Antibacterial antisense

The concept of using antisense antibiotics is revolutionary. Instead of targeting proteins or macromolecular complexes, as do traditional antibiotics, antisense oligomers target specific genes, rRNA or mRNA, and inhibit expression of the targeted sequence. Recent advances have shown that two types of antisense oligomer, peptide nucleic acids and phosphorodiamidate morpholino oligomers (PMOs), inhibit gene expression in a sequence-specific and dose-dependent manner at low micromolar concentrations. Cellular uptake has been improved by shortening the length of the antisense oligomer and/or attaching membrane-permeating peptides. In addition to Escherichia coli, other bacteria such as Staphylococcus aureus and Mycobacterium tuberculosis are susceptible to antisense antibiotics. The first animal studies demonstrated that PMOs reduced E. coli approximately 10-fold in mouse peritonitis infections. Non-therapeutic uses of bacterial antisense are providing novel tools to identify new targets, elucidate mechanisms of antibiotic action and design new antibiotics. Gene-specific antisense antibiotics now appear possible, and additional preclinical animal studies should move this technology towards that goal.

Noncanonical Wnt-4 signaling and EAF2 are required for eye development in Xenopus laevis

Wnt-4 is expressed in developing neural and renal tissue and is required for renal tubulogenesis in mouse and Xenopus. The function of Wnt-4 in neural differentiation is unknown so far. Here we demonstrate that Wnt-4 is required for eye development in Xenopus laevis. This effect of Wnt-4 depends on the activation of a beta-catenin-independent, noncanonical Wnt signaling pathway. Furthermore, we report the identification of EAF2, a component of the ELL-mediated RNA polymerase II elongation factor complex, as a target gene of Wnt-4 signaling. EAF2 is specifically expressed in the eye and EAF2 expression was dependent on Wnt-4 function. Loss of EAF2 function results in loss of eyes and loss of Wnt-4 function could be rescued by EAF2. In neuralized animal caps, EAF2 has properties characteristic for an RNA polymerase II elongation factor regulating the expression of the eye-specific transcription factor Rx. These data add a new layer of complexity to our understanding of eye development and give further evidence for the importance of noncanonical Wnt pathways in organ development.

Msx1 and Pax3 cooperate to mediate FGF8 and WNT signals during Xenopus neural crest induction

FGF, WNT, and BMP signaling promote neural crest formation at the neural plate boundary in vertebrate embryos. To understand how these signals are integrated, we have analyzed the role of the transcription factors Msx1 and Pax3. Using a combination of overexpression and morpholino-mediated knockdown strategies in Xenopus, we show that Msx1 and Pax3 are both required for neural crest formation, display overlapping but nonidentical activities, and that Pax3 acts downstream of Msx1. In neuralized ectoderm, Msx1 is sufficient to induce multiple early neural crest genes. Msx1 induces Pax3 and ZicR1 cell autonomously, in turn, Pax3 combined with ZicR1 activates Slug in a WNT-dependent manner. Upstream of this, WNTs initiate Slug induction through Pax3 activity, whereas FGF8 induces neural crest through both Msx1 and Pax3 activities. Thus, WNT and FGF8 signals act in parallel at the neural border and converge on Pax3 activity during neural crest induction.

The human ubiquitin-conjugating enzyme Cdc34 controls cellular proliferation through regulation of p27Kip1 protein levels

Ubiquitin-mediated degradation of the cyclin-dependent kinase inhibitor p27Kip1 was shown to be required for the activation of key cyclin-dependent kinases, thereby triggering the onset of DNA replication and cell cycle progression. Although the SCFSkp2 ubiquitin ligase has been reported to mediate p27Kip1 degradation, the nature of the human ubiquitin-conjugating enzyme involved in this process has not yet been determined at the cellular level. Here, we show that antisense oligonucleotides targeting the human ubiquitin-conjugating enzyme Cdc34 downregulate its expression, inhibit the degradation of p27Kip1, and prevent cellular proliferation. Elevation of p27Kip1 protein level is found to be the sole requirement for the inhibition of cellular proliferation induced upon downregulation of Cdc34. Indeed, reducing the expression of p27Kip1 with a specific antisense oligonucleotide is sufficient to reverse the anti-proliferative phenotype elicited by the Cdc34 antisense. Furthermore, downregulation of Cdc34 is found to specifically increase the abundance of the SCFSkp2) ubiquitin ligase substrate p27Kip1, but has no concomitant effect on the level of IkBalpha and beta-catenin, which are known substrates of a closely related SCF ligase.

