Multifunctional Aptamer-miRNA Conjugates for Targeted Cancer Therapy

Abstract

While microRNAs (miRNAs) clearly regulate multiple pathways integral to disease development and progression, the lack of safe and reliable means for specific delivery of miRNAs to target tissues represents a major obstacle to their broad therapeutic application. Our objective was to explore the use of nucleic acid aptamers as carriers for cell-targeted delivery of a miRNA with tumor suppressor function, let-7g. Using an aptamer that binds to and antagonizes the oncogenic receptor tyrosine kinase Axl (GL21.T), here we describe the development of aptamer-miRNA conjugates as multifunctional molecules that inhibit the growth of Axl-expressing tumors. We conjugated the let-7g miRNA to GL21.T and demonstrate selective delivery to target cells, processing by the RNA interference machinery, and silencing of let-7g target genes. Importantly, the multifunctional conjugate reduced tumor growth in a xenograft model of lung adenocarcinoma. Therefore, our data establish aptamer-miRNA conjugates as a novel tool for targeted delivery of miRNAs with therapeutic potential.

A combined microRNA-based targeted therapeutic approach to eradicate glioblastoma stem-like cells

“…Since the aptamer conjugates are internalized through a receptor mediated manner whose effectiveness is thus limited by the amount of available receptor present on the cell surface [21], we conjugated the miR-137 and the single chain miR-10b antagonist to two different aptamers in order to deliver them separately into the target cell by targeting two distinct RTKs. This approach has the double advantage to overcome the competition of conjugates for the same target receptor and to increase the selectivity of targeting of the miRNA/antimiR combination for cells that overexpress both receptors.…”

“…As shown above, both configurations work with similar efficacy, yet, the efficiency of aptamer uptake (either of GL21.T or Gint4.T) is restrained by the amount of target receptors on the cell surface [21]. Using two different aptamers together, would thus increase the efficiency of uptake of each conjugate and would inhibit the two target receptors.…”

“…In addition to inhibitory function of selected targets, aptamers raised against transmembrane receptors rapidly internalize into the target cell through recycling of the bound receptor [20]. So far, various therapeutic cargoes have been successfully conjugated to aptamers, including anti-cancer drugs, toxins, radionuclides, and short therapeutic RNAs (siRNAs and miRNAs) [19,21,22]. The main advantages for aptamer use in vivo as cell targeting moieties, include the extraordinary high binding specificity, long-term stability, little to no immunogenicity and off target toxicity [23].…”

“…As we have recently shown, both GL21.T and Gint4.T may act as carriers for the selective delivery of short miRNA mimics and single chain miRNA antagonists, antimiR, into receptor expressing tumor cells both in vitro and in vivo. Furthermore, we have demonstrated the combinatorial potential of conjugating the GL21.T aptamer to a miRNA (or antimiR) molecule that combines the clinical benefits of both moieties [21,22].…”

Gene Knockdown by EpCAM Aptamer–siRNA Chimeras Suppresses Epithelial Breast Cancers and Their Tumor-Initiating Cells

“…In principle, aptamer chimeras could be designed to deliver not only siRNAs but also miRNA mimics or antagomirs, antisense oligonucleotides that function by other mechanisms besides RNAi, or even longer mRNAs or noncoding RNAs (50,51). They could also be designed to incorporate more than one aptamer, multiple siRNAs, or even toxins or small-molecule anticancer drugs.…”