to transfect the lung by either intravenous injection or aerosolization. We then tested DNA/Peptide/DOTAP complexes formed at different Peptide/DNA and DOTAP/DNA charge ratios. Under optimal conditions, precompaction of DNA by peptide P2 gave a higher expression in the mouse lung using the luciferase reporter gene than DOTAP/DNA complexes. A further increase of transfection efficiency was obtained with the bifunctional peptide P2-9. Experiments performed with the GFP reporter gene showed expression in the alveolar parenchyme.

Vehicles for oligonucleotide delivery to tumours

The vasculature of a tumour provides the most effective route by which neoplastic cells may be reached and eradicated by drugs. The fact that a tumour's vasculature is relatively more permeable than healthy host tissue should enable selective delivery of drugs to tumour tissue. Such delivery is relevant to carrier-mediated delivery of genetic medicine to tumours. This review discusses the potential of delivering therapeutic oligonucleotides (ONs) to tumours using cationic liposomes and cyclodextrins (CyDs), and the major hindrances posed by the tumour itself on such delivery. Cationic liposomes are generally 100-200 nm in diameter, whereas CyDs typically span 1.5 nm across. Cationic liposomes have been used for the introduction of nucleic acids into mammalian cells for more than a decade. CyD molecules are routinely used as agents that engender cholesterol efflux from lipid-laden cells, thus having an efficacious potential in the management of atherosclerosis. A recent trend is to employ these oligosaccharide molecules for delivering nucleic acids in cells both in-vitro and in-vivo. Comparisons are made with other ON delivery agents, such as porphyrin derivatives (< 1 nm), branched chain dendrimers (approximately 10 nm), polyethylenimine polymers (approximately 10 nm), nanoparticles (20-1,000 nm) and microspheres (> 1 microm), in the context of delivery to solid tumours. A discourse on how the chemical and physical properties of these carriers may affect the uptake of ONs into cells, particularly in-vivo, forms a major basis of this review.

Molecular forces for the binding and condensation of DNA molecules

Atomic force microscopy has been used to investigate the binding between a double-stranded DNA and bilayers of cationic lipids and zwitterionic lipids in low ionic-strength solutions. The binding of a DNA molecule to freshly cleaved mica surface in solution has also been measured. The binding of DNA molecules to cationic lipid bilayers has a minimal strength of approximately 45 pN. On zwitterionic lipid bilayers and mica surface, the minimal binding strength is approximately twice that value. The binding also has a dynamic nature, with only a certain percentage of recorded force curves containing the binding characteristics. Divalent Mg(2+) ions enhance the binding by increasing that percentage without any effect on the binding strength. We have also observed a long-range attraction between DNA molecules and cationic lipid bilayers with a strength much larger than the minimum force and a range well over 50 nm, possibly related to the driving force responsible for the two-dimensional condensation of DNA.

Side-effects of a systemic injection of linear polyethylenimine-DNA complexes

BACKGROUND

Systemic administration of linear polyethylenimine-DNA complexes (L-PEI/DNA) results in transient expression of the transgene in the lung. This study analyzes the side-effects associated with L-PEI-mediated transfection.

METHODS

Mice weighing from 16 to 25 g received increasing amounts of L-PEI/DNA intravenously. Gene expression was evaluated using luciferase as a reporter gene. Toxicity was evaluated by monitoring the appearance of shock after injection, the survival of the animals, and the microscopic damage in the tissues. Adherence of blood cells and endothelium activation were observed after CD11-b and von Willebrand immunostaining. Anti-aggregant treatments were used in order to prevent the formation of thrombi.

RESULTS

Increasing the quantity of L-PEI/DNA resulted in a marked augmentation of the luciferase activity in the lung, but was associated with liver necrosis and death. Lethality was reached at lower doses in older mice, suggesting an age influence. Transfection was associated with activation of the lung endothelium and increased adhesion of small aggregates containing platelets and CD11-b-positive cells, without the appearance of large thrombi and of lung injury. Anti-aggregant treatments (aspirin, EDTA, heparin or clopidogrel) decreased the L-PEI-mediated transfection, supporting the hypothesis that platelets participate in the blocking of DNA complexes in the lung capillaries.

