Multiple mechanisms may contribute to the cellular anti-adhesive effects of phosphorothioate oligodeoxynucleotides

Enhanced affinity of racemic phosphorothioate DNA with transcription factor SATB1 arising from diastereomer-specific hydrogen bonds and hydrophobic contacts

Phosphorothioate modification is commonly introduced into therapeutic oligonucleotides, typically as a racemic mixture in which either of the two non-bridging phosphate oxygens is replaced by sulfur, which frequently increases affinities with proteins. Here, we used isothermal titration calorimetry and X-ray crystallography to investigate the thermodynamic and structural properties of the interaction between the primary DNA-binding domain (CUTr1) of transcription factor SATB1 and dodecamer DNAs with racemic phosphorothioate modifications at the six sites known to contact CUTr1 directly. For both the modified and unmodified DNAs, the binding reactions were enthalpy-driven at a moderate salt concentration (50 mM NaCl), while being entropy-driven at higher salt concentrations with reduced affinities. The phosphorothioate modifications lowered this susceptibility to salt, resulting in a significantly enhanced affinity at a higher salt concentration (200 mM NaCl), although only some DNA molecular species remained interacting with CUTr1. This was explained by unequal populations of the two diastereomers in the crystal structure of the complex of CUTr1 and the phosphorothioate-modified DNA. The preferred diastereomer formed more hydrogen bonds with the oxygen atoms and/or more hydrophobic contacts with the sulfur atoms than the other, revealing the origins of the enhanced affinity.

miR-21, Mediator, and Potential Therapeutic Target in the Cardiorenal Syndrome

Oligonucleotide-based therapies are currently gaining attention as a new treatment option for relatively rare as well as common diseases such as cardiovascular disease. With the remarkable progression of new sequencing technologies, a further step towards personalized precision medicine to target a disease at a molecular level was taken. Such therapies may employ antisense oligonucleotides to modulate the expression of both protein coding and non-coding RNAs, such as microRNAs. The cardiorenal syndrome (CRS) is a complex and severe clinical condition where heart and renal dysfunction mutually affect one another. The underlying mechanisms remain largely unknown and current treatments of CRS are mainly supportive therapies which slow down the progression of the disease, but hardly improve the condition. The small non-coding RNA, microRNA-21 (miR-21), is dysregulated in various heart and kidney diseases and has been repeatedly suggested as therapeutic target for the treatment of CRS. Impressive preclinical results have been achieved by an antisense oligonucleotide-based therapy to effectively block the pro-fibrotic traits of miR-21. Since microRNA-mediated pathways are generally very well-conserved, there is considerable commercial interest with regards to clinical translation. In this review, we will summarize the role of miR-21 within the heart–kidney axis and discuss the advantages and pitfalls of miR-21 targeting therapeutic strategies in CRS.

Inflammatory bowel disease: new therapies from antisense oligonucleotides

Inflammatory bowel diseases (IBD) are chronic inflammatory conditions of the gastrointestinal tract encompassing two main clinical entities: Crohn's disease (CD) and ulcerative colitis (UC). These disorders are characterized by various grades of tissue damage and development of local complications and extra-intestinal manifestations. The cause of IBD remains unknown but accumulating evidence indicates that both CD and UC arise in genetically predisposed individuals as a result of the action of multiple environmental factors, which ultimately trigger excessive and poorly controlled immune response against antigens of the luminal flora. Despite this realization, a full understanding of IBD pathogenesis is still out of reach and, consequently, treatment is far from optimal. However, in recent years, several pathways of intestinal damage have been delineated and the improved knowledge has contributed to the development of new therapies. Various approaches have been used to either inhibit the expression and/or function of inflammatory molecules or enhance counter-regulatory mechanisms. This review summarizes the available pre-clinical and clinical data for antisense oligonucleotides and oligonucleotide-based therapy to provide a comprehensive understanding of the rationale and mechanism of action of these compounds in IBD. Key messages Preclinical studies and clinical trials show that antisense oligonucleotide (ASO)-based therapy could be of benefit in inflammatory bowel diseases. ASOs have an excellent safety profile. Technical issues emerged from clinical trials suggest that changes in drug formulation and/or route of administration could improve ASO efficacy.

Electronic Structures of LNA Phosphorothioate Oligonucleotides

Important oligonucleotides in anti-sense research have been investigated in silico and experimentally. This involves quantum mechanical (QM) calculations and chromatography experiments on locked nucleic acid (LNA) phosphorothioate (PS) oligonucleotides. iso-potential electrostatic surfaces are essential in this study and have been calculated from the wave functions derived from the QM calculations that provide binding information and other properties of these molecules. The QM calculations give details of the electronic structures in terms of e.g., energy and bonding, which make them distinguish or differentiate between the individual PS diastereoisomers determined by the position of sulfur atoms. Rules are derived from the electronic calculations of these molecules and include the effects of the phosphorothioate chirality and formation of electrostatic potential surfaces. Physical and electrochemical descriptors of the PS oligonucleotides are compared to the experiments in which chiral states on these molecules can be distinguished. The calculations demonstrate that electronic structure, electrostatic potential, and topology are highly sensitive to single PS configuration changes and can give a lead to understanding the activity of the molecules.

Antisense Oligonucleotides: Treatment Strategies and Cellular Internalization

The clinical applicaton of antisense oligonucleotides (ASOs) is becoming more of a reality as several drugs have been approved for the treatment of human disorders and many others are in various phases in development and clinical trials. ASOs are short DNA/RNA oligos which are heavily modified to increase their stability in biological fluids and retain the properties of creating RNA-RNA and DNA-RNA duplexes that knock-down or correct genetic expression. This review outlines several strategies that ASOs utilize for the treatment of various congenital diseases and syndromes that develop with aging. In addition, we discuss some of the mechanisms for specific non-targeted ASO internalization within cells.

Antisense oligonucleotides in cancer

PURPOSE OF REVIEW

Over the past several dozen years, regardless of the substantial effort directed toward developing rational oligonucleotide strategies to silence gene expression, antisense oligonucleotide-based cancer therapy has not been successful. This review focuses on the most likely reasons for this lack of success, and on the barriers that still need to be overcome to make a clinical cancer treatment reality out of the promise of antisense therapy.

RECENT FINDINGS

Considerable progress has been made in the design and delivery of nucleic acid fragments. Chemical modifications have considerably improved oligonucleotide absorption, distribution and metabolism while at the same time reducing toxicity. Nevertheless, the delivery and the cellular uptake of these molecules are still not adequate to provide the desired therapeutic outcome. Recent therapeutic interventional phase III trials of antisense oligodeoxyribonucleotides for a cancer indication will be discussed, in addition to those studies that markedly improve the scientific understanding of the properties of these molecules.

SUMMARY

We still do not have a marketed antisense oligonucleotide for a cancer indication. This is because critical aspects of the cellular, tumor pharmacology and delivery properties of these agents are still not well understood.

