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

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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.

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Most cited references 50

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Reprogramming of human somatic cells to pluripotency with defined factors.

In-Hyun Park, Rui Zhao, Jason A. West … (2008)

Pluripotency pertains to the cells of early embryos that can generate all of the tissues in the organism. Embryonic stem cells are embryo-derived cell lines that retain pluripotency and represent invaluable tools for research into the mechanisms of tissue formation. Recently, murine fibroblasts have been reprogrammed directly to pluripotency by ectopic expression of four transcription factors (Oct4, Sox2, Klf4 and Myc) to yield induced pluripotent stem (iPS) cells. Using these same factors, we have derived iPS cells from fetal, neonatal and adult human primary cells, including dermal fibroblasts isolated from a skin biopsy of a healthy research subject. Human iPS cells resemble embryonic stem cells in morphology and gene expression and in the capacity to form teratomas in immune-deficient mice. These data demonstrate that defined factors can reprogramme human cells to pluripotency, and establish a method whereby patient-specific cells might be established in culture.

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Epithelial-mesenchymal transition induced by TNF-α requires NF-κB-mediated transcriptional upregulation of Twist1.

Chia-Wei Li, Weiya Xia, Longfei Huo … (2012)

Proinflammatory cytokines produced in the tumor microenvironment facilitate tumor development and metastatic progression. In particular, TNF-α promotes cancer invasion and angiogenesis associated with epithelial-mesenchymal transition (EMT); however, the mechanisms underlying its induction of EMT in cancer cells remain unclear. Here we show that EMT and cancer stemness properties induced by chronic treatment with TNF-α are mediated by the upregulation of the transcriptional repressor Twist1. Exposure to TNF-α rapidly induced Twist1 mRNA and protein expression in normal breast epithelial and breast cancer cells. Both IKK-β and NF-κB p65 were required for TNF-α-induced expression of Twist1, suggesting the involvement of canonical NF-κB signaling. In support of this likelihood, we defined a functional NF-κB-binding site in the Twist1 promoter, and overexpression of p65 was sufficient to induce transcriptional upregulation of Twist1 along with EMT in mammary epithelial cells. Conversely, suppressing Twist1 expression abrogated p65-induced cell migration, invasion, EMT, and stemness properties, establishing that Twist1 is required for NF-κB to induce these aggressive phenotypes in breast cancer cells. Taken together, our results establish a signaling axis through which the tumor microenvironment elicits Twist1 expression to promote cancer metastasis. We suggest that targeting NF-κB-mediated Twist1 upregulation may offer an effective a therapeutic strategy for breast cancer treatment.

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Twist transcriptionally up-regulates AKT2 in breast cancer cells leading to increased migration, invasion, and resistance to paclitaxel.

George Z Cheng, Joseph Chan, Qi Wang … (2007)

Metastasis, the cardinal feature of malignant tumors, is an important clinical variable in patient prognosis. To understand the basis for metastasis, we systematically selected for highly invasive cells from breast cancer cell lines, MCF7 and MDA-MB-453, with moderate to low invasive ability using Boyden chamber invasion assay. The four-cycle selected invasive lines, named MCF7-I4 and MDA-MB-453-I4, respectively, displayed epithelial-mesenchymal transition (EMT) and dramatically enhanced invasive ability. EMT changes were corroborated with decreased level of E-cadherin and increased vimentin, fibronectin, and beta(1) integrin. Twist, a basic helix-loop-helix transcription factor, and AKT2, a known proto-oncogene, were found to be elevated in the invasive cells compared with the parental. Ectopic expression and knockdown of Twist by short interference RNA resulted in significant increase and reduction, respectively, of AKT2 protein and mRNA expression. Twist bound to E-box elements on AKT2 promoter and enhanced its transcriptional activity. Moreover, silencing AKT2 decreased Twist-promoted migration, invasion, and paclitaxel resistance. Reintroducing AKT2 largely rescued the phenotype resulted from knockdown of Twist in I4 cells, suggesting that AKT2 is a downstream target and functional mediator of Twist. Finally, we observed a 68.8% correlation of elevated Twist and AKT2 expression in late-stage breast cancers as oppose to 13% in early-stage breast cancers. Our study identifies Twist as a positive transcriptional regulator of AKT2 expression, and Twist-AKT2 signaling is involved in promoting invasive ability and survival of breast cancer cells.

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Author and article information

Contributors

Fang Wu

Xiaoxia Ye

Peng Wang

Karen Jung

Chengsheng Wu

Donna Douglas

Norman Kneteman

Gilbert Bigras

Yupo Ma

Raymond Lai

Journal

Journal ID (nlm-ta): BMC Cancer

Journal ID (iso-abbrev): BMC Cancer

Title: BMC Cancer

Publisher: BioMed Central

ISSN (Electronic): 1471-2407

Publication date Collection: 2013

Publication date (Electronic): 1 July 2013

Volume: 13

Page: 317

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

Article

Publisher ID: 1471-2407-13-317

DOI: 10.1186/1471-2407-13-317

PMC ID: 3707762

PubMed ID: 23815808

SO-VID: e0fac054-152d-4669-87ca-c3d775468546

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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

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Abstract

Background

Methods

Results

Conclusion

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Karger: Oncology

Most cited references 50

Reprogramming of human somatic cells to pluripotency with defined factors.

Epithelial-mesenchymal transition induced by TNF-α requires NF-κB-mediated transcriptional upregulation of Twist1.

Twist transcriptionally up-regulates AKT2 in breast cancer cells leading to increased migration, invasion, and resistance to paclitaxel.

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