Inhibition of Breast Cancer Cell Invasion by Ras Suppressor-1 (RSU-1) Silencing Is Reversed by Growth Differentiation Factor-15 (GDF-15).

Vasiliki Gkretsi,Maria Louca,George M Spyrou,Andreas Stylianou,George Minadakis,Triantafyllos Stylianopoulos

doi:10.3390/ijms20010163

Abstract

Extracellular matrix (ECM)-related adhesion proteins are important in metastasis. Ras suppressor-1 (RSU-1), a suppressor of Ras-transformation, is localized to cell–ECM adhesions where it interacts with the Particularly Interesting New Cysteine-Histidine rich protein (PINCH-1), being connected to Integrin Linked Kinase (ILK) and alpha-parvin (PARVA), a direct actin-binding protein. RSU-1 was also found upregulated in metastatic breast cancer (BC) samples and was recently demonstrated to have metastasis-promoting properties. In the present study, we transiently silenced RSU-1 in BC cells, MCF-7 and MDA-MB-231. We found that RSU-1 silencing leads to downregulation of Growth Differentiation Factor-15 (GDF-15), which has been associated with both actin cytoskeleton reorganization and metastasis. RSU-1 silencing also reduced the mRNA expression of PINCH-1 and cell division control protein-42 (Cdc42), while increasing that of ILK and Rac regardless of the presence of GDF-15. However, the downregulation of actin-modulating genes PARVA, RhoA, Rho associated kinase-1 (ROCK-1), and Fascin-1 following RSU-1 depletion was completely reversed by GDF-15 treatment in both cell lines. Moreover, complete rescue of the inhibitory effect of RSU-1 silencing on cell invasion was achieved by GDF-15 treatment, which also correlated with matrix metalloproteinase-2 expression. Finally, using a graph clustering approach, we corroborated our findings. This is the first study providing evidence of a functional association between RSU-1 and GDF-15 with regard to cancer cell invasion.

Highlights

Despite significant advances in breast cancer (BC)-related research and treatment, the most difficult issue faced by BC patients still remains the possibility of metastasis, which accounts for most deaths in women due to cancer [1]
Based on our findings that Growth Differentiation Factor-15 (GDF-15) treatment reverses the mRNA expression changes observed upon Ras suppressor-1 (RSU-1) silencing in actin cytoskeleton-related genes, we investigated whether GDF-15 treatment could reverse the already known inhibitory effect of RSU-1 silencing on cell invasion [18,31]
As a response to RSU-1 silencing in both BC cell lines, PINCH-1 was downregulated at the mRNA level but was not affected at the protein level while PARVA was downregulated both at the mRNA and protein level (Figure 1c,d,g,h, respectively and Supplementary Figure S1)

Summary

Introduction

Despite significant advances in breast cancer (BC)-related research and treatment, the most difficult issue faced by BC patients still remains the possibility of metastasis, which accounts for most deaths in women due to cancer [1]. It has been long postulated that the extracellular matrix (ECM) and ECM-related adhesion proteins are important players in metastasis, being greatly disrupted in tumors. This disruption allows, in turn, dissociation of cancer cells from the initial tumor [2,3,4,5], invasion through adjacent tissues, intravasation into blood vessels, and the establishment of a metastatic tumor in a favorable environment close to or far away from the primary site [6]. Reorganization of the actin cytoskeleton is actively happening during all phases of metastasis enabling cancer cells to respond to external stimuli, undergo actin cytoskeleton remodeling, epithelial to mesenchymal transition (EMT), and migrate or invade through surrounding tissues [7,8]

Methods

Discussion

Conclusion