Antisense therapeutics: from theory to clinical practice

Topological capture of mRNA for silencing gene expression

We describe herein topological mRNA capture using branched oligodeoxynucleotides (ODNs) with multiple reactive functional groups. These fragmented ODNs efficiently formed topological complexes on template mRNA in vitro. In cell-based experiments targeting AcGFP mRNA, the bifurcated reactive ODNs showed a much larger gene silencing effect than the corresponding natural antisense ODN.

Endonuclease G modulates the alternative splicing of deoxyribonuclease 1 mRNA in human CD4+ T lymphocytes and prevents the progression of apoptosis

Apoptotic endonucleases act cooperatively to fragment DNA and ensure the irreversibility of apoptosis. However, very little is known regarding the potential regulatory links between endonucleases. Deoxyribonuclease 1 (DNase I) inactivation is caused by alternative splicing (AS) of DNase I pre-mRNA skipping exon 4, which occurs in response to EndoG overexpression in cells. The current study aimed to determine the role of EndoG in the regulation of DNase I mRNA AS and the modulation of its enzymatic activity. A strong correlation was identified between the EndoG expression levels and DNase I splice variants in human lymphocytes. EndoG overexpression in CD4⁺ T cells down-regulated the mRNA levels of the active full-length DNase I variant and up-regulated the levels of the non-active spliced variant, which acts in a dominant-negative fashion. DNase I AS was induced by the translocation of EndoG from mitochondria into nuclei during the development of apoptosis. The DNase I spliced variant was induced by recombinant EndoG or by incubation with EndoG-digested cellular RNA in an in vitro system with isolated cell nuclei. Using antisense DNA oligonucleotides, we identified a 72-base segment that spans the adjacent segments of exon 4 and intron 4 and appears to be responsible for the AS. DNase I-positive CD4⁺ T cells overexpressing EndoG demonstrated decreased progression towards bleomycin-induced apoptosis. Therefore, EndoG is an endonuclease with the unique ability to inactivate another endonuclease, DNase I, and to modulate the development of apoptosis.

Chronic myelogenous leukemia on target

Chronic myelogenous leukemia (CML) is commonly treated with tyrosine kinase inhibitors (TKIs) that inhibit the pro-leukemic activity of the BCR-ABL1 oncoprotein. Despite the therapeutic progress mediated by TKI use, off-target effects, treatment-induced drug resistance, and the limited effect of these drugs on CML stem cells (SCs) are major drawbacks frequently resulting in insufficient or unsustainable treatment. Therefore, intense research efforts have focused on development of improved TKIs and alternative treatment strategies to eradicate CML SCs. Alongside efforts to design superior protein inhibitors, the need to overcome the poor therapeutic effect of TKIs on CML SCs has led to a renaissance of antisense strategies, as they are reported as effective in more primitive cell types. Despite the greater drug design flexibility offered by antisense sequence variability and remarkable chemical improvements, antisense drugs exhibit unacceptable levels of off-target effects, precluding them from large-scale clinical testing. Recent advances in antisense drug design have led to a pioneering mRNA recognition concept that may offer a helping hand in eliminating off-target effects, and has potential to bridge the gap between research and clinical practice.

[Apoptotic endonuclease EndoG regulates alternative splicing of human telomerase catalytic subunit hTERT]

Human telomerase catalytic subunit hTERT is subjected to alternative splicing results in loss of its function and leads to decrease of telomerase activity. However, very little is known about the mechanism of hTERT pre-mRNA alternative splicing. Apoptotic endonuclease EndoG is known to participate this process. The aim of this study was to determine the role of EndoG in regulation of hTERT alternative splicing. Increased expression of b-deletion splice variant was determined during EndoG over-expression in CaCo-2 cell line, after EndoG treatment of cell cytoplasm and nuclei and after nuclei incubation with EndoG digested cell RNA. hTERT alternative splicing was induced by 47-mer RNA oligonucleotide in naked nuclei and in cells after transfection. Identified long non-coding RNA, that is the precursor of 47-mer RNA oligonucleotide. Its size is 1754 nucleotides. Based on the results the following mechanism was proposed. hTERT pre-mRNA is transcribed from coding DNA strand while long non-coding RNA is transcribed from template strand of hTERT gene. EndoG digests long non-coding RNA and produces 47-mer RNA oligonucleotide complementary to hTERT pre-mRNA exon 8 and intron 8 junction place. Interaction of 47-mer RNA oligonucleotide and hTERT pre-mRNA causes alternative splicing.

The impact of ion-pairing reagents on the selectivity and sensitivity in the analysis of modified oligonucleotides in serum samples by liquid chromatography coupled with tandem mass spectrometry

Present study highlights the usage of various ion-pairing agents and their impact on the process of separation and ionization of oligonucleotides in the fortified human serum samples. What is more, retention studies involved different stationary phases, including: octadecyl, phenyl, pentafluorophenyl groups and ligands with embedded polar groups. It was proved that retention of oligonucleotides strongly depends on the alkyl chain branching in the structure of ion pairing reagent. Furthermore ion-pairing agents build of straight alkyl chain are more easily adsorbed on the stationary phase modified with octadecyl groups, while branching of alkyl chain caused more effective adsorption of studied compounds at phenyl groups compared to octadecyl ones. The lowest limit of quantification values were obtained for 5mMN,N-dimethylbutylamine, while the highest values are characteristic for hexylamine. Moreover it was shown that a 2-fold increase of ion-pairing agent concentration results in higher LOQ. The greatest sensitivity was obtained for 2.5mMN,N-dimethylbutylamine/150mM hexafluoroisopropanol. On the other hand Hypersil GOLD aQ column was the most appropriate in terms of time and separation effectiveness. The developed method was successfully used for the determination of studied oligonucleotides and their metabolites in human serum samples. The compounds were separated in just 3.5min with high sensitivity (0.09-0.16ng).

Antisense Oligonucleotides Targeting Raf-1 Block Japanese Encephalitis Virus In Vitro and In Vivo

Japanese encephalitis virus (JEV) infections represent a major health concern in Southeast Asia since no effective treatments are available. Recently, several reports have demonstrated that inhibition of certain host cell proteins prevents viral infection. Raf-1 kinase is a central component of many signaling pathways involved in normal cell growth and oncogenic transformation, and Ras/Raf/ERK signaling activation has been observed during viral infections (including JEV infection). In this study, Raf-1 was confirmed to be upregulated by JEV infection, which suggested that Raf-1 might be important for JEV infection and might be a target for novel anti-JEV drugs. To determine the role of Raf-1 during the JEV infection process, antisense oligonucleotides (ASODNs) were used to downregulate Raf-1 expression in JEV-infected baby hamster kidney (BHK-21) cells and African green monkey kidney (Vero) cells. From five ASODNs candidates tested, Raf-1-1 (Raf-1 antisense) significantly downregulated Raf-1 protein expression levels, significantly inhibited cytopathic effect (CPE) in cultured cells, and reduced JEV RNA levels in cell medium without affecting cell viability. Furthermore, it also demonstrated that ASODN Raf-1-1 possessed therapeutic effects by using a lethal JEV infection mouse model. In conclusion, data presented in this report demonstrated that ASODN Raf-1-1 could suppress Raf-1 protein and that Raf-1 inhibition suppressed JEV replication in vitro and in vivo. These data provided evidence for targeting Raf-1 in the development of novel anti-JEV therapies. In addition, Raf-1-1 represents potential drugs that can be adapted for treating JEV infections.

