| 1. |
- Thiel, Kristina W., et al.
(author)
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Delivery of chemo-sensitizing siRNAs to HER2+-breast cancer cells using RNA aptamers
- 2012
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In: Nucleic Acids Research. - : Oxford University Press. - 0305-1048 .- 1362-4962. ; 40:13, s. 6319-6337
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Journal article (peer-reviewed)abstract
- Human epidermal growth factor receptor 2 (HER2) expression in breast cancer is associated with an aggressive phenotype and poor prognosis, making it an appealing therapeutic target. Trastuzumab, an HER2 antibody-based inhibitor, is currently the leading targeted treatment for HER2+-breast cancers. Unfortunately, many patients inevitably develop resistance to the therapy, highlighting the need for alternative targeted therapeutic options. In this study, we used a novel, cell-based selection approach for isolating cell-type specific, cell-internalizing RNA ligands (aptamers) capable of delivering therapeutic small interfering RNAs (siRNAs) to HER2-expressing breast cancer cells. RNA aptamers with the greatest specificity and internalization potential were covalently linked to siRNAs targeting the anti-apoptotic gene, Bcl-2. We demonstrate that, when applied to cells, the HER2 aptamer-Bcl-2 siRNA conjugates selectively internalize into HER2+-cells and silence Bcl-2 gene expression. Importantly, Bcl-2 silencing sensitizes these cells to chemotherapy (cisplatin) suggesting a potential new therapeutic approach for treating breast cancers with HER2+-status. In summary, we describe a novel cell-based selection methodology that enables the identification of cell-internalizing RNA aptamers for targeting therapeutic siRNAs to HER2-expressing breast cancer cells. The future refinement of this technology may promote the widespread use of RNA-based reagents for targeted therapeutic applications. © 2012 The Author(s).
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| 2. |
- Dassie, Justin P., et al.
(author)
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Targeted inhibition of prostate cancer metastases with an RNA aptamer to prostate-specific membrane antigen
- 2014
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In: Molecular Therapy. - : Nature Publishing Group. - 1525-0016 .- 1525-0024. ; 22:11, s. 1910-1922
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Journal article (peer-reviewed)abstract
- Cell-targeted therapies (smart drugs), which selectively control cancer cell progression with limited toxicity to normal cells, have been developed to effectively treat some cancers. However, many cancers such as metastatic prostate cancer (PC) have yet to be treated with current smart drug technology. Here, we describe the thorough preclinical characterization of an RNA aptamer (A9g) that functions as a smart drug for PC by inhibiting the enzymatic activity of prostate-specific membrane antigen (PSMA). Treatment of PC cells with A9g results in reduced cell migration/invasion in culture and metastatic disease in vivo. Importantly, A9g is safe in vivo and is not immunogenic in human cells. Pharmacokinetic and biodistribution studies in mice confirm target specificity and absence of non-specific on/off-target effects. In conclusion, these studies provide new and important insights into the role of PSMA in driving carcinogenesis and demonstrate critical endpoints for the translation of a novel RNA smart drug for advanced stage PC. © The American Society of Gene amp; Cell Therapy.
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| 3. |
- Hernandez, Luiza I., et al.
(author)
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Methods for evaluating cell-specific, cell-internalizing RNA aptamers
- 2013
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In: Pharmaceuticals. - : Multidisciplinary Digital Publishing Institute (M D P I AG). - 1424-8247. ; 6:3, s. 295-319
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Journal article (peer-reviewed)abstract
- Recent clinical trials of small interfering RNAs (siRNAs) highlight the need for robust delivery technologies that will facilitate the successful application of these therapeutics to humans. Arguably, cell targeting by conjugation to cell-specific ligands provides a viable solution to this problem. Synthetic RNA ligands (aptamers) represent an emerging class of pharmaceuticals with great potential for targeted therapeutic applications. For targeted delivery of siRNAs with aptamers, the aptamer-siRNA conjugate must be taken up by cells and reach the cytoplasm. To this end, we have developed cell- based selection approaches to isolate aptamers that internalize upon binding to their cognate receptor on the cell surface. Here we describe methods to monitor for cellular uptake of aptamers. These include: (1) antibody amplification microscopy, (2) microplate- based fluorescence assay, (3) a quantitative and ultrasensitive internalization method (QUSIM) and (4) a way to monitor for cytoplasmic delivery using the ribosome inactivating protein-based (RNA-RIP) assay. Collectively, these methods provide a toolset that can expedite the development of aptamer ligands to target and deliver therapeutic siRNAs in vivo. © 2013 by the authors; licensee MDPI, Basel, Switzerland.
