EphB2 activation is required for ependymoma development as well as inhibits differentiation and promotes proliferation of the transformed cell.

Phylip Chen,Nathan Rossi,Robert A Johnson,Christopher R Pierson,Adam W Studebaker,Samuel Priddy

doi:10.1038/srep09248

Phylip Chen, Nathan Rossi + Show 4 more

Open Access

https://doi.org/10.1038/srep09248

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Abstract

Our intracranial implantation mouse model of ependymoma clearly demonstrates overexpression of the ephrin receptor EphB2 in Ink4a/Arf(−/−) supratentorial embryonic neural stem cells (STeNSCs) to be essential for transformation and disease development; however the requirement for and consequence of receptor activation on transformation and neural stem cell function were not examined. We definitively illustrate the necessity for receptor activation in cellular transformation and the importance of implantation site and microenvironment in directing ependymoma development. In vitro assays of EphB2 overexpressing Ink4a/Arf(−/−) STeNSCs showed no changes in their neural stem cell characteristics (stem cell marker expression and self-renewal) upon receptor activation, but EphB2 driven tumor cells were inhibited significantly in differentiation and exhibited increased tumorsphere formation and cellular proliferation in response to ephrin-B ligand mediated receptor activation. Additionally, we observed substantial differences in the phosphorylation state of several key proteins involved in Ras and p38 MAPK signaling when comparing EphB2 overexpressing Ink4a/Arf(−/−) STeNSCs and tumor cells with relatively little change in total protein levels. We propose that EphB2 mediated ependymoma development is a multifactorial process requiring microenvironment directed receptor activation, resulting in changes in the phosphorylation status of key regulatory proteins, maintenance of a stem-like state and cellular proliferation.

Highlights

EphB2 activation is required for ependymoma development as well as inhibits differentiation and promotes proliferation of the transformed cell
We propose that EphB2 mediated ependymoma development is a multifactorial process requiring microenvironment directed receptor activation, resulting in changes in the phosphorylation status of key regulatory proteins, maintenance of a stem-like state and cellular proliferation
A key component of this model is the ability to grow EphB2 overexpressing Ink4a/ Arf(2/2) supratentorial E14.5 neural stem cells (STeNSCs), called utNSCs, in vitro as tight compact balls called neurospheres. These cells are obtained from the subventricular zone of the embryonic mouse brain a region known to express all three ephrin-B ligands it was necessary to determine if cultured utNSCs expressed ephrin-B ligand as well[37,38,39]

Summary

Introduction

EphB2 activation is required for ependymoma development as well as inhibits differentiation and promotes proliferation of the transformed cell. Loss of EphB2 expression has been implicated in the progression of colorectal cancer[21] As these studies illustrate, the current understanding of the connection between Eph activity and cancer is based predominantly on www.nature.com/scientificreports observing the impact that modulating receptor/ligand interaction or expression levels has on the survival, migration or proliferation of an established tumor. The current understanding of the connection between Eph activity and cancer is based predominantly on www.nature.com/scientificreports observing the impact that modulating receptor/ligand interaction or expression levels has on the survival, migration or proliferation of an established tumor Very informative, these studies were not designed to examine the potential function ephrin signaling has in tumor development. Given the extremely limited number of ependymoma model systems to study the disease, we developed our current mouse model system as a tool to identify the key genes and pathways deregulated in disease development, growth and survival

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