JNK1 and JNK2 oppositely regulate p53 in signaling linked to apoptosis triggered by an altered fibronectin matrix: JNK links FAK and p53

The extracellular matrix regulates many cellular processes, including survival, and alterations in the matrix or in matrix survival signals can trigger apoptosis. Previously, we showed that an altered fibronectin matrix triggers apoptosis in primary cells via a novel pathway regulated by transcriptionally mediated decreases in p53 and c-Myc levels. Here we report that this apoptotic mechanism is propagated by decreased phosphorylation of focal adhesion kinase (FAK), which is linked to increased phosphorylation of c-Jun N-terminal kinase (JNK) and to decreased levels of p53. FAK is physically and spatially linked to JNK and p53, which relocalize from the nucleus to the cell membrane to mediate this interaction. Further, p53 participates in a feedback mechanism with JNK to regulate this apoptotic process and is oppositely regulated by JNK1 and JNK2.

VEGF antisense therapy inhibits tumor growth and improves survival in experimental pancreatic cancer

BACKGROUND

Vascular endothelial growth factor (VEGF), a key mediator of angiogenesis, is overexpressed in pancreatic cancer. This study evaluated VEGF production in pancreatic cancer cells and the effect of VEGF antisense on growth and angiogenesis of human pancreatic cancer in a nude mouse model.

METHODS

In vitro: VEGF in cell culture supernatant of pancreatic cancer cells (AsPC-1, poorly differentiated; HPAF-2, moderately differentiated) was assessed by enzyme-linked immunosorbent assay. In vivo: A VEGF antisense oligonucleotide (AS-3) was synthesized. One-mm(3) fragments of subcutaneous pancreatic cancer donor tumors were implanted into the pancreas of nude mice also receiving AS-3 (10 mg/kg/day) or vehicle intraperitoneally for 14 weeks. Primary tumor volume, metastasis, and VEGF in plasma and ascites were determined at autopsy. Microvessel density was analyzed in CD31-stained tumors.

RESULTS

In vitro: Both pancreatic cancer cell lines secreted VEGF protein (AsPC-1, 4200 +/- 40 pg/10(6) cells; HPAF-2, 8120 +/- 60 pg/10(6) cells). In vivo: AS-3 reduced tumor volume in the HPAF-2 group (860 +/- 140 vs 3830 +/- 590 mm(3)) and metastatic spread in both groups (AsPC-1, 6.5 +/- 0.8 vs 16.7 +/- 0.9 points; HPAF-2, 2.5 +/- 0.2 vs 8.3 +/- 1.5 points). Tumor volume was not different in the AsPC-1 group (1050 +/- 80 vs 1400 +/- 150 mm(3)). Survival was increased in the AsPC-1 group. Plasma levels of VEGF and microvessel density in tumors were significantly reduced in treated animals. Only control animals (50%) developed ascites with high VEGF concentrations.

CONCLUSIONS

Human pancreatic cancer cells secrete VEGF at biologically relevant high levels. AS-3 therapy normalizes plasma VEGF and decreases neoangiogenesis, thereby reducing tumor growth and metastasis and improving survival. AS-3-treated animals developed no ascites, suggesting decreased vascular permeability by reducing VEGF expression in pancreatic cancer cells.

