Anti-sense phosphorothioate oligonucleotides have both specific and non-specific effects on cells containing human papillomavirus type 16

Detection of human papillomavirus infection in oral cancers reported at dental facility: assessing the utility of FFPE tissues

Incidence of human papillomavirus (HPV)-associated oral cancers is on the rise. However, epidemiological data of this subset of cancers are limited. Dental hospital poses a unique advantage in detection of HPV-positive oral malignancies. We assessed the utility of formalin-fixed paraffin-embedded (FFPE) tissues, which are readily available, for evaluation of high-risk HPV infection in oral cancer. For protocol standardization, we used 20 prospectively collected paired FFPE and fresh tissues of histopathologically confirmed oral cancer cases reported in Oral Medicine department of a dental hospital for comparative study. Only short PCRs (~ 200 bp) of DNA isolated using a modified xylene-free method displayed a concordant HPV result. For HPV analysis, we used additional 30 retrospectively collected FFPE tissues. DNA isolated from these specimens showed an overall 23.4% (11/47) HPV positivity with detection of HPV18. Comparison of HPV positivity from dental hospital FFPE specimens with overall HPV positivity of freshly collected oral cancer specimens (n = 55) from three cancer care hospitals of the same region showed notable difference (12.7%; 7/55). Further, cancer hospital specimens showed HPV16 positivity and displayed a characteristic difference in reported sub-sites and patient spectrum. Overall, using a xylene-free FFPE DNA isolation method clubbed with short amplicon PCR, we showed detection of HPV-positive oral cancer in dental hospitals.

Papillomavirus E6 oncoproteins

Papillomaviruses induce benign and malignant epithelial tumors, and the viral E6 oncoprotein is essential for full transformation. E6 contributes to transformation by associating with cellular proteins, docking on specific acidic LXXLL peptide motifs found on these proteins. This review examines insights from recent studies of human and animal E6 proteins that determine the three-dimensional structure of E6 when bound to acidic LXXLL peptides. The structure of E6 is related to recent advances in the purification and identification of E6 associated protein complexes. These E6 protein-complexes, together with other proteins that bind to E6, alter a broad array of biological outcomes including modulation of cell survival, cellular transcription, host cell differentiation, growth factor dependence, DNA damage responses, and cell cycle progression.

Papillomaviruses in the causation of human cancers - a brief historical account

Approximately 35 years ago a role of human papillomaviruses (HPV) in cervical cancer has been postulated. Today it is well established that this very heterogeneous virus family harbours important human carcinogens, causing not only the vast majority of cervical, but also a substantial proportion of other anogenital and head and neck cancers. In addition, specific types have been linked to certain cutaneous cancers. In females, HPV infections on a global scale account for more than 50% of infection-linked cancers, in males for barely 5%. Vaccines against the high risk HPV types 16 and 18 represent the first preventive vaccines directly developed to protect against a major human cancer (cervical carcinoma). This review will cover some of the historical aspects of papillomavirus research; it tries briefly to analyze the present state of linking HPV to human cancers and will discuss some emerging developments.

c-MYC antisense phosphosphorodiamidate morpholino oligomer inhibits lung metastasis in a murine tumor model

BACKGROUND

c-MYC amplification and overexpression has been correlated with progression and chemotherapy resistance in lung cancer. AVI-4126, a neutral antisense phosphorodiamidate morpholino oligomer (PMO) has been identified to specifically inhibit c-MYC expression in multiple disease models and identified in Phase I clinical studies to be safe and bioavailable in solid tumors. The present study evaluates AVI-4126 on the development of lung metastasis in the LLC1 syngeneic murine tumor model. Further, this is the first study to show in vivo mis-splicing of c-MYC post-AVI-4126 treatment.

METHODS AND RESULTS

Subcutaneous administration of AVI-4126 at local tumor site (50 microg/day) for 3 cycles of 5 days a week starting day 1 post-tumor cell implantation showed significantly decreased tumor burden, number of tumorlets formed in the lung in comparison to saline or control PMO treatment groups, although no significant reduction of the subcutaneous tumor was observed. AVI-4126 treated lung had markedly reduced mitotic activity but higher rate of apoptosis compared to the controls. HPLC-based analysis of tumor and lung lysates confirmed the presence of intact PMO. In addition to decrease in c-MYC expression, a moderate reduction in the levels of MMP-9 mRNA, a pro-angiogenic extracellular matrix protein postulated to be involved in extravasation of cells from the localized tumor or implantation into the distant metastatic site was observed in the LLC1 tumor tissue of AVI-4126 treated animals.

CONCLUSIONS

The study results are significant in the development of novel anti-tumoral therapeutic strategies directed to c-MYC-overexpressing tumors and establish AVI-4126 as a strong clinical candidate for metastatic disease.

Inhibition of HPV 16 E6 oncogene expression by RNA interference in vitro and in vivo

Substantial studies have demonstrated that the initiation and progression of cervical cancer were closely associated with human papillomavirus (HPV) E6 and E7 oncogenes. The therapeutic strategy with ribozyme or antisense oligonucleotides to inhibit the expression of HPV E6 or E7 oncogenes showed effect to some degree, but problems such as low efficiency, short-period maintenance, and high cost still remain. The aim of this study was to investigate in vitro and in vivo the effect of HPV 16 E6 small interfering RNA (HPV 16 E6 siRNA) on cervical cancer cell line CaSki cells. The specific siRNA of HPV 16 E6 was synthesized and transfected into CaSki cells by liposome. The number of apoptotic cells, HPV 16 E6 messenger RNA (mRNA) level, and E6 protein expression were measured before and after the transfection by flow cytometry, reverse transcriptase-polymerase chain reaction, and Western blot, respectively. Cervical cancer in nude mice was established, and siRNA was injected directly into the nude mice peritoneal cavity or subcutaneous tumor. The efficiency of siRNA was evaluated by tumor volume change, HPV 16 E6 protein expression, and apoptosis of tumor cells. Apoptosis rate of CaSki cells at days 1, 2, 5, and 9 after siRNA transfection were 7.7%, 11.8%, 37.4%, and 12.6%, respectively. The mRNA level of HPV 16 E6 at the same time points were reduced by 77%, 83%, 59%, and 41%, respectively. But the mRNA level of beta-actin, as an internal control, showed no significant change. The inhibition rates of E6 protein synthesis at days 1, 2, 5, and 9 after the transfection were 79.7%, 80.4%, 71.3%, and 57.4%, respectively, whereas the protein levels of Lamin A/C, as internal control, had no change. In vivo, E6 siRNA administration groups showed a dramatic effect in inhibiting tumor growth, suppressing expression of E6 protein, and inducing tumor necrosis and apoptosis as compared with the control group. Direct injection of siRNA into subcutaneous tumor resulted in tumor suppression effect similar to that via the peritoneal cavity, and with additional injection better results could be achieved in cervical cancer CaSki cells. RNA interference exists, and the interference to HPV 16 E6 is specific and highly efficient both in vitro and in vivo.