Lipid Nanoparticles Loaded with an Antisense Oligonucleotide Gapmer Against Bcl-2 for Treatment of Lung Cancer

PURPOSE

Bcl-2 is an anti-apoptotic gene that is frequently overexpressed in human cancers. G3139 is an antisense oligonucleotide against bcl-2 that has shown limited efficacy in clinical trials. Here, we report the synthesis of a new antisense oligonucleotide containing additional chemical modifications and its delivery using nanoparticles.

METHODS

An oligonucleotide G3139-GAP was synthesized, which has 2'-O-methyl nucleotides at the 5' and 3' ends based on a "gapmer" design. Furthermore, G3139-GAP was incorporated into lipid nanoparticles (LNPs) composed of DOTAP/egg PC/cholesterol/Tween 80. The LNP-loaded G3139-GAP was evaluated in A549 lung cancer cells both in vitro and in a murine xenograft model for biological activity and therapeutic efficacy.

RESULTS

The LNPs showed excellent colloidal and serum stability, and high encapsulation efficiency for G3139-GAP. They have a mean particle diameter and zeta potential of 134 nm and 9.59 mV, respectively. G3139-GAP-LNPs efficiently downregulated bcl-2 expression in A549 cells, as shown by 40% and 83% reduction in mRNA and protein levels, respectively. Furthermore, G3139-GAP-LNPs were shown to inhibit tumor growth, prolong survival, and downregulate tumor bcl-2 expression in an A549 murine xenograft tumor model. These data indicate that G3139-GAP-LNPs have excellent anti-tumor efficacy and warrant further evaluation.

Application of hydrophilic interaction liquid chromatography coupled with mass spectrometry in the analysis of phosphorothioate oligonucleotides in serum

Most of synthetic, modified oligonucleotides are candidates for therapeutics. Consequently, their quick, reliable and sensitive analysis has become a critical challenge for scientists. The main aim of the present study was an investigation of the influence of stationary phase type, mobile phase salt and its concentration on the separation and determination of the selected compounds by hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry. Three different columns, together with ammonium acetate and formate, were applied for this purpose. The separation of mixtures of phosphorothioate oligonucleotides and their synthetic metabolites was successfully performed. Moreover, an attempt to isolate these compounds from human serum samples was also made together with their separation, qualification and quantification by hydrophilic interaction liquid chromatography and tandem mass spectrometry. The method developed during the study appeared to be effective and sensitive, due to the limit of quantification which equaled 142-165ppb.

Oligonucleotide therapeutics in cancer

Alterations in pre-mRNA splicing can have profound effects on gene expression and lead to cellular transformation. Oligonucleotide therapeutics are drugs that manipulate gene expression and improve the disease state. Antisense oligonucleotides hybridize with a target mRNA to downregulate gene expression via an RNase H-dependent mechanism. Additionally, RNase H-independent splice switching oligonucleotides (SSO) modulate alternative or aberrant splicing, to favor the therapeutically relevant splicing product. This chapter summarizes the progress made in the application of these oligonucleotide drugs in the treatment of cancer.

One-Shot Immunomodulatory Nanodiamond Agents for Cancer Immunotherapy

The use of functional nanodiamonds (fNDs) to deliver CpG oligonucleotides (ODNs) for sustained immunostimulation is reported. It is demonstrated that monotherapy using this immunostimulatory agent significantly suppresses the tumor growth in two murine tumor models. This fND-based nanoagent opens new opportunities for immunotherapy, as well as clinical applications of various types of therapeutic nucleic acids.

Application of a cholesterol stationary phase in the analysis of phosphorothioate oligonucleotides by means of ion pair chromatography coupled with tandem mass spectrometry

The main aim of this study was the investigation of the influence of several ion pair reagents towards both the retention and the mass spectrometry sensitivity of phosphorothioate oligonucleotides. A cholesterol stationary phase was applied for the first time in the analysis of this group of compounds. The mobile phase composition was modified by changing the concentration and the type of amines and acetates or 1,1,1,3,3,3-hexafluoroisopropanol. It has been shown that the increase of amines concentration results in the retention factor increase for each oligonucleotide, on each adsorbent. The only exception was the mobile phase composed of triethylamine and 1,1,1,3,3,3-hexafluoroisopropanol. This is a consequence of interactions taking place between a cholesterol molecule and an alcohol. This effect was convenient when the mass spectrometry detection was applied, since it allowed an increase in the sensitivity. Moreover, optimization of the mobile phase composition and its impact on the efficiency of ionization process and on the sensitivity in mass spectrometry were also presented. The optimization of this new method, based on cholesterol stationary phase coupled with mass spectrometry detection, was finally applied for the determination of phosphorothioate oligonucleotides impurity in a real sample.

Development of a method based on ultra high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry for studying the in vitro metabolism of phosphorothioate oligonucleotides

Ultra high performance liquid chromatography hyphenated with quadrupole time-of-flight mass spectrometry was used to determine the products of the in vitro metabolism of phosphorothioate oligonucleotides. These compounds may be used during antisense therapy as synthetic fragments of genes. For this reason, both a sample preparation method and a qualification method were developed during this study. Liquid–liquid extraction, protein or oligonucleotide precipitation, and solid-phase extraction were tested and compared in order to select the method that yielded the highest recoveries. Ion pair chromatography was used for separation while mass spectrometry was applied for metabolite identification. The influence of the type of ion pair reagent used on the resolution and sensitivity was investigated. Results indicated that a mixture of 1,1,1,3,3,3-hexafluoro-2-propanol, N,N-dimethylbutylamine, and methanol was the best mobile phase for maximizing both of these parameters. The developed method was applied to investigate the compounds that form during the incubation of phosphorothioate oligonucleotides with human liver microsomes. Metabolites with short sequences were created after 8 hours, while oligonucleotides constructed from a large number of nucleotide units were obtained after 12 hours of incubation. Moreover, regardless of the length of the polynucleotide chain, metabolites were produced by the same mechanism: enzymatic cleavage at the 3′ end of the sequence.