Tbx2b is essential for neuronal differentiation along the dorsal/ventral axis of the zebrafish retina

The mechanisms by which retinal neurons are patterned along the dorsal/ventral axis remain largely unknown, yet this patterning is integral for the topographic mapping of visual space. With an interest in elucidating the mechanisms that regulate the development of this retinal axis, we have characterized a T-box family transcription factor, Tbx2b, during zebrafish retinogenesis. Tbx2b is expressed throughout all phases of retinal development with a striking asymmetry of distribution highest dorsally to lowest ventrally. To examine Tbx2b function during retinal development, two morpholino antisense oligonucleotides were created; one blocking the translational start site of Tbx2b and the other interfering with Tbx2b mRNA splicing. Injection of either of these morpholinos resulted in profound defects in the development of the dorsal retina. By using molecular markers for neuronal subtypes, the ventral retina contained all cell types, whereas in the dorsal retina, only retinal ganglion cells expressed markers of differentiation. The cells of the dorsal retina were postmitotic, however, as demonstrated by a lack of BrdUrd incorporation during the normal periods of retinal differentiation. Markers for dorsal and ventral retinal compartments were also expressed normally in Tbx2b morphants. Combined, these observations suggest that the cellular mechanisms regulating neuronal differentiation within the retina are asymmetric about the dorsal/ventral axis and that Tbx2b mediates this process within the dorsal retina.

Antisense oligodeoxynucleotides targeting the serine/threonine kinase Pim-2 inhibited proliferation of DU-145 cells

AIM

To investigate the effect of antisense oligodeoxynucleotides (ASODN) targeting Pim-2 on cell proliferation of DU-145 cells.

METHODS

Three ASODN targeting Pim-2 were designed and synthesized. After transfection with ASODN, cell proliferation was analyzed using an MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt] assay. In addition, Pim-2 mRNA, protein levels, and cell cycles were examined.

RESULTS

The ASODN designed and synthesized by our laboratory significantly reduced Pim-2 mRNA level and protein content in DU-145 cells. After transfection with ASODN for 48 h, a marked reduction in cell viability was observed in DU-145 cells in a dose-dependent manner. No remarkable apoptosis occurred in cells treated with ASODN compared with control cells. However, it should be noted that G1 phase arrest was clearly observed in ASODN-treated cells.

CONCLUSION

ASODN targeting Pim-2 resulted in a marked reduction in DU-145 cell proliferation, and induction of G1 phase cell cycle arrest is one of the important mechanisms for ASODN to reduce cell growth. Moreover, antisense inhibition of Pim-2 expression provides a new promising therapy target for prostate cancer.

The basic helix-loop-helix olig3 establishes the neural plate boundary of the trunk and is necessary for development of the dorsal spinal cord

olig genes encode a previously unrecognized group of vertebrate-specific basic helix-loop-helix transcription factors. As shown in mice, chickens, and zebrafish, two members of this group, olig1 and olig2, are involved in the differentiation of motoneurons and oligodendrocytes, but nothing is known about the role of the third member, olig3. Here, we show that olig3 plays an essential role in the establishment of the neural crest-lateral neural plate boundary. In zebrafish embryos, morpholino-induced olig3 inactivation dramatically increases the number of neural crest cells, but lateral neural plate fates (interneurons and astrocytes) are missing. Zebrafish swirl mutants that have impaired bone morphogenetic protein signaling and lack neural crest cells display an expanded olig3 expression domain. Moreover, olig3 is up-regulated in mindbomb mutants lacking the neural crest because of an impaired notch signaling, and olig3 repression in such mutants rescues the neural crest. In addition, olig3 regulates ngn1 and deltaA expression in interneuron precursors. Our results indicate that olig3 has an essential proneural activity in the dorsal spinal cord and cooperates with the Delta/Notch regulatory loop to establish the boundary between the neural crest and the lateral neural plate. Thus, a proper regulation of the olig gene family is essential for the formation of three cell types (oligodendrocytes, astrocytes, and neural crest) that are unique to vertebrates.

[Expression of mucin 1 and tumor invasiveness in breast carcinoma]

OBJECTIVE

To study the relationship of abnormal expression of mucin 1 with the invasiveness of breast carcinoma cells.

METHODS

Immunohistochemistry was used to detect the protein expression of mucin 1 in 5 specimens of juxta-cancerous normal tissues, 20 specimens of benign breast tumors, 35 specimens of early breast carcinoma, 22 specimens of infiltrating cancerous tissues, and 20 specimens of lymph node foci with metastatic breast carcinoma. Human breast cancer cells of the line MCF-7 were cultured and transfected with antisense oligodeoxynucleotide (ASODN) of mucin 1. The mucin 1 mRNA expression in the cells was detected by RT-PCR and the protein expression of mucin 1 in the cells was detected by flow cytometry. The cell invasiveness was detected by Matrigel invasion assays.

