RASSF10 Is a TGFβ-Target That Regulates ASPP2 and E-Cadherin Expression and Acts as Tumor Suppressor That Is Epigenetically Downregulated in Advanced Cancer.

Antje M. Richter,Mira Y. Gökyildirim,Reinhard H. Dammann,Michelle L. Woods,Marcus Krueger,Sara K. Walesch,Miriam M. Küster

doi:10.3390/cancers11121976

Abstract

The Ras Association Domain Family (RASSF) encodes members of tumor suppressor genes which are frequently inactivated in human cancers. Here, the function and the regulation of RASSF10, that contains a RA (Ras-association) and two coiled domains, was investigated. We utilized mass spectrometry and immuno-precipitation to identify interaction partners of RASSF10. Additionally, we analyzed the up- and downstream pathways of RASSF10 that are involved in its tumor suppressive function. We report that RASSF10 binds ASPP1 (Apoptosis-stimulating protein of p53) and ASPP2 through its coiled-coils. Induction of RASSF10 leads to increased protein levels of ASPP2 and acts negatively on cell cycle progression. Interestingly, we found that RASSF10 is a target of the EMT (epithelial mesenchymal transition) driver TGFβ (Transforming growth factor beta) and that negatively associated genes of RASSF10 are significantly over-represented in an EMT gene set collection. We observed a positive correlation of RASSF10 expression and E-cadherin that prevents EMT. Depletion of RASSF10 by CRISPR/Cas9 technology induces the ability of lung cancer cells to proliferate and to invade an extracellular matrix after TGFβ treatment. Additionally, knockdown of RASSF10 or ASPP2 induced constitutive phosphorylation of SMAD2 (Smad family member 2). Moreover, we found that epigenetic reduction of RASSF10 levels correlates with tumor progression and poor survival in human cancers. Our study indicates that RASSF10 acts a TGFβ target gene and negatively regulates cell growth and invasion through ASPP2. This data suggests that epigenetic loss of RASSF10 contributes to tumorigenesis by promoting EMT induced by TGFβ.

Highlights

Cancer is caused by a multistep genetic and epigenetic transformation of normal cells into highly invasive and immortal tumor cells
We studied human cancer cell lines (CCLE, cancer cell line encyclopedia, Broad Institute, n = 917, [28]) and found that expression of RASSF10 (238755_at) significantly correlated with the expression of genes associated with the GO terms cell periphery, plasma membrane, epidermal/epithelial cell differentiation and cell–cell junction (Table 1)
We are showing that RASSF10 expression inhibits signs of EMT in cancer cell lines, but we are reporting its mode of action as a tumor suppressor

Summary

Introduction

Cancer is caused by a multistep genetic and epigenetic transformation of normal cells into highly invasive and immortal tumor cells. Epithelial cells are immobile cells that are responsible for organ integrity and structure. A key event of the transformation of epithelial cells into invasive tumor cells is associated with increased motility and disruption of cell-adhesion referred to as epithelial. Cancers 2019, 11, 1976 to mesenchymal transition (EMT). EMT disrupts cell polarity and contact inhibition of epithelial cells transforming them in a mesenchymal phenotype with increased invasion and cell motility. Different genetic and epigenetic alterations have been identified that are associated with EMT [1]. Epithelial cadherin (CDH1) is a master mediator of cell–cell adherens junctions and loss of CDH1 expression is associated with disruption of apical-basal polarity and integrity of epithelial cells [2]

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