Delivery and pathway in MCF7 cells of DNA vectorized by cationic liposomes derived from cholesterol

PEGylated and non-PEGylated siRNA lipoplexes formulated with cholesteryl cytofectins promote efficient luciferase knockdown in HeLa tat luc cells

Delivery of small interfering RNAs (siRNAs) remains a major challenge in their development for therapeutic applications, and cationic liposomes are being actively investigated for this purpose. Six liposome formulations containing the cytofectins 3β[N-(N ',N '-dimethylaminopropane)-carbamoyl] cholesterol (Chol-T) or 3β[N-(N ',N ',-dimethylaminopropylsuccinamidohydrazido)-carbamoyl] cholesterol (MS09) and varying amounts of distearoylphosphatidylethanolamine poly(ethylene glycol)2000, were prepared. Lipoplexes formed with siRNA were characterized by gel retardation analysis and cryo-electron microscopy. All lipoplexes exhibited low cytotoxicity in the HeLa tat luc cell line while Chol-T lipoplexes, containing anti-luciferase siRNA, achieved 93.4% knockdown of the luciferase transcript at 30 nM siRNA. Poly(ethylene glycol)2000 incorporation only marginally reduced knockdown efficiency.

Novel targeted liposomes deliver sirna to hepatocellular carcinoma cells in vitro

Liposomes form a major class of non-viral vectors for short interfering RNA delivery, however tissue and cell-specific targeting are additional requirements in the design of short interfering RNA delivery systems with a therapeutic potential. Selective delivery of liposomes to hepatocytes may be achieved by directing complexes to the asialoglycoprotein receptor, which is expressed on hepatocytes, and which displays high affinity for the β-d-galactopyranosyl moiety. We aimed to show that the d-galactopyranosyl ring in direct β-glycosidic link to cholesterol, when formulated into liposomes with 3β[N-(N',N'-dimethylaminopropane) carbamoyl] cholesterol (Chol-T) or its quaternary trimethylammonium analogue (Chol-Q), may promote targeted delivery of cytotoxic short interfering RNA to the human hepatoma cell line HepG2 via the asialoglycoprotein receptor. Liposome-short interfering RNA interactions were characterized by electron microscopy, dye displacement, gel retardation and nuclease assays. Stable short interfering RNA-protective lipoplexes were formed at N/P ratios in the range 5:1-7:1. Targeted lipoplex 4 achieved high transfection efficiencies at 50 nm short interfering RNA (70%) and <10% in a competition assay, whilst untargeted complexes reached low levels at the same concentration (<25%). Transfection efficiencies of all lipoplexes in the asialoglycoprotein receptor-negative cell line HEK293 under the same conditions were low. Lipoplexes containing cholesteryl-β-d-galactopyranoside may therefore form the basis for the development of useful hepatotropic short interfering RNA delivery vectors.

Biotin-directed assembly of targeted modular lipoplexes and their transfection of human hepatoma cells in vitro

The asialoglycoprotein receptor, which is abundantly and near exclusively expressed on hepatocytes, has received much attention in the design of non-viral hepatotropic DNA delivery systems. Thus, asialoglycoproteins and hexopyranosyl ligands have been coupled to DNA-binding cationic polymers and liposomes in the assembly of complexes intended for uptake by liver parenchymal cells. The aim of the study was to construct a hepatocyte-targeted multimodular liposome-based transfecting complex, in which the biotin-streptavidin interaction provides the cohesive force between the ligand asialorosomucoid and the liposome bilayer, and to evaluate its transfection capabilities in the hepatocyte-derived human transformed cell line HepG2. Dibiotinylated asialoorosomucoid was attached to cationic liposomes constructed from 3beta[N-(N',N'-dimethylaminopropane)-carbamoyl] cholesterol (Chol-T):dioleoylphosphatidylethanolamine:biotinylcholesterylformylhydrazide (MSB1) (48:50:2 mole ratio) through streptavidin interposition. Liposome-pGL3 DNA interactions were studied by gel band shift and ethidium displacement assays. The cytotoxicity of assemblies was evaluated in the HepG2 cell line and transfection capabilities determined by measuring the activity of the transgene luciferase. Binding assays showed that all DNA was liposome associated at a DNA (negative):liposome (positive) charge ratio of 1:1. Accommodation of a streptavidin dibiotinylated asialoorosomucoid assembly was achieved at a DNA:liposome:streptavidin dibiotinylated asialoorosomucoid ratio of 1:4:9 (weight basis). Complexes showed optimal transfection activity at this ratio, which was reduced 10-fold by the presence of the competing ligand asialofetuin. The streptavidin-biotin interaction has been applied for the first time to the assembly of hepatocyte-targeted lipoplexes that display asialoorosomucoid and that are well tolerated by a human hepatoma cell line in which transfection is demonstrably achieved by receptor mediation. Favorable size and charge ratio characteristics suggest that this system may be suitable for in vivo application.