Identification of inhibitors to papillomavirus type 16 E6 protein based on three-dimensional structures of interacting proteins

Human papillomaviruses (HPV) cause cutaneous and genital warts. A subset of HPV types is associated with a high-risk for progression to malignancy. The E6 protein from the high-risk HPV types represents an attractive target for intervention because of its roles in viral propagation and cellular transformation. E6 functions in part by interaction with human cellular proteins, several of which possess a helical E6-binding motif. The role for each amino acid in this motif for binding E6 has been tested through structure determination and site-directed mutagenesis. These structural and molecular biological approaches defined the spatial geometry of functional groups necessary for binding to E6. This E6-binding information (the E6-binding pharmacophore) was transferred into a three-dimensional query format suitable for computational screening of large chemical databases. Compounds were identified and tested using in vitro and cell culture-based assays. Several compounds selectively inhibited E6 interaction with the E6-binding protein E6AP and interfered with the ability of E6 to promote p53 degradation. Such compounds provide leads for the development of new pharmacologic agents to treat papillomavirus infections and their associated cancers.

Human papillomaviruses and cervical cancer

Carcinoma of the uterine cervix, a leading cause of cancer death in women worldwide, is initiated by infection with high-risk types of human papillomaviruses (HPVs). This review summarizes laboratory studies over the past 20 years that have elucidated the major features of the HPV life cycle, identified the functions of the viral proteins, and clarified the consequences of HPV infection for their host cells. This information has allowed the development of various strategies to prevent or treat infections, including prophylactic vaccination with virus-like particles, therapeutic vaccination against viral proteins expressed in cancer cells, and antiviral approaches to inhibit virus replication, spread, or pathogenesis. These strategies have the potential to cause a dramatic reduction in the incidence of cervical carcinoma and serve as the prototype for comprehensive efforts to combat virus-induced tumors.

In vivo bioavailability and pharmacokinetics of a c-MYC antisense phosphorodiamidate morpholino oligomer, AVI-4126, in solid tumors

Phosphorodiamidate morpholino oligomers (PMO) inhibit targeted gene expression by preventing ribosomal assembly, thereby preventing mRNA translation. AVI-4126, a PMO targeted against c-MYC, has been extensively characterized in multiple cancer and other disease models and is currently in human clinical trials. A phase I clinical study was conducted to address the issue of PMO bioavailability in malignant tumors surgically excised from patients with adenocarcinoma of prostate and breast 1 day after i.v. administration of a single dose of 90 mg AVI-4126 PMO. The study objectives were to evaluate safety, to determine AVI-4126 concentration in tissue samples of the tumors, and to examine the distribution of AVI-4126 (margin versus tumor core). Significant concentrations of intact PMO similar to the animal models were detected in both human prostate and breast tumor tissues with increased distribution in the tumor core for the vascular breast tumors. No serious adverse events (graded according to National Cancer Institute Common Toxicity Criteria) were reported. Another phase I study was conducted in normal human volunteers to assess AVI-4126 plasma pharmacokinetics following single i.v. administration of 90 mg AVI-4126. Data from both human studies indicated similar plasma concentration-time profile. These studies show PMO bioavailability in tumor tissue and establish the feasibility of using PMO targeting specific genes in human cancer clinical trials.

Effective intracellular delivery of oligonucleotides in order to make sense of antisense

For more than two decades, antisense oligonucleotides (ODNs) have been used to modulate gene expression for the purpose of applications in cell biology and for development of novel sophisticated medical therapeutics. Conceptually, the antisense approach represents an elegant strategy, involving the targeting to and association of an ODN sequence with a specific mRNA via base-pairing, resulting in an impairment of functional and/or harmful protein expression in normal and diseased cells/tissue, respectively. Apart from ODN stability, its efficiency very much depends on intracellular delivery and release/access to the target side, issues that are still relatively poorly understood. Since free ODNs enter cells relatively poorly, appropriate carriers, often composed of polymers and cationic lipids, have been developed. Such carriers allow efficient delivery of ODNs into cells in vitro, and the mechanisms of delivery, both in terms of biophysical requirements for the carrier and cell biological features of uptake, are gradually becoming apparent. To become effective, ODNs require delivery into the nucleus, which necessitates release of internalized ODNs from endosomal compartments, an event that seems to depend on the nature of the delivery vehicle and distinct structural shape changes. Interestingly, evidence is accumulating which suggests that by modulating the surface properties of the carrier, the kinetics of such changes can be controlled, thus providing possibilities for programmable release of the carrier contents. Here, consideration will also be given to antisense design and chemistry, and the challenge of extra- and intracellular barriers to be overcome in the delivery process.

Antisense oligodeoxynucleotide inhibits expression of recombinant porcine follicle-stimulating hormone receptor

Follicle-stimulating hormone (FSH) regulates folliculogenesis in the ovary and spermatogenesis in the testis via specific, high affinity membrane-bound receptors (FSHR). To assess the role of FSHR gene expression in regulating expression of FSHR protein in the plasma membrane, the effects of a porcine FSHR cDNA antisense oligodeoxynucleotide (ODN) on FSHR mRNA levels and (125)I-FSH binding were determined in Chinese hamster ovary cells stably expressing recombinant porcine FSHR (pFSHR-CHO cells). An 18-mer phosphorothioated antisense ODN corresponding to the region surrounding the translation initiation codon of the porcine FSHR cDNA was synthesized. An 18-mer phosphorothioated nonsense sequence of identical nucleotide composition was synthesized for use as a control. pFSHR-CHO cells were cultured in the absence or presence of 1-20 microM antisense or nonsense ODN for 24 hr and then assayed for porcine FSHR mRNA, using quantitative reverse transcription and competitive polymerase chain reaction, and for (125)I-FSH binding activity. Treatment with 10 microM antisense ODN caused a paradoxical increase in porcine FSHR mRNA. Nonsense ODN had no effect on porcine FSHR mRNA. Antisense, but not nonsense, ODN (10 microM ) inhibited membrane binding of (125)I-FSH by 13.6 +/- 0.8% (mean +/- SEM, n = 3, P < 0.05) in 24 hr. Treatment of cells with antisense ODN (10 microM) for 48 hr resulted in a 76 +/- 1.5% (P < 0.05) inhibition of (125)I-FSH binding. These results indicate that an FSHR antisense ODN effectively inhibits porcine FSHR synthesis and inhibition of receptor synthesis causes a decrease in functional membrane-bound FSHR.

Structural modifications of antisense oligonucleotides

Antisense oligonucleotides are efficient tools for the inhibition of gene expression in a sequence specific way. Natural oligonucleotides are decomposed rapidly in biological systems, which strongly restrict their application. In contrast, artificial oligonucleotides are designed to be more stable against degradation than the target mRNA, which results in a catalytic effect of the drug. Modification of the phosphate linkage has been the first successful strategy for antisense drug developments and Fomivirsene the first antisense drug in therapy. The launch of Fomivirsene has resulted in a revolutionary spin off to antisense research leading to a second generation of antisense oligonucleotides, which are stable against oligonucleotide cleaving enzymes. Among these, oligonucleotides bearing an alkoxy substituent in position 2' were the most successful ones. The third generation of antisense oligonucleotides contains structure elements, which enhance the antisense action. Zwitterionic oligonucleotides show remarkable results, first, because the stability against ribozymes is largely increased, and secondly, because the electrostatic repulsion between the anionic sense and the zwitterionic antisense cords is minimized. Promising new target molecules in antisense research are oligonucleotide chimäres, which enhance the antisense action (chimäres with intercalators, chelators or polyamines) or enable an application as sequence specific detectors (chimäres with biotin, fluorescein or radioligands).

