Project description:Glioblastoma (GBM) is a highly lethal brain tumor presenting as one of two subtypes with distinct clinical histories and molecular profiles. The primary GBM subtype presents acutely as high-grade disease that typically harbors EGFR, PTEN and Ink4a/Arf mutations, and the secondary GBM subtype evolves from the slow progression of low-grade disease that classically possesses PDGF and p53 events1. Here, we show that concomitant CNS-specific deletion of p53 and Pten in the mouse CNS generates a penetrant acute-onset high-grade malignant glioma phenotype with striking clinical, pathological and molecular resemblance to primary GBM in humans. This genetic observation prompted p53 and PTEN mutational analysis in human primary GBM, demonstrating unexpectedly frequent inactivating mutations of p53 as well the expected PTEN mutations. Integrated transcriptomic profling, in silico promoter analysis and functional studies of murine neural stem cells (NSCs) established that dual, but not singular, inactivation of p53 and Pten promotes an undifferentiated state with high renewal potential and drives elevated c-Myc levels and its associated signature. Functional studies validated increased c-Myc activity as a potent contributor to the impaired differentiation and enhanced renewal of p53-Pten null NSCs as well as tumor neurospheres (TNSs) derived from this model. c-Myc also serves to maintain robust tumorigenic potential of p53-Pten null TNSs. These murine modeling studies, together with confirmatory transcriptomic/promoter studies in human primary GBM, validate a pathogenetic role of a common tumor suppressor mutation profile in human primary GBM and establish c-Myc as a key target for cooperative actions of p53 and Pten in the regulation of normal and malignant stem/progenitor cell differentiation, self-renewal and tumorigenic potential. We used microarrays to detail the gene expression difference of the p53-null and p53/Pten-doubly null neural stem cell after differentiation . Experiment Overall Design: transcriptome comparisons of 2 independent p53-null with 3 p53/Pten double-null murine NSCs at 1 day post exposure to the differentiation inducer.

Project description:Cancer results from molecular mutations occurring in specific cell types, thus determining the cell-of-origin is critical for effective cancer treatment. Inferring such information from terminal tumors can be misleading because malignant tumor cells tend to acquire aberrant properties. Animal models are widely used because one can initiate mutations in specific cell types. However, cell-of-mutation that harbors initial molecular changes may not directly transform, rather merely passes along mutations to its progeny cell lineage, which then serves as cell-of-origin and finally transforms into malignancy. Such a problem is exemplified in the glioma field: glioma can be induced either by mutating tumor suppressor genes in neural stem cells (NSCs) or by over-expressing oncogenes in restricted progenitor cells such as oligodendrocyte precursor cells (OPCs). However, for the NSC glioma model, it remains unknown whether NSCs directly transform or simply pass along mutations to OPC lineage for malignancy. Here we use a genetic system termed Mosaic Analysis with Double Markers (MADM) to study the earliest stage of gliomagenesis from mutated NSCs. At an in vivo single-cell resolution, we unbiasedly analyzed tumorigenic potential of NSCs and all cell lineages derived from them. At pathologically undetectable pre-transforming phases, we found no significant aberrant growth of mutant NSCs and their derivatives except for the OPC lineage. We then tracked the tumor progression from earliest stage and confirmed the expansion of OPCs lead to gliomagenesis. Consistently, transcriptome profiling reveals that terminal-stage tumor cells display salient OPC features and resemble human proneural subtype of glioblastoma multiform (GBM). Most importantly, introducing the same mutations directly into OPCs was sufficient for malignant transformation and these tumor cells are indistinguishable in their gene expression profiles from those in which the first mutations were introduced into NSCs. Our findings strongly implicate OPCs as the transforming cell type for glioma even when initial mutations could occur in NSCs, and highlight the importance of analyzing early phases of tumorigenesis to distinguish cell-of-origin from cell-of-mutation. 44K Mouse Development Oligo Microarrays from Agilent Technologies were used for microarray analysis. For each experiment, total RNA was fluorescently labeled and hybridized directly against a common reference sample generated from the RNA pool of four WT P17 mouse brain neocortex.

Project description:Glioblastoma (GBM) is a highly lethal brain tumor presenting as one of two subtypes with distinct clinical histories and molecular profiles. The primary GBM subtype presents acutely as high-grade disease that typically harbors EGFR, PTEN and Ink4a/Arf mutations, and the secondary GBM subtype evolves from the slow progression of low-grade disease that classically possesses PDGF and p53 events1. Here, we show that concomitant CNS-specific deletion of p53 and Pten in the mouse CNS generates a penetrant acute-onset high-grade malignant glioma phenotype with striking clinical, pathological and molecular resemblance to primary GBM in humans. This genetic observation prompted p53 and PTEN mutational analysis in human primary GBM, demonstrating unexpectedly frequent inactivating mutations of p53 as well the expected PTEN mutations. Integrated transcriptomic profling, in silico promoter analysis and functional studies of murine neural stem cells (NSCs) established that dual, but not singular, inactivation of p53 and Pten promotes an undifferentiated state with high renewal potential and drives elevated c-Myc levels and its associated signature. Functional studies validated increased c-Myc activity as a potent contributor to the impaired differentiation and enhanced renewal of p53-Pten null NSCs as well as tumor neurospheres (TNSs) derived from this model. c-Myc also serves to maintain robust tumorigenic potential of p53-Pten null TNSs. These murine modeling studies, together with confirmatory transcriptomic/promoter studies in human primary GBM, validate a pathogenetic role of a common tumor suppressor mutation profile in human primary GBM and establish c-Myc as a key target for cooperative actions of p53 and Pten in the regulation of normal and malignant stem/progenitor cell differentiation, self-renewal and tumorigenic potential. We used microarrays to detail the gene expression difference of the p53-null and p53/Pten-doubly null neural stem cell after differentiation . Keywords: cell type comparison

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INSM1 governs a neuronal progenitor state that drives glioblastoma in a human stem cell model

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