Oligonucleotide therapeutics: chemistry, delivery and clinical progress

Oligonucleotide therapeutics have the potential to become a third pillar of drug development after small molecules and protein therapeutics. However, the three approved oligonucleotide drugs over the past 17 years have not proven to be highly successful in a commercial sense. These trailblazer drugs have nonetheless laid the foundations for entire classes of drug candidates to follow. This review will examine further advances in chemistry that are earlier in the pipeline of oligonucleotide drug candidates. Finally, we consider the possible effect of delivery systems that may provide extra footholds to improve the potency and specificity of oligonucleotide drugs. Our overview focuses on strategies to imbue antisense oligonucleotides with more drug-like properties and their applicability to other nucleic acid therapeutics.

Evidence that TNF-β (lymphotoxin α) can activate the inflammatory environment in human chondrocytes

Introduction

Inflammatory cytokines play a key role in the pathogenesis of joint diseases such as rheumatoid arthritis (RA). Current therapies target mainly tumor necrosis factor α (TNF-α) as this has proven benefits. However, a large number of patients do not respond to or become resistant to anti-TNF-α therapy. While the role of TNF-α in RA is quite evident, the role of TNF-β, also called lymphotoxin-α (LT-α), is unclear. In this study we investigated whether TNF-β and its receptor play a role in chondrocytes in the inflammatory environment.

Methods

An in vitro model of primary human chondrocytes was used to study TNF-β-mediated inflammatory signaling.

Results

Cytokine-induced inflammation enhances TNF-β and TNF-β-receptor expression in primary human chondrocytes accompanied by the up-regulation of inflammatory (cyclooxygenase-2), matrix degrading (matrix metalloproteinase-9 and -13) and apoptotic (p53, cleaved caspase-3) signaling pathways, all known to be regulated by NF-κB. In contrast, anti-TNF-β, similar to the natural NF-κB inhibitor (curcumin, diferuloylmethane) or the knockdown of NF-κB by using antisense oligonucleotides (ASO), suppressed IL-1β-induced NF-κB activation and its translocation to the nucleus, and abolished the pro-inflammatory and apoptotic effects of IL-1β. This highlights, at least in part, the crucial role of NF-κB in TNF-β-induced-inflammation in cartilage, similar to that expected for TNF-α. Finally, the adhesiveness between TNF-β-expressing T-lymphocytes and the responding chondrocytes was significantly enhanced through a TNF-β-induced inflammatory microenvironment.

Conclusions

These results suggest for the first time that TNF-β is involved in microenvironment inflammation in chondrocytes during RA parallel to TNF-α, resulting in the up-regulation of NF-κB signaling and activation of pro-inflammatory activity.

Stimuli-responsive polymers in gene delivery

Recent interest in clinical therapy has been directed to deliver nucleic acids (DNA, RNA or short-chain oligonucleotides) that alter gene expression within a specific cell population, thereby manipulating cellular processes and responses, which in turn stimulate immune responses or tissue regeneration, or blocks expression at the level of transcription or translation for treatment of several diseases. Both ex vivo and in vivo gene delivery can be achieved mostly by using a delivery system (vector). Viral vectors exhibit high gene expression, but also have very significant side effects. Mainly cationic polymeric systems are used as nonviral vectors, although usually with low levels of transfection. Through the use of stimuli-responsive polymers as novel vectors for gene delivery, two benefits can be obtained: high gene expression efficiency and more selective gene expression.

Epidermal growth factor receptor targeting in cancer: a review of trends and strategies

The epidermal growth factor receptor (EGFR) is a cell-surface receptor belonging to ErbB family of tyrosine kinase and it plays a vital role in the regulation of cell proliferation, survival and differentiation. However; EGFR is aberrantly activated by various mechanisms like receptor overexpression, mutation, ligand-dependent receptor dimerization, ligand-independent activation and is associated with development of variety of tumors. Therefore, specific EGFR inhibition is one of the key targets for cancer therapy. Two major approaches have been developed and demonstrated benefits in clinical trials for targeting EGFR; monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs). EGFR inhibitors like, cetuximab, panitumumab, etc. (mAbs) and gefitinib, erlotinib, lapatinib, etc. (TKIs) are now commercially available for treatment of variety of cancers. Recently, many other agents like peptides, nanobodies, affibodies and antisense oligonucleotide have also shown better efficacy in targeting and inhibiting EGFR. Now a days, efforts are being focused to identify molecular markers that can predict patients more likely to respond to anti-EGFR therapy; to find out combinatorial approaches with EGFR inhibitors and to bring new therapeutic agents with clinical efficacy. In this review we have outlined the role of EGFR in cancer, different types of EGFR inhibitors, preclinical and clinical status of EGFR inhibitors as well as summarized the recent efforts made in the field of molecular EGFR targeting.

A triple-helix forming oligonucleotide targeting genomic DNA fails to induce mutation

Purine tracts in duplex DNA can bind oligonucleotide strands in a sequence specific manner to form triple-helix structures. Triple-helix forming oligonucleotides (TFOs) targeting supFG1 constructs have previously been shown to be mutagenic raising safety concerns for oligonucleotide-based pharmaceuticals. We have engineered a TFO, TFO27, to target the genomic Hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus to define the mutagenic potential of such structures at genomic DNA. We report that TFO27 was resistant to nuclease degradation and readily binds to its target motif in a cell free system. Contrary to previous studies using the supFG1 reporter construct, TFO27 failed to induce mutation within the genomic HPRT locus. We suggest that it is possible that previous reports of triplex-mediated mutation using the supFG1 reporter construct could be confounded by DNA quadruplex formation. Although the present study indicates that a TFO targeting a genomic locus lacks mutagenic activity, it is unclear if this finding can be generalised to all TFOs and their targets. For the present, we suggest that it is prudent to avoid large purine stretches in oligonucleotide pharmaceutical design to minimise concern regarding off-target genotoxicity.