Nano and microtechnologies for the delivery of oligonucleotides with gene silencing properties

Oligonucleotides (ONs) are synthetic fragments of nucleic acid designed to modulate the expression of target proteins. DNA-based ONs (antisense, antigene, aptamer or decoy) and more recently a new class of RNA-based ONs, the small interfering RNAs (siRNAs), have gained great attention for the treatment of different disease states, such as viral infections, inflammation, diabetes, and cancer. However, the development of therapeutic strategies based on ONs is hampered by their low bioavailability, poor intracellular uptake and rapid degradation in biological fluids. The use of a non-viral carrier can be a powerful tool to overcome these drawbacks. Lipid or polymer-based nanotechnologies can improve biological stability and cellular uptake of ONs, with possibility of tissue and/or cellular targeting. The use of polymeric devices can also produce a prolonged release of the ON, thus reducing the need of frequent administrations. This review summarizes advantages and issues related to the main non-viral vectors used for ON delivery.

Modifications in the Head Group and in the Spacer of Cholesterol-based Cationic Lipids Promote Transfection in Melanoma B16-F10 Cells and Tumours

A series of four cationic lipids derived from cholesterol was synthesised and their efficiencies to vectorise nucleic acids were compared. The investigation concerns the effects of systematic chemical modifications in the polar head and in the spacer. The cationic lipid molecules used are in the same family of 3beta[N-(N',N',N'-trimethylaminoethane)-carbamoyl] cholesterol iodide (TMAEC-Chol), presenting a spacer of two or three carbons and a quaternary ammonium polar head ramified with methyl or ethyl groups. These lipids formed stable liposomes sizing from 100 to 200 nm when prepared with the colipid dioleoyl phosphatidylethanolamine (DOPE). The goal of this work was to investigate the effect of the chemical structure of these cationic lipids on lipofection. Their ability to form complexes with DNA, their cytotoxicity and their transfection efficiency in vitro and in vivo were studied. Results were compared with those obtained from the well known cholesterol-based cationic lipid DC-Chol. In a melanoma cell line (B16-F10), results showed that either the polar head or the spacer affected the cytotoxicity. Cationic lipids with three ethyl groups in the head are more toxic than those with three methyl groups while cationic lipids with three carbons in the spacer are less toxic than those with two carbons in the spacer. The best transfection level was obtained in vitro and in vivo with cationic lipids having 3C in the spacer. Data indicated that among these lipids, in vivo gene transfer is advantaged by the methylated polar head while in vitro the best level was obtained with the ethylated one. Finally, it was observed that the chemical structure influences the transfection in the presence of serum while the complex charge and the DOPE ratios in liposomes preferentially affect the interaction with erythrocytes. Argumentations are proposed to explain the discrepancies between in vitro and in vivo transfection results concerning the optimal charge ratio and the chemical nature of the cationic lipid head group.

Cholesteryl cytofectins with primary amino head groups transfect transformed human epithelial cell lines efficiently

Two novel cholesterol-based cytofectins containing primary amino head groups, glycylcholesteryl formylhydrazide (MS10) and beta-alanylcholesterylformylhydrazide (MS11), have been prepared and incorporated into unilamellar cationic liposomes in equimolar amounts with dioleoylphosphatidylethanolamine (DOPE) as colipid. Stable lipoplexes were formed with pGL3 DNA which afforded protection to the DNA from serum nuclease digestion. Packing of the DNA was shown by ethidium displacement to be more effective in MS11 lipoplexes. High transfection levels in three human transformed epithelial cell lines HeLa (cervical), SNO (esophageal), HepG2 (hepatocyte-derived), and the murine fibroblast line NIH-3T3 were achieved by both lipoplexes at liposome: DNA ratios of 6:1 and 7:1 ((w)/(w)) corresponding to +/- charge ratios of 1.6:1 and 1.9:1. MS11 lipoplexes, in particular, afforded high transfection activities in the presence of fetal bovine serum.

