Efficacy of antisense morpholino oligomer targeted to c-myc in prostate cancer xenograft murine model and a Phase I safety study in humans. (1/324)

PURPOSE: The overexpression of c-myc associated with uncontrolled cell proliferation is a frequent genetic event in androgen-refractory prostatic neoplasia. The purpose of this study was to evaluate the bioavailability and efficacy of a novel antisense phosphorodiamidate morpholino oligomer directed against c-myc, AVI-4126, in PC-3 androgen-independent human prostate cancer xenograft murine model and its safety in a Phase I human clinical study. EXPERIMENTAL DESIGN: AVI-4126 administration in athymic mice bearing s.c. PC-3 xenografts was carried out to determine the bioavailability, tolerance, antitumor activity, and histological changes induced by targeted inhibition of c-Myc expression using a specific morpholine antisense oligomer. The Phase I safety study involved a single center, open label, dose-escalating design in healthy volunteers after i.v. administration of AVI-4126. RESULTS: The data reveal that AVI-4126 targets and inhibits c-myc translation in a sequence-specific manner and causes significant growth inhibition and apoptosis in prostate cancer cells and in s.c. tumor xenografts. A 75-80% reduction in tumor burden was observed in AVI-4126-treated animals compared with the scrambled oligomer and saline control groups. Histologically, tumors grown in the athymic mice treated with AVI-4126 were less cellular and vascular than those in control mice and showed an increased level of cellular degeneration, cytoplasmic vacuoles, and hyperchromatic nuclei. Phase I safety trials in humans via i.v. route of administration showed no toxicity or serious adverse events. CONCLUSIONS: The present study demonstrates that inhibition of c-Myc expression by antisense phosphorodiamidate morpholino oligomer is a promising new and safe therapeutic strategy for prostate cancer.  (+info)

Inhibition of gene expression in Escherichia coli by antisense phosphorodiamidate morpholino oligomers. (2/324)

Antisense phosphorodiamidate morpholino oligomers (PMOs) were tested for the ability to inhibit gene expression in Escherichia coli. PMOs targeted to either a myc-luciferase reporter gene product or 16S rRNA did not inhibit luciferase expression or growth. However, in a strain with defective lipopolysaccharide (lpxA mutant), which has a leaky outer membrane, PMOs targeted to the myc-luciferase or acyl carrier protein (acpP) mRNA significantly inhibited their targets in a dose-dependent response. A significant improvement was made by covalently joining the peptide (KFF)(3)KC to the end of PMOs. In strains with an intact outer membrane, (KFF)(3)KC-myc PMO inhibited luciferase expression by 63%. A second (KFF)(3)KC-PMO conjugate targeted to lacI mRNA induced beta-galactosidase in a dose-dependent response. The end of the PMO to which (KFF)(3)KC is attached affected the efficiency of target inhibition but in various ways depending on the PMO. Another peptide-lacI PMO conjugate was synthesized with the cationic peptide CRRRQRRKKR and was found not to induce beta-galactosidase. We conclude that the outer membrane of E. coli inhibits entry of PMOs and that (KFF)(3)KC-PMO conjugates are transported across both membranes and specifically inhibit expression of their genetic targets.  (+info)

Antisense morpholino-oligomers directed against the 5' end of the genome inhibit coronavirus proliferation and growth. (3/324)

Conjugation of a peptide related to the human immunodeficiency virus type 1 Tat represents a novel method for delivery of antisense morpholino-oligomers. Conjugated and unconjugated oligomers were tested to determine sequence-specific antiviral efficacy against a member of the Coronaviridae, Mouse hepatitis virus (MHV). Specific antisense activity designed to block translation of the viral replicase polyprotein was first confirmed by reduction of luciferase expression from a target sequence-containing reporter construct in both cell-free and transfected cell culture assays. Peptide-conjugated morpholino-oligomers exhibited low toxicity in DBT astrocytoma cells used for culturing MHV. Oligomer administered at micromolar concentrations was delivered to >80% of cells and inhibited virus titers 10- to 100-fold in a sequence-specific and dose-responsive manner. In addition, targeted viral protein synthesis, plaque diameter, and cytopathic effect were significantly reduced. Inhibition of virus infectivity by peptide-conjugated morpholino was comparable to the antiviral activity of the aminoglycoside hygromycin B used at a concentration fivefold higher than the oligomer. These results suggest that this composition of antisense compound has therapeutic potential for control of coronavirus infection.  (+info)

X-linked inhibitor of apoptosis protein inhibition induces apoptosis and enhances chemotherapy sensitivity in human prostate cancer cells. (4/324)