Selecting optimal antisense reagents

Selection of the appropriate target site is crucial to the success of an antisense experiment. The selection is difficult because RNAs fold to form secondary structures, rendering most of the molecule inaccessible to intermolecular base pairing with complementary nucleic acids. Conventional approaches, such as selection by 'sequence-walking' or computer-assisted design, have not brought significant success. Several empirical selection methods have been reported, a number of which are summarised in this review. Of notable significance are the 'global' methods based on mapping of transcripts with the endoribonuclease H (RNase H) and oligonucleotide scanning arrays.

Loss of muscarinic antinociception by antisense inhibition of M(1) receptors

The effect on cholinergic analgesia of inactivation of the M(1) gene by an antisense oligodeoxyribonucleotide (aODN) was investigated in the mouse hot plate test. Mice received a single intracerebroventricular (i.c.v.) injection of anti-M(1) aODN (0.3, 1. 0 or 2.0 nmol per injection), degenerate ODN (dODN) or vehicle on days 1, 4 and 7. A dose-dependent inhibition of the antinociception induced by the muscarinic agonists oxotremorine (0.1 mg kg(-1) s.c.) and McN-A-343 (30 microg per mouse i.c.v.) and the cholinesterase inhibitor physostigmine (0.2 mg kg(-1) s.c.) was observed 24 h after the last i.c.v. injection of aODN. Time-course experiments revealed that, after the end of the aODN treatment, sensitivity to analgesic drugs progressively appeared reaching the normal range at 96 h. The anti-M(1) aODN was selective against muscarinic antinociception since the enhancement of pain threshold produced by morphine and baclofen were not affected by the above-mentioned treatment. dODN, used as control, did not affect muscarinic antinociception. Binding studies evidenced a selective reduction of M(1) receptor levels in the hippocampus of aODN-treated mice. Neither aODN, dODN nor vehicle produced any behavioural impairment of mice as revealed by the rota-rod and Animex experiments. These results indicate that activation of M(1) muscarinic receptor subtype is fundamental to induce central cholinergic analgesia in mice.

Immortalization of human cells and their malignant conversion by high risk human papillomavirus genotypes

Papillomaviruses cause certain common human cancers, most notably carcinoma of the cervix. The viral oncoproteins E6 and E7 are essential components in malignant conversion, although, in spite of being necessary, they are not sufficient for the development of the malignant phenotype. High risk HPV oncogenes fulfill dual functions in genome-harboring cells: their derived oncoproteins stimulate cell growth by pleiotropic effects. At the same time they act as progression factors by inducing mutations in host cell DNA and aneuploidy. The mechanism underlying the process towards malignant conversion, usually covering a long latency period between primary infection and cancer emergence, is presently not fully understood. It emerges, however, that cancer development depends on the interruption of at least two signalling cascades (labeled as CIF I and CIF II) that interfere with the function of viral oncoproteins (CIF I) and with the transcription of viral oncogenes (CIF II). Further modifications of host cell genes most likely mediate the escape from immune surveillance mechanisms of the host and the development of metastases.

Antisense 'knockdowns' of M1 receptors induces transient anterograde amnesia in mice

The effect on memory processes of inactivation of the M1 gene by an antisense oligodeoxyribonucleotide (aODN) was investigated in the mouse passive avoidance test. Mice received a single intracerebroventricular (i.c.v.) injection of M1 aODN (0.3, 1.0 or 2.0 nmol per injection), degenerated ODN (dODN) or vehicle on days 1, 4 and 7. An amnesic effect, comparable to that produced by antimuscarinic drugs, was observed 12, 24, 48 and 72 h after the last i.c.v. aODN injection, whereas dODN and vehicle, used as controls, did not produce any effect. Reduction in the entrance latency to the dark compartment induced by aODN disappeared 7 days after the end of aODN treatment, which indicates the absence of any irreversible damage or toxicity caused by aODN. Quantitative reverse transcription-polymerase chain reaction analysis demonstrated that a decrease in M1 mRNA levels occurred only in the aODN-treated group, being absent in all control groups. Furthermore, a reduction in M1 receptors was observed in the hippocampus of aODN-treated mice. Neither aODN, dODN nor vehicle produced any behavioral impairment of mice. These results indicate that the integrity and functionality of M1 receptors are fundamental in the modulation of memory processes.

Antisense oligonucleotides to gastrin inhibit growth of human pancreatic cancer

Human pancreatic cancer is stimulated by the autocrine production of gastrin. In this study, the effects of administration of antisense oligonucleotides to gastrin on growth of pancreatic cancer were evaluated in vitro and in vivo. Log phase BxPC-3 human pancreatic cancer cells in culture were exposed to increasing concentrations (0.5-10 microM) of a synthetic 20-mer antisense phosphorothioate oligonucleotide to gastrin for 48 h and growth was assessed by the cellular proliferation assay. Growth was inhibited up to 88% by anti-gastrin oligonucleotides in a dose-related fashion compared to cells treated with diluent or a randomized sequence with the same composition as the anti-gastrin oligonucleotide. In vivo nude mice bearing BxPC-3 xenografts were treated daily for 14 days with a 0.1-ml intratumoral injection of either anti-gastrin (5 microM), the scrambled sequence control phosphorothioate oligonucleotide (5 microM), or buffer. Tumors from the anti-gastrin-treated mice were significantly smaller in volume and weight and had less gastrin detected by radioimmunoassay than either controls. These results support the role of gastrin as a stimulatory peptide for growth of human pancreatic cancer. Antisense oligonucleotide to gastrin may have a role in the future treatment of patients with pancreatic cancer.

Enhancement of anti-herpetic activity of antisense phosphorothioate oligonucleotides 5' end modified with geraniol

We have previously shown that antisense phosphorothioate oligonucleotide (SON) targeted against immediate early (IE) pre-mRNA5 of the herpes simplex virus type I (HSV-I) possessed potent anti-herpetic activities in vitro system. However, anti-herpetic activities of SON were not still efficient enough. Lipophilic compounds have been often conjugated with antisense oligonucleotide to enhance the biological activity. In this study, we selected geraniol as a lipophilic compound and newly synthesized SON bearing 5' terminal geraniol (geranyl-SON) toward IE pre-mRNA 5 of the HSV-1 to enhance the anti-herpetic activity. Geraniol is a olefinic terpene alcohol which is found in many essential oils. It possesses lipophilic characteristic. It is thought to be absorbed in tissue. Geraniol enhanced the anti-herpetic activity of SON with less cytotoxicity in a sequence specific manner. Terminal modification with geraniol did not affect binding affinity with complimentary DNA. Cytoplasm distribution of geranyl-SON was confirmed by confocal microscope. While some of the geranyl-SON was seen in the nucleus, unmodified SON had a punctate distribution in the cytoplasm with little in the nucleus. These results suggested that geranyl modification enhances anti-herpetic activity by changing the subcellular distribution of the oligonucleotides. Consequently geraniol-modifica-tion could provide new means for the efficient delivery of oligo-nucleotides.