CONCLUSION

This study demonstrates that L-PEI/DNA activates the lung endothelium and forms small aggregates, a side-effect linked to the transfection efficiency.

Efficient liposome-mediated gene transfection and expression in the intact human uterus

Although gene therapy has been used for correction of metabolic defects in diseases such as cystic fibrosis, as adjuvant treatment in cancer, and in the treatment of infectious diseases, there has been no report of gene transfer to the intact female reproductive tract. We assessed the ability to transfect the human uterus ex vivo and thereby evaluate the applicability of gene therapy to gynecology. The uterine lumen was accessed transcervically, using an intrauterine insemination catheter. pcDNA3.1 plasmid containing the Escherichia coli lacZ reporter gene was delivered to each uterus via liposome-mediated transfection. Control uteri were transfected with empty pcDNA3.1. Immunohistochemical analysis revealed beta-galactosidase expression in the lacZ-treated uteri in endometrial epithelial cells, endometrial stromal cells, and myometrium to a depth of 1.75 cm from the endometrial-myometrial junction. Highest expression was seen in endometrial glandular epithelial cells, with significant expression in the stroma and adjacent myometrium. Each of these cell types in the control uteri showed no beta-galactosidase expression. Successful gene transfection and expression in the intact human uterus can be accomplished easily, rapidly, and efficiently. Gene therapy may have wide applicability in the treatment and study of gynecologic disease.

Delivery of novel macromolecular drugs against HIV-1

The development of new low molecular weight drugs against human immunodeficiency virus Type 1 (HIV-1) targets other than reverse transcriptase (RT) and protease, such as the integrase and the envelope glycoprotein, is likely to take many years. Macromolecular drugs, including antisense oligonucleotides, ribozymes, RNA decoys and transdominant mutant proteins, may be able to interfere with a relatively large number of viral targets, thereby decreasing the likelihood of the emergence of drug-resistant strains. It may also be relatively easy to alter the sequence of some of the macromolecular drugs to counter emerging drug-resistant viruses. The delivery of antisense oligonucleotides and ribozymes to HIV-1 infected or potentially infectable cells by antibody-targeted liposomes, certain cationic lipid formulations and pH-sensitive liposomes results in significant anti-HIV-1 activity. These carriers not only facilitate cytoplasmic delivery but also protect the drugs from nuclease digestion. Delivery of therapeutic genes (another form of macromolecular drug) to target cells is an important challenge of gene therapy. Following delivery by a viral vector, sufficient levels of gene expression must be maintained over an extended period of time to have therapeutic activity. Robust expression of therapeutically useful ribozymes, antisense, decoys and aptamers can be achieved by the use of Pol III expression systems. Moloney murine leukaemia virus- (MoMuLV), adeno-associated virus (AAV)-, or HIV-derived vectors expressing a variety of therapeutic genes have been used successfully to inhibit HIV-1 replication in cultured cells.

Rapid and wide-reaching delivery of HIV-1 env DNA vaccine by intranasal administration

Although the potential of DNA vaccination is now beginning to be greatly appreciated, no detailed study of its localization in tissue or its expression kinetics has been reported. In this study, we investigated these issues using HIV-1 DNA plasmids administered either intranasally or intramuscularly. Fluorescence in situ hybridization (FISH) revealed that the human immunodeficiency virus (HIV) plasmids administered intranasally localized in the alveoli, lung, liver, spleen, regional lymph nodes, kidney, fetus, and esophagus. These HIV plasmids were detected 2 to 4 weeks after administration. We detected messenger RNA production of HIV env gene in the lung, liver and spleen, and human immunodeficiency virus type 1 (HIV-1)-specific proteins were detectable in the lung. These observations may provide important information for understanding the mechanisms of strong immune activation induced by DNA vaccination via the intranasal route. This technology of DNA administration suggests possible practical applications for vaccination and probably for gene therapy.

