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Open Access Highly Accessed Research article

Sox2 suppresses the invasiveness of breast cancer cells via a mechanism that is dependent on Twist1 and the status of Sox2 transcription activity

Fang Wu1, Xiaoxia Ye1, Peng Wang1, Karen Jung2, Chengsheng Wu1, Donna Douglas3, Norman Kneteman3, Gilbert Bigras1, Yupo Ma4 and Raymond Lai125*

Author Affiliations

1 Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada

2 Department of Oncology, University of Alberta, Edmonton, Alberta, Canada

3 Department of Surgery, University of Alberta, Edmonton, Alberta, Canada

4 Department of Pathology, Stonybrook University, Stonybrook, NY, USA

5 DynaLIFEDX Medical Laboratories, Edmonton, Alberta, Canada

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BMC Cancer 2013, 13:317  doi:10.1186/1471-2407-13-317

Published: 1 July 2013

Abstract

Background

Sox2, an embryonic stem cell marker, is aberrantly expressed in a subset of breast cancer (BC). While the aberrant expression of Sox2 has been shown to significantly correlate with a number of clinicopathologic parameters in BC, its biological significance in BC is incompletely understood.

Methods

In-vitro invasion assay was used to evaluate whether the expression of Sox2 is linked to the invasiveness of MCF7 and ZR751 cells. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and/or Western blots were used to assess if Sox2 modulates the expression of factors known to regulate epithelial mesenchymal transition (EMT), such as Twist1. Chromatin immunoprecipitation (ChIP) was used to assess the binding of Sox2 to the promoter region of Twist1.

Results

We found that siRNA knockdown of Sox2 expression significantly increased the invasiveness of MCF7 and ZR751 cells. However, when MCF7 cells were separated into two distinct subsets based on their differential responsiveness to the Sox2 reporter, the Sox2-mediated effects on invasiveness was observed only in ‘reporter un-responsive’ cells (RU cells) but not ‘reporter responsive’ cells (RR cells). Correlating with these findings, siRNA knockdown of Sox2 in RU cells, but not RR cells, dramatically increased the expression of Twist1. Accordingly, using ChIP, we found evidence that Sox2 binds to the promoter region of Twist1 in RU cells only. Lastly, siRNA knockdown of Twist1 largely abrogated the regulatory effect of Sox2 on the invasiveness in RU cells, suggesting that the observed Sox2-mediated effects are Twist1-dependent.

Conclusion

Sox2 regulates the invasiveness of BC cells via a mechanism that is dependent on Twist1 and the transcriptional status of Sox2. Our results have further highlighted a new level of biological complexity and heterogeneity of BC cells that may carry significant clinical implications.

Keywords:
Sox2; Transcription activity; Invasiveness; Twist1; Breast cancer