Sirt-1 is required for the inhibition of apoptosis and inflammatory responses in human tenocytes

Tendon overuse injuries and tendinitis are accompanied by catabolic processes and apoptosis of tenocytes. However, the precise molecular mechanisms of the destructive processes in tendon are not fully understood. Sirt-1, a nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase, has been linked to transcriptional silencing and appears to play a key role in inflammation. The purpose of this study was to examine whether down-regulation of Sirt-1 using antisense oligonucleotides (ASO) affects inflammatory and apoptotic signaling in tenocytes. Transient transfection of tenocytes with ASO against Sirt-1 induced expression of Bax and other proteins involved in apoptosis (cleaved caspase-3 and poly(ADP-ribose)polymerase), acetylation of tumor suppressor p53, and mitochondrial degradation. Interestingly, Sirt-1 was found to interact directly with p53. In contrast, Sirt-1 activator resveratrol inhibited interleukin-1β (IL-1β)- and nicotinamide-induced NF-κB activation and p65 acetylation and suppressed the activation of IκB-α kinase. Resveratrol also reversed the IL-1β- or nicotinamide-induced up-regulation of various gene products that mediate inflammation (cyclooxygenase-2) and matrix degradation (matrix metalloproteinase-9) that are known to be regulated by NF-κB. Knockdown of Sirt-1 by using ASO abolished the inhibitory effects of resveratrol on inflammatory and apoptotic signaling including Akt activation and SCAX suppression. Down-regulation of histone deacetylase Sirt-1 by mRNA interference abrogated the effect of resveratrol on NF-κB suppression, thus highlighting the crucial homeostatic role of this enzyme. Overall, these results suggest for the first time that Sirt-1 can regulate p53 and NF-κB signaling via deacetylation, demonstrating a novel role for resveratrol in the treatment of tendinitis/tendinopathy.

Synthesis, physicochemical and biological properties of oligonucleotides incorporated with amino-isonucleosides

Antisense oligonucleotides (ASONs) and siRNAs have been applied extensively for the regulation of cellular and viral gene expression, and RNAi is currently one of the most promising new approaches for anti-tumor and anti-viral therapy. In order to improve bioactivity properties and physicochemical properties of siRNA, we synthesized a novel class of ASONs II–VII incorporated with amino-isonucleoside (isoA₁ and isoA₂) for investigation on basic physicochemical properties. Then we designed amino-isonucleoside (isoA₁, isoA₂ and isoT₁) incorporated siRNA 2–7. Some meaningful results have been obtained from the physicochemical property experiments in ASONs. In RNAi potency experiments, we investigated RNAi potency of each strand of the siRNA. These amino-isonucleosides incorporated siRNAs showed promising bioactivity properties and had position specificity. Reduced off target effect from sense strand loading in siRNA application was observed.

Antisense oligodeoxynucleotide targeting HER2 mRNA sensitized docetaxel in breast cancer treatment

CONTEXT

Human epidermal growth factor receptor 2 (HER2) is one of the oncogenes closely associated with the development and prognosis of breast carcinoma. Down-regulation of HER2 mRNA by antisense oligodeoxynucleotide (ASO) HER2 has been suggested to be a feasible treatment for patients with breast carcinoma.

OBJECTIVE

The antitumor effects of ASO HA6722 were investigated in vitro and in vivo.

MATERIALS AND METHODS

In this study, SK-BR-3, a HER2-overexpressing breast carcinoma cell line, was used as the model for in vitro experiments. Inhibitory effects of the ASO HA6722 were detected by methyl-thiazoldiphenyl tetrazolium (MTT) assay. Meanwhile, HER2 mRNA levels were monitored by reverse transcription polymerase chain reaction (RT-PCR). The in vivo antitumor effects were evaluated in nude mice xenograft model.

RESULTS

Our results showed that HA6722 alone could inhibit the growth of SK-BR-3 cells in a dose-dependent manner with the IC(50) value of 41.8 ± 8.1 nM. In addition, the antitumor effect of docetaxel (TXT) could be sensitized by low dose of HA6722 both in vitro and in vivo, suggesting that ASO HA6722 could inhibit the growth of breast cancer cells and enhance the cytotoxic effects of TXT.

DISCUSSION AND CONCLUSION

The combination treatment of TXT and HA6722 could be a more effective approach for breast cancer treatment. The future study should focus on the antitumor effect in other models.

Chitosan-coated liposomes for intracellular oligonucleotides delivery: characteristics and cell uptake behavior

Surface modification of liposomes with polymer to optimize drug delivery was well developed recently. The objective of the present work was to evaluate the feasibility of chitosan-coated liposomes (CSLP) as vehicles for anti-sense oligodeoxynucleotides (ASON). CSLP was obtained by adding chitosan dropwise to liposomes under magnetic stirring. The effect of chitosan content on size, zeta potential, and coating efficiency was investigated, which showed that chitosan increased the size and zeta potential of CSLP, and the coating efficiency increased with chitosan content increasing. Agarose gel electrophoresis was employed to evaluate the loading efficiency of CSLP for ASON, from which one could see ASON was completely combined to CSLP when the mass ratio of total lipids:ASON was more than 50:1. MTT assay showed that CSLP took on very low cytotoxicity, which is much lower than chitosan. At last, cell uptake behavior was investigated by a flow cytometer, which showed that CSLP enhanced significantly the COS7 cells uptake of ASON. All the results indicated that the CSLP could be a promising non-viral ASON vehicle.

Amelioration of dextran sulfate sodium-induced colitis by neuropeptide Y antisense oligodeoxynucleotide

BACKGROUND

Neuropeptide Y (NPY) from enteric neurons has been shown to play an important role in immune and inflammatory responses. The purpose of the present study was to investigate the effects of NPY antisense oligodeoxynucleotides (ODNs) on an experimental model of ulcerative colitis (UC).

METHODS

NPY antisense ODNs were administered in experimental colitis induced by dextran sulfate sodium (DSS). The disease activity index (DAI) and histological score were observed. The tumor necrosis factor (TNF)-alpha and NPY levels were measured by enzyme-linked immunosorbent assay. Phosphorylated Akt (p-Akt) expression was determined by immunohistochemical staining. Activated nuclear factor (NF)-kappaB was assessed by western blot analysis. Myeloperoxidase (MPO) activity was determined by using MPO assay kit.

RESULTS

A significant improvement was observed in DAI and histological score in rats with NPY antisense ODNs, and the increase in NPY and TNF-alpha levels, MPO activity, and the expression p-Akt and p-NF-kappaB in rats with DSS-induced colitis was significantly reduced following the administration of NPY antisense ODNs.

CONCLUSION

The administration of NPY antisense ODNs leads to an amelioration of DSS-induced colitis, suggesting that NPY plays an important role in modulating inflammation in colitis, and NPY antisense ODNs may be a useful therapeutic approach to the treatment of UC.

