title: The nucleolin targeting aptamer AS1411 destabilizes Bcl-2 messenger RNA in human breast cancer cells.
abstract: We sought to determine whether nucleolin, a bcl-2 mRNA-binding protein, has a role in the regulation of bcl-2 mRNA stability in MCF-7 and MDA-MB-231 breast cancer cells. Furthermore, we examined the efficacy of the aptamer AS1411 in targeting nucleolin and inducing bcl-2 mRNA instability and cytotoxicity in these cells. AS1411 at 5 micromol/L inhibited the growth of MCF-7 and MDA-MB-231 cells, whereas 20 micromol/L AS1411 had no effect on the growth rate or viability of normal MCF-10A mammary epithelial cells. This selectivity of AS1411 was related to a greater uptake of AS1411 into the cytoplasm of MCF-7 cells compared with MCF-10A cells and to a 4-fold higher level of cytoplasmic nucleolin in MCF-7 cells. Stable siRNA knockdown of nucleolin in MCF-7 cells reduced nucleolin and bcl-2 protein levels and decreased the half-life of bcl-2 mRNA from 11 to 5 hours. Similarly, AS1411 (10 micromol/L) decreased the half-life of bcl-2 mRNA in MCF-7 and MDA-MB-231 cells to 1.0 and 1.2 hours, respectively. In contrast, AS1411 had no effect on the stability of bcl-2 mRNA in normal MCF-10A cells. AS1411 also inhibited the binding of nucleolin to the instability element AU-rich element 1 of bcl-2 mRNA in a cell-free system and in MCF-7 cells. Together, the results suggest that AS1411 acts as a molecular decoy by competing with bcl-2 mRNA for binding to cytoplasmic nucleolin in these breast cancer cell lines. This interferes with the stabilization of bcl-2 mRNA by nucleolin and may be one mechanism by which AS1411 induces tumor cell death.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Sridharan
authors.initials: S
authors.lastname: Soundararajan
authors.forename: Weiwei
authors.initials: W
authors.lastname: Chen
authors.forename: Eleanor K
authors.initials: EK
authors.lastname: Spicer
authors.forename: Nigel
authors.initials: N
authors.lastname: Courtenay-Luck
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Fernandes
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D052157:Aptamers, Nucleotide; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000628:therapy*; D045744:Cell Line, Tumor; D019254:Genes, bcl-2; D006801:Humans; D009838:Oligodeoxyribonucleotides / Q000235:genetics / Q000494:pharmacology*; D010750:Phosphoproteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D000097796:Nucleolin
chemical_list: D052157:Aptamers, Nucleotide; D009838:Oligodeoxyribonucleotides; D010750:Phosphoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000097796:Nucleolin; C513936:AGRO 100