Specific lipoplex-mediated antisense against Bcl-2 in breast cancer cells: a comparison between different formulations

G3139 is an antisense oligonucleotide (ODN) that can down-regulate bcl-2, thus potentially acting as a potent anticancer drug. However, effective therapy requires efficient ODN delivery, which may be achieved by employing G3139 lipoplexes. Yet, lipofection is a complex, multifactorial process that is still poorly understood. In order to shed more light on this issue, we prepared 18 different G3139 lipoplex formulations and compared them in terms of their capability to transfect MCF-7 breast cancer cells. Each formulation was composed of a cationic lipid and sometimes a helper lipid. The cationic lipid was either DOTAP (N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride), DC-CHOL (3ss[N-(N',N'-dimethylaminoethane)carbamoyl]-cholesterol), or CCS (ceramide carbomoyl spermine). The helper lipid was either DOPC, DOPE, or cholesterol. Each lipid combination existed in two different structural forms--either large unilamellar vesicles (approximately 100 nm LUV) or unsized heterolamellar vesicles (UHV). Cell proliferation assays were used to evaluate the cytotoxicity of G3139 lipoplexes, control cationic lipid assemblies, and free G3139. Western blots were used to confirm the specific activity of G3139 as an anti-bcl-2 antisense agent. We determined that treatment of MCF-7 cells with G3139:CCS lipoplexes (UHV-derived) produced a maximal 50-fold improvement in antisense efficacy compared to treatment with free G3139. The other G3139 lipoplexes were not superior to free G3139. Thus, successful lipofection requires precise optimization of lipoplex lipid composition, structure, and concentration.

Selective gene delivery for cancer therapy using cationic liposomes: in vivo proof of applicability

Targeted gene therapy is essential if cancer treatment is to become a reality with this form of therapy. In the past few years, cationic liposomes, discovered 2 decades ago, and at present, the most commonly used class of transfection reagents, have been tested in various clinical trials for diseases not restricted to cancer. They have been shown to be selective for tumour vascular endothelial cells raising hopes for antiangiogenic and antivascular therapies. They are also capable of being selectively delivered to the lungs and liver when administered intravenously. These vesicles are also being targeted to the tumour in various parts of the body by using advanced liposomal systems such as antibody-antigen and ligand-receptor combinations. This review looks at the state of play in this rapidly growing field.

A cationic cytofectin with long spacer mediates favourable transfection in transformed human epithelial cells

The synthesis and transfection potential of a novel cationic cholesterol cytofectin with a dimethylamino head group and a long 12 atom, 15A spacer incorporating relatively polar amido and dicarbonyl hydrazine linkages are reported. Thus N,N-dimethylaminopropylamidosuccinylcholesterylformylhydrazide (MS09) in equimolar admixture with dioleoylphosphatidylethanolamine (DOPE) forms stable unilamellar liposomes (80-150 nm) which cluster into very effective transfecting, serum nuclease-resistant, lipoplexes with DNA (180-200 nm) at a liposome+/DNA- molar charge ratio of 2.8:1 (12:1, w/w). Gel retardation and ethidium displacement assays confirmed that DNA was fully liposome-associated and maximally compacted at this ratio. Transfection levels in three human transformed epithelial cell lines, as established by luciferase transgene activity, was found to be optimal at this charge ratio and in the following order: cervical carcinoma (HeLa)>oesophageal carcinoma (SNO)>hepatoblastoma (HepG2). Activity in the murine fibroblast line NIH-3T3 was comparable to that in HepG2 cells. MS09 lipoplexes achieved approximately three-times and two-times greater activity than Lipofectin complexes in HeLa and SNO cells, respectively, whilst comparable levels were recorded in HepG2 and NIH-3T3 cells. MS09 lipoplexes were well tolerated by HepG2, HeLa and SNO cells with cell numbers found to be 80, 85 and 75% of untreated cultures, respectively, at the optimal transfection concentration. These lipoplexes also exhibited high activity in the presence of 10% foetal bovine serum (FBS) in HeLa (17% inhibition) and HepG2 (33% inhibition) cells.

Cyclodextrins and oligonucleotide delivery to solid tumours

Cyclodextrins (CyDs) have traditionally been used for dissolving hydrophobic chemicals into aqueous media, and more recently, for inducing cholesterol efflux from lipid-laden cells as a proposed mechanism for reversal of cardiovascular disease. This review discusses the potential of delivering therapeutic oligonucleotides to solid tumours using CyD molecules. The physicochemical properties of these oligosaccharide molecules, and the barriers posed by the solid tumour itself, factors that affect may affect the uptake of oligonucleotides by CyDs, are the major foci of this review.