Limited use of cationic liposomes as tools to enhance the antiherpetic activities of oligonucleotides in vero cells infected with herpes simplex virus type 1

We used commercially available cationic liposomes, lipofectin, DOTAP, and transfectam, to enhance the antiherpetic activities of phosphodiester oligonucleotides (D-oligos) or phosphorothioate oligonucleotides (S-oligos) targeted against immediate-early pre-mRNA4/5 of herpes simplex virus type 1 (HSV-1). With a 5-fold excess of S-oligos/D-oligos, formation of complexes with some of the S-oligos/D-oligos and the cationic liposomes could be visualized on agarose gel. A >5-fold excess of cationic liposomes enhanced the antiherpetic activities of Doligos, whereas there was not enhancement of the antiherpetic activities of S-oligos. As nuclear localization of D-oligos in the presence of cationic liposomes was not clear, we could not clarify the relation between antiherpetic activities of D-oligos and nuclear distribution of oligos. Subcellular distribution of S-oligos in the presence of lipofectin or DOTAP showed nuclear localization by confocal laser scanning microscopy. Transfectam had no effect on the nuclear distribution of S-oligos. These data showed that cationic liposomes would not be appropriate carriers to enhance the antiherpetic activities of S-oligos. Also, distribution of S-oligos into the nucleus does not necessarily enhance their biologic activity. Questions remain about the effectiveness of cationic liposomes in the enhancement of the antivirus activity of S-oligos.

Intracutaneous vaccination of rabbits with the E6 gene of cottontail rabbit papillomavirus provides partial protection against virus challenge

DNA vaccination of rabbit skin with the L1 gene of cottontail rabbit papillomavirus (CRPV) has previously been shown to induce prophylactic immunity against CRPV. We now describe the effects of vaccination with the CRPV E6 gene, using the same approach. The experimental vaccine pdCMV-E6 encoded both the truncated and full length forms of CRPV E6 protein. The control vaccine pCMV-beta encoded beta galactosidase. Rabbits were vaccinated with DNA-coated gold particles, using a gene gun. Each rabbit received an initial vaccination with 30 micrograms DNA and 3 weeks later a booster vaccination, also with 30 micrograms DNA. pdCMV-E6-vaccinated rabbits developed E6-specific cellular immunity as determined by proliferation assays using peripheral blood mononuclear cells from animals prior to challenge, but did not develop detectable humoral immunity to E6 proteins, as evaluated by ELISA using two different E6 antigen preparations. Control rabbits developed humoral immunity to beta galactosidase. All rabbits were challenged by infection of nine skin sites with live CRPV virus and monitored for papilloma formation. None of four control rabbits was protected at any of the challenge sites. Of six rabbits vaccinated with pdCMV-E6, two were completely protected and one was virtually completely protected (tiny papillomas at just two of nine challenge sites). These three rabbits also exhibited significant E6-specific in vitro proliferative responses. The four E6 DNA-vaccinated rabbits that were not completely protected exhibited evidence of partial protection: some challenge sites did not form papillomas; papilloma onset was delayed; papilloma burden was less. These results demonstrate that partial prophylaxis against papillomavirus-induced disease can be achieved by intracutaneous vaccination with a recombinant plasmid encoding the papillomavirus.

Gene therapy for infectious diseases

Gene therapy is being investigated as an alternative treatment for a wide range of infectious diseases that are not amenable to standard clinical management. Approaches to gene therapy for infectious diseases can be divided into three broad categories: (i) gene therapies based on nucleic acid moieties, including antisense DNA or RNA, RNA decoys, and catalytic RNA moieties (ribozymes); (ii) protein approaches such as transdominant negative proteins and single-chain antibodies; and (iii) immunotherapeutic approaches involving genetic vaccines or pathogen-specific lymphocytes. It is further possible that combinations of the aforementioned approaches will be used simultaneously to inhibit multiple stages of the life cycle of the infectious agent.

Blockade of clomipramine and amitriptyline analgesia by an antisense oligonucleotide to mKv1.1, a mouse Shaker-like K+ channel

The effect of an antisense oligonucleotide to the K+ channel coding mKv1.1 mRNA on antinociception induced by the tricyclic antidepressants, clomipramine (20-35 mg kg(-1) s.c.) and amitriptyline (10-25 mg kg(-1) s.c.), was investigated in the mouse hot-plate test. Antisense oligonucleotide (0.5-1.0-2.0-3.0 nmol per i.c.v. injection) produced a dose-dependent inhibition of clomipramine and amitriptyline antinociception 72 h after the last i.c.v. injection. The sensitivity to both analgesic drugs returned 7 days after antisense oligonucleotide injection, indicating the absence of irreversible damage or toxicity. Treatment with a degenerated oligonucleotide did not modify the clomipramine- and amitriptyline-induced antinociception in comparison with that in naive (unpretreated controls), vector and saline i.c.v.-injected mice. A quantitative reverse transcription-polymerase chain reaction (RT-PCR) study demonstrated a reduction in mRNA levels only in the antisense oligonucleotide treated group. Antisense oligonucleotide, degenerated oligonucleotide or vector pretreatment, in the range of doses used, did not produce any behavioural impairment as revealed by the mouse rotarod and hole-board tests. The present results indicate that modulation of the mKv1.1 K+ channel plays an important role in the central analgesia induced by the tricyclic antidepressants, clomipramine and amitriptyline.

Effect of K+ channel modulation on mouse feeding behaviour

The K+ channel antagonists, glucose (100 microg per mouse i.c.v.), tetraethylammonium (1 microg per mouse i.c.v.) and apamin (1 ng per mouse i.c.v.), reduced food intake of mice comparably to the two anorectic drugs, amphetamine (10 microg per mouse i.c.v.) and cocaine (50 microg per mouse i.c.v.). Conversely, the K+ channel openers, minoxidil (5 microg per mouse i.c.v.) and pinacidil (10 microg per mouse i.c.v.), elicited an orectic effect of the same intensity as that induced by 2-deoxyglucose (200 microg per mouse i.c.v.), aurothioglucose (200 microg per mouse i.c.v.) and neuropeptide Y (0.5 microg per mouse i.c.v.). The antisense oligodeoxyribonucleotide (1-3 nmol per injection) to mKv1.1 gene produced, at 72 h, a dose-dependent increase in food intake. A quantitative reverse transcription-polymerase chain reaction (RT-PCR) study demonstrated a reduction in cerebral mRNA levels only in the antisense oligodeoxyribonucleotide-treated group, indicating the absence of a sequence-independent action. Mice receiving the K+ channel modulators or antisense oligodeoxyribonucleotide had unmodified motor coordination and inspection activity as revealed, respectively, by the rotarod and hole-board tests. The integrity and functionality of central K+ channels appears, therefore, to be fundamental in the regulation of food intake by mice.

