In vitro modeling of glioblastoma initiation using PDGF-AA and p53-null neural progenitors

Abstract

Background Imagining ways to prevent or treat glioblastoma (GBM) has been hindered by a lack of understanding of its pathogenesis. Although overexpression of platelet derived growth factor with two A-chains (PDGF-AA) may be an early event, critical details of the core biology of GBM are lacking. For example, existing PDGF-driven models replicate its microscopic appearance, but not its genomic architecture. Here we report a model that overcomes this barrier to authenticity. Methods Using a method developed to establish neural stem cell cultures, we investigated the effects of PDGF-AA on subventricular zone (SVZ) cells, one of the putative cells of origin of GBM. We microdissected SVZ tissue from p53-null and wild-type adult mice, cultured cells in media supplemented with PDGF-AA, and assessed cell viability, proliferation, genome stability, and tumorigenicity. Results Counterintuitive to its canonical role as a growth factor, we observed abrupt and massive cell death in PDGF-AA: wild-type cells did not survive, whereas a small fraction of null cells evaded apoptosis. Surviving null cells displayed attenuated proliferation accompanied by whole chromosome gains and losses. After approximately 100 days in PDGF-AA, cells suddenly proliferated rapidly, acquired growth factor independence, and became tumorigenic in immune-competent mice. Transformed cells had an oligodendrocyte precursor-like lineage marker profile, were resistant to platelet derived growth factor receptor alpha inhibition, and harbored highly abnormal karyotypes similar to human GBM. Conclusion This model associates genome instability in neural progenitor cells with chronic exposure to PDGF-AA and is the first to approximate the genomic landscape of human GBM and the first in which the earliest phases of the disease can be studied directly.

The HIF1α-PDGFD-PDGFRα axis controls glioblastoma growth at normoxia/mild-hypoxia and confers sensitivity to targeted therapy by echinomycin

“…PDGF-A stimulation or overexpression and PDGF-B overexpression in glial or neural progenitors of mice have been demonstrated each acting a driver for gliomalike neoplasm or glioma-genesis in those mouse models [53][54][55]. However, their roles in the growth and malignancy of human glioma cells including GBM cell lines have not been revealed.…”

Molecular Determinants of Prognosis and Evolution in Diffuse-Lower Grade Astrocytomas

“…Although enrichment of ECM pathways was expected (3) given the invasive nature of LGAs, the prominence of the PDGF pathway was of interest because overexpression of PDGFA has been implicated in the etiology of IDH WT GBM (4) and the PDGFA ligand has been shown to initiate GBM in animal model systems (4,5).…”

“…Given the poor prognosis of IDH WT and PDGFA overexpressing LGAs, we then assessed additional biological features that might explain their propensity for GBM-like behavior. Having recently reported that in vitro exposure to PDGFA leads to chromosomal instability in neural progenitor cells (5) we assessed aneuploidy in LGAs in relation to IDH mutational status and PDGFA expression. In this analysis we observed that IDH WT LGAs were significantly more aneuploid than their IDH mutant counterparts (Fig.…”

“…We then assessed the mutational status of the p53 pathway, because loss or inactivation of TP53 has been hypothesized to cooperate with PDGF signaling to promote IDH WT GBM (4), and because TP53 compromise (i.e., null or heterozygous) is a prerequisite for PDGFA-mediated transformation of neural progenitor cells (5). We first assessed single nucleotide variants (SNVs) in TP53.…”

“…Whether PDGF inhibitors might be effective therapies for IDH WT LGAs is unknown and currently very difficult to test. Testing will require new tools for early detection of WT cases, because in a new in vitro model of GBM initiation by PDGFA, pathway inhibitors are effective only at the earliest stages of transformation (5). ).…”