RESULTS

Top membrane positive expression of mucin 1 was observed in the normal breast tissues and breast benign tumors and whole membrane positive expression of mucin 1 was observed in the 30 of the 35 specimens of early breast carcinoma, 18 of the 22 specimens of breast infiltrating carcinoma, and 17 of the 20 specimens of lymph node metastatic tissues. The mRNA and protein expressions of mucin 1 in the breast carcinoma cells treated with ASODN of mucin 1 were significantly decreased (both P < 0.05). The number of invasive cells decreased significantly in the cell treated with ASODN of mucin 1 in comparison with those treated with sense nucleotide (P < 0.05).

CONCLUSION

The abnormal distribution of mucin 1 contributes to the invasiveness of carcinoma cells and may not make difference in the lymphogenous metastasis of the carcinoma. The invasiveness of breast carcinoma cells can be inhibited by the ASODN complementary to the start site of mucin1 mRNA.

Rap2 is required for Wnt/beta-catenin signaling pathway in Xenopus early development

The Wnt/beta-catenin signaling pathway is critical for the establishment of organizer and embryonic body axis in Xenopus development. Here, we present evidence that Xenopus Rap2, a member of Ras GTPase family, is implicated in Wnt/beta-catenin signaling during the dorsoventral axis specification. Ectopic expression of XRap2 can lead to neural induction without mesoderm differentiation. XRap2 dorsalizes ventral tissues, inducing axis duplication, organizer-specific gene expression and convergent extension movements. Knockdown of XRap2 causes ventralized phenotypes including shortened body axis and defective dorsoanterior patterning, which are associated with aberrant Wnt signaling. In line with this, XRap2 depletion inhibits beta-catenin stabilization and the induction of ectopic dorsal axis and Wnt-responsive genes caused by XWnt8, Dsh or beta-catenin, but has no effect on the signaling activities of a stabilized beta-catenin. Its knockdown also disrupts the vesicular localization of Dsh, thereby inhibiting Dsh-mediated beta-catenin stabilization and the membrane recruitment and phosphorylation of Dsh by frizzled signaling. Taking together, we suggest that XRap2 is involved in Wnt/beta-catenin signaling as a modulator of the subcellular localization of Dsh.

Inhibition of aldose reductase attenuates TNF-alpha-induced expression of adhesion molecules in endothelial cells

Increased expression of adhesion molecules by the activated endothelium is a critical feature of vascular inflammation associated with several disease states such as atherosclerosis. However, mechanisms regulating the endothelial induction of adhesion molecules are not entirely clear. Herein we report that inhibition of the polyol pathway enzyme aldose reductase (AR) prevents the increase in ICAM-1 and VCAM-1 in human umbilical vein endothelial cells (HUVECs) and decreases monocyte adhesion to these cells. In TNF-alpha-stimulated HUVECs, treatment with AR inhibitors sorbinil and tolrestat diminished NF-kappaB activity, phosphorylation and degradation of Ikappa-Balpha, and the nuclear translocation of NF-kappaB. Inhibition of AR abrogated TNF-alpha-induced activation and membrane translocation of PKC, and antisense ablation of AR prevented both TNF-alpha-induced PKC and NF-kappaB activation. However, inhibition of AR did not prevent phorbol ester-induced activation of PKC or NF-kappaB, indicating that inhibition of AR does prevents events upstream of PKC activation. These results identify a novel regulator of endothelial activation and suggest that AR is an obligatory mediator of TNF-alpha signaling leading to an increase in the expression of adhesion molecules and increased binding of monocytes to the endothelium.