Fully phosphorothioate-modified CpG ODN with PolyG motif inhibits the adhesion of B16 melanoma cells in vitro and tumorigenesis in vivo

Adhesion to the extracellular matrix and endothelial lining of blood vessels is critical for tumor cells to grow at original or metastatic sites. Inhibition of tumor cell adhesion can be an antitumor strategy. Guanosine-rich (G-rich) oligodeoxynucleotides (ODNs) can inhibit the adhesion of certain tumor cells. However, no data exist on how inclusion of the CpG motif in the G-rich sequence influences tumor cell adhesion and subsequent tumorigenesis. In this study, in vitro and in vivo assays were used to evaluate how a panel of ODN-containing contiguous guanosines and the CpG motif influenced adhesion of B16 melanoma cells. The results showed that a self-designed ODN, named BW001, containing the polyG motif and a full phosphorothioate modification backbone could inhibit B16 melanoma cell adhesion on a culture plate or on a plate coated with various substances. In vivo data revealed that B16 melanoma cells co-administered with BW001 and intraperitoneally injected into mice formed fewer tumor colonies in peritoneal cavities. This effect was related to the polyG motif and the full phosphorothioate modification backbone and enhanced by the existence of the CpG motif. Additional in vivo data showed that survival of tumor-bearing mice in the BW001 group was significantly prolonged, subcutaneous melanoma developed much more slowly, and lung dissemination colonies formed much less often than in mice inoculated with B16 melanoma cells only. The effect was CpG motif-dependent. These results suggest that BW001 may exert an integrated antitumor effect.

Efficient stabilization of phosphodiester (PO), phosphorothioate (PS), and 2'-O-methoxy (2'-OMe) DNA·RNA hybrid duplexes by amino sugars

Antisense strategies that target DNA·RNA hybrid structures offer potential for the development of new therapeutic drugs. The α-sarcin loop region of the 23S [corrected] rRNA domain has been shown to be a high value target for such strategies. Herein, aminoglycoside interaction with three RNA·DNA α-sarcin targeted duplexes (rR·dY, rR·S-dY, and rR·2'OMe-rY) have been investigated to determine the overall effect of aminoglycoside interaction on the stability, affinity, and conformation of these hybrid duplexes. To this end, UV thermal denaturation, circular dichroism spectroscopy, fluorescence intercalator displacement, and ITC as well as DSC calorimetry experiments were carried out. The results suggest the following. (1) Of all the aminoglycosides studied, neomycin confers the highest thermal stability on all three hybrid duplexes studied. (2) There is no appreciable difference in aminoglycoside-induced thermal stability between the unmodified rR·dY and phophorothioate modified rR·S-dY duplexes. (3) The rR·2'OMe-rY duplexes thermal stability is slightly less than the other two hybrids. (4) In all three duplexes, aminoglycoside-induced thermal stability decreased as the number of amino groups decreased. (5) CD scans revealed similar spectra for the rR·dY and rR·S-dY duplexes as well as a more pronounced A-form signal for the rR·2'OMe-rY duplex. (6) FID assays paralleled the CD results, yielding similar affinity values between the rR·dY and rR·S-dY duplexes and higher affinities with the rR·2'OMe-rY duplex. (7) The overall affinity trend between aminoglycosides and the three duplexes was determined to be neomycin > paromomycin > neamine > ribostamycin. (8) ITC K(a) values revealed similar binding constants for the rR·dY and rR·S-dY duplexes with rR·dY having a K(1) of (1.03 ± 0.58) × 10(7) M(-1) and K(2) of (1.13 ± 0.07) × 10(5) M(-1) while rR·S-dY produced a K(1) of (1.17 ± 0.54) × 10(7) M(-1) and K(2) of (1.27 ± 0.69) × 10(5) M(-1). (8) The rR·2'OMe-rY produced a slightly higher binding constant values with a K(1) of (1.25 ± 0.24) × 10(7) M(-1) and K(2) of (3.62 ± 0.18) × 10(5) M(-1). (9) The ΔT(m)-derived K(Tm) of 3.81 × 10(7) M(-1) for rR·S-dY was in relative agreement with the corresponding K(1) of 1.17 × 10(7) M(-1) derived constant from the fitted ITC. These results illustrate that the increased DNA·RNA hybrid duplex stability in the presence of aminoglycosides can help extend the roles of aminoglycosides in designing modified ODNs for targeting RNA.

β-1,3-Glucan/antisense oligonucleotide complex stabilized with phosphorothioation and its gene suppression

Most of antisense oligonucleotides (ASOs) subjected to current clinical evaluation belong to phosphorothioate (PS) analogues. Although PS has great advantage in DNase resistance, it can induce nonspecific side-effects. Thus it is important to investigate the influence of ASOs with different PS contents. In this paper, we prepared the complex consisting of schizophyllan (SPG) and ASOs attached a dA₄₀ tail with different PS contents to the 3' end of the ODN, which is introduced to stabilize the complex with SPG. With increase of PS content in the dA₄₀, its complexation ability with SPG was improved and the complex showed high thermal stability. The thermal stability of the fully phosphorothioated ASOs was obtained by only replacing 20% of the oxygen of the phosphodiester moiety. The ability of gene suppression between PS and phosphodiester for antisense sequences was almost the same, indicating that the antisense sequences need not to be PS backbone. These data may provide new insight for the interaction between β-1,3-glucan and DNA and help to deliver therapeutic ODNs.

Specific VDAC inhibitors: phosphorothioate oligonucleotides

VDAC channels are ancient, highly-conserved voltage-gated channels in the mitochondrial outer membrane. They are the pathways by which metabolites travel between the cytosol and mitochondria. They are involved in the apoptotic process and probably other functions as well. The lack of specific inhibitors has hampered research in the past but now phosphorothioate oligonucleotides can serve this function. These molecules were generated to be stable in the cytosol of cells but, unlike the oligonucleotides with the physiological phosphodiester linkage, these have the ability to bind to and block VDAC channels. They are potent, specific, and available commercially. At 1 microM concentration they block VDAC channels in mitochondria but do not affect the respiration complexes, the adenine nucleotide translocator or the ATP synthase.

Immune Mechanisms and Therapeutic Potential of CpG Oligodeoxynucleotides

Unmethylated CpG motifs in bacterial DNA and synthetic oligodeoxynucleotides activate immune cells that express Toll-like Receptor 9. Activation through this receptor triggers cellular signaling that leads to production of a proinflammatory and a Th1-type, antigen-specific immune response. The immunostimulatory effects of CpG oligodeoxynucleotides confer protection against infectious disease, allergy and cancer in animal models, and clinical trials have been initiated. However, CpG oligodeoxynucleotides may exacerbate disease in some situations. We will review current concepts in the mechanisms of activating Toll-like Receptor 9 with CpG oligodeoxynucleotides and highlight opportunities for using large animal models to better determine the mechanisms of action.

Antiadhesive effects of GRN163L--an oligonucleotide N3'->P5' thio-phosphoramidate targeting telomerase

We determined previously that a novel human telomerase RNA (hTR) antagonist, GRN163L, inhibited the tumorigenic potential of A549-luciferase (A549-luc) lung cancer cells in vitro and in vivo. Further studies revealed that A549-luc cells were also morphologically altered by GRN163L. A549-luc cells treated before cell attachment with a single dose of GRN163L only weakly attached to the substrate and remained rounded, whereas control mismatch-treated cells exhibited typical epitheloid appearance and adhesion properties. These morphologic changes were independent of hTR expression and telomerase inhibition and were unrelated to telomere length. This effect is dependent on the molecular properties of the lipid moiety, the phosphorothioate backbone, and the presence of triplet-G sequences within the GRN163L structure. Altered adhesion was manifested by a 50% reduction in rapid cellular attachment and a 3-fold decrease in total cell spreading surface area. Administration of a single dose of GRN163L (15 mg/kg) at the time of cell inoculation, using an in vivo model of lung cancer metastasis, resulted in significant reductions in tumor burden at days 13, 20, and 27 of tumor progression. Thus, the potent antimetastatic effects of GRN163L may be related, in part, to the antiadhesive effects of this novel cancer therapeutic conferred via specific structural determinants and that these effects are independent of telomerase inhibition or telomere shortening.

