Studies On Targeted Delivery Of MicroRNA And Its Antitumor Activity

MicroRNAs(miRNAs)are a family of endogenous,small non-coding RNAs,which contain approximately 18-25 nucleotides and play pivotal roles in regulating gene expression.Previous biomedical research results have indicated that miRNAs are involved in not only normal physiologies but also pathologies.The aberrant expression and function of miRNAs are closely related to a variety of human diseases,including cancers.Therefore,endogenous miRNAs are emerging as promising targets for biomedical investigations.miRNAs have been used as diagnostic markers or therapeutic targets,which have also attracted a lot attention form chemical biologists.Oligonucleotides including miRNA mimics that can replace endogenous miRNAs and anti-miRNAs that can inhibit endogenous miRNAs are able to regulate miRNAs to achieve therapeutic outcomes.However,negative charge and easy degradation property of oligonucleotides prevent them from crossing cellular membrane.Additional carriers such as virus vectors,lipids and nanovectors that can transport oligonucleotides are thus necessary.However,the poor biocompatibility of these carriers greatly hinders their further applications in therapeutics.How to develop carriers with good biocompatibility and high efficiency in miRNA delivery is thus of great interest to chemical biologist.In this thesis,we a used biocompatible cationic short peptide fragment cationic nona-arginine(R9)as the carrier and constructed multi-functional peptide conjugates through modifying R9.The multi-functional peptide conjugates were used to self-assemble with miRNA/anti-miRNA to form miRNA nanocomplexes,which were further used for targeted miRNA/anti-miRNA delivery and therapeutics.1.Self-assembled miRNA nanocomplexes for targeted delivery of anti-miR-21 and studies on antitumor activitySingle-stranded anti-miRNAs that are designed to inhibit oncogenic miRNAs,have been demonstrated in miRNA-based therapeutics.In the first section,we selected oncogenic miR-21 that is overexpressed in many cancer cells as the target biomolecule to construct a targeted delivery system based on miRNA nanocomposites.After modifying the folic acid that can target the folate receptor on the cell membrane surface at R9,we investigated its ability to self-assemble with anti-miR-21 to form miRNA nanocomplexes.To compare the effect of linkers between folic acid and R9 on the self-assembly and delivery efficiencies,linkers with different lengths were used to conjugate folic acid and R9.The resulted multi-functional peptide conjugates were then used to form miRNA nancomplexes with anti-miR-21.We then compared the self-assembly and delivery efficiencies by these peptide conjugates.Moreover,we also investigated the potential of miRNA nanocomplexes in therapeutic treatment through inhibiting endogenous miR-21 in HeLa cells.2.Self-assembled miRNA nanocomplexes for targeted delivery of miR-34a/PNAanti-miR-21 and studies on antitumor activityCancer-related miRNAs can be classified into tumor suppressive miRNAs and oncogenic miRNAs.Therapeutic treatments could be achieved through up-regulating tumor-suppressive miRNAs with miRNA mimics or down-regulating oncogenic miRNAs with anti-miRNAs.Therefore,simultaneous regulation of tumor-suppressive miRNA and oncogneic miRNA should lead to amplified therapeutic effect,which still remain to be explored.In the second section,we developed a multi-functional peptide conjugate that is consisted of folic acid,R9 and peptide nucleic acid targeting miR-21(PNAanti-miR-21).The multi-functional peptide conjugate was used to form miRNA nanocomplexes with miR-34a.We then investigated the delivery efficiencies of miR-34a/PNAanti-miR-21 by the miRNA naocomplexes.We also explored the therapeutic potential of miRNA nanocomplexes in promoting cellular apoptosis.