Antisense inhibition of silica-induced tumor necrosis factor in alveolar macrophages

Tumor necrosis factor-alpha (TNFalpha) has been shown to play an important role in the pathogenesis of silicotic fibrosis. In this study, antisense oligonucleotides targeted to TNFalpha mRNA were used to inhibit silica-induced TNFalpha gene expression in alveolar macrophages. To achieve macrophage-specific oligonucleotide delivery, a molecular conjugate consisting of mannosylated polylysine that exploits endocytosis via the macrophage mannose receptor was used. Complexes were formed between the mannosylated polylysine and oligonucleotides and added to the cells in the presence of silica. Enzyme-linked immunoadsorbent assay showed that the complex consisting of the conjugate and antisense oligomer effectively inhibited TNFalpha production, whereas the oligomer alone had much less effect. Reverse transcriptase-polymerase chain reaction analysis revealed that the reduction in TNFalpha secretion was associated with specific ablation of targeted TNFalpha mRNA. The conjugate alone or conjugate complexed with inverted or sense sequence oligonucleotide had no effect. The promoting effect of the conjugate on antisense activity was shown to be due to enhanced cellular uptake of the oligomer via mannose receptor-mediated endocytosis. Cells lacking mannose receptors showed no susceptibility to the conjugate treatment. These results indicate that effective and selective inhibition of macrophage TNFalpha expression can be achieved using the antisense mannosylated polylysine system.

Improved oligonucleotide uptake and stability by a new drug carrier, the SupraMolecular Bio Vector (SMBV)

Antisense oligodeoxynucleotides are potential therapeutic agents, but their development is still limited by both a poor cellular uptake and a high degradation rate in biological media. The strategy that we propose to face these problems is to use small synthetic carriers, around 30 nm diameter, the SupraMolecular Bio Vectors (SMBV). We used positively charged SMBV and settled the ionic incorporation of negatively charged oligonucleotides into these carriers. A minimal leakage of 10% of total incorporated oligonucleotides was then measured during two months. Both protection and uptake of oligonucleotides were then analyzed. On the one hand, we showed that the incorporation of oligonucleotides into the selected SMBV allows to significantly increase, 8 times, their half-life, in cell growth medium. On the other hand, the internalization of the SMBV, into cells, by an endosomal pathway has been characterized. The essential point is that the SMBV uptake elicits the simultaneous oligonucleotide uptake. The oligonucleotide amount that goes through cells within 5 h can be up to 30 times higher than for free oligonucleotides and the fraction of oligonucleotides that is present in the cytosol is increased up to 10 fold after incorporation into the SMBV. This study demonstrates the ability of SMBV to improve oligonucleotide cellular behaviour.

Contiguous four-guanosine sequence in c-myc antisense phosphorothioate oligonucleotides inhibits cell growth on human lung cancer cells: possible involvement of cell adhesion inhibition

A contiguous four-guanosine (4G) sequence in c-myc antisense phosphorothioate oligonucleotides caused an antiproliferative effect in smooth muscle cells. To investigate the antiproliferative effect of c-myc antisense oligonucleotides on human lung cancer cell lines, we synthesized oligonucleotides of various lengths and sequences, focusing on the contiguous four-guanosine (4G) sequence. While a c-myc antisense oligonucleotide (20AS1 (4G)) targeted to the translation initiation codon of c-myc mRNA inhibited cell growth of A549 cells by 69% at 10 microM, a scrambled oligonucleotide (20SCR1 (4G)) containing the contiguous four-guanosine (4G) sequence also inhibited cell growth by 72% at the same dose. Although treatment with either 20AS1 (4G) or 20SCR1 (4G) inhibited cell adhesion by 70% at 10 microM, expression of c-myc protein was significantly suppressed only by 20AS1 (4G) (62%), and was only weakly inhibited by 20SCR1 (4G) (32%). Furthermore, a small cell lung carcinoma cell line, Lu65, which can grow in suspension form, was highly resistant to 20AS1 (4G) treatment (IC50>20 microM). These results suggest that the cell growth inhibition by c-myc antisense oligonucleotides containing the contiguous four-guanosine (4G) sequence was possibly correlated with inhibition of cell adhesion, but not with inhibition of c-myc protein expression, via a sequence-specific non-antisense mechanism.

Antisense inhibition of virus infections

This chapter summarizes the new approaches to identify novel antiviral drug targets and to develop novel antiviral strategies. The chapter also reviews genetic pharmacology as it relates to antiviral antisense research and drug development. Antisense oligonucleotides are selective compounds by virtue of their interaction with specific segments of RNA. For potential antivirals, identification of appropriate target RNA sequences for antisense oligonucleotides is performed at two levels: the optimal gene within the virus, and the optimal sequence within the RNA. The importance of these oligonucleotide modifications in designing effective drugs is just now being evaluated, both in animal model systems and in the clinic. The first generation of widely used antisense oligonucleotides has been the phosphorothioate (PS) compounds and a body of data on biodistribution, pharmacokinetics, and metabolism in animals and in humans is now available. Since the identification and sequencing of human immunodeficiency virus (HIV), there has been a strong interest in identifying a potent oligonucleotide inhibitor that would have the potential for development as a therapy for acquired immunodeficiency syndrome (AIDS). Numerous phosphorothioate oligonucleotides, with no apparent antisense sequence specificity, can have an anti-herpes simplex virus (HSV) effect. Oligonucleotides can be effective anti-influenza agents in cell culture assays. Hepatitis B virus (HBV) X protein that is a transactivator has been also reported to be targeted successfully by antisense oligonucleotides in vivo. Several of picornaviruses have been targets for antisense oligonucleotide inhibition, and the studies demonstrate the versatility of the antisense approach. However, the fact that oligonucleotides may contribute numerous mechanisms toward the antiviral activity, in addition to the antisense mechanism, may in some cases be an asset in the pursuit of clinically useful antiviral drugs.

Activation of human B cells by phosphorothioate oligodeoxynucleotides

To investigate the potential of DNA to elicit immune responses in man, we examined the capacity of a variety of oligodeoxynucleotides (ODNs) to stimulate highly purified T cell-depleted human peripheral blood B cells. Among 47 ODNs of various sequences tested, 12 phosphorothioate oligodeoxynucleotides (sODNs) induced marked B cell proliferation and Ig production. IL-2 augmented both proliferation and production of IgM, IgG, and IgA, as well as IgM anti-DNA antibodies, but was not necessary for B cell stimulation. Similarly, T cells enhanced stimulation, but were not necessary for B cell activation. After stimulation with the active sODNs, more than 95% of B cells expressed CD25 and CD86. In addition, B cells stimulated with sODNs expressed all six of the major immunoglobulin VH gene families. These results indicate that the human B cell response to sODN is polyclonal. Active sODN coupled to Sepharose beads stimulated B cells as effectively as the free sODN, suggesting that stimulation resulted from engagement of surface receptors. These data indicate that sODNs can directly induce polyclonal activation of human B cells in a T cell-independent manner by engaging as yet unknown B cell surface receptors.

