Abstract 3327: Role of Microrna221 in Breast Cancer Stem Cell Expansion and Induction of EMT

Abstract Breast cancer can be grouped by expression profiling into categories that differ in biological and clinical characteristics. Molecular characterization of these subtypes on the basis of stem cell markers has shown that basal and claudin-low tumor bear stem cell like characteristics with a higher population of CD44+/CD24- and CD49f+/EpCAM- cells, which also display characteristics of epithelial mesenchymal tumor transition (EMT). There are several genetic and epigenetic signaling pathways that regulate the stem cell like characteristics of these subtypes. We examined the role of microRNA221 (mir-221) in sub populations of normal breast cells isolated from reduction mammoplasties as well as in cancer cell lines from different molecular subtypes of breast cancer. We found that mir-221 drives cells towards more basal subtype and induces EMT in both normal mammary cells and breast cancer cell lines. On the basis of CD49f and ESA staining in the cells isolated from normal mammary tissue, we found high mir-221 expression in the CD49f+/EpCAM- population. Furthermore, we showed that ALDH+ cells from mammospheres expressed significantly higher mir-221 compared to ALDH- cells. In order to determine the effect of mir-221 on the stem cell population, we overexpressed mir-221 in cells from primary mammospheres and showed that overexpression of mir-221 increases the CD49f+/EpCAM- population with increased expression of mesenchymal biomarkers, an effect also seen in a non-transformed breast cell line MCF10A. Overexpression of mir-221 in luminal breast cancer cell lines MCF-7 and T47D cell lines increased the proportion of CD44+/CD24- cells. Furthermore, overexpression of mir-221 significantly stimulated the tumor growth of MCF7 xenographs in NOD/SCID mice. These studies suggest that mir-221 regulates breast CSCs by promoting EMT. This may play an important role in tumor behavior and treatment resistance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3327. doi:1538-7445.AM2012-3327