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EGFRvIII gene rearrangement is an early event in glioblastoma tumorigenesis and expression defines a hierarchy modulated by epigenetic mechanisms.

Abstract：

:Amplification and rearrangements of the epidermal growth factor receptor (EGFR) gene are frequently found in glioblastoma multiforme (GBM). The most common variant is EGFR variant III (EGFRvIII). Research suggests that EGFRvIII could be a marker for a cancer stem cell or tumor-initiating population. If amplification and rearrangement are early events in tumorigenesis, this implies that they should be preserved throughout the tumor. However, in primary GBM, EGFRvIII expression is focal and sporadic. Unexpectedly, we found EGFR amplification and rearrangement throughout the tumor, including regions with no EGFRvIII expression, suggesting that mechanisms exist to modulate EGFRvIII expression even in the presence of high gene amplification. To study this phenomenon, we characterized three GBM cell lines with endogenous EGFRvIII. EGFRvIII expression was heterogeneous, with both positive and negative populations maintaining the genetic alterations, akin to primary tumors. Furthermore, EGFRvIII defined a hierarchy where EGFRvIII-positive cells gave rise to additional positive and negative cells. Only cells that had recently lost EGFRvIII expression could re-express EGFRvIII, providing an important buffer for maintaining EGFRvIII-positive cell numbers. Epigenetic mechanisms had a role in maintaining heterogeneous EGFRvIII expression. Demethylation induced a 20-60% increase in the percentage of EGFRvIII-positive cells, indicating that some cells could re-express EGFRvIII. Surprisingly, inhibition of histone deacetylation resulted in a 50-80% reduction in EGFRvIII expression. Collectively, this data demonstrates that EGFR amplification and rearrangement are early events in tumorigenesis and EGFRvIII follows a model of hierarchical expression. Furthermore, EGFRvIII expression is restricted by epigenetic mechanisms, suggesting that drugs that modulate the epigenome might be used successfully in glioblastoma tumors.

journal_name

Oncogene

journal_title

Oncogene

authors

Del Vecchio CA,Giacomini CP,Vogel H,Jensen KC,Florio T,Merlo A,Pollack JR,Wong AJ

doi

10.1038/onc.2012.280

subject

Has Abstract

pub_date

2013-05-23 00:00:00

pages

2670-81

issue

eissn

0950-9232

issn

1476-5594

pii

onc2012280

journal_volume

pub_type

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EGFRvIII gene rearrangement is an early event in glioblastoma tumorigenesis and expression defines a hierarchy modulated by epigenetic mechanisms.