Synergistic antitumor effect of combined use of adenoviral-mediated p53 gene transfer and antisense oligodeoxynucleotide targeting clusterin gene in an androgen-independent human prostate cancer model

Our recent studies showed that antisense oligodeoxynucleotide targeting antiapoptotic gene, clusterin, enhanced apoptosis induced by conventional therapeutic modalities using several prostate cancer models. In this study, to establish a more effective therapeutic strategy against prostate cancer, we investigated the effect of combined treatment with antisense clusterin oligodeoxynucleotide and adenoviral-mediated p53 gene transfer (Ad5CMV-p53) in an androgen-independent human prostate PC3 tumor model. Treatment of PC3 cells with 500 nmol/L antisense clusterin oligodeoxynucleotide decreased clusterin mRNA by >80% compared with that with 500 nmol/L mismatch control oligodeoxynucleotide. Clusterin mRNA expression in PC3 cells was highly up-regulated by Ad5CMV-p53 treatment; however, antisense clusterin oligodeoxynucleotide treatment further suppressed clusterin expression in PC3 cells after Ad5CMV-p53 treatment. Antisense clusterin oligodeoxynucleotide treatment significantly enhanced the sensitivity of Ad5CMV-p53 in a dose-dependent manner, reducing the IC50 of Ad5CMV-p53 by 75%. Apoptotic cell death was detected after combined treatment but not after treatment with either agent alone. In vivo administration of antisense clusterin oligodeoxynucleotide and Ad5CMV-p53 resulted in a significant inhibition of s.c. PC3 tumor growth as well as lymph node metastases from orthotopic PC3 tumors compared with administration of either agent alone. Furthermore, combined treatment with antisense clusterin oligodeoxynucleotide, Ad5CMV-p53, and mitoxantrone completely eradicated s.c. PC3 tumors and lymph node metastases from orthotopic PC3 tumors in 60% and 100% of mice, respectively. These findings suggest that combined treatment with antisense clusterin oligodeoxynucleotide and Ad5CMV-p53 could be a novel strategy to inhibit progression of hormone-refractory prostate cancer and that further addition of chemotherapeutic agents may help to enhance the efficacy of this combined regimen.

[Inhibition of proliferation of human lens epithelial cell line HLE-B3 by adenovirus-mediated transfer of antisense c-myc gene]

OBJECTIVE

To investigate the effects of adenovirus-mediated transfer of antisense c-myc gene on proliferation and survival of human lens epithelial cell.

METHODS

Immortalized human lens epithelial cell line (HLE-B3) was infected by replication-deficient adenovirus of antisense c-myc gene (Ad-AS-myc). The expression of c-myc mRNA and protein was detected by RT-PCR and Western blotting respectively. Cell proliferation was analyzed by cell growth curve and MTT colorimetric assay, cell death and cell cycle of HLE-B3 were examined by flow cytometry.

RESULTS

More than 80% of HLE-B3 cells were infected successfully after 48 hours incubation with Ad-AS-myc adenovirus. The expression of c-myc mRNA and protein was decreased. Ad-AS-myc suppressed the growth rate, enhanced the cell death (18.33% after 48 hours and 26.93% after 96 hours transduction). The proportions of G1 phase cells were increased to (60.50 +/- 7.59)% after 48 hours and (81.90 +/- 8.60)% after 96 hours transduction, while the proportions of S phase cells were decreased to (28.40 +/- 3.38)% after 48 hours and (16.75 +/- 8.97)% after 96 hours infection.

CONCLUSIONS

Adenovirus-mediated antisense c-myc may inhibit proliferation and induce apoptosis of HLE-B3.

Effects of estrogen on neuronal growth and differentiation

Previous work from our laboratory has shown that in cultures of hypothalamic neurons obtained from male fetuses at embryonic day 16 the axogenic response to estradiol (E2) is contingent upon culture with medium conditioned by astroglia from a target region for hypothalamic axons. E2 also induced increased levels of TrkB that were necessary for the axonal growth to occur. This convergence between estrogenic and neurotrophic signals prompted investigation of the mitogen activated protein kinase (MAPK) cascade. Analysis of the temporal course of MAPK activation showed increased levels of phosphorylated ERK up to 60 min after E2 exposure, with a maximal response at 5-15 min. UO126 (specific inhibitor of MEK 1/2) blocked E2 induced axonal elongation and ERK phosphorylation, confirming the involvement of ERK in the neuritogenic effect of E2. The membrane impermeable construct E2-BSA proved as effective as free E2 to induce axon elongation, suggesting that E2 exerted its effect through a membrane-associated receptor. This possibility received additional support from experiments showing that E2-BSA also increased ERK phosphorylation with the same time course than E2. These results indicate that ERK signaling is necessary for E2 to induce axon growth and this activation is mediated by a membrane bound estrogen receptor.