Targeted gene delivery into HepG2 cells using complexes containing DNA, cationized asialoorosomucoid and activated cationic liposomes

Unilamellar activated cationic liposomes containing 3beta[N-(N',N'-dimethylaminopropane)-carbamoyl] cholesterol, dioleoyl phosphatidylethanolamine (DOPE) and the N-hydroxysuccinimide ester of cholesteryl hemisuccinate (4:5:1, molar ratio) have been prepared and their DNA-binding capacity has been assessed in a gel retardation assay. Ternary complexes composed of activated cationic liposomes, carbodiimide-cationized asialoorosomucoid (Me+AOM) and pRSVL plasmid DNA were assembled for receptor-mediated DNA delivery into cells expressing the asialoglycoprotein receptor (ASGP-R). Binding of complexes in which Me+AOM was replaced by fluoresceinated Me+AOM (FMe+AOM) to the human hepatocellular cell line HepG2 at 4 degrees C was severely reduced by co-incubation with asialoorosomucoid (AOM). Moreover, assemblies containing liposomes, pRSVL DNA and Me+AOM (8:1:4, w/w/w) promoted high levels of luciferase activity in this cell line (1.3 x 10(7) relative light units/mg soluble cell protein). Assays conducted in the presence of a hundred-fold excess of the ligand AOM afforded considerably lower levels of transfection (2.5 x 10(5) relative light units/mg soluble cell protein). In contrast, the highest level of luciferase activity achieved with liposome, pRSVL DNA, AOM complexes was only a quarter of the best levels obtained with liposome, pRSVL DNA, Me+AOM assemblies. These findings strongly support the notion that complexes gain entry into hepatocyte-derived cells by ASGP-R mediation and that they are potentially useful gene carriers to liver hepatocytes.

A hydroxyethylated cholesterol-based cationic lipid for DNA delivery: effect of conditioning

We have synthesised a novel cholesterol-based cationic lipid to promote DNA transfer in cells. This lipid, dimethyl hydroxyethyl aminopropane carbamoyl cholesterol iodide (DMHAPC-Chol) contains a biodegradable carbamoyl linker and a hydroxyethyl group in the polar amino head moiety and is characterised by NMR. Liposomes prepared from this lipid and dioleoyl phosphatidyl ethanolamine (DOPE) in equimolar proportion showed a weak cytotoxicity as revealed by MTT assays and are efficient to deliver plasmids DNA evaluated by the expression of reporter genes in vitro and in vivo. In this paper, we present an original method to determine the lipid concentration based on the colorimetric detection of the colipid DOPE and the measure of the molar ratio DOPE/cationic lipid in the liposome by FTIR spectroscopy. The liposomes and lipid/DNA complexes structures were characterized by transmission electron microscopy (TEM) and by quasi-elastic light scattering (QLS). TEM indicated that the complexes correspond to aggregates containing globular substructures with liposomes size. The method of immuno-gold labelling was used to detect plasmid in the complex and reveals the presence of DNA inside the aggregates. Transfection results showed efficient DNA transfer depending on the charge ratio and liposomes conditioning. Gel retardation results indicated that at a molar charge ratio between X = 1.5 and X = 2.5 (depending on the liposome conditioning), all DNA was taken by liposomes. We showed that conditioning by freeze-drying (lyophilization) facilitates storage and improves transfection efficiency. When the liposomes were lyophilized prior to DNA addition or when the complexes were subjected to freeze-thawing cycles, the obtained complexes showed a transfection with levels enhanced up to four and five-fold respectively for the lyophilized liposomes and freeze-thawed complexes. NMR was used to characterize the modifications under freezing which showed an effect on 31P spectra.

Endocrine aspects of cancer gene therapy

The field of cancer gene therapy is in continuous expansion, and technology is quickly moving ahead as far as gene targeting and regulation of gene expression are concerned. This review focuses on the endocrine aspects of gene therapy, including the possibility to exploit hormone and hormone receptor functions for regulating therapeutic gene expression, the use of endocrine-specific genes as new therapeutic tools, the effects of viral vector delivery and transgene expression on the endocrine system, and the endocrine response to viral vector delivery. Present ethical concerns of gene therapy and the risk of germ cell transduction are also discussed, along with potential lines of innovation to improve cell and gene targeting.