Inhibitory effect of ribbon-type NF-kappaB decoy oligodeoxynucleotides on osteoclast induction and activity in vitro and in vivo

In this study we examined the effect of ribbon-type (circular-type) NF-κB decoy oligodeoxynucleotides (RNODN) on osteoclast induction and activity. We extracted bone marrow cells from the femurs of rats and incubated non-adherent cells with receptor activator of nuclear factor κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). First, transfer efficiency into osteoclasts and their precursors, resistance to exonuclease, and binding activity of decoy to NF-κB were examined. Next, to examine the effect of RNODN on osteoclast induction and activity, osteoclast differentiation and pit formation assays were performed. RNODN were injected into the ankle joints of rats with collagen-induced arthritis. Joint destruction and osteoclast activity were examined by histological study. The resistance of RNODN to exonuclease and their binding activity on NF-κB were both greater than those of phosphorothionated NF-κB decoy oligodeoxynucleotides. The absolute number of multinucleate cells scoring positive for tartrate-resistant acid phosphatase was significantly decreased in the RNODN-treated group. The average calcified matrix resorbed area was significantly decreased in the RNODN-treated group. Histological study showed marked suppression of joint destruction and osteoclast activity by intra-articular injection of RNODN. These results suggest the inhibitory effect of RNODN on the induction and activity of osteoclasts. Direct intra-articular injection of RNODN into the joints may be an effective strategy for the treatment of arthritis.

The DNAzymes Rs6, Dz13, and DzF have potent biologic effects independent of catalytic activity

DNAzymes are catalytic DNA molecules capable of cleaving RNA substrates and therefore constitute a possible gene-suppression technology. We examined whether the previously reported potency of a DNAzyme targeting c-jun (Dz13) could be improved with judicious use of sequence and chemical modifications. Catalytic activity was measured to establish correlations between catalytic activity and biological potency. Surprisingly, Dz13 had significant cytotoxic activity against cells of rodent origin (IC(50) = 20-50 nM) despite having greatly reduced catalytic activity against a rodent target substrate (<25%), the latter being the result of a mismatch to the rodent c-jun sequence. In contrast, a modified Dz13 matching the rodent c-jun sequence (DT1501b) had no activity at similar concentrations against human or rodent cells despite being able to efficiently cleave the rodent c-jun sequence. Overall, catalytic activity against synthetic substrates did not correlate with cytotoxic activity and catalytically inactive mutants had in some cases equal or superior potency in cell cytotoxicity assays. Further examination of other previously published DNAzymes (Rs6 and DzF) revealed other occurrences of this anomalous behaviour. The active sequences all have G-rich 5 termini, suggesting that G-quadruplex formation might be involved. Consistent with this, deaza-guanosine substitutions abrogated cytotoxicity of Dz13. However, Dz13 did not show evidence of quadruplex formation as determined by circular dichroism studies and native electrophoresis. These data reveal that the biologic activity of several published DNAzymes is not mediated through the catalytic degradation of target mRNA.

G3139 and Other CpG-Containing Immunostimulatory Phosphorothioate Oligodeoxynucleotides Are Potent Suppressors of the Growth of Human Tumor Xenografts in Nude Mice

Several phosphorothioate antisense oligodeoxynucleotides (ODN) are developed to target factors potentially involved in tumor growth and apoptosis suppression. Among them, the 18-mer G3139 (Oblimersen), which targets Bcl-2, is currently being tested in phase II and phase III clinical trials for various tumors in combination with chemotherapy. On the other hand, ODNs containing CpG dinucleotides (CpG-ODN) within specific-sequence contexts (CpG motifs) have been shown to activate rodent or primate immune cells via toll-like receptor 9 (TLR9) and have demonstrated remarkable T cell-dependent antitumor efficacy in a series of murine tumor models. However, immune cell activation by CpG-ODN is largely diminished upon C-5 methylation at CpG cytosine. As G3139 contains CpG motifs, we questioned whether the antitumor effects seen in human tumor xenografts might be abrogated by cytosine C-5 methylation of G3139, which retained the ability of G3139 to suppress Bcl-2 expression in tissue culture, or by similar derivatization of other phosphorothioate ODNs developed for the immune activation of rodent or human cells. The in vivo antitumor efficacy of the immunostimulatory H1826 and H2006 ODNs was compared with that of G3139. Bcl-2 suppression achieved by G3139 purportedly sensitizes tumor cells toward cytotoxic agents, and some of the experiments employed combinations of ODN with such drugs as cisplatin or etoposide. H1826, H2006, and G3139 all produced similar, striking, growth inhibitory effects on either H69 SCLC, A2780 ovarian carcinoma, or A549 lung adenocarcinoma human tumor xenografts at doses of 0.3 mg/kg and 1 mg/kg (H1826, H2006) or 12 mg/kg (G3139) per day. In contrast, the H2006-mC (1 mg/kg) or G3139-mC (12 mg/kg) derivatives demonstrated no significant antitumor effects. The combination of G3139 (12 mg/kg) with cisplatin produced some additive antitumor efficacy, which was not seen in combinations of G3139-mC (12 mg/kg) or H1826 (1 mg/kg) with cisplatin. G3139, at a dose of 12 mg/kg, alone induced extensive enlargement of the spleen. Immunostimulation was evaluated in vitro by flow cytometric measurements of the CD80 and CD86 activation markers found on CD19+ murine splenocytes. The CpG-ODN producing strong antitumor effects in vivo also induced these activation markers in vitro, in contrast to the in vivo inactive G3139-mC. Our data indicate a significant contribution of the immunostimulatory properties of CpG-ODN (including G3139) to the antitumor effects observed in nude mouse xenograft models. This is in contrast to previous data presented by other authors indicating that the activity of G3139 in human tumor xenografts was Bcl-2 specific. Furthermore, as nude mice are devoid of T cells, a T cell-mediated immune response apparently is not required for the potent antitumor responses observed here; innate immune responses are sufficient.

Differences in macrophage activation by bacterial DNA and CpG-containing oligonucleotides

Bacterial DNA activates mouse macrophages, B cells, and dendritic cells in a TLR9-dependent manner. Although short ssCpG-containing phosphodiester oligonucleotides (PO-ODN) can mimic the action of bacterial DNA on macrophages, they are much less immunostimulatory than Escherichia coli DNA. In this study we have assessed the structural differences between E. coli DNA and PO-ODN, which may explain the high activity of bacterial DNA on macrophages. DNA length was found to be the most important variable. Double-strandedness was not responsible for the increased activity of long DNA. DNA adenine methyltransferase (Dam) and DNA cytosine methyltransferase (Dcm) methylation of E. coli DNA did not enhance macrophage NO production. The presence of two CpG motifs on one molecule only marginally improved activity at low concentration, suggesting that ligand-mediated TLR9 cross-linking was not involved. The major contribution was from DNA length. Synthetic ODN >44 nt attained the same levels of activity as bacterial DNA. The response of macrophages to CpG DNA requires endocytic uptake. The length dependence of the CpG ODN response was found to correlate with the presence in macrophages of a length-dependent uptake process for DNA. This transport system was absent from B cells and fibroblasts.

