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miRNA therapeutics in cancer: alteration of biological functions of oncomicroRNAs with Peptide Nucleic Acids (PNAs)

By Gambari R.

Abstract

MicroRNAs (miRNAs, miRs) are a family of small (19 to 25 nucleotides in length) noncoding RNAs that regulate gene expression by sequence-selective targeting of mRNAs (1-4), leading to a translational repression or mRNA degradation, depending on the degree of complementarity between miRNAs and the target sequences. Since a single miRNA can target several mRNAs and a single mRNA may contain several signals for miRNA recognition, it is calculated that at least 10-40% of human mRNAs are targets of microRNAs. In general, a low expression of a given miRNA is expected to be potentially linked with an accumulation of targets mRNAs; conversely, a high expression of miRNAs is expected to be the cause of a low expression of the target mRNAs. In cancer OncomiRNAs and MetastamiRNAs have been associated to tumor onset and progression. Accordingly, targeting these tumor-associated microRNAs with biomolecules interfering with their biological activity might be of great interest. In this context peptide nucleic acids (PNAs) targeting miR-221 have been described able to specifically interact with miR-221 expressed in breast cancer and gliomas. In order to maximize uptake in target cells a polyarginine-peptide (R8) was conjugated, generating an anti miR-221 PNA (R8-PNA-a221) displaying very high affinity for RNA and efficient uptake within target cells without the need of transfection reagents. Unmodified PNA with the same sequence displayed RNA binding, but cellular uptake was very poor. Consistently, only R8-PNA-a221 strongly inhibited miR-221 in breast cancer MDA-MB-231 and in glioma cell lines U251, U373 and T98G. Targeting miR-221 by PNA resulted in (a) lowering of the hybridization levels of miR-221 measured by RT-qPCR, (b) up-regulation of p27Kip1, mRNA and protein, measured by RT-qPCR and Western Blot analysis. These results together with several evidences reported in the literature allow to propose anti-miR PNAs as potent reagents in miRNA therapeutics

Publisher: D.A. Spandidos
Year: 2013
OAI identifier: oai:iris.unife.it:11392/1929612
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