Antisense downregulation of mutant huntingtin in a cell model

BACKGROUND

Huntington's disease (HD) is an inherited neurodegenerative disorder which is caused by an expansion of a CAG repeat sequence in the HD gene. The repeat encodes an expanded polyglutamine tract in the protein huntingtin. The still unknown pathological mechanisms leading to death of specific neurons in the brains of HD patients correlate with the expression of mutant huntingtin. Therefore, we have studied whether mutant huntingtin expression can be downregulated by antisense technique.

METHODS

NT2 precursor cells and differentiated postmitotic NT2-N neurons, respectively, were transfected with plasmid constructs containing exon 1 of the HD gene with expanded CAG repeats in frame with the reporter protein EGFP. The transfected cell cultures were treated with a phosphorothioated antisense oligonucleotide (PS-ASHD/20+) or a control oligonucleotide either by cotransfection or by addition to the culture medium.

RESULTS

Expression of the fusion protein containing the mutant huntingtin fragment resulted in diffuse green fluorescence in the cytoplasm and formation of aggregates in some of the NT2 cells and NT2-N neurons. We obtained antisense sequence-specific inhibition of expression of the fusion protein and/or suppression of the aggregate formation in both cell types. In the NT2 cells the antisense effect was dependent on the way of administration of the oligo.

CONCLUSIONS

The PS-antisense oligo is effective in downregulation of mutant huntingtin, and the reduction of aggregate formation is a sensitive biological marker. The findings suggest that antisense knockdown of huntingtin could be a useful strategy for treatment of HD, and could also be suitable for studies of the normal and pathological function of huntingtin in different cellular model systems.

Transfer into a mesothelioma cell line of tumor suppressor gene p16 by cholesterol-based cationic lipids

In this work, the tumor suppressor gene p16 was efficiently transferred into FR cells isolated from a patient with malignant mesothelioma using cationic liposomes prepared from trimethyl aminoethane carbamoyl cholesterol (TMAEC-Chol) and triethyl aminopropane carbamoyl cholesterol (TEAPC-Chol). This transfer was performed after preliminary assays were undertaken to find the optimal transfection conditions. Results showed that an efficient transfer of plasmids containing the reporter gene pCMV-beta galactosidase vectorized by TMAEC-Chol/DOPE and TEAPC-Chol/DOPE liposomes into mesothelioma FR cells was obtained as assessed by luminometric measurements of beta-galactosidase activity. Cytotoxicity studied by MTT test showed that at concentrations used for this study, the cationic liposomes have no effect on cell growth. Transfer into mesothelioma FR cells of a plasmid construct containing the tumor suppressor gene p16 was carried out with these liposomes. Western blotting and immunofluorescence showed the presence of p16 in treated cells. An inhibition of cell growth was observed, indicating that efficient tumor suppressor gene transfer can be performed by using cationic liposomes.

Evaluation and optimization of DNA delivery into gliosarcoma 9L cells by a cholesterol-based cationic liposome

This paper reports results concerning the transfection of gliosarcoma cells 9L using an original cholesterol-based cationic liposome as carrier. This cationic liposome was prepared from triethyl aminopropane carbamoyl cholesterol (TEAPC-Chol) and a helper lipid, dioleoyl phosphatidyl ethanolamine (DOPE). The used concentration of liposome was not cytotoxic as revealed by the MTT test. TEAPC-Chol/DOPE liposomes allowed the plasmids encoding reporter genes to enter the nucleus as observed both by electron microscopy and functionality tests using fluorescence detection of green fluorescent protein (GFP) and luminometric measurements of luciferase activity. By changing the cationic lipid/DNA molar charge ratio, optimal conditions were determined. Further, improvement of the transfection level has been obtained by either precondensing plasmid DNA with poly-L-lysine or by adding polyethylene glycol (PEG) in the transfection medium. The optimal conditions determined are different depending on whether the transfection is made with cells in culture or with tumors induced by subcutaneous (s.c.) injection of cells in Nude mice. For in vivo assays, a simple method to overcome the interference of haemoglobin with the chemiluminescence intensity of luciferase has been used. These results would be useful for gaining knowledge about the potential for the cationic liposome TEAPC-Chol/DOPE to transfect brain tumors efficiently.