Liver-targeted gene transfer into a human hepatoblastoma cell line and in vivo by sterylglucoside-containing cationic liposomes

We investigated the transfection efficiency of beta-sitosterol beta-D-glucoside (Sit-G)-containing liposome/DNA complex (Sit-G-liposome/DNA complex) for liver targeting. The Sit-G-liposome/DNA complex was composed of Tfx-20 reagent (Tfx), ie synthetic cationic lipid [N,N,N',N'-tetramethyl-N,N'-bis(2-hydroxyethyl)-2,3-di(oleoyloxy)-1,4-butanediammonium iodide] with L-dioleoylphosphatidylethanolamine (DOPE), 3 beta[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol) and Sit-G with plasmid DNA. The in vitro studies were performed in HepG2 cells in serum-containing medium and the in vivo studies were carried out in the mice following intravenous injection. The Sit-G-liposome produced a Sit-G-liposome/DNA complex of relatively small size (100--250 nm). Transfection efficiency of the luciferase marker gene by Sit-G-liposome/DNA complex was increased in the presence of 10% serum in vitro, and was selectively high in the mouse liver reaching expression values up to an average of 14.9 pg luciferase/mg tissue protein, compared with Tfx/DNA complex, which showed approximately three-fold higher gene expression than Sit-G-liposome/DNA complex in vitro. High in vitro transfection efficiency by Sit-G-liposome/DNA complex seemed to be possible even with large lipid precipitates, whereas high in vivo activity seemed to be related to small and dispersed complexes. The interaction of liposome/DNA complexes with serum may be a key point to predict the in vivo efficiency of a liposome vector.

Anti-HIV-1 activity of an antisense phosphorothioate oligonucleotide bearing imidazole and primary amine groups

We have previously shown that RNA cleaving reagents with imidazole and primary amine groups on the 5'-end of antisense oligodeoxyribonucleotides could site-specifically cleave CpA as the target sequence of the substrate tRNA in vitro. In this study, a RNA cleaving reagent, composed of imidazole and primary amine groups on an antisense phosphorothioate oligonucleotide (Im-anti-s-ODN), was synthesized and evaluated for anti-HIV-1 activity in MT-4 cells. The sequence of the Im-anti-s-ODN was designed to be complementary to the HIV-1 gag-mRNA and to bind adjacent to the CpA cleavage site position. Im-anti-s-ODN encapsulated with the transfection reagent, DMRIE-C, had higher anti-HIV-1 activity than the unmodified antisense phosphorothioate oligonucleotide (anti-s-ODN) at a 2 microM concentration. Furthermore, the Im-anti-ODN encapsulated with DMRIE-C conferred sequence-specific inhibition.

Targeted ultrasonic contrast agents for molecular imaging and therapy

Targeted contrast agents are expanding the detectability and diagnosis of pathology from a strict anatomic to biochemical basis. Moreover, these new agents, in their various forms, offer the potential for site-specific drug and gene delivery, ie, the "magic bullet" first postulated by Paul Erhlich 100 years ago. The ability to direct drugs to the molecular signatures of disease, to confirm noninvasively their presence at the site-of-interest, and to quantify the adequacy of local drug concentration at the time of treatment, ie, rational targeted drug delivery, offers exciting new clinical paradigms in the near future.

