Antisense molecules

Cell membranes are lipophilic and designed to be barriers against large anionic molecules, although there is a natural mechanism for intercellular transport of anionic oligonucleotides. In order to enhance membrane transport, antisense oligonucleotides are frequentiy modified by covalent attachment of carrier molecules or lipophilic groups. 

A different antiviral approach uses intracellular expression of unmodified antisense molecules corresponding to viral sequences. Such an intracellular immunization approach may require a gene therapy protocol to deliver the antiviral transgene. In a phase I chnical trial, Levine et at. used intraceUularly expressed... 

Peptoids have also shown great utility in their ability to complex with and deliver nucleic acids to cells, a critical step toward the development of antisense drugs, DNA vaccines, or gene-based therapeutics. Most non-viral nucleic acid delivery systems are based on cationic molecules that can form complexes with the polyan-... 

The triplet-sensitized photorearrangement of allylphosphites [65- 67] offers a rapid and efficient access (60-70% yields) to oligonucleotides, which are key molecules in the antisense approach to antiviral and antitumor therapy (Scheme 40) [39,40,73]. 

The potential of the chemically modified nucleic acid molecules has been proven by in vitro studies however, the in vivo therapeutic applicability of these molecules seems to be unsatisfactory because of their possible toxic effects (largely unknown) and adverse bioavailability. In this view, both antisense and transfection technologies require reliable and efficient systems for their delivery into target cells. On the basis of this consideration, the development of an efficient nucleic acid delivery system represents one of the key steps for these therapeutic agents, which are necessary for a practical clinical utilization of natural or unnatural oligonucleotides. 

Nanosized objects perform various functions in the biomedical field. In the human body, nanosized particulate substances behave very differently from larger particles. In 1986, Maeda et al. found that the stained albumin, having a size of several nanometers, naturally accumulates in the region of cancerous tissues, which is now well known as the enhanced permeability and retention (EPR) effect. Many studies in the field of nanoparticles are based on this finding. Another application of nanoparticles is the delivery system using various polyplexes that are composed of carrier molecules and plasmid DNA or nucleic acid drugs such as antisenses and siRNA. In addition, nanofibers are mainly used for biodegradable scaffolds in tissue... 

Unlike the situation with the integrins discussed earlier, it is loss of cadherin E that promotes metastasis. The evidence linking loss or decreased expression of cadherin E with cancer spread is as follows (M2). Firstly, a negative correlation exists between the expression of cadherin E and invasion for many different cancer cell lines. Secondly, in cell lines lacking cadherin E, invasion could be prevented by transfection with cDNA for this cadherin. Thirdly, reduction in cadherin E mRNA levels by antisense sequences induced the invasive phenotype in E-cadherin positive cells. Fourthly, antibodies inactivating cadherin E induced the invasive phenotype. These combined experiments are strong evidence that loss of cadherin E is associated with development of invasive phenotype and furthermore suggests that this adhesion molecule may be a suppressor of metastasis. 

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