Aerosolization of lipoplexes using AERx Pulmonary Delivery System

The lung represents an attractive target for delivering gene therapy to achieve local and potentially systemic delivery of gene products. The objective of this study was to evaluate the feasibility of the AERx Pulmonary Delivery System for delivering nonviral gene therapy formulations to the lung. We found that "naked" DNA undergoes degradation following aerosolization through the AERx nozzle system. However, DNA formulated with a molar excess of cationic lipids (lipoplexes) showed no loss of integrity. In addition, the lipoplexes showed no significant change in particle size, zeta (zeta) potential, or degree of complexation following extrusion. The data suggest that complexation with cationic lipids had a protective effect on the formulation following extrusion. In addition, there was no significant change in the potency of the formulation as determined by a transfection study in A-549 cells in culture. We also found that DNA formulations prepared in lactose were aerosolized poorly. Significant improvements in aerosolization efficiency were seen when electrolytes such as NaCl were added to the formulation. In conclusion, the data suggest that delivery of lipoplexes using the AERx Pulmonary Delivery System may be a viable approach for pulmonary gene therapy.

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.

Cellular pathway of plasmids vectorized by cholesterol-based cationic liposomes

We investigated by transmission electron microscopy the cellular route in tumor MCF7 cells of DNA labeled with digoxigenin, carried by cationic liposomes (Lip+) prepared from TMAEC-Chol [3 beta(N-(N',N',N'-trimethylaminoethane)-carbamoyl)cholesterol iodide] and TEAPC-Chol [3 beta(N-(N',N',N'-triethylaminopropane)-carbamoyl)cholesterol iodide], two cholesterol-based cationic lipids containing a quaternary ammonium. In a previous work we showed the pathway of cationic lipid/plasmid complexes from the beginning of endocytosis until their entry into the perinuclear area. Beyond this limit, unlabeled exogenous plasmids cannot be distinguished with nuclear DNA. This work dealt with the cellular fate of cationic liposome-vectorized plasmids labeled with digoxigenin using an immunogold procedure. Early after the beginning of transfection (30 min, 1 hr, 5 hr), gold particles were observed only in the cytoplasm and in endosome-like vesicles, whereas after 24 hr gold particles were densely present in the nucleus. These results demonstrate the nuclear localization of plasmids vectorized by the cationic liposomes used. The results are discussed in comparison with transfection efficiency measurements.

Cytotoxicity issues pertinent to lipoplex-mediated gene therapy in-vivo

Cationic liposomes bind with nucleic acids such as plasmids and oligodeoxynucleotides to form complexes known as lipoplexes. Although these lipoplexes have several advantages over other forms of nucleic acid transfer methods in cell culture and in-vivo, toxicity remains a problem, especially in-vivo. Nevertheless, these carriers have been used in clinical trials against cystic fibrosis and cancer and their usage is attributed mainly to their versatility, especially when it comes to the range of routes available for administration of nucleic-acid-based drugs in-vivo.

A simple method to overcome the interference of hemoglobin in the detection of reporter genes in vivo

The determination of chemiluminescent intensity of reporter gene expression in vivo is generally disturbed by the presence of hemoglobin. Current methods consist in using perfusion to eliminate blood from investigated tumors or organs. In this work we propose a simple method to overcome this difficulty. The method consists in establishing an absorbance-dependence plot of the ratio R% = phi/phi(0) between the chemiluminescent intensities measured when hemoglobin is present or absent. For every measurement of the luminescent intensity phi on sample containing blood, if the absorbance A of the hemoglobin is determined, it allows one to have the intensity ratio R% which in turn gives the corrected intensity phi(0) when the absorption by hemoglobin is eliminated. The method is particularly adapted for comparative measurements of transfection levels in tumors where perfusion cannot be easily performed.

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.

Mitochondria transfection by oligonucleotides containing a signal peptide and vectorized by cationic liposomes

The progress of research in gene therapy allows hope for treatment of mitochondrial genetic disorders provided that efficient methods for gene transfer into mitochondria can be found. In this work, we have used an oligonucleotide coupled covalently to a mitochondria-targeted peptide at one end and a cationic liposome prepared from trimethyl aminoethane carbamoyl cholesterol iodide (TMAEC-Chol) to carry it in living cells. With a fluorescent probe to label the oligonucleotide at the other end and by means of confocal microscopy, we show that such modified oligonucleotides complexed to liposomes enter into the cytoplasm of human fibroblasts in primary culture, and then, after dissociation from the complexes, they penetrate into the mitochondria. The fluorescence was still observed after 8 days, suggesting the continued presence of oligonucleotides. At the concentrations used for this study, the cationic liposomes have practically no effect on cell growth, as revealed by the MTT assay.