Antitumor efficacy of bcl-2 and c-myc antisense oligonucleotides in combination with cisplatin in human melanoma xenografts: relevance of the administration sequence

PURPOSE

bcl-2 and c-myc oncogenes are frequently overexpressed in different human tumors, including melanoma. Here, we evaluate the combined efficacy of two antisense oligonucleotides targeting bcl-2 mRNA (ODN bcl-2) and c-myc mRNA (ODN c-myc) in combination with cis-diammine dichloroplatinum (cisplatin, DDP) on three human melanoma lines (LM, NG, and M20).

EXPERIMENTAL DESIGN

Two different sequences were designed to treat tumor-bearing mice: in the first one, ODN bcl-2 at a dose of 0.2 mg/day x4, followed by DDP given i.p. at a dose of 3.3 mg/kg/day x3 and ODN c-myc i.v. at 0.5 mg/day x7, whereas the other sequence consisted of ODN c-myc given as first agent followed by DDP and ODN bcl-2 at the same doses. Mice received three complete cycles of treatment in 1-week intervals.

RESULTS

The treatment sequence with ODN bcl-2/DDP/ODN c-myc combination completely inhibited growth in NG tumor and induced a 35-day delay in LM tumor growth. In contrast, the M20 tumor growth was unaffected by the combination. A discrete amount of c-Myc and bcl-2 protein expression in both LM and NG tumors was detected, whereas no detectable levels of the two proteins were observed in M20 tumors. Compared with the other combination, the sequence (ODN bcl-2/DDP/ODN c-myc) produced the most effective results, producing a significant decrease in bcl-2 and c-Myc protein expression, which in turn significantly increased the survival of NG- and LM-bearing mice, with 4 mice out of 11 and 1 out of 7 mice being cured, respectively. Finally, this combination increased the apoptotic rate and produced an antiangiogenetic effect.

CONCLUSIONS

These results show that an antisense approach to the treatment of melanoma xenografts overexpressing either bcl-2 or c-myc oncogenes represents a successful strategy to improve the response to chemotherapy in melanoma, with particular attention to the treatment sequence.

Phosphorothioate oligodeoxynucleotides and G3139 induce apoptosis in 518A2 melanoma cells

In a previous study, we showed that G3139, an antisense phosphorothioate oligonucleotide that down-regulates the expression of Bcl-2 protein, did not cause chemosensitization of 518A2 melanoma cells. In this work, we show that G3139, and the 2-base mismatch, G4126, can initiate apoptosis in this and other melanoma cell lines as shown by increased cell surface Annexin V expression, typical nuclear phenotypic changes as assessed by 4′,6-diamidino-2-phenylindole staining, activation of caspase-3 (but not caspase-8) and Bid, appearance of DEVDase (but not IETDase) activity, and cleavage of poly(ADP-ribose)-polymerase 1. Depolarization of the mitochondrial membrane occurs as a relatively late event. All of these processes seem to be substantially, but perhaps not totally, Bcl-2 independent as shown by experiments employing an anti-Bcl-2 small interfering RNA, which as shown previously down-regulated Bcl-2 protein expression but did not produce apoptosis or chemosensitization in melanoma cells. In fact, these G3139-induced molecular events were not dramatically altered in cells that forcibly overexpressed high levels of Bcl-2 protein. Addition of irreversible caspase inhibitors (e.g., the pan-caspase inhibitor zVAD-fmk) to G3139-treated cells almost completely blocked cytotoxicity. Examination of the time course of the appearance of caspase-3 and cleaved poly(ADP-ribose)-polymerase 1 showed that this could be correlated with the release of cytochrome c from the mitochondria, an event that begins only ∼4 hours after the end of the oligonucleotide/LipofectAMINE 2000 5-hour transfection period. Thus, both G3139 and cytotoxic chemotherapy activate the intrinsic pathway of apoptosis in these cells, although Bcl-2 expression does not seem to contribute strongly to chemoresistance. These findings suggest that the attainment of G3139-induced chemosensitization in these cells will be difficult.

Changes in gene expression induced by phosphorothioate oligodeoxynucleotides (including G3139) in PC3 prostate carcinoma cells are recapitulated at least in part by treatment with interferon-beta and -gamma

PURPOSE

G3139 is an antisense bcl-2 phosphorothioate oligodeoxyribonucleotide that is currently being evaluated in Phase III clinical trials in several human cancers. The aim of the present work was to further identify the apparent non-bcl-2-dependent mechanism of this action of this compound in PC3 prostate cancer cells.

EXPERIMENTAL DESIGN

We performed Affymetrix U95A oligonucleotide microarray studies on mRNA isolated from cells treated with G3139 and related oligonucleotides.

RESULTS

Hierarchical clustering revealed the presence of a set of genes of which the expression was elevated on both 1 and 3 days after oligonucleotide treatment. Significantly, the persistence of expression of the up-regulation of these genes, many of which are members of the IFN cascade, was greater for G3139 than for any other oligomer evaluated. Furthermore, many of the genes with the greatest up-regulation of expression are also those of which the expression is up-regulated after treatment of cells with IFNs. Treatment of PC3 cells with either IFN-beta or -gamma recapitulated some of the aspects of the molecular and phenotypic changes observed after treatment with a G3139/Lipofectin complex. These include down-regulation of bcl-2 protein expression itself, down-regulation of protein kinase C alpha protein expression (but not that of other protein kinase C isoforms), alteration in p21/Waf1/Cip1 protein expression, up-regulation of MHC-I cell surface expression, and profound suppression of cell growth in the absence of a notable increase in cellular apoptosis. However, G3139 (when complexed with Lipofectin) did not induce the up-regulation of expression of either type I or type II IFNs, nor could IFNs be found in conditioned media from treated cells.

CONCLUSIONS

Oligonucleotide microarray experiments demonstrated that G3139 could induce elements of the IFN cascade in PC3 cells in vitro. In addition, the cellular phenotype obtained after treatment with exogenous IFN could, at least in part, recapitulate that obtained after G3139 treatment. Nevertheless, the oligonucleotide microarray experiments we performed also demonstrated that there are extremely large qualitative and quantitative differences between the two treatments.

Designing transcription factor architectures for drug discovery

Recent advances in the design, selection, and engineering of DNA binding proteins have led to the emerging field of designer transcription factors (TFs). Modular DNA-binding protein domains can be assembled to recognize a given sequence of a DNA in a regulatory region of a targeted gene. TFs can be readily prepared by linking the DNA-binding protein to a variety of effector domains that mediate transcriptional activation or repression. Furthermore, the interaction between the TF and the genomic DNA can be regulated by several approaches, including chemical regulation by a variety of small molecules. Genome-wide single target specificity has been demonstrated using arrays of sequence-specific zinc finger (ZF) domains, polydactyl proteins. Any laboratory today can easily construct polydactyl ZF proteins by linkage of predefined ZF units that recognize specific triplets of DNA. The potential of this technology to alter the transcription of specific genes, to discover new genes, and to induce phenotypes in cells and organisms is now being applied in the areas of molecular therapeutics, pharmacology, biotechnology, and functional genomics.