Telomerase-targeting antisense oligonucleotides carried by polycation liposomes enhance the growth inhibition effect on tumor cells

In this study, a novel nonviral gene delivery system, which could enhance the inhibition effect of antisense oligonucleotides (ASODN) against the tumor cells, was developed. The polycation liposomes (PCLs) were prepared using the film hydration method with dioleoylphosphatidylethanolamine (DOPE) and amphipathic compound polyethylenimine-cholesterol (PEI 800-Chol), synthesized by low-molecular-weight polyethylenimine (PEI, MW 800) covalent conjugation with cholesterol. The formation of PEI 800-Chol was confirmed by IR and critical micelle concentration detection. The transfection efficiency of PCLs mediating Green Fluorescence Protein plasmid (pEGFP) in HeLa cells was evaluated and the highest gene expression was obtained by PCLs containing DOPE, which was 1.6-fold of that induced by commercial Lipofectamine 2000, and the gene expression efficiency was influenced in the present of serum. Subsequently, human telomerase reverse transcriptase gene antisense oligonucleotides (hTERT-ASODN) were used as therapeutic gene, and the results showed that PCLs, which demonstrated very low cytotoxicity itself, could significantly enhance the inhibition efficiency of hTERT-ASODN in the growth of tumor cells. These results suggested that the PCLs could be widely applied for ASODN delivery.

Synthesis and hybridization of oligonucleotides modified at AMP sites with adenine pyrrolidine phosphonate nucleotides

Three structurally diverse types of the protected pyrrolidine nucleoside phosphonates were prepared as the monomers for the introduction of pyrrolidine nucleotide units into modified oligonucleotides on the solid phase. Two different chemistries were used for incorporation of modified and natural units: the phosphotriester method for the former, i.e., monomers containing N-phosphonoalkyl and N-phosphonoacyl moieties attached to the pyrrolidine ring nitrogen atom, and phosphoramidite chemistry for the latter. Since the synthesized pyrrolidine nucleoside phosphonic acids are close mimics of the 3′-deoxynucleoside 5′-phosphates, the incorporation of one modified unit into oligonucleotides gives rise to one 2′,5′ internucleotide linkage. A series of nonamers containing two or three modified units, as well as the fully modified adenine 15-mer, were synthesized in reverse order, i.e., from the 5′ to the 3′ end of the strand. The measurement of thermal characteristics of the complexes of modified nonamers with the complementary strand revealed a destabilizing effect of the introduced modification. The modified adenine homooligonucleotide, was found to form the most stable complex with oligothymidylate of all the tested modified oligonucleotides in terms of ΔTm per modification.

In vitro and in vivo tumor suppressive activity induced by human telomerase transcriptase-targeting antisense oligonucleotides mediated by cationic liposomes

The objective of this study was to investigate the in vitro and in vivo influence of cationic liposomes on the tumor suppressive effect of antisense telomerase oligodeoxynucleotides to human cervical adenocarcinoma cells (HeLa). Antisense oligodeoxynucleotides (ASODN) against the human telomerase transcriptase (hTERT) served as telomerase inhibitors. The cholesterol derivative, 3beta [N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol), was synthesized, and cationic liposomes (CL) were prepared using DC-Chol and dioleoylphosphatidylethanolamine (DOPE). The in vitro IC50 of the CL-ASODN complex was 1.88 mumol/l, while the IC50 of the cells treated with free ASODNs or CL alone was 25.24 mumol/l and 55.18 mumol/l, respectively. The CL-ASODN complex inhibited HeLa cell growth for at least 120 h. In vivo, the CL-ASODN complex inhibited the tumor growth rate by 55.11%, which increased to 89.47% when CL-ASODN was combined with 5-fluorouracil treatment. ASODNs alone failed to induce tumor-suppressive activity, suggesting that CL prepared from DOPE and DC-Chol can significantly enhance the growth inhibitory effect of ASODN on tumor cells both in vitro and in vivo.

NF-kappaB p65 antisense oligonucleotides may serve as a novel molecular approach for the treatment of patients with ulcerative colitis

BACKGROUND

Activation of nuclear factor-kappa B (NF-kappaB), which controls transcription of various proinflammatory cytokine genes, has been shown to play a critical role in the pathogenesis of ulcerative colitis (UC). The aim of this study was to investigate if NF-kappaB p65 antisense oligonucleotides may affect the expression of NF-kappaB p65 and cytokines in lamina propria mononuclear cells (LPMCs) from patients with UC.

METHODS

LPMCs, which were isolated from intestinal mucosal biopsy specimens from patients with UC, were cultured with or without NF-kappaB p65 antisense oligonucleotides, missense oligonucleotides and dexamethasone. NF-kappaB p65 expression was determined by Western blot analysis. The expression of cytokine mRNA was studied by reverse transcription-polymerase chain reaction (RT-PCR). Cytokine levels were measured by enzyme-linked immunosorbent assay.

RESULTS

NF-kappaB p65 antisense oligonucleotides resulted in downregulation of NF-kappaB p65 expression, blocked the expression of IL-1beta mRNA and IL-8 mRNA, and strikingly reduced the production of IL-1beta and IL-8. These effects were greater than those of dexamethasone in cultured LPMCs from patients with UC (p <0.05).

CONCLUSIONS

Application of NF-kappaB p65 antisense oligonucleotides may serve as a novel molecular approach for the treatment of patients with UC.

A Simple Quartz Crystal Microbalance Nucleic Acid Sensor for Detection of Telomerase

A simple, fast, inexpensive sensitive/selective nucleic acid sensor based on the quartz crystal microbalance system (QCM) was developed for the detection of telomerase. A specially designed oligonucleotide probe, that is complementary to the template region of the telomerase enzyme, was immobilized onto the silver electrodes of piezoelectric crystals with polyethyleneimine adhesion cross-linked with glutaraldehyde. Optimum coating and immobilization conditions were determined. The QCM nucleic acid sensor was used for the detection of telomerase enzyme in human cervix carcinoma cell (HeLa) lysates. A significant difference between the telomerase negative cells (BHK) from HeLa cells, which was used for qualitative and quantitative detection of telomerase. An almost a linear correlation with the protein concentration was obtained with a R 2 value of 0.9621. The linear correlation coefficients (R2) for HeLa and BHK cell lysate obtained by applying Langmuir adsorption model, were 0.9630 and 0.9766, respectively. Telomerase activity was confirmed by stretch-PCR and fluorometric (F)-TRAP within HeLa extracts. The results obtained both with the QCM system developed in this study and F-TRAP method applied is significantly correlated (r = 0.968, p<0.001).

Process research on the preparation of DMT protected 2'-O-methoxyethylguanosine for oligonucleotide synthesis in therapeutic applications

An optimized process to synthesize DMT protected 2 '-O-methoxyethylguanosine is described. A key step involves the enzymatic deamination of a mixture of alkylated products to selectively afford the desired material without resorting to chromatography for purification. This approach was scaled up to kilogram quantities for use in oligonucleotide therapeutics. [Formula: see text].