Inhibition of human lens epithelial B-3 cell proliferation by adenovirus-mediated transfer of antisense c-myc construct

PURPOSE

To investigate the effects of adenovirus-mediated transfer of antisense c-myc construct on human lens epithelial B-3 (HLE B-3) cell proliferation, apoptosis and cell cycle.

METHODS

HLE B-3 cell cultures were transduced with replication-defective adenovirus bearing either a nuclear-targeted beta-galactosidase (Ad-lacZ) or an antisense c-myc construct (Ad-AS-myc). The presence of beta-galactosidase activity in the transduced cultures was detected by immunohistochemical X-Gal staining, while c-myc mRNA and protein expression levels were evaluated by RT-PCR and Western blot analysis. HLE B-3 cell proliferation within 96 h after the transduction was analyzed by cell counting and MTT colorimetric assay. Apoptosis and cell cycle of the HLE-B3 cells were examined by flow-cytometric analysis.

RESULTS

The mean transduction efficiency was 80% for HLE B-3 cells. Downregulation of c-myc mRNA and protein expression was noticed at 48, 96 and 144 h after the transduction with Ad-AS-myc. Cytostatic effects of Ad-AS-myc in HLE B-3 cells were obvious within 96 h after the transduction. An increased incidence of apoptosis and G1-phase arrest was identified in the Ad-AS-myc-transduced HLE B-3 cells.

CONCLUSIONS

HLE B-3 cells were successfully transduced with adenovirus-mediated antisense c-myc construct. Ad-AS-myc transduction could significantly inhibit cell proliferation and induce cell apoptosis and G1-phase arrest in HLE B-3 cells. It may provide a novel approach for prevention of posterior capsular opacification.

Balance between survivin, a key member of the apoptosis inhibitor family, and its specific antibodies determines erosivity in rheumatoid arthritis

Rheumatoid arthritis (RA) is a highly heterogeneous disease with respect to its joint destructivity. The reasons underlying this heterogeneity are unknown. Deficient apoptosis in rheumatoid synovial tissue has been recently demonstrated. We have therefore decided to study the synovial expression of survivin, a key member of the apoptosis inhibitor family. The levels of survivin and antibodies against survivin were assessed by an ELISA in matched blood and synovial fluid samples collected from 131 RA patients. Results were related to joint erosivity at the time of sampling. Monocytes were transfected with survivin anti-sense oligonucleotides and were assessed for their ability to produce inflammatory cytokines. Survivin levels were significantly higher in patients with destructive disease as compared with in RA patients displaying a non-erosive disease. High survivin levels were an independent prognostic parameter for erosive RA. In contrast, high levels of antibodies against survivin were found in patients with non-erosive RA, and were negatively related to erosivity. Survivin levels in RA patients were influenced by treatment, being significantly lower among patients treated with disease-modifying anti-rheumatic drugs. Specific suppression of survivin mRNA resulted in downregulation of IL-6 production. We conclude that survivin determines the erosive course of RA, whereas survivin antibodies lead to a less aggressive course of the disease. These findings together with decreased survivin levels upon disease-modifying anti-rheumatic drug treatment, and the downregulation of inflammatory response using survivin anti-sense oligonucleotides, suggest that extracellular survivin expression mediates the erosive course of joint disease whereas autoimmune responses to the same molecule, manifested as survivin targeting antibodies, mediate protection.