Antisense therapy: recent advances and relevance to prostate cancer

Currently employed treatment options for patients with advanced and metastatic cancer such as surgery, radiation, hormone therapy, and chemotherapy are limited. In particular, the well known limitations of chemotherapy are at least in part due to a lack of specificity. The activation of dominant oncogenes and inactivation of tumor suppressor genes may represent novel targets for cancer therapy. Antisense therapy has been widely used to specifically and selectively inhibit the expression of selected genes at the messenger RNA level. Combinations of antisense oligonucleotides with chemotherapeutic agents may offer important advantages in cancer treatment. Several antisense drugs, especially oblimersen (G3139), have shown interesting results in experiments in animals, and have entered clinical trials. However, control oligonucleotides must be carefully chosen to separate antisense effects from the many potential nonspecific effects of oligonucleotides. This review summarizes the advantages and limitations of antisense therapy and its use in the treatment of androgen-independent prostate cancer.

Molecular therapy to inhibit NFkappaB activation by transcription factor decoy oligonucleotides

Molecular therapy is emerging as a potential strategy for the treatment of various diseases for which few known effective therapies exist. One strategy for combating disease processes has been to target the transcriptional process. Two approaches have been used to accomplish this: the use of antisense complimentary to the mRNA of interest and the use of ribozymes, a unique class of RNA molecules that not only store information but also process catalytic activity. Ribozymes are known to catalytically cleave specific target RNA, leading to its degradation, whereas antisense molecules inhibit translation by binding to mRNA sequences on a stoichiometric basis. More recently, small interfering RNA has been shown to inhibit target gene expression. The application of oligonuclotide technology, such as antisense, to regulate the transcription of disease-related genes in vivo has important therapeutic potential. Transfection of cis-element double-stranded oligodeoxynucleotides has been reported as a powerful tool in a new class of anti-gene strategies for molecular therapy.

Tumor regression by combination antisense therapy against Plk1 and Bcl-2

Increased expression of the cell proliferation-associated polo-like kinase 1 (PLK1) and apoptosis-associated BCL-2 genes has been observed in different human malignancies. Inhibition of cell proliferation and reactivation of apoptosis are basic principles in anticancer therapy. The efficiency of this approach is often limited by insuf-ficient targeting and delivery of anticancer drugs into the tumors. Phosphorothioate antisense oligodeoxynucleotides (ODNs) directed against PLK1 and BCL-2 were administered systemically via the tail vein into nude mice bearing A549, MDA-MB-435, and Detroit562 xenografts. To enhance tumor-specific uptake and to reduce systemic toxicity of antisense ODNs membrane electroporation transfer was applied in vivo. Northern and Western blot analyses were used to assess PLK1 and BCL-2 expression. Tumor mass was assessed after resection of tumors. All three cell lines and corresponding xenografts expressed high levels of PLK1 and were sensitive towards antisense PLK1 treatment. Antisense BCL-2 therapy was effective in tumors expressing high levels of BCL-2, but not in A549 cells and corresponding xenografts, which express low levels of BCL-2. Administration of antisense ODNs in a dose of 5 mg/kg, twice weekly during four weeks supported by the membrane electroporation transfer, eradicated 60-100% of the xenografted tumors. Antitumor effect in BCL-2 overexpressing MDA-MB-435 cells was synergistic for BCL-2 and PLK1 combination therapy. This study provides evidence that combined systemic administration of antisense ODNs against proliferation and pro- survival associated targets and in vivo electroporation of tumors represents a promising antitumor therapeutic approach.

Recent progress in gene therapy for cardiovascular disease

Gene therapy is emerging as a potential strategy for the treatment of cardiovascular diseases, such as peripheral arterial disease, ischemic heart disease, restenosis after angioplasty, vascular bypass graft occlusion and transplant coronary vasculopathy, for which no known effective therapy exists. The first human trial in cardiovascular disease started in 1994 treating peripheral vascular disease with vascular endothelial growth factor (VEGF) and since then, many different potent angiogenic growth factors have been tested in clinical trials for the treatment of peripheral arterial disease. In addition, therapeutic angiogenesis using the VEGF gene has been used to treat ischemic heart disease since 1997. The results from these clinical trials have exceeded expectations; improvement in the clinical symptoms of peripheral arterial disease and ischemic heart disease has been reported. Another strategy for combating the disease processes, targeting the transcriptional process, has been tested in a human trial. IN particular, transfection of cis-element double-stranded (ds) oligodeoxynucleotides (ODN) (= decoy) is a powerful tool in a new class of anti-gene strategies. Transfection of ds-ODN corresponding to the cis sequence will attenuate the authentic cis-trans interaction, leading to removal of trans-factors from the endogenous cis-elements and subsequent modulation of gene expression. Genetically modified vein grafts transfected with a decoy against E2F, an essential transcription factor in cell cycle progression, appear to have long-term potency in human patients. There is great potential in gene therapy for cardiovascular disease.

Bromodeoxyuridine-labeled oligonucleotides as tools for oligonucleotide uptake studies

The mechanisms by which various oligonucleotides (ODNs) and their analogs enter cells are not fully understood. A common technique used in studies on cellular uptake of ODNs is their conjugation with fluorochromes. However, fluorescently labeled ODNs may vary from the parent compounds in charge and hydrophilicity, and they may interact differently with some components of cellular membranes. In this report, we present an alternative method based on the immunofluorescent detection of ODNs with incorporated 5-bromo-2'-deoxyuridine (BrdUrd). Localization of BrdUrd-modified ODNs has been achieved using FITC-labeled anti-BrdUrd antibodies. This technique allowed determination of the differences in cellular uptake of phosphodiester (PO) and phosphorothioate (PS) ODNs and their derivatives conjugated with cholesterol and menthol. The immunocytochemical method also has shown that the cellular uptake of some ODNs may be influenced by specific sequences that are responsible for the formation of higher-order structures.

Novel E2F decoy oligodeoxynucleotides inhibit in vitro vascular smooth muscle cell proliferation and in vivo neointimal hyperplasia

The transcription factor, E2F, plays a critical role in the trans-activation of several genes involved in cell cycle regulation. Previous studies showed that the transfection of cis element double-stranded decoy oligodeoxynucleotides (ODNs) corresponding to E2F binding sites inhibited the proliferation of vascular smooth muscle cells (VSMCs) and neointimal hyperplasia in injured vessels. We have developed a novel E2F decoy ODN with a circular dumbbell structure (CD-E2F) and compared its effects with those of the conventional phosphorothioated E2F decoy (PS-E2F) ODN. CD-E2F ODN was more stable than PS-E2F ODN, largely preserving its structural integrity after incubation in the presence of nucleases and sera. Moreover, CD-E2F ODN inhibited high glucose- and serum-induced transcriptional expression of cell cycle regulatory genes more strongly than PS-E2F ODN. Transfection of CD-E2F ODN resulted in more effective inhibition of VSMC proliferation in vitro and neointimal formation in vivo, compared with PS-E2F ODN. An approximately 40-50% lower dose of CD-E2F ODN than PS-E2F ODN was sufficient to attain similar effects. In conclusion, our results indicate that CD-E2F ODN may be a valuable tool in gene therapy protocols for inhibiting VSMC proliferation and studying transcriptional regulation.

