A constitutively active epidermal growth factor receptor cooperates with disruption of G₁ cell-cycle arrest pathways to induce glioma-like lesions in mice

Abstract

The epidermal growth factor receptor (EGFR) gene is amplified or mutated in 30%-50% of human gliobastoma multiforme (GBM). These mutations are associated usually with deletions of the INK4a-ARF locus, which encodes two gene products (p16 INK4a and p19 ARF ) involved in cell-cycle arrest and apoptosis. We have investigated the role of EGFR mutation in gliomagenesis, using avian retroviral vectors to transfer a mutant EGFR gene to glial precursors and astrocytes in transgenic mice expressing tv-a, a gene encoding the retrovirus receptor. TVA, under control of brain cell type-specific promoters. We demonstrate that expression of a constitutively active, mutant form of EGFR in cells in the glial lineage can induce lesions with many similarities to human gliomas. These lesions occur more frequently with gene transfer to mice expressing tv-a from the progenitor-specific nestin promoter than to mice expressing tv-a from the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter, suggesting that tumors arise more efficiently from immature cells in the glial lineage. Furthermore, EGFR-induced gliomagenesis appears to require additional mutations in genes encoding proteins involved in cell-cycle arrest pathways. We have produced these combinations by simultaneously infecting tv-a transgenic mice with vectors carrying cdk4 and EGFR or by infecting tv-a transgenic mice bearing a disrupted INK4a-ARF locus with the EGFR-carrying vector alone. Moreover, EGFR-induced gliomagenesis does not occur in conjunction with p53 deficiency, unless the mice are also infected with a vector carrying cdk4. The gliomagenic combinations of genetic lesions required in mice are similar to those found in human gliomas.[Key Words: EGFR; gliomagenesis; cell cycle arrest] Received July 29, 1998; accepted in revised form October 14, 1998. Gliomas are the most common forms of primary brain tumors and are classified into four clinical grades (Kleihues et al. 1993). The most aggressive tumors, grade 4, also known as glioblastoma multiforme (GBM), appear to arise either de novo as GBMs or present initially as lower grade tumors that progress to higher grades over time . Certain mutations and other properties are highly correlated with one or the other of these two pathogenic pathways. Gliomas that are first detected as grade 4 tumors usually lack an intact INK4a-ARF tumor suppressor locus (Schmidt et al. 1994;He et al. 1995;Ichimura et al. 1996); and they are thus unable to make the two INK4a-ARF gene products, p16 INK4a and p19 ARF , which arrest the cell cycle by different pathways in G 1 and in both G 1 and G 2 , respectively ( Fig. 1; Serrano et al. 1993;Quelle et al. 1995). In addition, these tumors occur frequently in older patients, contain mutations or amplification of the EGFR gene, tend to be more aggressive, and are generally diploid He et al. 1994;Schlegel et al. 1994;Ono et al. 1996;Hayashi et al. 1997). In contrast, gliomas that progress from lower to higher grade lesions are usually wild type for INK4a-ARF , but have an ampl...

Cancer stem cells in glioblastoma—molecular signaling and therapeutic targeting

“…GBMs frequently display EGFR amplification and/or expression of the constitutively active variant EGFRvIII that leads to increased EGFR-Akt signaling in GBM cancer cells (Moscatello et al, 1998;Choe et al, 2003). Overexpression of EGFRvIII in genetically engineered models induces glioma-like tumors (Holland et al, 1998;Ding et al, 2003). It is not then surprising that EGFR activity is required for the maintenance of GSCs as EGFR kinase inhibitors attenuates GSC proliferation and neurosphere formation in vitro (Soeda et al, 2008;Griffero et al, 2009).…”

MicroRNA-146a Inhibits Glioma Development by Targeting Notch1

“…Subsequent activation of EGFR signaling through expression of a constitutively active EGFR vIII mutant transforms these astrocytes into tumorigenic and neurosphere-forming glioma stem-like cells when cultured in defined medium for NSCs (5,24). In vivo, concomitant activation of EGFR and inactivation of Ink4a/Arf and Pten produce rapid-onset and fully penetrant high-grade gliomas that resemble GBM in humans (60), suggesting cooperative actions of these signaling pathways on cell proliferation.…”

Neural development and the ontogeny of central nervous system tumors

“…Expression of a constitutively active form of EGFR that is targeted to either an early, nestin-expressing glial lineage or mature cells that express glial fibrillary acidic protein in Ink4a/ArfA − / − mice induces glioma growth, but the efficiency of glioma induction is higher in the immature, nestin-expressing cells (Holland et al, 1998). The differential increased sensitivity of immature cells was not seen in Ink4a/ArfA − / − cells transduced with EGFR in vitro prior to orthotopic transplantation.…”