GFAP Promoter Driven Transgenic Expression of PDGFB in the Mouse Brain Leads to Glioblastoma in a Trp53 null Background

Glioblastomas are the most common and malignant astrocytic brain tumors in human adults. The tumor suppressor gene TP53 is commonly mutated and/or lost in astrocytic brain tumors and the TP53 alterations are often found in combination with excessive growth factor signaling via PDGF/PDGFR alpha. Here, we have generated transgenic mice over-expressing human PDGFB in brain, under control of the human GFAP promoter. These mice showed no phenotype, but on a Trp53 null background a majority of them developed brain tumors. This occurred at 2-6 months of age and tumors displayed human glioblastoma-like features with integrated development of Pdgfr alpha(+) tumor cells and Pdgfr beta(+)/Nestin(+) vasculature. The transgene was expressed in sub-ependymal astrocytic cells, in glia limitans, and in astrocytes throughout the brain substance, and subsequently, microscopic tumor lesions were initiated equally in all these areas. With tumor size, there was an increase in Nestin positivity and variability in lineage markers. These results indicate an unexpected plasticity of all astrocytic cells in the adult brain, not only of SVZ cells. The results also indicate a contribution of widely distributed Pdgfr alpha(+) precursor cells in the tumorigenic process. (C) 2008 Wiley-Liss, Inc.