Advances in antisense oligonucleotide development for target identification, validation, and as novel therapeutics

Antisense oligonucleotides (As-ODNs) are single stranded, synthetically prepared strands of deoxynucleotide sequences, usually 18–21 nucleotides in length, complementary to the mRNA sequence of the target gene. As-ODNs are able to selectively bind cognate mRNA sequences by sequence-specific hybridization. This results in cleavage or disablement of the mRNA and, thus, inhibits the expression of the target gene. The specificity of the As approach is based on the probability that, in the human genome, any sequence longer than a minimal number of nucleotides (nt), 13 for RNA and 17 for DNA, normally occurs only once. The potential applications of As-ODNs are numerous because mRNA is ubiquitous and is more accessible to manipulation than DNA. With the publication of the human genome sequence, it has become theoretically possible to inhibit mRNA of almost any gene by As-ODNs, in order to get a better understanding of gene function, investigate its role in disease pathology and to study novel therapeutic targets for the diseases caused by dysregulated gene expression. The conceptual simplicity, the availability of gene sequence information from the human genome, the inexpensive availability of synthetic oligonucleotides and the possibility of rational drug design makes As-ODNs powerful tools for target identification, validation and therapeutic intervention. In this review we discuss the latest developments in antisense oligonucleotide design, delivery, pharmacokinetics and potential side effects, as well as its uses in target identification and validation, and finally focus on the current developments of antisense oligonucleotides in therapeutic intervention in various diseases.

Effect of anti-sense c-myc oligodeoxynucleotide on MKN28 gastric cancer cells transfected with FHIT gene

AIM: To explore the effect of anti-sense c-myc oligodeoxynucleotide on the proliferation and apoptosis of gastric cancer cells transfected with the Frogile histindine triad (FHIT) gene.

METHODS: The FHIT gene was transfected into human gastric cancer MKN28 cells through liposomes. The antis-sense c-myc oligodeoxynucleotide was transfected into the FHIT gene. FHIT gene transfection was detected by RT-PCR and Western blot. Expression of c-myc was detected by Western blot. Proliferation of gastric cancer cells was determined by MTT. Cell apoptosis was detected by AO/EB staining and FCM.

RESULTS: The expression of MKN28 cells transfected with the FHIT gene was observed. However, no FHIT gene segment and FHIT protein were found in the cells transfected with void vector. C-myc transfected with the FHIT gene exhibited significant inhibitory effects on the expression of c-myc protein in MKN28 cells and induced cell apoptosis in a time-dependent manner. However, the inhibition rate (F = 177.480, P < 0.05) (F = 41.500, P < 0.05), apoptosis rate, and apoptosis portion of anti-sense c-myc oligodeoxynucleotide for C-myc were higher than those for FHIT⁺ MKN28 cells.

CONCLUSION: The expression of c-myc and FHIT oncogenes plays an important role in suppressing the growth of tumor cells and may provide the theoretical basis for the gene therapy of tumors.

In vitro and in vivo Protection against the Highly Pathogenic H5N1 Influenza virus by an Antisense Phosphorothioate Oligonucleotide

Background

Current vaccination strategies and antiviral drugs only provide limited protection against influenza virus infection. In this study, we investigated the use of a novel antisense oligonucleotide (named IV-AS), which is specific for the 5’-terminal conserved sequence found in all eight viral RNA segments of influenza A virus.

Methods

The activity of IV-AS was monitored both in vitro, in Madin-Darby canine kidney (MDCK) cells, and in vivo using a mouse model. IV-AS was given intranasally to H5N1-infected mice once daily for 6 days starting 6 h after infection. A three-base mismatch of IV-AS was used as a control.

Results

IV-AS inhibited influenza virus A induced cytopathic effects in MDCK cells with the 50% effective concentration (EC50) ranging from 2.2 to 4.4 μM. IV-AS was effective against H5N1 virus in preventing death, lessening weight reduction, inhibiting lung consolidation and reducing lung virus titres. Dosages of 40 and 60 mg/kg/day provided 40% and 60% survival rates and prolonged mean survival days in comparison with the infected control group ( P<0.05). The lung index in mice treated with IV-AS, at a dose of 20, 40 or 60 mg/kg/day, had been inhibited on day 4 or 6 ( P<0.05 or P<0.01); virus titres in lung had declined to 2.42, 1.51 and 1.54 log10 TCID50/g of lung, respectively, whereas the yields in the infected control mice were 6.00 log10 TCID50/g of lung.

Conclusions

Our results suggest that the 5’-terminal conserved region of influenza A virus RNA segments can be targeted using antisense technology; therefore, IV-AS is a potential drug for prophylaxis and control of influenza virus infections.

Nanostructure of polyplexes formed between cationic diblock copolymer and antisense oligodeoxynucleotide and its influence on cell transfection efficiency

Although various cationic polymers have been used to condense anionically charged DNA to improve their transfection efficiency, there is still a lack of fundamental understanding about how to control the nanostructure and charge of the polyplexes formed and how to relate such information to cell transfection efficiency. In this work, we have synthesized a weak cationic and phosphorylcholine-containing diblock copolymer and used it as a model vector to deliver an antisense oligodeoxynucleotide (ODN) into HeLa cells. Small angle neutron scattering (SANS) was used to determine the copolymer/ODN polyplex structure. The SANS data revealed the formation of polyplex nanocylinders at high copolymer (N)/ODN (P) charge ratios, where N symbolizes the amine groups on the copolymer and P symbolizes the phosphate groups. However, the cylindrical lengths remained constant, indicating that the ODN binding over this region did not alter the cylindrical shape of the copolymer in solution. As the N/P ratio decreased and became close to unity the polyplex diameters remained constant, but their lengths increased substantially, suggesting the end-to-end bridging by ODN binding between copolymer cylinders. As the N/P ratios went below unity (with ODN in excess), the polyplex diameters increased substantially, indicating different ODN bridging to bundle the small polyplexes together. Transfection studies from HeLa cells indicated a steady increase in transfection efficiency with increasing cationic charge and decreasing polyplex size. Cell growth inhibition assay showed significant growth inhibition by the polyplexes coupled with weak cytotoxicity, indicating effective ODN delivery. While this study has confirmed the overall charge effect, it has also revealed progressive structural changes of the polyplexes against varying charge ratio, thereby providing useful insight into the mechanistic process behind the ODN delivery.

