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  2. The nucleolin targeting aptamer AS1411 destabilizes Bcl-2 messenger RNA in human breast cancer cells

The nucleolin targeting aptamer AS1411 destabilizes Bcl-2 messenger RNA in human breast cancer cells

  • Cancer Res. 2008 Apr 1;68(7):2358-65. doi: 10.1158/0008-5472.CAN-07-5723.
Sridharan Soundararajan 1 Weiwei Chen Eleanor K Spicer Nigel Courtenay-Luck Daniel J Fernandes
Affiliations

Affiliation

  • 1 Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
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.

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