PATH-11. PDGFA INITIATES ABERRANT MITOSIS AND MALIGNANT TRANSFORMATION OF NEURAL PROGENITOR CELLS

BACKGROUND Imagining ways to prevent or treat glioblastoma (GBM) have been hindered by a lack of understanding of its pathogenesis. Although platelet derived growth factor-A (PDGFA) overexpression may be an early event, critical details of the biology of GBM, and tools to study its initiation have been lacking. Indeed, many PDGF-driven models replicate its microscopic appearance, but not genomic architecture. Recently, we reported an in vitro model of GBM initiation that overcomes this barrier to authenticity. METHODS We used a method developed to establish neural stem cell cultures to investigate the effects of PDGF-A on cells derived from the subventricular zone (SVZ), a putative region where the cells of origins for GBM are derived. We micro-dissect SVZ tissue from p53-null and wild-type adult mice, culture cells in media supplemented with PDGF-A, and assess cell viability, proliferation, mitotic capacity, and genome stability. RESULTS Paradoxical to its canonical role as a growth factor, we observe abrupt and substantial cell death in PDGF-A. Abnormal mitosis was the first observable alteration and occurred immediately in cells of both p53 wild-type and null genotypes: wild-type cells did not survive in PDGF-A, whereas a fraction of null cells evade apoptosis. Evading cells displayed attenuated proliferation accompanied by early chromosomal gains and losses. After approximately 100 days in PDGF-A, surviving cells suddenly proliferate rapidly, acquire growth factor independence, and become tumorigenic in immune-competent mice. Transformed cells continue to display highly abnormal mitotic phenotypes with complex karyotypes similar to GBM, had a neural progenitor cell (NPC) lineage profile, and were resistant to PDGFR-alpha inhibition. CONCLUSION Abnormal mitosis induced by PDGF-A initiates and perpetuates the genome instability that transforms p53-null neural progenitor cells to yield cancers with the types of recurring chromosomal gains and losses that characterize human GBM.