Brothers in arms: DNA enzymes, short interfering RNA, and the emerging wave of small-molecule nucleic acid-based gene-silencing strategies

The past decade has seen the rapid evolution of small-molecule gene-silencing strategies, driven largely by enhanced understanding of gene function in the pathogenesis of disease. Over this time, many genes have been targeted by specifically engineered agents from different classes of nucleic acid-based drugs in experimental models of disease to probe, dissect, and characterize further the complex processes that underpin molecular signaling. Arising from this, a number of molecules have been examined in the setting of clinical trials, and several have recently made the successful transition from the bench to the clinic, heralding an exciting era of gene-specific treatments. This is particularly important because clear inadequacies in present therapies account for significant morbidity, mortality, and cost. The broad umbrella of gene-silencing therapeutics encompasses a range of agents that include DNA enzymes, short interfering RNA, antisense oligonucleotides, decoys, ribozymes, and aptamers. This review tracks current movements in these technologies, focusing mainly on DNA enzymes and short interfering RNA, because these are poised to play an integral role in antigene therapies in the future.

Downregulation of Sirt1 by antisense oligonucleotides induces apoptosis and enhances radiation sensitization in A549 lung cancer cells

Sirt1, a conserved nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase, has been implicated in modulating transcriptional silencing and cell survival, and seems to play a key role in carcinogenesis through deacetylation of important regulatory proteins. This makes it a potential target in cancer therapy. The purpose of this study was to determine whether inhibition of Sirt1 by using antisense oligonucleotides (ASODN) induces apoptosis and enhances radiation sensitization in A549 lung cancer cells. Initially, transient transfection of A549 lung cancer cells with ASODN against Sirt1 specifically reduced Sirt1 expression in a dose-dependent and sequence-specific manner, at both mRNA and proteins levels. The inhibition of Sirt1 obviously decreased A549 cells survival, induced G1 arrest as well as apoptosis. Furthermore, the inhibition of Sirt1 by ASODN greatly increased radiation-induced antiproliferation effects involving in increasing acetylation of tumour suppressor p53 and Bax expression in A549 lung cancer cells. In summary, our results indicate that downregulation of Sirt1 by ASODN decreases survival and increases radiation-induced antiproliferation effects of human lung cancer cells and suggest that inhibition of Sirt1 by ASODN may be a potential gene therapy approach to the treatment of lung cancer.

Recent developments in the use of adenoviruses and immunotoxins in cancer gene therapy

Despite setbacks in the past and apparent hurdles ahead, gene therapy is advancing toward reality. The past several years have witnessed this new field of biomedicine developing rapidly both in breadth and depth, especially for the treatment of cancer, thanks largely to the better understanding of molecular and genetic basis of oncogenesis and the development of new and improved vectors and technologies for gene delivery and targeting. This article is intended to provide a brief review of recent advances in cancer gene therapy using adenoviruses, both as vectors and as oncolytic agents, and some of the recent progress in the development of immunotoxins for use in cancer gene therapy.

NMR studies of the conformational effect of single and double 3'-S-phosphorothiolate substitutions within deoxythymidine trinucleotides

NMR spectroscopy has been used to investigate the conformational effects of single and two consecutive 3'-S-phosphorothiolate modifications within a deoxythymidine trinucleotide. The presence of a single 3'-phosphorothioate modification shifts the conformation of the sugar ring it is attached to, from a mainly south to north pucker; this effect is also transmitted to the 3'-neighbour deoxyribose. This transmission is thought to be caused by favourable stacking of the heterocyclic bases. Similar observations have been made previously by this group. When two adjacent modifications are present, the conformations of the attached deoxyribose rings are again shifted almost completely to the north, however, there is no transmission to the 3' deoxyribose ring. Base proton chemical shift analysis and molecular modelling have been used to aid elucidation of the origin of this feature. The observation for the dimodified sequence is consistent with our previously reported results for a related system in which spaced modifications are more thermodynamically stable than consecutive ones.

[Oligonucleotide therapeutics - an emerging novel class of compounds]

Oligonucleotide therapeutics are short, single- or double-stranded DNA or RNA molecules consisting of strands of 10-50 nucleotides. By targeted modulation of gene expression oligonucleotides provide the chance of targeting diseases at their molecular level. Within this novel emerging class of compounds oligonucleotide therapeutics are discriminated by their structure, function and mode of action. While antisense oligonucleotides, ribozymes and siRNAs suppress the expression of a protein by complementary hybridizing with their target mRNA, aptamers bind like antibodies to their target protein and thereby inhibit its function. Immunostimulatory oligonucleotides are due to sequence motifs within their nucleotide sequence able to trigger a therapeutic exploitable immune response. Currently, there are only two oligonucleotide therapeutics approved by the FDA, namely the antisense oligonucleotide Fomivirsen and the aptamer Macugen. In this review the mode of action of the diverse oligonucleotide therapeutics and their current status in clinical development will be discussed.

Novel isosteric, isopolar phosphonate analogs of oligonucleotides: preparation and properties

A synthetic approach leading to novel-type modified oligothymidylates containing an isosteric, isopolar, enzyme-stable C3'-O-P-CH(2)-O-C4'' phosphonate alternative to phosphodiester internucleotide bond was elaborated. The suitable monomers were prepared from 4'-phosphonomethoxy derivatives of alpha-L-threo and beta-D-erythro-2',5'-dideoxythymidine, which were considered interesting as structurally related to nucleoside 5'-monophosphates. The phosphotriester method was applied to the automated synthesis of both homooligomeric phosphonate 15-mer chains and alternating phosphonate-phosphate constructs. The fully modified homooligomers did not hybridize while homooligomers with alternating sequences containing alpha-L-threo-configured units (but not beta-D-erythro-) showed a significant decrease in T(m) values in comparison with natural dT(15). For a comparative study, phosphodiester 4'-CH(3)-substituted oligothymidylate was synthesized and physical studies (NMR, CD, MDS modeling) were undertaken to shed more light on the changes in conformational behavior arising from the chosen structural alterations.

The future of antisense oligonucleotides in the treatment of respiratory diseases

Antisense oligonucleotides (ASO) are short synthetic DNA molecules designed to inhibit translation of a targeted gene to protein via interaction with messenger RNA. More recently, small interfering (si)RNA have been developed as potent tools to specifically inhibit gene expression. ASO directed against signaling molecules, cytokine receptors, and transcription factors involved in allergic immune and inflammatory responses, have been applied in experimental models of asthma and demonstrate potential as therapeutics. Several ASO-based drugs directed against oncogenes have been developed for therapy of lung cancer, and some have recently reached clinical trials. ASO and siRNA to respiratory syncytial virus infection have demonstrated good potential to treat this condition, particularly in combination with an antiviral drug. Although ASO-based therapeutics are promising for lung diseases, issues of specificity, identification of correct molecular targets, delivery and carrier systems, as well as potential adverse effects must be carefully evaluated before clinical application.