Targeting transgene expression for cystic fibrosis gene therapy

We have developed an expression cassette for cystic fibrosis (CF) gene therapy using control elements from the human cytokeratin 18 gene (KRT18, also known as K18). KRT18 is naturally expressed in a spatial pattern similar to that of CFTR, the gene mutated in CF. We delivered a KRT18-driven lacZ plasmid complexed with cationic liposomes intravenously to mice and examined expression in various tissues. We found expression in nasal and bronchial epithelium, airway submucosal glands, gall bladder, and kidneys. Expression was low in pancreas and gut, and absent from liver and alveolar lung. This is consistent with the expression pattern reported for a K18lacZ transgenic mouse. Following delivery of a cytomegalovirus (CMV) major immediate-early promoter/enhancer-driven lacZ plasmid, we found expression in bronchi, submucosal glands, alveolar cells, liver, and kidney. We did not detect expression in nose, pancreas, gall bladder, or gut. Using fluorescently labeled plasmid delivered by means of liposomes, we identified the liver, alveolar lung, and kidneys as the major plasmid deposition sites. Our data demonstrate that a KRT18-driven expression vector delivered systemically can target gene expression to CF-affected tissues, despite an uneven distribution of plasmid DNA. A KRT18-based vector may be a useful alternative to viral promoter-based vectors in clinical gene therapy trials to treat CF.

Mechanism of lipoplex gene delivery in mouse lung: binding and internalization of fluorescent lipid and DNA components

We introduce a lung inflation-fixation protocol to examine the distribution and gene transfer efficiency of fluorescently tagged lipoplexes using fluorescence confocal microscopy within thick lung tissue sections. Using this technique, we tested the hypothesis that factors related to lipoplex distribution were the predominant reason that intravenous (i.v.) administration of lipoplex was superior to intratracheal (i.t.) administration for gene transfer in the murine lung. Lipoplex distribution was analyzed using digitized images of overlapping fields, reconstructed to view an entire lung lobe. Intravenously administered lipoplexes were confined to the capillary network and homogenously distributed throughout the lung lobe. In contrast, i.t. administration resulted in regional distribution of lipoplex, concentrated around bronchioles and distal airways. Not all the bronchioles were stained with lipoplex, suggesting that the airway-administered solution became channeled through certain bronchiolar pathways. A fluorescent oligonucleotide was used as a marker for cytoplasmic release of nucleic acids. Quantification of the resulting fluorescent nuclei was used to define the relationship between cytoplasmic release of nucleic acids and gene expression. Endothelial cells were stained after i.v. administration, and epithelial cells were stained after i.t. administration. The delivery of nucleic acids was also more homogeneous with i.v. administration of lipoplex than with i.t. administration. After i.t. administration, it was notable that high concentrations of fluorescent nuclei correlated with low GFP expression. This suggested that toxicity was associated with high local concentrations of cationic lipoplexes. The ratio of GFP-expressing cells to fluorescent nuclei indicated that capillary endothelial cells were more efficient in gene expression per delivery event than were pulmonary epithelial cells. Thus, the greater gene expression efficiency of i.v. administered lipoplexes was due not only to the initial distribution but also to the greater efficiency of the vascular endothelial cells to appropriately traffic and express the foreign gene.

Nonviral vectors in the new millennium: delivery barriers in gene transfer

Development of an efficient method for introducing a therapeutic gene into target cells in vivo is the key issue in treating genetic and acquired diseases by gene therapy. To this end, various nonviral vectors have been designed and developed, and some of them are in clinical trials. The simplest approach is naked DNA injection into local tissues or systemic circulation. Physical (gene gun, electroporation) and chemical (cationic lipid or polymer) approaches have also been utilized to improve the efficiency and target cell specificity of gene transfer by plasmid DNA. After administration, however, nonviral vectors encounter many hurdles that result in diminished gene transfer in target cells. Cationic vectors sometimes attract serum proteins and blood cells when entering into blood circulation, which results in dynamic changes in their physicochemical properties. To reach target cells, nonviral vectors should pass through the capillaries, avoid recognition by mononuclear phagocytes, emerge from the blood vessels to the interstitium, and bind to the surface of the target cells. They then need to be internalized, escape from endosomes, and then find a way to the nucleus, avoiding cytoplasmic degradation. Successful clinical applications of nonviral vectors will rely on a better understanding of barriers in gene transfer and development of vectors that can overcome these barriers.