Oligodeoxynucleotides directed to early growth response gene-1 mRNA inhibit DNA synthesis in the smooth muscle cell

Vascular smooth muscle cell proliferation plays a central role in the pathophysiology of cardiovascular diseases. The induction of the early growth response gene-1 (egr-1) mRNA is associated with different cellular processes such as cell proliferation. Antisense oligodeoxynucleotides seem to provide a promising new pharmaceutical tool for effective modification of the expression of specific genes. Hence, in the present study, the effect of 15-mer antisense oligodeoxynucleotides (targeted to the initial codon region of the egr-1 mRNA) on the angiotensin II- and platelet-derived growth factor-BB-induced growth promoting effects of aortic smooth muscle cells was evaluated. Angiotensin II- and platelet-derived growth factor-BB induced egr-1 mRNA (3.4 kb) and Egr-1 protein (80 kDa) in a time- and concentration-dependent fashion. No effects of the sense and antisense oligodeoxynucleotides on the agonist-induced elevation of the egr-1 mRNA and on the Egr-1 protein could be demonstrated. However, they effectively inhibited the angiotensin II- and the platelet-derived growth factor-BB-induced DNA synthesis. Our findings provide evidence that the oligodeoxynucleotides inhibit vascular smooth muscle cell growth via nonantisense mechanism(s).

Antiviral agents in dermatology: current status and future prospects

The majority of current antiviral agents have become available only during the past decade. The above mentioned antiviral drugs, especially the viral-TK-specific agents have attempted to bring antiviral therapy on par with antimicrobial therapy. The fact, that cells infected with viruses can be selected against the relatively low toxicity to the patient, highlights the present state of antiviral therapy. Since viral infection can be viewed as an integral component of the self (i.e., a condition that cannot simply be surgically eliminated), the science of medicine is turning to the components of the self to overcome such conditions. By administering immune-system-derived agents (e.g., interferons) or compounds that stimulate the immune system (e.g., adjuvants like imiquimod), previously unmanageable conditions become manageable. The future of antiviral therapy will undoubtedly be at the molecular level. With greater understanding of the virus and the immune system with which it interacts, more specific and efficacious antiviral agents will be added to the arsenal of the clinician.

Single base discrimination for ribonuclease H-dependent antisense effects within intact human leukaemia cells

We have previously demonstrated, in vitro, that phosphodiester and phosphorothioate antisense oligodeoxynucleotides could direct ribonuclease H to cleave non-target RNA sites and that chimeric methylphosphonodiester/phosphodiester analogue structures were substantially more specific. In this report we show that such chimeric molecules can promote point mutation-specific scission of target mRNA by both Escherichia coli and human RNases H in vitro. Intact human leukaemia cells 'biochemically microinjected' with antisense effectors demonstrated efficient suppression of target mRNA expression. It was noted that the chimeric methylphosphonodiester/phosphodiester structures showed single base discrimination, whereas neither the phosphodiester nor phosphorothioate compounds were as stringent. Finally, we show that the antisense effects obtained in intact cells were due to endogenous RNase H activity.

Antisense oligodeoxyribonucleotide inhibition of TGF-beta 1 gene expression and alterations in the growth and malignant properties of mouse fibrosarcoma cells

Transforming growth factor (TGF-beta) is a family of multifunctional signalling molecules that play a fundamental role in both normal and malignant cell behavior. Procedures that alter mouse TGF-beta 1 gene expression provide an important approach for analyzing the complex regulatory processes associated with this member of the growth factor family. Therefore, we have designed oligodeoxyribonucleotides (oligos) in an antisense orientation, which are complementary to regions of the TGF-beta 1 message, in an attempt to obtain an oligo sequence that specifically reduces TGF-beta 1 synthesis. We observed that oligos containing a mixture of phosphorothioate and phosphodiester linkages were less toxic and more specific when compared to those only containing phosphorothioate. A non-toxic sequence was identified that markedly reduced the levels of TGF-beta 1 in oligo-treated malignant mouse fibrosarcoma cells. The invasive and metastatic properties of these fibrosarcoma cells were also significantly decreased following treatment with the antisense oligo. The results indicate an important role for altered TGF-beta 1 expression in the regulation of malignant cell proliferation, invasion and metastasis. These results also indicate that this oligo sequence is a useful tool for studies directed towards understanding the complex relationships between TGF-beta 1 and cellular regulation.

Gene therapy--its potential in the management of oral cancer

Gene therapy is an important new approach to the treatment of many diseases. This review summarises the methods that are available for developing gene therapy, and demonstrates that oral cancer is probably susceptible to these approaches.

Antisense oligonucleotide strategies in physiology

Antisense oligonucleotides can inhibit gene expression in living cells by binding to complementary sequences of DNA, RNA or mRNA. The mechanisms include inhibition of RNA synthesis, RNA splicing, mRNA export, binding of initiation factors, assembly of ribosome subunits and of sliding of the ribosome along the mRNA coding sequence. The most efficient antisense oligonucleotides also activate RNAse H, an ubiquitous enzyme that cleaves the mRNA at sites of mRNA/oligonucleotide duplex formation. A staggering number of oligonucleotide modifications have been proposed to retard degradation by nucleases, enhance cellular uptake, increase binding to the target sequence, and minimize non-specific binding to related nucleic acid sequences. Phosphorothioates are the most popular oligonucleotides used in cell culture and in vivo, although sequence non-specificity remains an underreported problem. Recently developed chimeras between methylphosphonates and phosphodiester oligonucleotides appear to combine the advantages of water solubility, nuclease resistance, enhanced cellular uptake, activation of RNAse H, and high sequence selectivity. Antigene oligonucleotides are also promising, because they can inhibit gene expression by triple helix formation with DNA or by binding to one of the DNA strands. They have so far been little used in physiological studies. Cost is still a prohibitive factor, especially for suppressing the expression of a hormone or hormone receptor gene in rats, for example. However, patch-clamp dialysis of single cells or nuclear microinjections in culture, exposure of cultures to extracellular oligonucleotides, and intra-cerebral microinjections of oligonucleotides are feasible and highly rewarding approaches in physiology.

Cationic liposomes mediated delivery of antisense oligonucleotides targeted to HPV 16 E7 mRNA in CaSki cells

The "high risk" types 16 and 18 of human papillomavirus (HPV) are involved in the etiology of genital squamous cell carcinoma. The early genes 6 and 7 (E6-E7) of these viruses code for the major transforming proteins, capable of inducing cell transformation alone or acting synergistically with other oncogenes. Antisense oligonucleotides, recently applied to inhibit the functions of a number of cellular and viral proteins, might provide the basis for a new therapeutic strategy against HPV-induced malignancies. We studied the proliferation of CaSki cells by the MTT assay after their exposure to HPV 16 E7 mRNA antisense oligonucleotides with and without cationic liposomes (containing dimethyldioctadecylammonium bromide DDAB, and dioleylphosphatidylethanolamine, DOPE). Unmodified oligonucleotides (either 12- or 23-mers) did not have any effect on either CaSki cell proliferation or morphology when compared with the untreated cells. The cellular uptake of oligonucleotides was significantly enhanced by the cationic liposomes as assessed by confocal laser scanning microscopy (CLSM). The cationic liposomes were toxic to the cells as demonstrated by the reduced cell number and altered cell morphology. Only a slight reduction of the cell proliferation was seen when antisense 12-mer was protected from its 3'- and 5'-ends with thiolate and FITC, respectively. Both the 12- and the 23-mers with the cationic liposomes inhibited cell proliferation, the inhibitory effect being longer with the 23-mer. Overall, the MTT assay was less sensitive than light microscopy to reveal the toxic effects on CaSki cells. The results suggest that antisense oligonucleotides targeted to HPV 16 E7 mRNA can be introduced into CaSki cells with cationic liposomes.

