Project description:Notch-targeted gamma-secretase inhibitors (GSIs) exhibited limited efficacy in glioblastoma patients. We identified that farnesyltransferase inhibitors (FTIs) increased sensitivity to GSIs in glioblastoma stem cells. To interrogate the mechanisms mediating the interaction between these two classes of compounds, we studied the impact on gene expression profiles by the combination of tipifarnib (FTI) and RO4929097 (GSI). We found that this combination treatment significantly suppressed genes implicated cell cycle progression. Real-time PCR validated the activities of tipifarnib to modulate expression of cell cycle regulators. We also showed that RO4929097 sensitized glioblastoma stem cells to compounds targeting some of these cell cycle regulators, such as AURKB and CDK4/6. These results suggest that regulation of cell cycle progression partially mediates the ability of FTIs to sensitize glioblastoma stem cells to GSIs.
Project description:We have previously determined the insulin-like growth factor 1 receptor (IGF1R) to be amplified and overexpressed in paediatric glioblastoma. In order to probe the efficacy and mechanisms of action of various inhibitors of the receptor, we have carried out expression profiling of paediatric glioblastoma cells treated with 5x IC50 of the compounds PPP and NVP-AEW541 over a 24 hour time-course.
Project description:Glioblastoma is one of the most malignant brain tumors with poor prognosis and their development and progression are known to be driven by glioblastoma stem cells. Although glioblastoma stem cells lose their cancer stemness properties during cultivation in serum-containing medium, little is known about the molecular mechanisms regulating signaling alteration in relation to reduction of stemness. In order to elucidate the global phosphorylation-related signaling events, we performed a SILAC-based quantitative phosphoproteome analysis of serum-induced dynamics in glioblastoma stem cells established from the tumor tissues of the patient. Among a total of 2,876 phosphorylation sites on 1,584 proteins identified in our analysis, 732 phosphorylation sites on 419 proteins were regulated through the alteration of stem cell characteristics.
Project description:Glioblastomas grow in a rich neurochemical mileu, but targeting neurochemical signaling as a potential therapeutic avenue for these incurable tumors has been underexplored. Thus, we probed patient derived glioblastoma stem cells with a focused library of neurochemicals, to identify new therapeutic targets. Dopaminergic, serotonergic and cholinergic pathways were found to be active against glioblastoma. In particular, dopamine receptor D4 (DRD4) antagonists selectively inhibited glioblastoma growth in vitro and in vivo, in addition to showing synergistic effect with temozolomide. Small molecule or genetic antagonism of DRD4 suppressed ERK1/2 signaling and impaired autophagic flux causing accumulation of autophagic vacuoles and ubiquitinated proteins, associated with G0/G1 cell cycle arrest. These data suggest a new mechanism for treating glioblastoma through modulating dopamine DRD4 signaling. We used Affymetrix microarrays to characterize the mechanism of action for dopamine receptor D4 antagonist (PNU 96415E) in human glioblastoma derived neural stem cells. We treated the human glioblastoma derived neural stem cells (GNS cells) with PNU 96415E for period of 0h, 24h and 48h and extracted RNA for hybridaization on Affymetrix microarrary (Human gene 1.0 ST array) on two GNS lines.
Project description:Overexpression of the Polycomb group protein Enhancer of Zeste Homolog 2 (EZH2) occurs in diverse malignancies, including prostate cancer, breast cancer, and glioblastoma multiforme (GBM) (1). Based on its ability to modulate transcription of key genes implicated in cell cycle control, DNA repair and cell differentiation, EZH2 is believed to play a crucial role in tissue-specific stem cell maintenance and tumor development. Here we show that targeted pharmacologic disruption of EZH2 by the S-adenosylhomocysteine hydrolase inhibitor 3-Deazaneplanocin A (DZNep), or its specific down-regulation by shRNA, strongly impairs GBM cancer stem cell self-renewal in vitro and tumor-initiating capacity in vivo. Using genome-wide expression analysis of DZNep-treated GBM cancer stem cells, we found the expression of c-myc, recently reported to be essential for GBM cancer stem cells, to be strongly repressed upon EZH2 depletion. Specific shRNA-mediated down-regulation of EZH2 in combination with chromatin immunoprecipitation (ChIP) experiments revealed that c-myc is a direct target of EZH2 in GBM cancer stem cells. Taken together, our observations provide evidence that direct transcriptional regulation of c-myc by EZH2 may constitute a novel mechanism underlying GBM cancer stem cell maintenance and suggest that EZH2 may be a valuable new therapeutic target for GBM management. Experiment Overall Design: Three samples of cancer stem-cell enriched gliospheres from primary glioblastoma multiforme cell cultures were treated with DZNep. Untreated gliospheres from the same cultures were used as controls.
Project description:Glioblastoma multiforme is one of the most devastating cancers and presents unique challenges to therapy due to its aggressive behaviour. Cancer stem cells have been described to be the only cell population with tumorogenic capacity in glioblastoma. Therefore, effective therapeutic strategies targeting these cells may be beneficial. We have established different cultures of glioblastoma stem cells (GSCs) derived from surgical specimens and found that, after induction of differentiation, NFκB was activated, which allows intermediate tumor precursor cells to remain cycling. We also showed that blockade of NFκB signaling in differentiating GSCs by different genetic strategies or treatment with small molecule inhibitors, promoted replication arrest, progression to a mature phenotype, mainly neuronal cells, and senescence. This effect was partly mediated by downregulation of the NFκB target gene cyclin D1. Furthermore, intravenous treatment of immunodeficient mice bearing human GSC-derived tumors with a novel small-molecule inhibitor of the NFκB pathway induced senescence of tumor cells but no ultraestructural alterations of the brain parenchymal cells were detected. These findings reveal that activation of NFκB may keep differentiating GSCs from acquiring a mature postmitotic phenotype, thus allowing cell proliferation, and support the rationale for therapeutic strategies aimed at promoting premature senescence in GSCs undergoing differentiation. Gene expression in differentiated cells relative to stem cells in three different glioblastoma cultures