Transfection of urothelial cells using methyl-beta-cyclodextrin solubilized cholesterol and Dotap

the murine urothelial cell line, mb49 was transfected with the reporter gene pcmvlacz using a number of commercial transfection agents. the transfection efficiency of these agents, as determined by beta-galactosidase activity, is in the order of dotap>superfect>Fugene. The addition of methyl-beta-cyclodextrin solubilized cholesterol (MBC) to Dotap and Superfect further improved their transfection efficiency by 3.8-fold and 2.6-fold, respectively. beta-Galactosidase activity was detectable within 1 h of transfection and peaked at 48 h. Nuclear and cytoplasmic separation showed that with Dotap + methyl-beta-cyclodextrin solubilized cholesterol (DMBC), the DNA plasmid complex was found in both the nucleus and the cytoplasm. In vivo, murine bladders were transfected with an intravesical instillation of DMBC + DNA for 2 h. Two days later the bladder, lungs, liver, spleen and heart were assayed for the presence of the beta-galactosidase gene by staining and PCR. Expression of the gene was confined to the bladder. Both in vitro and in vivo expression was observed after as little as a 15 min exposure to DMBC:DNA. Expression of the marker gene was present up to 30 days after transfection in vivo. From our data it appears that DMBC is the best nonviral agent for the transfection of urothelial cells in vitro and in vivo.

Cationic liposome-mediated gene delivery to the liver and to hepatocellular carcinomas in mice

The potential of cationic liposomes as nonviral vectors for in vivo gene delivery to the liver and to intrahepatic hepatocellular carcinoma (HCC) was investigated. Mice were injected via the tail vein or portal vein with a cationic lipid complexed to plasmid DNA (pDNA) encoding the chloramphenicol acetyltransferase (CAT) reporter gene at various cationic lipid:pDNA molar ratios to analyze the efficiency of gene delivery after intravenous administration. Tail vein injection resulted in high CAT expression levels in lung and spleen and low levels in the liver. Portal vein injection, by comparison, significantly enhanced hepatic reporter gene expression but also resulted in pronounced hepatic toxicity. Gene delivery to intrahepatic tumors produced by intrahepatic injection of human HCC cells was analyzed in nude mice. Tail vein injection as well as portal vein injection resulted in low levels of gene expression in intrahepatic tumors. By comparison, high levels of gene expression were achieved by direct, intratumoral injection of liposome-pDNA complexes, with only minimal expression in the surrounding normal liver. Therefore, direct liposome-pDNA complex injection appears far superior to systemic or portal intravenous administration for gene therapy of localized intrahepatic tumors, and may be a useful adjunct in the treatment of human HCCs.

Sequential Injection of Cationic Liposome and Plasmid DNA Effectively Transfects the Lung with Minimal Inflammatory Toxicity

A major hurdle to lipoplex-based systemic gene delivery is acute inflammatory toxicity. In this study, a safe, simple, and effective alternative to lipoplex administration, specifically, sequential injection of cationic liposome and plasmid DNA, was evaluated. When plasmid DNA was injected into the tail vein of mice 2-5 min after the injection of cationic liposomes, 50-80% lower levels of proinflammatory cytokines, including TNF-alpha, IL-12, and IFN-gamma, were observed compared to lipoplex injection. The sequential injection technique yielded a two- to fivefold higher level of transgene expression in the lung and was more effective in repeated dosing than lipoplex. Other types of lipoplex-associated toxicities, such as neutropenia, lymphopenia, thrombocytopenia, and complement depletion, were also significantly reduced with sequential injection. The reduction in cytokine release was observed with several different liposome formulations and appeared to be a general phenomenon.

