The DNA Damage Response and Tumorigenesis in the Brain

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Summary - Project 2 Brain tumors are the most common solid malignancies of childhood and are a leading cause of cancer-related death in children. 15-20% of pediatric CNS tumors are high-grade gliomas (HGG), and individuals with these tumors have a 2-year survival rate of 10-30%. Despite extensive research into the molecular basis of gliomagenesis, current therapies remain ineffective, and the majority of patients die from their disease. More effective therapeutic strategies are likely to come from a detailed understanding of glioma pathogenesis. We have developed a unique series of new HGG mouse models, relevant to the human disease, which are characterized by a range of histopathology reflective of the specific defect in the DNA damage response. In Aim 1 of this proposal we will determine the genomic alterations and gene expression profiles that underpin these gliomas, particularly in the context of human disease and other mouse glioma models, either established or under development in other projects in this program. We will also determine the basis for tumor heterogeneity in these models by ascertaining the detailed developmental origins of these gliomas and the relative susceptibility of different neural progenitors to transformation. These analyses will illuminate critical aspects of the pathogenesis of gliomas for which there is a paucity of definitive information. Finally, we will also determine cooperativity in these models with other mutations found in human pediatric HGG, including histone H3 mutations, taking advantage of novel models generated by other projects within the program. In Aim 2 we propose experiments to establish which DNA repair pathways are critical for genome stability at different cortical progenitor stages and how this is linked to chromatin. Because histone mutations and other epigenetic alterations have recently been identified as causative molecular changes in pediatric HGG, our study will be of central importance for understanding connections between DNA damage signaling, epigenetics and tumorigenesis. In Aim 3 we will determine if DNA breaks associated with early replicating fragile sites account for DNA structural alterations central to gliomagenesis. Collectively, findings from this study will provide fundamental new information to delineate glioma biology that will be important for developing targeted therapy for these diseases.