| 19264808 |
Wickramasinghe NS, Manavalan TT, Dougherty SM, Riggs KA, Li Y, Klinge CM: Estradiol downregulates miR-21 expression and increases miR-21 target gene expression in MCF-7 breast cancer cells. Nucleic Acids Res. 2009 May;37(8):2584-95. Epub 2009 Mar 5.
Select changes in microRNA (miRNA) expression correlate with estrogen receptor alpha (ER alpha) expression in breast tumors. miR-21 is higher in ER alpha positive than negative tumors, but no one has examined how estradiol (E (2)) regulates miR-21 in breast cancer cells. Here we report that E (2) inhibits miR-21 expression in MCF-7 human breast cancer cells. The E (2)-induced reduction in miR-21 was inhibited by 4-hydroxytamoxifen (4-OHT), ICI 182 780 (Faslodex), and siRNA ER alpha indicating that the suppression is ER alpha-mediated. ER alpha and ER beta agonists PPT and DPN inhibited and 4-OHT increased miR-21 expression. E (2) increased luciferase activity from reporters containing the miR-21 recognition elements from the 3'-UTRs of miR-21 target genes, corroborating that E (2) represses miR-21 expression resulting in a loss of target gene suppression. The E (2)-mediated decrease in miR-21 correlated with increased protein expression of endogenous miR-21-targets Pdcd4, PTEN and Bcl-2. siRNA knockdown of ER alpha blocked the E (2)-induced increase in Pdcd4, PTEN and Bcl-2. Transfection of MCF-7 cells with antisense (AS) to miR-21 mimicked the E (2)-induced increase in Pdcd4, PTEN and Bcl-2. These results are the first to demonstrate that E (2) represses the expression of an oncogenic miRNA, miR-21, by activating estrogen receptor in MCF-7 cells. |
4(0,0,0,4) |