Contribution of plasmid DNA to hepatotoxicity after systemic administration of lipoplexes

Several studies have demonstrated that intravenous administration of DNA complexed with cationic lipid vectors induces the production of large quantities of proinflammatory cytokines. In this study we confirm these observations, using cationic lipid DOTAP and cationic phospholipid compounds. Moreover, we demonstrate that although intravenous administration of lipid-DNA complexes does not induce toxic effects in the lung, high transgene expression in lung correlates with histopathological lesions in liver, this fact being documented by high transaminase levels in serum of treated mice. We examine the contribution of various components of the lipoplexes in this observed liver toxicity, as well as in the increasing level of transaminases, and more particularly the role of nonmethylated CpG sequences of plasmid DNA. We show that blood samples from animals treated either with cationic lipid alone, or with cationic lipid complexed with methylated plasmid DNA, contain low levels of transaminases. The significant decrease in transaminase levels after injection of cationic lipid-methylated pDNA complexes leads us to believe that nonmethylated CpG sequences could play a major role in this hepatoxicity. Similar results were observed when using a vector that did not encode a transgene, demonstrating that the expression of luciferase in lung was not responsible for this liver toxicity. All these observations suggest that significant work should be devoted to understand more clearly the mechanism of cationic lipid-DNA complex toxicity, and to overcome the problems subsequent to administration of non-methylated CpG sequences of plasmid DNA.

Antisense therapy of influenza

The liposomally encapsulated and the free antisense phosphorothioate oligonucleotides (S-ODNs) with four target sites (PB1, PB2, PA, and NP) were tested for their abilities to inhibit virus-induced cytopathogenic effects by a MTT assay using MDCK cells. The liposomally encapsulated S-ODN complementary to the sites of the PB2-AUG initiation codon showed highly inhibitory effects. On the other hand, the inhibitory effect of the liposomally encapsulated S-ODN targeted to PB1 was considerably decreased in comparison with those directed to the PB2 target sites. The liposomally encapsulated antisense phosphorothioate oligonucleotides exhibited higher inhibitory activities than the free oligonucleotides, and showed sequence-specific inhibition, whereas the free antisense phosphorothioate oligonucleotides were observed to inhibit viral absorption to MDCK cells. Therefore, the antiviral effects of S-ODN-PB2-AUG and PA-AUG were examined in a mouse model of influenza virus A infection. Balb/c mice exposed to the influenza virus A (A/PR/8/34) strain at dose of 100 LD(50)s were treated i.v. with various doses (5-40 mg/kg) of liposomally (Tfx-10) encapsulated PB2-AUG or PA-AUG before virus infection and 1 and 3 days postinfection. PB2-AUG oligomer treated i.v. significantly prolonged the mean survival time in days (MDS) and increased the survival rates with a dose-dependent manner. We demonstrate the first successful in vivo antiviral activity of antisense administered i.v. in experimental respiratory tract infections induced with influenza virus A.

Non-viral vectors in cancer gene therapy: principles and progress

This review focuses on the use of synthetic (non-viral) delivery systems for cancer gene therapy. Therapeutic strategies such as gene replacement/mutation correction, immune modulation and molecular therapy/'suicide' gene therapy type approaches potentially offer unique and novel ways of fighting cancer, some of which have already shown promise in early clinical trials. However, the specific and efficient delivery of the genetic material to remote tumors/metastases remains a challenge, which is being addressed using a variety of viral and non-viral systems. Each of these disparate systems has distinct advantages and disadvantages, which need to be taken into account when a specific therapeutic gene is being used. The review concentrates on particulate gene delivery systems, which are formed through non-covalent complexation of cationic carrier molecules (e.g. lipids or polymers) and the negatively charged plasmid DNA. Such systems tend to be comparatively less efficient than viral systems, but have the inherent advantage of flexibility and safety. The DNA-carrier complex acts as a protective package, and needs to be inert and stable while in circulation. Once the remote site has been reached the complex needs to efficiently transfect the targeted (tumor) cells. In order to improve overall transfection specificity and efficiency it is necessary to optimize intracellular trafficking of the DNA complex as well as the performance after systemic administration. Common principles and specific advantages or disadvantages of the individual synthetic gene delivery systems are discussed, and their interaction with tumor-specific and generic biological barriers are examined in order to identify potential strategies to overcome them.

