Abstract 532: Evaluation of the role of miRNA-4728-3p, a miRNA located in an intron of HER2 gene, in breast cancer stem cells

Abstract

Background: Cancer stem cells (CSCs) contribute to tumor metastasis, chemotherapy resistance, and are highly tumorigenic when injected into immunodeficient mice. High levels of aldehyde dehydrogenase (ALDH1) are characteristic of stem cells and allow the isolation of subpopulations of CSCs, including those derived from breast cancer. HER2+ tumors, which are more aggressive than tumors with no amplification of this oncogene, are enriched in CSCs, a finding that suggests the participation of this oncogene in the generation and maintenance of CSCs. miR-4728-3p is a poorly investigated miRNA, which is located inside an intron of HER2. Its expression is increased in HER2+ tumors and cell lines, but its role in CSC formation and tumor behavior has not been investigated. Aim: to contribute to the better understanding of the role of miRNA-4728-3p in the biology of CSCs in HER2+ breast cancer cell lines. Methods: miR-4728-3p levels were evaluated in breast cancer cell lines MCF-7, BT-474 and SKBR3 grown in adherent conditions and in conditions that favor the formation of mammospheres for 7, 14, 21 and 28 days. Overexpression of miR-4728-3p was performed using lentiviral transduction with plasmids for the overexpression of this miRNA. Flow cytometry was performed to analyze ALDH1 expression in adherent cells and cells derived from mammospheres and also in cells overexpressing miRNA-4728-3p. Results: Mammospheres in culture for 7 days showed high levels of ALDH1 for all cells lines evaluated. The overexpression of miR-4728-3p induced a significant increment (>10-fold) of ALDH1+ subpopulations in MCF-7 and SKBR3, reinforcing its possible role in the biology of CSCs. Conclusion: HER2-amplification is an event that intrinsically leads to the amplification of miR-4728-3p. The effects of the amplification of this oncogene and this miRNA have to be evaluated together as both may have important consequences for tumor behavior and CSC formation. This increased expression of ALDH1 after miR-4728-3p overexpression suggest the importance of this miRNA in the biology of CSC formation. Note: This abstract was not presented at the meeting. Citation Format: Juliana Laino do Val Carneiro, Diana Noronha Nunes, Emmanuel Dias-Neto. Evaluation of the role of miRNA-4728-3p, a miRNA located in an intron of HER2 gene, in breast cancer stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 532. doi:10.1158/1538-7445.AM2014-532