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David R Corey

Publications and source records attributed to David R Corey.

44 records · Page 3Linked to original sources
PubMed2002

Novel antisense and peptide nucleic acid strategies for controlling gene expression.

Antisense oligonucleotides have the potential to make revolutionary contributions to basic science and medicine. Oligonucleotides can bind mRNA and inhibit translation. Because they can be rapidly synthesized to be complementary to any sequence, they offer ideal tools for exploiting the massive amount of genome information now available. However, until recently, this potential was largely theoretical, and antisense experiments often produced inconclusive or misleading outcomes. This review will discuss the chemical and biological properties of some of the different types of oligomers now available and describe the challenges confronting in vitro and in vivo use of oligonucleotides. Oligomers with improved chemical properties, combined with advances in cell biology and success in clinical trials, are affording powerful new options for basic research, biotechnology, and medicine.

Animals↗
PubMed2002

Toward synthetic transcription activators: recruitment of transcription factors to DNA by a PNA-peptide chimera.

A PNA-peptide chimera designed to mimic the biochemical function of transcription activators has been synthesized and characterized. The bis-PNA segment binds specifically to a DNA site while the 20-residue peptide is capable of binding to the transcription factors Gal11 and Gal80. The PNA-peptide chimera thus mimics one of the central functions of a native transcription activator, recruitment of transcription factors to a specific DNA site.

DNA↗
PubMed2002

Non-Watson-Crick interactions between PNA and DNA inhibit the ATPase activity of bacteriophage T4 Dda helicase.

Peptide nucleic acid (PNA) is a DNA mimic in which the nucleobases are linked by an N-(2-aminoethyl) glycine backbone. Here we report that PNA can interact with single-stranded DNA (ssDNA) in a non-sequence-specific fashion. We observed that a 15mer PNA inhibited the ssDNA-stimulated ATPase activity of a bacteriophage T4 helicase, Dda. Surprisingly, when a fluorescein-labeled 15mer PNA was used in binding studies no interaction was observed between PNA and Dda. However, fluorescence polarization did reveal non-sequence-specific interactions between PNA and ssDNA. Thus, the inhibition of ATPase activity of Dda appears to result from depletion of the available ssDNA due to non-Watson-Crick binding of PNA to ssDNA. Inhibition of the ssDNA-stimulated ATPase activity was observed for several PNAs of varying length and sequence. To study the basis for this phenomenon, we examined self-aggregation by PNAs. The 15mer PNA readily self-aggregates to the point of precipitation. Since PNAs are hydrophobic, they aggregate more than DNA or RNA, making the study of this phenomenon essential for understanding the properties of PNA. Non-sequence-specific interactions between PNA and ssDNA were observed at moderate concentrations of PNA, suggesting that such interactions should be considered for antisense and antigene applications.

Adenosine Triphosphatases↗
PubMed2002

Telomerase inhibition, oligonucleotides, and clinical trials.

Telomerase is expressed in most types of tumors but not in most somatic cells. This observation has led to two hypotheses; (i) telomerase activity is necessary for the proliferation of cancer cells; and (ii) telomerase inhibitors are a powerful strategy for cancer chemotherapy. Testing the latter hypothesis requires the development of potent and selective inhibitors of telomerase and their testing in clinical trials. Assaying the efficacy of telomerase inhibitors will not be simple because telomere erosion will be slow and antiproliferative effects will probably require weeks to become apparent. This review will describe the properties of 2'-O-alkyl oligonucleotide inhibitors of telomerase. Oligonucleotides that block expression of other cancer targets have favorable pharmacokinetic properties and are already in clinical trials. This experience is likely to facilitate clinical trials of anti-telomerase oligomers.

Antineoplastic Agents↗
PubMed2002

Imaging gene expression in the brain in vivo in a transgenic mouse model of Huntington's disease with an antisense radiopharmaceutical and drug-targeting technology.

