title: miRNA oligonucleotide and sponge for miRNA-21 inhibition mediated by PEI-PLL in breast cancer therapy.
abstract: MicroRNA-21 (miR-21) inhibition is a promising biological strategy for breast cancer therapy. However its application is limited by the lack of efficient miRNA inhibitor delivery systems. As a cationic polymer transfection material for nucleic acids, the poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer combines the high transfection efficiency of polyethylenimine (PEI) and the good biodegradability of polyllysine (PLL). In this work, PEI-PLL was successfully synthesized and confirmed to transfect plasmid and oligonucleotide more effectively than PEI in MCF-7 cells (human breast cancer cells). In this regard, two kinds of miR-21 inhibitors, miR-21 sponge plasmid DNA (Sponge) and anti-miR-21 oligonucleotide (AMO), were transported into MCF-7 cells by PEI-PLL respectively. The miR-21 expression and the cellular physiology were determined post transfection. Compared with the negative control, PEI-PLL/Sponge or PEI-PLL/AMO groups exhibited lower miR-21 expression and cell viability. The anti-tumor mechanism of PEI-PLL/miR-21 inhibitors was further studied by cell cycle and western blot analyses. The results indicated that the miR-21 inhibition could induce the cell cycle arrest in G1 phase, upregulate the expression of Programmed Cell Death Protein 4 (PDCD4) and thus active the caspase-3 apoptosis pathway. Interestingly, the PEI-PLL/Sponge and PEI-PLL/AMO also sensitized the MCF-7 cells to anti-tumor drugs, doxorubicin (DOX) and cisplatin (CDDP). These results demonstrated that PEI-PLL/Sponge and PEI-PLL/AMO complexes would be two novel and promising gene delivery systems for breast cancer gene therapy based on miR-21 inhibition.
  
  
  CONCLUSIONS
  This work was a combination of the high transfection efficiency of polyethylenimine (PEI), the good biodegradability of polyllysine (PLL) and the breast cancer-killing effect of miR-21 inhibitors. The poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer was employed as the vector of miR-21 sponge plasmid DNA (Sponge) or anti-miR-21 oligonucleotide (AMO). PEI-PLL showed more transfection efficiency and lower cytotoxicity in human breast cancer cells than PEI. Moreover, the breast cancer cells exhibited significantly lower miR-21 expression and cell viability post transfection with sponge or AMO. Interestingly, the PEI-PLL/miR-21 inhibitor complexes also sensitized the cancer cells to anti-cancer chemotherapy drugs, doxorubicin (DOX) and cisplatin (CDDP). This synergistic effect provides a good application prospect of co-delivery miR-21 inhibitors and chemical drugs in breast cancer therapy.
authors.affiliation: Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; Graduate School of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Shiqian
authors.initials: S
authors.lastname: Gao
authors.affiliation: Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
authors.forename: Huayu
authors.initials: H
authors.lastname: Tian
authors.affiliation: School of Life Science, Northeast Normal University, Changchun 130024, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
authors.forename: Yuce
authors.initials: Y
authors.lastname: Li
authors.affiliation: Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
authors.forename: Zhaopei
authors.initials: Z
authors.lastname: Guo
authors.affiliation: School of Life Science, Northeast Normal University, Changchun 130024, China.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China. Electronic address: xschen@ciac.ac.cn.
authors.forename: Xuesi
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000473:pathology / Q000628:therapy*; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D024202:Electrophoretic Mobility Shift Assay; D004705:Endocytosis / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000037:antagonists & inhibitors* / Q000235:genetics; D009841:Oligonucleotides / Q000235:genetics* / Q000633:toxicity; D010316:Particle Size; D011094:Polyethyleneimine / Q000737:chemistry* / Q000633:toxicity; D011107:Polylysine / Q000737:chemistry*; D011161:Porifera / Q000737:chemistry*; D066244:Proton Magnetic Resonance Spectroscopy; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D014162:Transfection
chemical_list: C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D009841:Oligonucleotides; D011107:Polylysine; D011094:Polyethyleneimine
keywords: Breast cancer therapy; MiRNA-21 AMO; MiRNA-21 sponge; Polyethylenimine; Polylysine