Triplex-forming oligonucleotide binding represses transcription of the human c-erbB gene in glioma

Mixed purine-pyrimidine oligodeoxynucleotides were designed to form collinear DNA triplexes with pyrimidine-rich elements in the EGFR gene promoter. Their effects as mediators of human epidermal growth factor receptor (EGFR) gene transcription and subsequent gene expression were evaluated using human squamous cell carcinoma (A431) and human glioma cell line (U251MG and U87MG). Gel shift analysis indicated that the oligonucleotide forms a collinear triplex within the duplex Sp-1 binding site. An in vitro assay system revealed a correlation between triplex formation and the repression of EGFR transcription. We postulate that guanine residues are not always optimum in apposition to G-C pairs to form triple helices in the target. Site-specific oligodeoxynucleotides binding to a DNA duplex may serve as the basis for an alternative program of gene control in vitro.

Improved anti-herpes simplex virus type 1 activity of a phosphodiester antisense oligonucleotide containing a 3'-terminal hairpin-like structure

We synthesized a series of 20-mer antisense phosphodiester oligonucleotides constituting of a 5'-dodecameric sequence, complementary to the acceptor splice junction of herpes simplex virus type 1 (HSV-1) pre-mRNAs IE4 and IE5, flanked in 3' by octameric sequences adopting hairpin-like structures of different stabilities. The presence of the minihairpins in 3' protected the 20-mer phosphodiester oligonucleotides against serum nuclease degradation, this protection being well correlated to the reported melting temperatures of the minihairpins, and to the gel mobilities of the 20-mer oligonucleotides. While no protection was observed using a linear 8-mer, the addition in 3' of the most stable minihairpin--H8--increased more than eightfold the nuclease resistance of the linear antisense dodecamer. We analyzed the effect of such a protection on the anti-HSV-1 antisense activities of the oligonucleotides. When bearing H8 in 3', the antisense dodecamer was 10 times more active than in the absence of 3'-flanking sequence, while a linear 20-mer control containing the antisense sequence was only 3 times more active. This work provides the basis for a further rational design of phosphodiester antisense oligonucleotides, taking advantage of the specific properties conferred by their conformations.

2D 1H and 31P NMR spectra and distorted A-DNA-like duplex structure of a phosphorodithioate oligonucleotide

Assignment of the 1H and 31P NMR spectra of a phosphorodithioate modified oligonucleotide decamer duplex, d(CGCTTpS2-AAGCG)2 (10-mer-S; a site of dithioate substitution is designated with the symbols pS2-), was achieved by two-dimensional homonuclear TOCSY, NOESY and 1H-31P Pure Absorption phase Constant time (PAC) heteronuclear correlation spectroscopy. In contrast to the parent palindromic decamer sequence (1) which has been shown to exist entirely in the duplex B-DNA conformation under comparable conditions (100 mM KCl), the dithiophosphate analogue forms a hairpin loop. However, the duplex form of the dithioate oligonucleotide can be stabilized at lower temperatures, higher salt and strand concentration. The solution structure of the decamer duplex was calculated by an iterative hybrid relaxation matrix method (MORASS) combined with 2D NOESY-distance restrained molecular dynamics. These backbone modified compounds, potentially attractive antisense oligonucleotide agents, are often assumed to possess similar structure as the parent nucleic acid complex. Importantly, the refined structure of the phosphorodithioate duplex shows a significant deviation from the parent unmodified, phosphoryl duplex. An overall bend and unwinding in the phosphorodithioate duplex is observed. The structural distortion of the phosphorodithioate duplex was confirmed by comparison of helicoidal parameters and groove dimensions. Especially, the helical twists of the phosphorodithioate decamer deviate significantly from the parent phosphoryl decamer. The minor groove width of phosphorodithioate duplex 10-mer-S varies between 8.4 and 13.3 A which is much wider than those of the parent phosphoryl decamer d(CGCTTAAGCG)2 (4.2 approximately 9.4 A). The larger minor groove width of 10-mer-S duplex contributes to the unwinding of the backbone and indicates that the duplex has an overall A-DNA-like conformation in the region surrounding the dithiophosphate modification.

Growth dependence of human papillomavirus 16 DNA-positive cervical cancer cell lines and human papillomavirus 16-transformed human and rat cells on the viral oncoproteins

The dependence on human papillomavirus (HPV) oncoproteins of the growth of cervical cancer cell lines [C4-1, HeLa (both containing HPV 18 DNA), CaSki and SiHa (both containing HPV 16 DNA)], HPV 16-transformed human embryonic kidney cells, and HPV 16-transformed rat brain and 3Y1 cells was examined by using antisense RNA approaches. The cells were transfected with plasmids expressing RNA antisense to the HPV 16 or 18 open reading frames E6E7, together with plasmids expressing the hygromycin B resistance gene, and drug-resistant colonies were scored three weeks later. In all the human cell lines, the efficiency of colony formation was lowered by RNA antisense to the resident HPV type. Some of the rat cell lines responded to the antisense plasmids, but some did not. From a nonresponding rat tumor line (3Y1HP-1T), cell clones with various levels of E7 protein were isolated after transfection with the antisense plasmid, and were examined for anchorage-independent growth in soft agar. The colonies formed by the clones with lower E7 levels tended to be smaller and fewer than those formed by the clones with higher E7 levels. These findings strongly suggest that some of the transformed or cancer phenotypes of cells in vitro are dependent, even after extensive passages and malignant changes, on expression of the oncoproteins of the resident HPV.

A more efficient and specific strategy in the ablation of mRNA in Xenopus laevis using mixtures of antisense oligos

Previously, antisense oligodeoxyribonucleotides (oligos) have been used to ablate specific mRNAs from the maternal RNA pool of Xenopus laevis oocytes. However, this strategy is limited by the dose of oligo which can be used and the fact that 100% cleavage of the target RNA is rare. Further, non-specific cleavage of other RNAs can also occur. We demonstrate that the use of several oligos against the histone H4 RNA results in a marked improvement in the efficiency of target degradation, due to synergistic action between oligos and the existence of RNA in at least two different secondary structures. We show, by using a set of overlapping oligos complementary to the entire H4 RNA, that the amount of oligo required for efficient target ablation is greatly lowered and non-specific effects are reduced.