Androgen-insensitive prostate cancer cells are highly resistant to several chemotherapeutic drugs and are characterized by the appearance of apoptosis-resistant cells. In this study, we identified the critical role of X-linked inhibitor of apoptosis protein (XIAP), a potent antiapoptotic factor, in conferring chemotherapy resistance in an androgen-insensitive DU145 human prostate cancer cell line. Results reveal that DU145 cells were highly resistant to cisplatin, but this resistance was overridden when the cells were treated for a prolonged time (>96 hours) with cisplatin (IC(50) = 27.5 to 35.5 micromol/L). A decrease in levels of XIAP and Akt/phospho-Akt and an increase in caspase-3 activity were identified to be key factors in cisplatin sensitivity (40% to 55% decrease in cell viability) at later time points. In contrast, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) treatment caused a 40% to 50% decrease in cell viability within 6 hours (IC(50) = 135 to 145 ng/mL). However, increasing concentrations or prolonged treatment with TRAIL did not change drug potency. A significant increase in caspase-3 activity was observed with TRAIL treatment with no apparent change in XIAP levels. Specific inhibition of XIAP expression using an antisense XIAP phosphorodiamidate morpholino oligomer induced apoptosis and increased caspase-3 activity. Combination of cisplatin with XIAP antisense potentiated cisplatin sensitivity by decreasing the IC(50) from >200 micromol/L with cisplatin alone to 9 to 20 micromol/L and decreasing incubation time required for activity from 96 to 24 hours. Similarly, TRAIL in combination with XIAP antisense phosphorodiamidate morpholino oligomer enhanced TRAIL potency by 12- to 13-fold. In conclusion, abrogation of XIAP expression is essential for therapeutic apoptosis and enhanced chemotherapy sensitization in androgen-refractory prostate cancer cells.  (+info)

Down-regulation of SNAIL suppresses MIN mouse tumorigenesis: modulation of apoptosis, proliferation, and fractal dimension. (5/324)

OBJECTIVES: Emerging evidence implicates the SNAIL family of transcriptional repressors in cancer development; however, the role of SNAIL in colorectal cancer has not been established. To investigate the importance of SNAIL in colorectal carcinogenesis, we examined the phenotypic and cellular consequences of SNAIL down-regulation in the MIN mouse. METHODS: Twenty-eight male MIN mice were randomized to treatment with an antisense phosphorodiamidate morpholino oligomer (AS-PMO) to SNAIL, saline, or a scrambled sequence control for 6 weeks. Tumors were scored and the molecular/cellular effects of anti-SNAIL treatment were evaluated through immunohistochemical analysis of the uninvolved intestinal mucosa for SNAIL and E-cadherin levels along with rates of apoptosis and proliferation. Furthermore, microarchitectural alterations were determined through measurement of fractal dimension. RESULTS: In the uninvolved mucosa, SNAIL AS-PMO treatment moderately decreased SNAIL protein when compared with saline-treated animals (immunohistochemistry scores 3.0 +/- 0.8 versus 2.1 +/- 0.6, respectively; P=0.01) with a concomitant increase in E-cadherin expression (1.8 +/- 0.6 versus 2.4 +/- 0.5; P < 0.05). Anti-SNAIL PMO, but not scramble control, resulted in a significant decrease in both total tumor number and incidence of tumors >2 mm (22% and 54%, respectively; P < 0.05). Furthermore, this was accompanied by an increased apoptosis rate (2-fold), decreased proliferation (3-fold), and normalization of the fractal dimension in the uninvolved intestinal mucosa. CONCLUSIONS: We show, for the first time, that SNAIL overexpression is important in intestinal tumorigenesis. While this PMO regimen afforded modest SNAIL suppression and hence tumor reduction, this provides compelling evidence for the role of SNAIL overexpression in colonic neoplasia.  (+info)

Antisense phosphorodiamidate morpholino oligomer length and target position effects on gene-specific inhibition in Escherichia coli. (6/324)

Phosphorodiamidate morpholino oligomers (PMOs) are synthetic DNA analogs that inhibit gene expression in a sequence-dependent manner. PMOs of various lengths (7 to 20 bases) were tested for inhibition of luciferase expression in Escherichia coli. Shorter PMOs generally inhibited luciferase greater than longer PMOs. Conversely, in bacterial cell-free protein synthesis reactions, longer PMOs inhibited equally or more than shorter PMOs. Overlapping, isometric (10-base) PMOs complementary to the region around the start codon of luciferase inhibited to different extents in bacterial cell-free protein expression reactions. Including the anti-start codon in PMOs was not required for maximal inhibition. PMOs targeted to 5' nontranslated or 3' coding regions within luciferase mRNA did not inhibit, except for one PMO targeted to the ribosome-binding site. Inhibition of luciferase expression correlated negatively with the predicted secondary structure of mRNA regions targeted by PMO but did not correlate with C+G content of targeted regions. The effects of PMO length and position were corroborated by using PMOs (6 to 20 bases) targeted to acpP, a gene required for viability. Because inhibition by PMOs of approximately 11 bases was unexpected based on previous results in eukaryotes, we tested an 11-base PMO in HeLa cells and reticulocyte cell-free protein synthesis reactions. The 11-base PMO significantly inhibited luciferase expression in HeLa cells, although less than did a 20-base PMO. In reticulocyte cell-free reactions, there was a trend toward more inhibition with longer PMOs. These studies indicate that strategies for designing PMOs are substantially different for prokaryotic than eukaryotic targets.  (+info)