Potential roles of antisense oligonucleotides in cancer therapy. The example of Bcl-2 antisense oligonucleotides

Antisense oligonucleotides have been widely used to specifically and selectively downregulate gene expression at the messenger RNA level. Even though oligonucleotides are commonly used in laboratories and clinical trials, they can induce non-specific effects that can lead to misinterpretation of experimentally-derived results. This review summarizes precautions one should take when using oligonucleotides. In addition, the role of one oligonucleotide, G3139, which is targeted to the coding region of bcl-2 messenger RNA, in inhibiting tumor progression in vitro and in clinical trials, is described.

The quest for an efficacious antiviral for 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, hospitalized and the elderly. To date, ribavirin (Virazole) remains the only therapeutic agent approved for the treatment of RSV. The prophylactic administration of palivizumab is problematic and costly. The quest for an efficacious RSV antiviral has produced a greater understanding of the viral fusion process, a new hypothesis for the mechanism of action of ribavirin, and a promising antisense strategy combining the 2'-5' oligoadenylate antisense (2-5A-antisense) approach and RSV genomics.

Antisense oligonucleotides selectively regulate aspartyl beta-hydroxylase and its truncated protein isoform in vitro but distribute poorly into A549 tumors in vivo

Alternative splicing of the human beta-aspartyl (asparaginyl) hydroxylase (BAH) gene results in the expression of humbug, a truncated form of BAH that lacks the catalytic domain of the enzyme. Overexpression of BAH and humbug has been associated with a variety of human cancers, and although humbug lacks enzymatic activity, it is expressed at levels comparable with that of BAH in various cancer cell lines. Phosphorothioate antisense oligonucleotides (ONs) were designed to dissect out the function of these hydroxylase protein isoforms. In A549 cells, these ONs differentially down-regulated BAH and humbug at the mRNA and protein level. Phosphorothioate ON uptake and antisense studies were conducted in parallel in nude mice bearing A549 tumor xenografts. Microscopic examination of the tumor after administration of a fluorescein-labeled ON showed strong labeling of the outer layers of the tumor connective tissue but cells within the interior of the tumor were sparsely labeled. A modest but significant effect on tumor growth was observed in animals treated with an antisense ON directed against both BAH and humbug transcripts. However, Northern analysis of tumor RNA did not indicate a down-regulation of the targeted mRNA species. These results demonstrate the successful development of antisense ONs that selectively differentiate between the closely related beta-hydroxylase protein isoforms. However, determination of the biological function of these proteins in vivo was limited by the poor uptake properties of phosphorothioate ONs in A549 tumors.

CpG motifs in bacterial DNA and their immune effects

Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs. Oligodeoxynucleotides (ODN) containing CpG motifs activate host defense mechanisms leading to innate and acquired immune responses. The recognition of CpG motifs requires Toll-like receptor (TLR) 9, which triggers alterations in cellular redox balance and the induction of cell signaling pathways including the mitogen activated protein kinases (MAPKs) and NF kappa B. Cells that express TLR-9, which include plasmacytoid dendritic cells (PDCs) and B cells, produce Th1-like proinflammatory cytokines, interferons, and chemokines. Certain CpG motifs (CpG-A) are especially potent at activating NK cells and inducing IFN-alpha production by PDCs, while other motifs (CpG-B) are especially potent B cell activators. CpG-induced activation of innate immunity protects against lethal challenge with a wide variety of pathogens, and has therapeutic activity in murine models of cancer and allergy. CpG ODN also enhance the development of acquired immune responses for prophylactic and therapeutic vaccination.

Molecular strategy using cis-element 'decoy' of E2F binding site inhibits neointimal formation in porcine balloon-injured coronary artery model

Transcription factor E2F plays a pivotal role in the transactivation of cell cycle regulatory genes, leading to vascular lesion formation. Double-stranded DNA with high affinity for E2F as 'decoy' cis elements may block the activation of genes mediating the cell cycle, resulting in an effective therapeutic agent for treating intimal hyperplasia. In this study, we tested the feasibility of E2F decoy therapy to treat neointimal formation in a porcine coronary artery balloon injury model. An angioplasty catheter was inserted in the left anterior descending coronary artery of pigs to cause vascular injury. Initially, we tested the feasibility of transfection of FITC-labeled E2F decoy ODN using a hydrogel balloon catheter. Fluorescence due to E2F decoy ODN could be detected throughout the medial layer. Therefore, we transfected E2F decoy ODN into the balloon-injured artery using hydrogel catheter. Of importance, intravascular ultrasound (IVUS) and histological evaluation demonstrated that plaque area in the balloon-injured artery was significantly reduced by E2F decoy ODN compared with mismatched decoy ODN at 1 month after a single transfection (P < 0.01). In contrast, luminal and total vessel areas were significantly increased in vessels treated with E2F decoy ODN as compared with mismatched decoy. Endothelial function after angioplasty was not affected by E2F decoy transfection. Finally, we tested the acute toxicity of E2F decoy ODN in monkeys, and no apparent side-effects were detected. Here, we report the successful in vivo transfer of E2F decoy ODN using a hydrogel catheter to inhibit vascular lesion formation in balloon-injured porcine coronary artery without any apparent side-effects.

Inhibition of potentially anti-apoptotic proteins by antisense protein kinase C-alpha (Isis 3521) and antisense bcl-2 (G3139) phosphorothioate oligodeoxynucleotides: relationship to the decreased viability of T24 bladder and PC3 prostate cancer cells

Isis 3521 and G3139 are 20- and 18-mer phosphorothioate oligonucleotides, respectively, targeted to the protein kinase C (PKC)-alpha and bcl-2 mRNAs. Treatment of T24 bladder and PC3 prostate carcinoma cells with full-length and 3'-truncation mutants of Isis 3521 causes down-regulation of PKC-alpha protein and mRNA. However, at the level of a 15-mer and shorter, down-regulation of mRNA expression is no longer observed. Further, no diminution in cellular viability, as measured by 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide assay, in response to increasing concentrations of paclitaxel, can be observed for these shorter oligomers. These observations not only indicate that PKC-alpha protein expression can be down-regulated by both RNase H-dependent and -independent mechanisms but also that down-regulation of PKC-alpha is insufficient by itself to "chemosensitize" cells. G3139, which down-regulates bcl-2 protein and mRNA expression, also down-regulates PKC-alpha protein and mRNA expression but not that of PKC-betaI, -epsilon, or -zeta. However, the down-regulation of PKC-alpha and bcl-2 are not linked. When the carrier Eufectin 5 is employed, only bcl-2 is down-regulated in both T24 and PC3 cells at 50 nM oligonucleotide concentration. At 100 nM, both bcl-2 and PKC-alpha expression are down-regulated, and only at this concentration can "chemosensitization" to paclitaxel and carboplatin be observed. In contrast, the down-regulation of bcl-2 seems to be linked with that of RelA (p65). However, this too is also not sufficient for chemosensitization, even though it leads to the loss of expression of genes under the putative control of nuclear factor-kappaB and to detachment of the cells from plastic surfaces. These results underscore the complexity of the intracellular requirements for the initiation of chemosensitization to anti-neoplastic agents.

relA over-expression reduces tumorigenicity and activates apoptosis in human cancer cells

We previously demonstrated that bcl-2 over-expression increases the malignant behaviour of the MCF7 ADR human breast cancer cell line and enhances nuclear factor-kappa B (NF-kappa B) transcriptional activity. Here, we investigated the direct effect of increased NF-kB activity on the tumorigenicity of MCF7 ADR cells by over-expressing the NF-kappa B subunit relA/p65. Surprisingly, our results demonstrated that over-expression of relA determines a considerable reduction of the tumorigenic ability in nude mice as indicated by the tumour take and the median time of tumour appearance. In vitro studies also evidenced a reduced cell proliferation and the activation of the apoptotic programme after relA over-expression. Apoptosis was associated with the production of reactive oxygen species, and the cleavage of the specific substrate Poly-ADP-ribose-polymerase. Our data indicate that there is no general role for NF-kappa B in the regulation of apoptosis and tumorigenicity. In fact, even though inhibiting NF-kappa B activity has been reported to be lethal to tumour cells, our findings clearly suggest that an over-induction of nuclear NF-kappa B activity may produce the same effect.

