Related Experiment Video
Updated: Jul 6, 2026
Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells
Published on: August 12, 2015
The nucleolin targeting aptamer AS1411 destabilizes Bcl-2 messenger RNA in human breast cancer cells
Sridharan Soundararajan1, Weiwei Chen, Eleanor K Spicer
1Department 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.
Insights
The aptamer AS1411 targets nucleolin, a protein that stabilizes bcl-2 mRNA in breast cancer cells. AS1411 induces bcl-2 mRNA instability and cancer cell death, sparing normal cells.
Area of Science:
- Molecular Biology
- Cancer Research
- Drug Discovery
Background:
- Nucleolin is a nucleolar and cytoplasmic protein that binds to bcl-2 mRNA.
- Nucleolin plays a role in regulating bcl-2 mRNA stability.
- The aptamer AS1411 is being investigated for its therapeutic potential in cancer.
Purpose of the Study:
- To determine if nucleolin regulates bcl-2 mRNA stability in breast cancer cells.
- To examine the efficacy of AS1411 in targeting nucleolin and affecting bcl-2 mRNA stability and cytotoxicity.
- To investigate the selectivity of AS1411 for cancer cells over normal cells.
Main Methods:
- Cell culture of MCF-7, MDA-MB-231 (breast cancer), and MCF-10A (normal mammary epithelial) cells.
- Treatment with AS1411 aptamer at various concentrations.
- siRNA knockdown of nucleolin.
- Measurement of cell growth, viability, nucleolin and bcl-2 protein levels, and bcl-2 mRNA half-life.
- Assessment of nucleolin-bcl-2 mRNA binding in vitro and in cells.
Main Results:
- AS1411 inhibited growth of MCF-7 and MDA-MB-231 cells but not MCF-10A cells.
- AS1411 uptake and cytoplasmic nucleolin levels were higher in cancer cells.
- Nucleolin knockdown decreased bcl-2 protein and mRNA stability.
- AS1411 significantly reduced bcl-2 mRNA half-life in cancer cells but not normal cells.
- AS1411 inhibited nucleolin binding to the bcl-2 mRNA instability element.
Conclusions:
- Nucleolin stabilizes bcl-2 mRNA in breast cancer cells.
- AS1411 acts as a molecular decoy, competing with bcl-2 mRNA for nucleolin binding.
- This mechanism contributes to AS1411-induced tumor cell death and highlights its potential as a targeted cancer therapy.
Related Concept Videos
02:55The Nucleolus
02:57Targeted Cancer Therapies
There are several types of targeted therapies against specific...
01:31The Intrinsic Apoptotic Pathway