Inhibition of flavivirus infections by antisense oligomers specifically suppressing viral translation and RNA replication. (7/324)

RNA elements within flavivirus genomes are potential targets for antiviral therapy. A panel of phosphorodiamidate morpholino oligomers (PMOs), whose sequences are complementary to RNA elements located in the 5'- and 3'-termini of the West Nile (WN) virus genome, were designed to anneal to important cis-acting elements and potentially to inhibit WN infection. A novel Arg-rich peptide was conjugated to each PMO for efficient cellular delivery. These PMOs exhibited various degrees of antiviral activity upon incubation with a WN virus luciferase-replicon-containing cell line. Among them, PMOs targeting the 5'-terminal 20 nucleotides (5'End) or targeting the 3'-terminal element involved in a potential genome cyclizing interaction (3'CSI) exhibited the greatest potency. When cells infected with an epidemic strain of WN virus were treated with the 5'End or 3'CSI PMO, virus titers were reduced by approximately 5 to 6 logs at a 5 muM concentration without apparent cytotoxicity. The 3'CSI PMO also inhibited mosquito-borne flaviviruses other than WN virus, and the antiviral potency correlated with the conservation of the targeted 3'CSI sequences of specific viruses. Mode-of-action analyses showed that the 5'End and 3'CSI PMOs suppressed viral infection through two distinct mechanisms. The 5'End PMO inhibited viral translation, whereas the 3'CSI PMO did not significantly affect viral translation but suppressed RNA replication. The results suggest that antisense PMO-mediated blocking of cis-acting elements of flavivirus genomes can potentially be developed into an anti-flavivirus therapy. In addition, we report that although a full-length WN virus containing a luciferase reporter (engineered at the 3' untranslated region of the genome) is not stable, an early passage of this reporting virus can be used to screen for inhibitors against any step of the virus life cycle.  (+info)

Antisense phosphorodiamidate morpholino oligomer inhibits viability of Escherichia coli in pure culture and in mouse peritonitis. (8/324)

OBJECTIVES: Antisense phosphorodiamidate morpholino oligomers (PMOs) are synthetic DNA mimics that specifically inhibit gene expression in pure cultures of Escherichia coli. Previously, an 11 base PMO targeted to an essential gene (acpP) for phospholipid biosynthesis was shown to inhibit growth of a pure culture of E. coli AS19, which has an abnormally permeable outer membrane. The objectives of experiments in this report are to show that the AcpP PMO significantly inhibits growth of strain SM105, which has a normal, intact outer membrane, both in pure culture and in infected mice. METHODS: In pure culture, SM105 was grown in rich broth supplemented with 20 muM AcpP PMO, and growth was monitored by optical density and viable cell count. Mice were infected by intraperitoneal injection with a non-lethal inoculum of either E. coli AS19 or SM105. Following infection, mice were treated intraperitoneally with 300 mug of the 11 base antisense PMO targeted to acpP, a scrambled sequence PMO or PBS. RESULTS: Growth of SM105 was slower and viable cells were significantly reduced by up to 61% in pure cultures supplemented with AcpP PMO compared with untreated cultures or cultures supplemented with a scrambled sequence PMO. A single dose of AcpP PMO reduced peritoneal cfu of E. coli AS19 about 39- to 600-fold compared with controls at 2, 7, 13 and 23 h after treatment. The same PMO significantly reduced cfu of E. coli SM105 75% compared with controls at 12 h after treatment. However, there was no difference in cfu at 2, 7 or 24 h. A second dose at 24 h again reduced SM105 cfu about 10-fold by 48 h post-infection. In other experiments with infected mice, multiple doses of AcpP PMO sustained the approximately 10-fold reduction in SM105 cfu at 6, 12 and 24 h post-infection. Compared with equivalent (micromolar) doses of ampicillin, AcpP PMO was significantly more effective at all time points. Specificity of PMO inhibition was shown in other experiments by treating infected mice with a PMO targeted to a non-essential reporter gene for luciferase. A luciferase-specific PMO reduced both the amount and activity of luciferase to the same extent, whereas scrambled PMO had no effect. CONCLUSIONS: An 11 base antisense PMO targeted to acpP significantly inhibited viability of a strain of E. coli with a normal, intact outer membrane both in pure culture and in infected mice. Inhibition by PMOs was sequence-specific.  (+info)