Epidermal Growth Factor Receptor Variant III–Induced Glioma Invasion Is Mediated through Myristoylated Alanine-Rich Protein Kinase C Substrate Overexpression

Johann Micallef,Abhijit Guha,Sidney Croul,Michael F Moran,Joydeep Mukherjee,Michael Taccone,Jennifer Busby

doi:10.1158/0008-5472.can-08-4783

Abstract

Glioblastoma multiforme (GBM) is the most common and most malignant adult brain tumor. A characteristic of GBM is their highly invasive nature, making complete surgical resection impossible. The most common gain-of-function alteration in GBM is amplification, overexpression, and mutations of the epidermal growth factor receptor (EGFR). The constitutively activated mutant EGFR variant III (EGFRvIII), found in approximately 20% of GBM, confers proliferative and invasive advantage. The signaling cascades downstream of aberrant EGFR activation contributing to the invasive phenotype are not completely understood. Here, we show myristoylated alanine-rich protein kinase C substrate (MARCKS), previously implicated in cell adhesion and motility, contributes to EGFR-mediated invasion of human GBM cells. EGFRvIII-expressing or EGF-stimulated human GBM cells increased expression, phosphorylation, and cytosolic translocation of MARCKS in a protein kinase C-alpha-dependent manner. Down-regulation of MARCKS expression with small interfering RNA in GBM cells expressing EGFRvIII led to decreased cell adhesion, spreading, and invasion. Elucidation of mechanisms that promote EGFRvIII-mediated tumorigenesis in GBM, such as MARCKS, provides additional understanding and potential biological targets against this currently terminal human cancer.

Highlights

Glioblastoma multiforme (GBM) is the most common and malignant adult brain tumor [1]
myristoylated alanine-rich protein kinase C substrate (MARCKS), a protein that plays a role in cell motility, has previously been linked to wild-type EGFR (wtEGFR)-protein kinase C (PKC) signaling, both of which are involved in glioma invasion
We show for the first time that MARCKS as well as its phosphorylated form is up-regulated in both wtEGFR- and EGFRvIII-expressing glioma cell lines, xenografts, and operative specimens

Summary

Introduction

Glioblastoma multiforme (GBM) is the most common and malignant adult brain tumor [1]. The highly invasive nature of these tumors precludes complete surgical resection and leads to the demise of patients. Amplification and overexpression of the epidermal growth factor receptor (EGFR), the most common gain-of-function mutation, is a major contributor to the invasive phenotype. EGFR amplification ( found in f50% of GBM) is frequently associated with intragenic rearrangements and/or deletions [2] that lead to expression of several mutant EGFRs [3]. The most common mutant receptor, found in f40% of GBM that. Doi:10.1158/0008-5472.CAN-08-4783 have EGFR gene amplification or f20% of all GBM, is EGFR variant III (EGFRvIII), known to increase the invasiveness of glioma cells I2009 American Association for Cancer Research. doi:10.1158/0008-5472.CAN-08-4783 have EGFR gene amplification or f20% of all GBM, is EGFR variant III (EGFRvIII), known to increase the invasiveness of glioma cells

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