Pharmacological aspects of targeting cancer gene therapy to endothelial cells

Targeting cancer gene therapy to endothelial cells seems to be a rational approach, because (a) a clear correlation exists between proliferation of tumor vessels and tumor growth and malignancy, (b) differences of cell membrane structures between tumor endothelial cells and normal endothelial cells exist which could be used for targeting of vectors and (c) tumor endothelial cells are accessible to vector vehicles in spite of the peculiarities of the transvascular and interstitial blood flow in tumors. Based on the knowledge on the pharmacokinetics of macromolecules it can be concluded that vectors targeting tumor endothelial cells should own a long blood residence time after intravascular application. This precondition seems to be fulfilled best by vectors exhibiting a slight anionic charge. A long blood residence time would allow the formation of a high amount of complexes between tumor endothelial cells and vector particles. Such high amount of complexes should enable a high transfection rate of tumor endothelial cells. In view of their pharmacokinetic behavior nonviral vectors seem to be more suitable for in vivo targeting tumor endothelial cells than viral vectors. Specific binding of nonviral vectors to tumor endothelial cells should be enhanced by multifunctional ligands and the transduction efficiency should be improved by cationic carriers. Effector genes should encode proteins potent enough to induce reactions which eliminate the tumor tissue. To be effective to that degree such proteins should induce self-amplifying antitumor reactions. Examples for proteins which have the potential to induce such self-amplifying tumor reactions are proteins endowed with antiangiogenic and antiproliferative activity, enzymes which convert prodrugs into drugs and possibly also proteins which induce embolization of tumor vessels. The pharmacological data for such examples are discussed in detail.

Structure and function of lipid-DNA complexes for gene delivery

Owing to the rapid development of in vivo applications for nonviral gene delivery vectors, it is necessary to have a better understanding of how the structure-activity relationships of these lipid-DNA complexes are affected by their environment. Indeed, research in gene therapy first focused on in vitro cell culture studies to determine the mechanisms involved in the delivery of DNA into the cell. New biophysical techniques such as electron microscopy and X-ray diffraction have been developed to discern the structure of the lipid-DNA complex. However, further studies have revealed discrepancies between optimal lipid-DNA formulations for in vitro transfection and for in vivo administration of these vectors. Furthermore, some immune stimulatory effects have been associated with in vivo lipid-DNA administration. This review summarizes the current state of knowledge on in vitro and in vivo lipid-DNA complex transfections. New prospects of vectors for in vivo gene transfer are also discussed.

Inhibitory effects of tumor necrosis factor-alpha on cationic lipid-mediated gene delivery to airway cells in vitro

Cationic liposomes have been used successfully for DNA delivery to airway cells in vitro and are being tested in human clinical trials for their efficacy in cystic fibrosis transmembrane conductance regulator (CFTR) gene delivery in cystic fibrosis patients. While cationic liposomes are effective for transfection of airway cells in culture, they have not been effectively used for gene delivery to human airway cells in vivo. Several barriers in cystic fibrosis lungs, including increased amounts of mucus, phagocytic cell activity and cytokine-rich milieu caused by inflammation, may cause inhibition of gene transfection. As presented in this paper, we examined the effects of inflammatory cytokines on cationic lipid-mediated transfection of model airway cells. The results of these experiments indicate that tumor necrosis factor (TNF)-alpha dramatically inhibits Lipofectin-mediated transfection efficiency of H441 cells. Addition of anti-TNF-alpha neutralizing antibody results in recovery of efficiency. Results of temporal studies are consistent with the concept that TNF-alpha reduces transfection efficiency by a mechanism(s) other than or in addition to gene expression. These results are corroborated by fluorescence microscopic experiments which demonstrate that endocytosis of lipoplex is altered in the presence of TNF-alpha.