Different Effects of BORIS/CTCFL on Stemness Gene Expression, Sphere Formation and Cell Survival in Epithelial Cancer Stem Cells.

Loredana Alberti,Jean Benhattar,Serge Leyvraz,Lorena Losi

doi:10.1371/journal.pone.0132977

Loredana Alberti, Jean Benhattar + Show 2 more

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https://doi.org/10.1371/journal.pone.0132977

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Abstract

Cancer stem cells are cancer cells characterized by stem cell properties and represent a small population of tumor cells that drives tumor development, progression, metastasis and drug resistance. To date, the molecular mechanisms that generate and regulate cancer stem cells are not well defined. BORIS (Brother of Regulator of Imprinted Sites) or CTCFL (CTCF-like) is a DNA-binding protein that is expressed in normal tissues only in germ cells and is re-activated in tumors. Recent evidences have highlighted the correlation of BORIS/CTCFL expression with poor overall survival of different cancer patients. We have previously shown an association of BORIS-expressing cells with stemness gene expression in embryonic cancer cells. Here, we studied the role of BORIS in epithelial tumor cells. Using BORIS-molecular beacon that was already validated, we were able to show the presence of BORIS mRNA in cancer stem cell-enriched populations (side population and spheres) of cervical, colon and breast tumor cells. BORIS silencing studies showed a decrease of sphere formation capacity in breast and colon tumor cells. Importantly, BORIS-silencing led to down-regulation of hTERT, stem cell (NANOG, OCT4, SOX2 and BMI1) and cancer stem cell markers (ABCG2, CD44 and ALDH1) genes. Conversely, BORIS-induction led to up-regulation of the same genes. These phenotypes were observed in cervical, colon and invasive breast tumor cells. However, a completely different behavior was observed in the non-invasive breast tumor cells (MCF7). Indeed, these cells acquired an epithelial mesenchymal transition phenotype after BORIS silencing. Our results demonstrate that BORIS is associated with cancer stem cell-enriched populations of several epithelial tumor cells and the different phenotypes depend on the origin of tumor cells.

Highlights

Enormous evidences support the view that human cancer could be considered as a stem cell disease [1,2,3]
To investigate the presence of BORIS mRNA in cancer stem cells (CSCs)-enriched populations of epithelial tumor cells, we used as models the human HeLa, HT29, MCF7 and MDA-MB-231 tumor cell lines
No significant change in expression was noticed in the other epithelial mesenchymal transition (EMT)-related genes, SNAI2 (SLUG), N-cadherin and fibronectin. All these results suggested that BORIS could affect the EMT process in luminal-like non-invasive breast cancer cells and indicated that BORIS may regulate some of the EMTrelated genes, such as CDH1 (ECADH), SNAIL, Twist-related protein 1 (TWIST) and VIMENTIN

Summary

Introduction

Enormous evidences support the view that human cancer could be considered as a stem cell disease [1,2,3]. The cancer stem cells (CSCs) theory assumes that cancers are viewed as complex tissues where aberrant cell growth is driven by a small population of cells defined as tumor-initiating cells These cells are characterized by three main properties: uncontrolled proliferation capacity, ability of self-renewal and ability to differentiate into a non-CSC progeny [3, 4]. An additional in vitro approach is based on non-adherent serum-free culture [8, 18] Using this method, the cells from different type of tumors (including brain, breast and colon), which have the capacity of self-renewal and to maintain stem-cell properties, can form spheroid colonies named spheres [19]

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