Research Papers:

Identification of Ras suppressor-1 (RSU-1) as a potential breast cancer metastasis biomarker using a three-dimensional in vitro approach

Vasiliki Gkretsi, Andreas Stylianou, Maria Louca and Triantafyllos Stylianopoulos _

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Oncotarget. 2017; 8:27364-27379. https://doi.org/10.18632/oncotarget.16062

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Vasiliki Gkretsi1, Andreas Stylianou1, Maria Louca1, Triantafyllos Stylianopoulos1

1Cancer Biophysics Laboratory, Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus

Correspondence to:

Triantafyllos Stylianopoulos, email: [email protected]

Keywords: Ras suppressor-1, extracellular matrix stiffness, invasion, tumor spheroids, atomic force microscopy

Received: July 16, 2016    Accepted: February 20, 2017    Published: March 09, 2017


Breast cancer (BC) is the most common malignant disease in women, with most patients dying from metastasis to distant organs, making discovery of novel metastasis biomarkers and therapeutic targets imperative. Extracellular matrix (ECM)-related adhesion proteins as well as tumor matrix stiffness are important determinants for metastasis. As traditional two-dimensional culture does not take into account ECM stiffness, we employed 3-dimensional collagen I gels of increasing concentration and stiffness to embed BC cells of different invasiveness (MCF-7, MDA-MB-231 and MDA-MB-231-LM2) or tumor spheroids. We tested the expression of cell-ECM adhesion proteins and found that Ras Suppressor-1 (RSU-1) is significantly upregulated in increased stiffness conditions. Interestingly, RSU-1 siRNA-mediated silencing inhibited Urokinase Plasminogen Activator, and metalloproteinase-13, whereas tumor spheroids formed from RSU-1-depleted cells lost their invasive capacity in all cell lines and stiffness conditions. Kaplan-Meier survival plot analysis corroborated our findings showing that high RSU-1 expression is associated with poor prognosis for distant metastasis-free and remission-free survival in BC patients. Taken together, our results indicate the important role of RSU-1 in BC metastasis and set the foundations for its validation as potential BC metastasis marker.

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