Hsp27 anti-sense oligonucleotides sensitize the microtubular cytoskeleton of Chinese hamster ovary cells grown at low pH to 42 degrees C-induced reorganization

Chinese hamster ovary (CHO) cells maintained in vitro at pH 6.7 were used to model cells in the acidic environment of tumours. CHO cells grown at pH 6.7 develop thermotolerance during 42 degrees C heating at pH 6.7 and their cytoskeletal systems are resistant to 42 degrees C-induced perinuclear collapse. Hsp27 levels are elevated in cells grown at pH 6.7 and are further induced during 42 degrees C heating, while Hsp70 levels remain low or undetectable, suggesting that Hsp27 is responsible for some of the novel characteristics of these cells. An anti-sense oligonucleotide strategy was used to test the importance of Hsp27 by lowering heat-induced levels of the protein. The response of the microtubular cytoskeleton to heat was used as an endpoint to assess the effectiveness of the anti-sense strategy. Treatment with anti-sense oligonucleotides prevented the heat-induced increase of Hsp27 levels measured immediately following heat. Treatment with anti-sense oligonucleotides also sensitized the cytoskeleton of cells grown at low pH to heat-induced perinuclear collapse. However, cytoskeletal collapse was not evident in cells grown at pH 6.7 and treated with 4-nt mismatch oligonucleotides or in control cells maintained and heated at pH 6.7. The cytoskeleton collapsed around the nucleus in cells cultured and heated at pH 7.3. These results confirm that over-expression of Hsp27 confers heat protection to the microtubular cytoskeleton in CHO cells grown at low pH.

Fast formation of the P3-P7 pseudoknot: a strategy for efficient folding of the catalytically active ribozyme

Formation of the P3-P7 pseudoknot structure, the core of group I ribozymes, requires long-range base pairing. Study of the Tetrahymena ribozyme appreciates the hierarchical folding of the large, multidomain RNA, in which the P3-P7 core folds significantly slower than do the other domains. Here we explored the formation of the P3-P7 pseudoknot of the Candida ribozyme that has been reported to concertedly fold to the catalytically active structure with a rate constant of 2 min(-1). We demonstrate that pseudoknot formation occurs during the rapid ribozyme compaction, coincident with formation of many tertiary interactions of the ribozyme. A low physiological concentration of magnesium (1.5 mM) is sufficient to fully support the pseudoknot formation. The presence of nonnative intermediates containing an unfolded P3-P7 region is evident. However, catalysis-based analysis shows these nonnative intermediates are stable and fail to convert to the catalytically active structure, suggesting that rapid pseudoknot formation is essential for folding of the active ribozyme. Interestingly, RNAstructure predicts no stable Alt P3 structure for the Candida ribozyme, but two stable Alt P3s for the Tetrahymena ribozyme, explaining the dramatic difference in folding of the P3-P7 core of these two ribozymes. We propose that rapid formation of the P3-P7 pseudoknot represents a folding strategy ensuring efficient production of the catalytically active structure of group I ribozymes, which sheds new light on the mechanism of effective ribozyme folding in vivo.

[Effect of vascular endothelial growth factor antisense oligodeoxynucleotides on angiogenesis in lymphoma of nude mice]

BACKGROUND & OBJECTIVE

It has been reported that vascular endothelial growth factor (VEGF) plays an important role in progression of lymphoma, and lymphoma with high level of VEGF is likely to metastasise at early stage. This study was to explore effects of antisense oligodeoxynucleotides (ASODN) targeting VEGF on angiogenesis of lymphoma through in vitro, and in vivo experiments.

METHODS

Human lymphoma cell line Namalwa cells were incubated with VEGF ASODN (final concentrations were 10, 20, and 30 micromol/L, respectively), or scrambled sequence for 24 h or 48 h. VEGF mRNA expression in treated cells was detected by reverse transcriptase-polymerase chain reaction (RT-PCR), and its protein expression was detected by SP immunohistochemistry. After incubation of 30 micromol/L of VEGF ASODN, 30 micromol/L of scrambled sequence, and PBS as negative control, Namalwa cells were injected into nude mice. Diameters of tumors in ASODN group (6 mice), scrambled sequence group (6 mice), and PBS group (4 mice) were measured, microvessel density (MVD) was detected via immunohistochemistry.

RESULTS

Expression of VEGF mRNA in cells treated with 10, 20, and 30 micromol/L of ASODN were 1.28, 0.86, and 0.47, respectively; those of PBS-treated cells, and scrambled sequence-treated cells were 1.79, and 1.84. Positive rate of VEGF protein in ASODN-treated cells was significantly lower than those in scrambled sequence-treated cells, and PBS-treated cells (23.3% vs. 46.9%, and 47.8%, P<0.05). MVDs of ASODN group, scrambled sequence group, and PBS group were 12.26+/-0.78, 23.92+/-1.14, and 24.13+/-1.21, respectively.