Administration of antisense oligonucleotide against pro-opiomelanocortin prevents enduring hormonal alterations induced by neonatal handling in male mice

Early life events have been implicated in the programming of adult chronic diseases. Several investigations suggest that the role of early environment in influencing development mainly involves the hypothalamic-pituitary-adrenal axis. Therefore, we examined whether 1) daily neonatal handling, applied from birth to weaning induces HPA hormones alterations in mice lasting up to the adult age; and 2) if the administration of an antisense oligodeoxynucleotide versus pro-opiomelanocortin (As-POMC) prevents hormonal alterations observed in previously handled mice (Handled). In the adult phase (90 days), Handled are overweight and have higher basal plasma immuno-reactive (ir)-corticosterone and adrenocorticotropin (ir-ACTH), and higher pituitary ir-ACTH; while they have lower hypothalamic ir-ACTH and corticotropin-releasing hormone (ir-CRH) in comparison with the non-handled mice. As-POMC (0.05-0.1 nmol/g body weight per day) administered during the same period dose-dependently prevents the increase in body weight, in plasma ir-corticosterone, ir-ACTH, and pituitary ir-ACTH, also preventing the decrease in hypothalamic ir-CRH and ir-ACTH; while the mismatch oligonucleotide is nearly inactive. This data indicates that pharmacological treatment in neonatal life may have enduring effects, reducing the alterations in hormonal homeostatic programming mechanisms induced by early repeated handling.

In vivo disposition and stability of DNA frayed wires in mice

DNA frayed wires (DNA(FW)) are an alternate form of DNA organization formed by the self-association of several strands of guanine-rich oligonucleotides. The purpose of this study was to define for the first time the blood clearance kinetics, tissue distribution, and stability of DNA(FW) in vivo in mice. Single bolus doses (1200 pmol/mouse) of (32)P-DNA(FW) and (32)P-random DNA were administered intravenously (IV) and intraperitoneally (IP) followed by scheduled blood, urine, fecal and tissue samplings. Blood clearance kinetics was described well by a first order two-compartment open model. The overall half-lives of elimination from the central compartment (T(1/2))(K10) were 3.57+/-0.1h for IV and 2.38+/-0.11 h for IP. In contrast, random DNA was completely degraded after 15 min regardless of the route of administration. Tissue distribution results demonstrated that DNA(FW) were primarily distributed and retained in the liver, intestines, kidneys, and heart. Low levels could also be detected in brain. Autoradiographs of blood, tissues, feces and urine extracts established that DNA(FW) remained intact after administration as no measurable levels of metabolites or degradation products were found after 24h. (32)P-DNA(FW) was primarily eliminated via hepato-biliary excretion into feces after either IV or IP administration (51.8+/-4.53% and 36.2+/-3.4%, respectively). The improved stability and longer half-life of DNA(FW), previously shown in vitro, is also seen in vivo, indicating that DNA(FW) may provide a stable delivery system for DNA gene therapies. In conclusion, this is the first study demonstrating the in vivo stability, pharmacokinetics, and disposition of DNA superstructures.

Antisense approaches for inhibiting respiratory syncytial virus

Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalised and the elderly. To date, ribavirin (Virazole, ICN Pharmaceuticals, Inc.) remains the only therapeutic agent approved for the treatment of RSV. However, its clinical benefits are small and occur only in a fraction of RSV-infected patients. The prophylactic administration of palivizumab (Synagis, MedImmune, Inc.) is problematic and costly and, therefore, only recommended for use in high-risk infants. Clearly, the need for an effective and safe drug remains high. This review discusses several different antisense approaches and compares them with traditional strategies, such as RSV-targeting antibodies and antivirals, as well as developments in vaccine research.

Efficient delivery of a Bcl-2-specific antisense oligodeoxyribonucleotide (G3139) via transferrin receptor-targeted liposomes

A novel transferrin receptor (TfR)-targeted liposomal formulation was synthesized and evaluated for the delivery of a phosphorothioate antisense oligodeoxyribonucleotide (ODN) (G3139, oblimerson sodium, or Genasense) to Bcl-2 in K562 leukemia cells. Liposomes composed of DC-Chol/egg PC/PEG-DSPE (25:73.5:1.5, mol/mol/mol) were loaded with G3139 with high efficiency (70-80%). To prepare targeted liposomes, transferrin was first coupled to PEG-DSPE and then incorporated into the bilayer by post-insertion. The liposomes had a mean diameter of 100 to 150 nm and exhibited colloidal stability for up to 8 weeks. Uptake of Tf-conjugated G3139-containing liposomes in TfR positive K562 cells was found to be more efficient than that of the non-targeted control formulation and could be blocked by excess free Tf. Treatment with Tf-conjugated liposomes resulted in Bcl-2 protein downregulation in K562 cells that was approximately 2-fold greater than with non-targeted liposomes (p<0.05) and 10-fold greater than with free G3139. Treatment with 2 microM G3139 in Tf-conjugated liposomes resulted in >80% reduction in Bcl-2 transcript. In addition, Tf-conjugated liposomal G3139-sensitized K562 cells to daunorubicin, lowering IC50 from 1.8 microM to 0.18 microM. In conclusion, Tf-conjugated liposomes are effective delivery vehicles for G3139 antisense oligos in TfR positive K562 cells and warrant further investigation as an in vivo oligo delivery vehicle.

One-pot synthesis of TBMPS (bis [tert-butyl)-1 pyrenylmethyl-silyl) chloride as a novel fluorescent silicon-based protecting group for protection of 5'-OH nucleosides and its use as purification handle in oligonucleotide synthesis

An efficient and novel synthesis of bis(tert-butyl)- 1-pyrenylmethyl-silyl group (TBMPS) has been reported having fluorescent properties conferred by the pyrenyl group. This silyl group being base labile is efficiently used for one-pot protection of the 5-OH of the nucleosides. While incorporated terminally at the 5-OH of long sequences viz. AA TGG AGC CAG T and GC TAT GTCAGT TCC CCT TGG TTC TC, this group is also helpful in subsequent purification by HPLC as well as PAGE. Besides these, a labeled dimer (T*T) and a labeled tetramer (T*TTT) were also synthesized to compare the fluorescence properties of short and long labeled sequences. Fluorescence properties of these sequences were studied in detail to find the suitability of the approach.

Cell-specific targeting of lipid-based carriers for ODN and DNA

It is well recognized that there is an urgent need for non-toxic systemically applicable vectors for biologically active nucleotides to fully exploit the current potential of molecular medicine in gene therapy. Cell-specific targeting of non-viral lipid-based carriers for ODN and DNA is a prerequisite to attain the concentration of nucleic acids required for therapeutic efficacy in the target tissue. In this review we will address the most promising approaches to selective targeting of liposomal nucleic acid carriers in vivo. In addition, the routes of entry and intracellular processing of these carrier systems are discussed as well as physiological factors potentially interfering with the biological and/or therapeutic activity of their nucleotide pay-load.