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| 4. |
- Huang, Yang Zhong, et al.
(author)
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RNA aptamer-based functional ligands of the neurotrophin receptor, TrkB
- 2012
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In: Molecular Pharmacology. - Bethesda, United States : American Society for Pharmacology and Experimental Therapeutics. - 0026-895X .- 1521-0111. ; 82:4, s. 623-635
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Journal article (peer-reviewed)abstract
- Many cell surface signaling receptors, such as the neurotrophin receptor, TrkB, have emerged as potential therapeutic targets for diverse diseases. Reduced activation of TrkB in particular is thought to contribute to neurodegenerative diseases. Unfortunately, development of therapeutic reagents that selectively activate particular cell surface receptors such as TrkB has proven challenging. Like many cell surface signaling receptors, TrkB is internalized upon activation; in this proof-of-concept study, we exploited this fact to isolate a pool of nuclease-stabilized RNA aptamers enriched for TrkB agonists. One of the selected aptamers, C4-3, was characterized with recombinant protein-binding assays, cell-based signaling and functional assays, and, in vivo in a seizure model in mice. C4-3 binds the extracellular domain of TrkB with high affinity (KD ∼2 nM) and exhibits potent TrkB partial agonistic activity and neuroprotective effects in cultured cortical neurons. In mice, C4-3 activates TrkB upon infusion into the hippocampus; systemic administration of C4-3 potentiates kainic acid-induced seizure development. We conclude that C4-3 is a potentially useful therapeutic agent for neurodegenerative diseases in which reduced TrkB activation has been implicated. We anticipate that the cell-based aptamer selection approach used here will be broadly applicable to the identification of aptamer-based agonists for a variety of cell-surface signaling receptors. Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics.
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| 5. |
- Rockey, William M., et al.
(author)
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Rational truncation of an RNA aptamer to prostate-specific membrane antigen using computational structural modeling
- 2011
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In: Nucleic Acid Therapeutics. - : Mary Ann Liebert. - 2159-3337 .- 2159-3345. ; 21:5, s. 299-314
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Journal article (peer-reviewed)abstract
- RNA aptamers represent an emerging class of pharmaceuticals with great potential for targeted cancer diagnostics and therapy. Several RNA aptamers that bind cancer cell-surface antigens with high affinity and specificity have been described. However, their clinical potential has yet to be realized. A significant obstacle to the clinical adoption of RNA aptamers is the high cost of manufacturing long RNA sequences through chemical synthesis. Therapeutic aptamers are often truncated postselection by using a trial-and-error process, which is time consuming and inefficient. Here, we used a rational truncation approach guided by RNA structural prediction and protein/RNA docking algorithms that enabled us to substantially truncateA9, an RNA aptamer to prostate-specific membrane antigen (PSMA),with great potential for targeted therapeutics. This truncated PSMA aptamer (A9L; 41mer) retains binding activity, functionality, and is amenable to large-scale chemical synthesis for future clinical applications. In addition, the modeled RNA tertiary structure and protein/RNA docking predictions revealed key nucleotides within the aptamer critical for binding to PSMA and inhibiting its enzymatic activity. Finally, this work highlights the utility of existing RNA structural prediction and protein docking techniques that may be generally applicable to developing RNA aptamers optimized for therapeutic use. © 2011 Mary Ann Liebert, Inc.
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