Gene therapy in vascular medicine: recent advances and future perspectives

Gene therapy is emerging as a potential strategy for the treatment of cardiovascular diseases, such as restenosis after angioplasty, vascular bypass graft occlusion, and transplant coronary vasculopathy, for which no known effective therapy exists. The first human trial in cardiovascular disease was started in 1994 to treat peripheral vascular disease using vascular endothelial growth factor. In addition, therapeutic angiogenesis using the vascular endothelial growth factor gene was applied in the treatment of ischemic heart disease. The results from these clinical trials seem to exceed expectation. Improvement of clinical symptoms in peripheral arterial disease and ischemic heart disease has been reported. At least five different potent angiogenic growth factors have been tested in clinical trials to treat peripheral arterial disease or ischemic heart disease. In addition, another strategy for combating disease processes, to target the transcriptional process, has been tested in a human trial. Transfection of cis-element double-stranded oligodeoxynucleotides is an especially powerful tool in a new class of antigen strategies for gene therapy. Transfection of double-stranded oligodeoxynucleotides corresponding to the cis sequence will result in the attenuation of the authentic cis-trans interaction, leading to the removal of trans-factors from the endogenous cis-elements, with subsequent modulation of gene expression. Genetically modified vein grafts transfected with a decoy against E2F, an essential transcription factor in cell cycle progression, revealed apparent long-term potency in human patients. This review focuses on the future potential of gene therapy for the treatment of cardiovascular disease.

Antisense oligonucleotides: promise and reality

Antisense oligonucleotides have been used for more than a decade to downregulate gene expression. Phosphodiester oligonucleotides are nuclease sensitive, and the more nuclease-resistant phosphorothioate oligonucleotides are now in common use in the laboratory and have entered clinical trials. However, these molecules are highly bioactive and may inhibit gene expression by more than one mechanism. Although some dramatic successes have been demonstrated, it can still be difficult to properly interpret experimental data derived from the use of this class of oligonucleotide. This review discusses some of these issues with particular reference to a major area of current interest--inhibition of bcl-2 expression in tumor cells.

Antisense oligonucleotides in cutaneous therapy

Antisense oligonucleotides have been the subject of intense interest as research tools to elucidate the functions of gene products and as therapeutic agents. Initially, their mode of action was poorly understood and the biological effects of oligonucleotides were often misinterpreted. However, research into these gene-based inhibitors of cellular action recently has succeeded in realising their exciting potential, particularly as novel therapeutic agents. An emerging application of this technology is in cutaneous therapy. The demand for more effective dermatological drugs will ensure further development of antisense strategies in skin, with key issues being drug delivery, therapeutic target selection, and clinical applicability.

Antisense therapy in cancer

This review discusses laboratory and clinical studies of antisense oligodeoxynucleotides as potential treatments for haematological malignancies and solid tumours. Mechanisms of action, pharmacokinetics, toxicities and potential clinical applications of these agents are described.

NF-kappa B as a central mediator in the induction of TGF-beta in monocytes from patients with idiopathic myelofibrosis: an inflammatory response beyond the realm of homeostasis

Immune-mediated mechanisms have been implicated in the etiology of idiopathic bone marrow fibrosis (IMF). However, the mechanism remains poorly defined. Compared with healthy controls, IMF monocytes are overactivated, with increased production of TGF-beta and IL-1. TGF-beta is central to the progression of fibrosis in different organs. In the lung, fibrosis is associated with up-regulation of TGF-beta-inducible genes. Because IL-1 and TGF-beta have pro- and antiinflammatory properties and neither appears to regulate the high levels of each other in IMF, we studied the mechanism of this paradigm. We focused on the role of RelA, a subunit of the transcription factor, NF-kappaB that is associated with inflammatory responses. We transiently knocked out RelA from IMF monocytes with antisense oligonucleotides and showed that RelA is central to IL-1 and TGF-beta production and to the adhesion of IMF monocytes. Because the NF-kappaB family comprises subunits other than RelA, we used aspirin and sodium salicylate to inhibit kinases that activate NF-kappaB and showed effects similar to those of the RelA knockout system. It is unlikely that RelA could be interacting directly with the TGF-beta gene. Therefore, we determined its role in TGF-beta production and showed that exogenous IL-1 could induce TGF-beta and adherence of IMF monocytes despite the depletion of NF-kappaB. The results indicate that IL-1 is necessary for TGF-beta production in IMF monocytes, but NF-kappaB activation is required for the production of endogenous IL-1. Initial adhesion activates NF-kappaB, which led to IL-1 production. Through autocrine means, IL-1 induces TGF-beta production. In total, these reactions maintain overactivation of IMF monocytes.

Bcl-2 antisense oligonucleotides (G3139) inhibit Merkel cell carcinoma growth in SCID mice

Merkel cell carcinoma was first described in 1972 by Toker and is an aggressive neuroendocrine skin tumor with a high metastatic potential. Merkel cell carcinoma is thought to derive from the neuroendocrine (Merkel) cells of the skin, although in contrast to fetal and especially adult Merkel cells, Merkel cell carcinomas express high levels of the Bcl-2 oncoprotein. Bcl-2 is capable of blocking programmed cell death and has been shown to play an important role in normal cell turnover, tumor biology, and chemoresistance. High Bcl-2 expression leading to prolonged survival of cells may therefore be of importance in the biological and clinical characteristics of Merkel cell carcinoma. In a SCID mouse xenotransplantation model for human Merkel cell carcinoma, we investigated the influence of the bcl-2 antisense oligonucleotide G3139 (Genta) on tumor growth in comparison with control oligonucleotides or cisplatin. Bcl-2 antisense treatment, targeting the first six codons of the bcl-2 mRNA, resulted in either a dramatic reduction of tumor growth or complete remission, whereas reverse sequence and two-base mismatch control oligonucleotides or cisplatin had no significant antitumor effects compared with saline-treated controls. Apoptosis was enhanced 2.4-fold in the bcl-2 antisense treated tumors compared with the saline-treated group, and no other treatment showed a comparable increase in apoptosis. Our findings suggest that bcl-2 antisense treatment may be a novel approach to improve treatment outcome of human Merkel cell carcinoma.

Polo-like kinase1, a new target for antisense tumor therapy

The Polo-like kinase 1 (Plk1) is a highly conserved mitotic serine/threonine kinase which is commonly overexpressed in cancer cell lines. Plk1 positively regulates mitotic progression by activating the CDC25C-CDK1 amplification loop and by regulating late mitotic events, primarily the ubiquitin-dependent proteolysis. In the present study, an antisense strategy against Plk1 mRNA was developed to specifically inhibit cell proliferation of cancer cells in cell culture and in the nude-mouse tumor model. Among 41 phosphorothioate antisense oligodeoxynucleotides tested, the 20-mer JWG2000 strongly inhibited expression of Plk1 in cultured A549 cells, leading to loss of cell viability, and exhibited anti-tumor activity in nude mice A549 xenograft. JWG2000 did not inhibit growth and viability of primary human mesangial cells and human amnion fibroblasts.