Transient inhibition of foot-and-mouth disease virus infection of BHK-21 cells by antisense oligonucleotides directed against the second functional initiator AUG

The antiviral activity of antisense oligonucleotides corresponding to different regions of foot-and-mouth disease virus (FMDV) genome has been assessed in BHK-21 cells. The locations of the oligonucleotides used were: (i) two regions within the internal ribosome entry site (IRES), involved in the regulation of the translation initiation of the viral polyprotein; (ii) each of the two functional initiator AUGs; (iii) an internal sequence of P2A gene; and (iv) a region at the 3' end non-coding region. Cytoplasmic microinjection of oligodeoxyribonucleotides and oligoribonucleotides complementary to the second AUG resulted in a transient inhibition of viral VP1 expression in infected cells. Significant inhibitions, ranging from 35 to 52%, were obtained at 5 h post-infection using oligonucleotide concentrations of 125 microM and higher. The extent and duration of this inhibition seemed to be mediated by both a rapid transport to the nucleus and the short half-life of the oligonucleotide. This inhibition of FMDV protein synthesis was correlated with a reduction of virus yield of about 50%, as observed after the addition to the cell culture of an oligodeoxyribonucleotide phosphorothioate complementary to the second AUG.

Inhibition of cervical carcinoma cell line proliferation by the introduction of a bovine papillomavirus regulatory gene

Human papillomavirus (HPV) E6 and E7 oncogenes are expressed in the great majority of human cervical carcinomas, whereas the viral E2 regulatory gene is usually disrupted in these cancers. To investigate the roles of the papillomavirus E2 genes in the development and maintenance of cervical carcinoma, the bovine papillomavirus (BPV) E2 gene was acutely introduced into cervical carcinoma cell lines by infection with high-titer stocks of simian virus 40-based recombinant viruses. Expression of the BPV E2 protein in HeLa, C-4I, and MS751 cells results in specific inhibition of the expression of the resident HPV type 18 (HPV18) E6 and E7 genes and in inhibition of cell growth. HeLa cells, in which HPV gene expression is nearly completely abolished, undergo a dramatic and rapid inhibition of proliferation, which appears to be largely a consequence of a block in progression from the G1 to the S phase of the cell cycle. Loss of HPV18 gene expression in HeLa cells is also accompanied by a marked increase in the level of the cellular p53 tumor suppressor protein, apparently as a consequence of abrogation of HPV18 E6-mediated destabilization of p53. The proliferation of HT-3 cells, a human cervical carcinoma cell line devoid of detectable HPV DNA, is also inhibited by E2 expression, whereas two other epithelial cell lines that do not contain HPV DNA are not inhibited. Thus, a number of cervical carcinoma cell lines are remarkably sensitive to growth inhibition by the E2 protein. Although BPV E2-mediated inhibition of HPV18 E6 and E7 expression may contribute to growth inhibition in some of the cervical carcinoma cell lines, the BPV E2 protein also appears to exert a growth-inhibitory effect that is independent of its effects on HPV gene expression.

Modulation of human prorenin gene expression by antisense oligonucleotides in transfected CHO cells

Four phosphorothioate oligonucleotides whose sequences are complementary to the 5' untranslated region, the initiation codon or the coding region of human prorenin mRNA, were studied for their capacity to inhibit gene expression in stably transfected Chinese hamster ovary (CHO) cells constitutively producing human prorenin. In contrast to oligomers complementary to the initiation codon and the coding region, antisense oligomers directed towards the 5' untranslated region have no inhibitory effects. The intracellular delivery of a biotinylated phosphorothioate oligonucleotide (biotin-CATCCATGCTTCCCTC) was monitored in immunofluorescence studies. In the absence of a cationic liposome preparation, Lipofectin, the oligomer failed to penetrate the cells. In the presence of Lipofectin, the 35S-labelled oligomer entered the cells and was distributed in proportions of 54% to the nuclei and 35% to the cytosol. The effects of regular oligonucleotides and of 3'-end and/or 5'-end-modified phosphodiester oligonucleotides on prorenin production were tested. Terminal modification by biotinylation at the 5'-end and/or 3'-dodecyl esterification stabilized oligonucleotides towards exonucleases, but did not translate into a significant inhibition of prorenin production and did not improve the intracellular delivery and or stability of the oligomers. We have shown that it is possible to inhibit prorenin production intracellularly using specific antisense oligonucleotides. Stability and delivery are crucial factors in the design of potent and specific compounds directed at prorenin mRNA.

In vitro evaluation of phosphorothioate oligonucleotides targeted to the E2 mRNA of papillomavirus: potential treatment for genital warts

Papillomaviruses induce benign proliferative lesions, such as genital warts, in humans. The E2 gene product is thought to play a major role in the regulation of viral transcription and DNA replication and may represent a rational target for an antisense oligonucleotide drug action. Phosphorothioate oligonucleotides complementary to E2 mRNAs were synthesized and tested in a series of in vitro bovine papillomavirus (BPV) and human papillomavirus (HPV) models for the ability to inhibit E2 transactivation and virus-induced focus formation. The most active BPV-specific compounds were complementary to the mRNA cap region (ISIS 1751), the translation initiation region for the full-length E2 transactivator (ISIS 1753), and the translation initiation region for the E2 transrepressor mRNA (ISIS 1755). ISIS 1751 and ISIS 1753 were found to reduce E2-dependent transactivation and viral focus formation in a sequence-specific and concentration-dependent manner. ISIS 1755 increased E2 transactivation in a dose-dependent manner but had no effect on focus formation. Oligonucleotides with a chain length of 20 residues had optimal activity in the E2 transactivation assay. On the basis of the above observations, ISIS 2105, a 20-residue phosphorothioate oligonucleotide targeted to the translation initiation of both HPV type 6 (HPV-6) and HPV-11 E2 mRNA, was designed and shown to inhibit E2-dependent transactivation by HPV-11 E2 expressed from a surrogate promoter. These observations support the rationale of E2 as a target for antiviral therapy against papillomavirus infections and specifically identify ISIS 2105 as a candidate antisense oligonucleotide for the treatment of genital warts induced by HPV-6 and HPV-11.

Effects of sequence of thioated oligonucleotides on cultured human mammary epithelial cells

We have compared the effects of a number of different oligonucleotides on the growth and morphology of normal finite life span and immortally transformed human mammary epithelial cells. The oligonucleotide sequences chosen initially for study were based on that of the NB-1 gene, which encodes a calmodulin-like protein of unknown function. We found that certain thioated oligonucleotides 15-20 residues in length altered the morphology and decreased the growth rate of the normal cells in a concentration-dependent manner. These effects were rapid, occurring within 24-48 h of oligonucleotide addition. The effects, which occurred without an accompanying detectable decrease in the levels of NB-1 mRNA or protein, were most pronounced in the normal epithelial cells, less apparent in the immortalized epithelial cells, and unobserved in normal breast fibroblasts. Identical sequences having mixed phosphodiester and phosphorothioate backbones, or phosphodiester backbones alone, had little or no effect on normal epithelial cell morphology or growth. Two out of seven additional thioated oligonucleotides which were not complementary to NB-1 mRNA, also affected normal epithelial cell morphology and growth when used at similar concentrations (10 microM). Taken together, the observed effects on normal epithelial cells indicate that certain thioated oligonucleotides may have pharmacological consequences that do not depend on strict complementarity of their sequences to known mRNAs.