Role of microRNA221 in regulating normal mammary epithelial hierarchy and breast cancer stem-like cells

Jia Ke,Suling Liu,Sean Mcdermott,Jiahui Xu,Zhiju Zhao,Tahra Luther,Xiaojian Wu,Ping Lan,Li Shang,Zhen He,Christophe Ginestier,Max S Wicha,Fayaz Malik,Lei Zhou,Shawn G Clouthier,Rachel Martin-Trevino,Ingrid Ibarra,Shoumei Bai ,Kun Wu ,Yan Yi ,Su Hyung Hong

doi:10.18632/oncotarget.2888

Abstract

Increasing evidence suggests that lineage specific subpopulations and stem-like cells exist in normal and malignant breast tissues. Epigenetic mechanisms maintaining this hierarchical homeostasis remain to be investigated. In this study, we found the level of microRNA221 (miR-221) was higher in stem-like and myoepithelial cells than in luminal cells isolated from normal and malignant breast tissue. In normal breast cells, over-expression of miR-221 generated more myoepithelial cells whereas knock-down of miR-221 increased luminal cells. Over-expression of miR-221 stimulated stem-like cells in luminal type of cancer and the miR-221 level was correlated with clinical outcome in breast cancer patients. Epithelial-mesenchymal transition (EMT) was induced by overexpression of miR-221 in normal and breast cancer cells. The EMT related gene ATXN1 was found to be a miR-221 target gene regulating breast cell hierarchy. In conclusion, we propose that miR-221 contributes to lineage homeostasis of normal and malignant breast epithelium.

Highlights

Mammary stem cells (MaSCs) are defined in part by the ability to self-renew and differentiate
Endothelial and mature red blood cells by fluorescence-activated cell sorting (FACS) [12, 13], epithelial cells from normal breast reduction mammoplasty were separated into four subpopulations using two marker sets (ESA/CD49f and epithelial surface antigen (ESA)/CD10): stem-like cells (ESA−CD49f+, ESA−CD10−), luminal progenitor cells (ESA+CD49f+, ESA+CD10+), mature luminal cells (ESA+CD49f−, ESA+CD10−), and stromal/ myoepithelial cells (ESA−CD49f−, ESA−CD10+) (Figure 1A and 1B) [2,3,14]
The Aldehyde Dehydrogenase (ALDH) positive stem-like cells from the mammospheres, which are capable of self-renewal and multi-lineage differentiation [15], showed a significantly higher miR-221 expression level compared to ALDH− cells, as assessed by Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) (Figure 1F)

Summary

Introduction

Mammary stem cells (MaSCs) are defined in part by the ability to self-renew and differentiate They initially generate uncommitted progenitors and give rise to mature luminal cells with secretory functions and basal/myoepithelial cells with contractile functions. Corresponding to the lineages of normal breast tissue, human breast cancers can be classified into the subtypes as luminal, basal, Her2+, and Claudin-low by transcriptional profiling. These subtypes exhibit critical differences in patient survival and response to treatment [1]. Profiling of cell subpopulations purified from normal and malignant breast tissue revealed that, the mRNA signature of normal luminal progenitor cells is most similar to the basal type of breast cancer, whereas the MaSCs signature most closely resembles Claudin-low type of breast cancer [2]. The connections between normal and malignant hierarchies suggest a similar regulatory mechanism, which require further investigation

Methods

Results

Conclusion