Inhibition of c-myc expression in cells by targeting an RNA-protein interaction using antisense oligonucleotides

Antisense oligodeoxynucleotides (ODNs) are designed to bind to and inhibit a target mRNA. We used a novel approach for the design of ODNs to the c-myc mRNA using protein binding sites as targets for ODN action. Our strategy was to identify ODNs that could interfere with the coding region determinant-binding protein (CRD-BP), a protein that binds to the CRD region of the c-myc mRNA. Using an in vitro gel shift assay, we show that ODN molecules can occlude the CRD-BP from the mRNA. The best ODN, CRD-ODN4, was able to inhibit RNA binding of the CRD-BP by 75%. This effect was sequence-specific and concentration dependent. K562 cells treated with a 2'-O-methyl derivative of CRD-ODN4 showed a concentration-dependent decrease in both c-myc mRNA and protein levels, with a maximal 65% inhibition of protein expression at 200 nM CRD-ODN4. In contrast, a 2'-O-methyl ODN derivative targeting the translation initiation codon (antimyc-aug) reduced c-myc protein but actually increased mRNA levels, an effect resulting at least partly from stabilization of the c-myc mRNA. CRD-ODN4 treatment did not alter the c-myc mRNA half-life. CRD-ODN4 was more effective in inhibiting K562 cell growth than antimyc-aug, reducing cell number by approximately 70% after 48 h of exposure to 750 nM. The correlation between ODN effects on RNA-protein interactions in vitro and those observed in cells supports the hypothesis that CRD-ODN4 inhibits the interaction between the CRD-BP and the c-myc mRNA and that disrupting this RNA-protein interaction reduces c-myc expression in cells.

Antisense intercellular adhesion molecule-1 (ICAM-1) oligodeoxyribonucleotide delivered during organ preservation inhibits posttransplant ICAM-1 expression and reduces primary lung isograft failure

Transiently increased expression of leukocyte adhesion receptors after lung preservation contributes to early graft demise by recruiting leukocytes, activating complement, and causing microcirculatory stasis. We hypothesized that inhibiting intercellular adhesion molecule-1 (ICAM-1) expression even briefly may significantly improve lung graft function and that the preservation period might provide a unique window to deliver a therapeutic pulse of antisense oligonucleotide ICAM-1 to inhibit ICAM-1 expression after transplantation. Interleukin-1beta-treated rat pulmonary endothelial cells given a 20-mer phosphorothioate oligonucleotide comprising an antisense span targeted to the 3'-untranslated region of rat ICAM-1 demonstrated an oligonucleotide dose-dependent reduction in ICAM-1 expression. Using a cationic liposomal carrier, this same antisense oligonucleotide (but not the sense control) instilled into the pulmonary vasculature at the time of preservation reduced subsequent graft ICAM-1 expression and graft leukostasis and markedly improved oxygenation, pulmonary blood flow, and graft survival. These experiments demonstrate that the preservation period presents a window during which to target an anti-ICAM-1 expression strategy to inhibit early adhesion receptor expression and improve functional outcome after lung transplantation.

Aberrant rel/nfkb genes and activity in human cancer

Rel/NF-kappaB transcription factors are key regulators of immune, inflammatory and acute phase responses and are also implicated in the control of cell proliferation and apoptosis. Remarkable progress has been made in understanding the signal transduction pathways that lead to the activation of Rel/NF-kappaB factors and the consequent induction of gene expression. Evidence linking deregulated Rel/NF-kappaB activity to oncogenesis in mammalian systems has emerged in recent years, consistent with the acute oncogenicity of the viral oncoprotein v-Rel in animal models. Chromosomal amplification, overexpression and rearrangement of genes coding for Rel/NF-kappaB factors have been noted in many human hematopoietic and solid tumors. Persistent nuclear NF-kappaB activity was also described in several human cancer cell types, as a result of constitutive activation of upstream signaling kinases or mutations inactivating inhibitory IkappaB subunits. Studies point to a correlation between the activation of cellular gene expression by Rel/NF-kappaB factors and their participation in the malignant process. Experiments implicating NF-kappaB in the control of the apoptotic response also support a role in oncogenesis and in the resistance of tumor cells to chemotherapy. This review focuses on the status of the rel, nfkb and ikb genes and their activity in human tumors and their association with the onset or progression of malignancies.

Immunostimulatory CpG-oligodeoxynucleotides induce a factor that inhibits macrophage adhesion

Selected phosphorothioate oligodeoxynucleotides containing CpG (CpG-ODN) activate immune responses, including immunoglobulin synthesis, B cell proliferation, and cytokine production by monocytes. We examined the effect of a CpG-ODN (#1760) on the adhesion of macrophages derived from human blood monocytes in vitro. CpG-ODN (6 microg/mL) completely inhibited the adherence of macrophages to plastic or glass during 7 or more days of culture. A non-CpG control ODN (#1814) was without effect. Two other CpG-ODNs (#1826 and #1842) also completely inhibited macrophage adherence. The specific inhibitor of CpG-ODN, quinacrine (0.1 micromol/L), blocked this action. CpG-ODN reduced the rate of senescence and cell death of monocytes in culture but did not influence their phagocytosis, procoagulant activity, or support of the mixed lymphocyte response. Four days of exposure of monocytes to CpG-ODN up-regulated the expression of the endotoxin receptor CD14 and down-regulated the mannose (scavenger) receptor, a result that is consistent with blocking the maturation of monocytes to macrophages. Incubation of peripheral blood monocytes (PBMCs) with CpG-ODN resulted in the generation of a heat labile factor that inhibited macrophage differentiation and accounts for the efficacy of the CpG-ODN. T cells selected from PBMCs by magnetic beads generated the majority of this factor. Cytokines (interleukin-3 (IL-3), IL-4, IL-6, IL-10, interferon-gamma, tumor necrosis factor-alpha, transforming growth factor-beta, granulocyte-macrophage colony-stimulating factor, monocyte chemotactic protein-1) did not inhibit macrophage adherence like CpG-ODN did. Antibodies to IL-6 or IL-10 did not block the activity of CpG-ODN. Dexamethasone inhibited macrophage adherence, and lipopolysaccharide had a minor effect. We conclude that immunostimulatory CpG-ODNs inhibit macrophage adherence by provoking the production of an unidentified heat-labile factor.

Utilization of antisense oligodeoxynucleotides with embryonic tissues in culture

Experimental embryology has long used manipulation of interacting tissues to examine questions of tissue interaction and differentiation. The potential for specific manipulation of gene expression in such tissues has made the utilization of antisense techniques desirable. However, problems with this methodology have discouraged many investigators from using this approach. Selection of target sequences for antisense oligonucleotides, delivery of oligonucleotides into cells or tissues, and the type of modification of the oligonucleotide to be used all present concerns that must be addressed. This paper describes our approach to selection of target sequence and methods of delivery and describes the synthesis of a methoxyethylamidate-modified antisense oligonucleotide that has proved useful in our studies. This approach has enabled us to explore aspects of tissue interaction in the embryonic heart that would have been difficult to explore in a genetic model.