UNLABELLED: Disease-specific genes of unknown function can be imaged in vivo with antisense radiopharmaceuticals, providing the transcellular transport of these molecules is enabled with drug-targeting technology. The current studies describe the production of 16-mer peptide nucleic acid (PNA) that is antisense around the methionine initiation codon of the huntingtin gene of Huntington's disease (HD). METHODS: The PNA is biotinylated, which allows for rapid capture by a conjugate of streptavidin and the rat 8D3 monoclonal antibody (mAb) to the mouse transferrin receptor (TfR), and contains a tyrosine residue, which enables radiolabeling with 125I. The reformulated PNA antisense radiopharmaceutical that is conjugated to the 8D3 mAb is designated 125I-PNA/8D3. This form of the PNA is able to access endogenous transferrin transport pathways at both the blood-brain barrier and the brain cell membrane and undergoes both import from the blood to the brain and export from the brain to the blood through the TfR. RESULTS: The ability of the PNA to hybridize to the target huntingtin RNA, despite conjugation to the mAb, was shown both with cell-free translation assays and with ribonuclease protection assays. The 125I-PNA/8D3 conjugate was administered intravenously to either littermate control mice or to R6/2 transgenic mice, which express the exon 1 of the human HD gene. The mice were sacrificed 6 h later for frozen sectioning of the brain and quantitative autoradiography. The studies showed a 3-fold increase in sequestration of the 125I-PNA/8D3 antisense radiopharmaceutical in the brains of the HD transgenic mice in vivo, consistent with the selective expression of the HD exon-1 messenger RNA in these animals. CONCLUSION: These results support the hypothesis that gene expression in vivo can be quantitated with antisense radiopharmaceuticals, providing these molecules are reformulated with drug-targeting technology. Drug targeting enables access of the antisense agent to endogenous transport pathways, which permits passage across the cellular barriers that separate blood and intracellular compartments of target tissues.

Animals↗
PubMedDate not supplied

Small molecule, oligonucleotide-based telomerase template inhibition in combination with cytolytic therapy in an in vitro androgen-independent prostate cancer model.

PURPOSE: Determine the efficacy and timing of small molecule oligonucleotide-based inhibitors to the enzyme telomerase in an in vitro model of androgen-independent, osseous prostate cancer. MATERIALS AND METHODS: Telomerase was inhibited in prostate cancer cell lines C4-2/C4-2B and in controls by using small molecule antisense oligonucleotide-based inhibitors alone or in various combinations of small-dose Taxotere (sanofi-aventis, Bridgewater, NJ) and/or conditionally replication competent adenovirus (AD-BSP-E1a). After transfection and proliferation, telomerase telomeric repeat amplification protocol and telomere restriction fragment assays were performed, with specific times for evaluating telomere length. Specimens were stained for analysis with hematoxylin and eosin (H&E), terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL), and prostate-specific antigen (PSA). RESULTS: C4-2/C4-2B cell lines had the shortest initial mean telomere length (approximately 2.5 kilobase [kb]) compared to PC-3 (approximately 5.5 kb). Dose-dependent inhibition of telomerase activity was seen using match oligonucleotide-based inhibitors to telomerase (50% inhibitory concentration 3-5 nm), whereas mismatch compound showed no telomerase inhibition. Significant growth delay and apoptosis in cell lines occurred after > 50 days of treatment. Cells treated with combination "triple therapy" (i.e., telomerase inhibitors, adenovirus, and Taxotere) had the highest amount of apoptosis. Compared to controls, all combination treatment groups had statistically significant reductions in prostate-specific antigen in the conditioned media. CONCLUSIONS: Combining cytotoxic regimens with small molecule inhibitors to telomerase with oligonucleotide-based agents could be beneficial in controlling osseous hormone refractory prostate cancer, as evidenced by these in vitro, preclinical investigations. Telomerase inhibition needs to move into in vivo models and human studies.

Androgens↗
PubMedDate not supplied

Inhibition of transcription by bisPNA-peptide conjugates.

Homopyrimidine bisPNAs have been reported to arrest transcription elongation by invading double-stranded DNA and forming a stable (PNA)2/DNA complex. We previously reported that attachment of a designed cationic peptide to the bisPNA enhances the efficiency of strand invasion. Here we investigate whether conjugation to cationic peptides can also improve inhibition of transcription. We observe that a conjugate between a bisPNA and a peptide containing eight lysines is a superior agent for inhibition of transcription, but that inhibition of transcription is reduced as pH and the concentration of magnesium are increased. Our studies provide useful characterization of bisPNAs as agents for inhibiting transcription.

Base Sequence↗