CONCLUSION

VEGF ASODN can down-regulate expression of VEGF, and suppress angiogenesis in lymphoma.

Differential expression of metallothionein isoforms in nasopharyngeal cancer and inhibition of cell growth by antisense down-regulation of metallothionein-2A

Biological functions of metallothionein (MT) proteins which are encoded by 10 functional MT isoforms, include cell proliferation, differentiation and apoptosis. The aim of this study was to compare the relative expression levels of functional MT mRNA isoforms in three nasopharyngeal cancer (NPC) cell lines with laryngeal carcinoma and embryonic lung cell lines by quantitative real-time RT-PCR. All the NPC lines exhibited expression of the MT-2A transcript, whereas the MT-1E isoform was expressed in well differentiated HK1 and moderately differentiated TW01 but not in poorly differentiated CNE2 cells. Interestingly, TW01 and HEp-2 laryngeal cancer cells exhibited similar expression profiles with both MT-1E and MT-2A isoforms being detected at levels below those of MRC-5 embryonic lung fibroblasts. Functional studies of the MT-2A isoform by down-regulating expression of this gene with MT-2A antisense oligonucleotide in CNE2 cells, showed a reduction in cell viability and proliferation. These findings may provide valuable information in the search for novel therapeutic strategies against NPC.

[Effect of CDK7 gene silencing against hepatoblastoma HepG2 cell proliferation]

OBJECTIVE

To screen the antisense oligodeoxynucleotides (ASODN) that inhibit cultured hepatoblastoma HepG2 cell proliferation, and evaluate the antiproliferative potency of modified ASODN.

METHODS

ASODN sequences were selected based on the secondary structure of human CDK7 mRNA predicted with RNAStructure 3.71 software. The binding thermodynamics of CDK7 mRNA to ASODN was analyzed by OligoWalk program. The sequences with the strongest effect against cultured HepG2 cell proliferation in vitro were selected, and the fragments complementary to 1-5 bases upstream or downstream to the complementary region were structurally modified and screened.

RESULTS

The partial phosphorothioate ASODN complementary to 284-303 region of human CDK7 mRNA was the most powerful inhibitor, and the antiproliferative activity reached 40.4+/-12.6%; in the second round of screening, the antiproliferative activity of the full phosphorothioate ASODN complementary to the 287-306 region of the mRNA on HepG2 cells was 68.3+/-2.6%, with IC50 of 51.9+/-8.6 nmol/L.

CONCLUSION

Proliferation of HepG2 cells can be significantly inhibited by the screened ASODN, which might be used as a lead compound in the development of specific CDK7 inhibitors.

Targeted knockdown of insulin-like growth factor binding protein-2 disrupts cardiovascular development in zebrafish embryos

IGF binding protein-2 (IGFBP-2) is an evolutionarily conserved protein that binds IGFs and modulates their biological activities. Although the actions of IGFBP-2 have been well studied in vitro, we have a poor understanding of its in vivo functions, particularly during early development. Using the transparent zebrafish embryo as a model, we show that IGFBP-2 mRNA is expressed in lens epithelium and cranial boundary regions during early embryonic development and becomes localized to the liver by the completion of embryogenesis. Targeted knock-down of IGFBP-2 by antisense morpholino-modified oligonucleotides resulted in delayed development, reduced body growth, reduced IGF-I mRNA levels, and disruptions to cardiovascular development, including reduced blood cell number, reduced blood circulation, cardiac dysfunction, and brain ventricle edema. Detailed examination of vascular tissues, using a stable transgenic line of zebrafish expressing green fluorescent protein in vascular endothelial cells, revealed specific angiogenic (vessel sprouting) defects in IGFBP-2 knockdown embryos, with effects being localized in regions associated with IGFBP-2 mRNA expression. These findings suggest that IGFBP-2 is required for general embryonic development and growth and plays a local role in regulating vascular development in a model vertebrate organism.