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Small-molecule inhibitors targeting growth factor receptors have failed to show efficacy for brain cancers,potentially due to their inability to achieve sufficient drug levels in the CNS. Targeting non-oncogene tumor co-dependencies provides an alternative approach,particularly if drugs with high brain penetration can be identified. Here we demonstrate that the highly lethal brain cancer glioblastoma (GBM) is remarkably dependent on cholesterol for survival,rendering these tumors sensitive to Liver X receptor (LXR) agonist-dependent cell death. We show that LXR-623,a clinically viable,highly brain-penetrant LXRα-partial/LXRβ-full agonist selectively kills GBM cells in an LXRβ- and cholesterol-dependent fashion,causing tumor regression and prolonged survival in mouse models. Thus,a metabolic co-dependency provides a pharmacological means to kill growth factor-activated cancers in the CNS. View Publication

Global cerebral ischemia induces selective acute neuronal injury of the CA1 region of the hippocampus. The type of cell death that ensues may include different programmed cell death mechanisms namely apoptosis and necroptosis,a recently described type of programmed necrosis. We investigated whether necroptosis contributes to hippocampal neuronal death following oxygen-glucose deprivation (OGD),an in vitro model of global ischemia. We observed that OGD induced a death receptor (DR)-dependent component of necroptotic cell death in primary cultures of hippocampal neurons. Additionally,we found that this ischemic challenge upregulated the receptor-interacting protein kinase 3 (RIP3) mRNA and protein levels,with a concomitant increase of the RIP1 protein. Together,these two related proteins form the necrosome,the complex responsible for induction of necroptotic cell death. Interestingly,we found that caspase-8 mRNA,a known negative regulator of necroptosis,was transiently decreased following OGD. Importantly,we observed that the OGD-induced increase in the RIP3 protein was paralleled in an in vivo model of transient global cerebral ischemia,specifically in the CA1 area of the hippocampus. Moreover,we show that the induction of endogenous RIP3 protein levels influenced neuronal toxicity since we found that RIP3 knock-down (KD) abrogated the component of OGD-induced necrotic neuronal death while RIP3 overexpression exacerbated neuronal death following OGD. Overexpression of RIP1 also had deleterious effects following the OGD challenge. Taken together,our results highlight that cerebral ischemia activates transcriptional changes that lead to an increase in the endogenous RIP3 protein level which might contribute to the formation of the necrosome complex and to the subsequent component of necroptotic neuronal death that follows ischemic injury. View Publication

The PI3K/AKT/mTOR pathway is commonly over activated in glioblastoma (GBM),and Rictor was shown to be an important regulator downstream of this pathway. EGFR overexpression is also frequently found in GBM tumors,and both EGFR and Rictor are associated with increased proliferation,invasion,metastasis and poor prognosis. This research evaluated in vitro and in vivo whether the combined silencing of EGFR and Rictor would result in therapeutic benefits. The therapeutic potential of targeting these proteins in combination with conventional agents with proven activity in GBM patients was also assessed. In vitro validation studies were carried out using siRNA-based gene silencing methods in a panel of three commercially available human GBM cell lines,including two PTEN mutant lines (U251MG and U118MG) and one PTEN-wild type line (LN229). The impact of EGFR and/or Rictor silencing on cell migration and sensitivity to chemotherapeutic drugs in vitro was determined. In vivo validation of these studies was focused on EGFR and/or Rictor silencing achieved using doxycycline-inducible shRNA-expressing U251MG cells implanted orthotopically in Rag2M mice brains. Target silencing,tumor size and tumor cell proliferation were assessed by quantification of immunohistofluorescence-stained markers. siRNA-mediated silencing of EGFR and Rictor reduced U251MG cell migration and increased sensitivity of the cells to irinotecan,temozolomide and vincristine. In LN229,co-silencing of EGFR and Rictor resulted in reduced cell migration,and increased sensitivity to vincristine and temozolomide. In U118MG,silencing of Rictor alone was sufficient to increase this line's sensitivity to vincristine and temozolomide. In vivo,while the silencing of EGFR or Rictor alone had no significant effect on U251MG tumor growth,silencing of EGFR and Rictor together resulted in a complete eradication of tumors. These data suggest that the combined silencing of EGFR and Rictor should be an effective means of treating GBM. View Publication

PURPOSE p53 pathway alterations are key molecular events in glioblastoma (GBM). MDM2 inhibitors increase expression and stability of p53 and are presumed to be most efficacious in patients with TP53 wild-type and MDM2-amplified cancers. However,this biomarker hypothesis has not been tested in patients or patient-derived models for GBM. EXPERIMENTAL DESIGN We performed a preclinical evaluation of RG7112 MDM2 inhibitor,across a panel of 36 patient-derived GBM cell lines (PDCL),each genetically characterized according to their P53 pathway status. We then performed a pharmacokinetic (PK) profiling of RG7112 distribution in mice and evaluated the therapeutic activity of RG7112 in orthotopic and subcutaneous GBM models. RESULTS MDM2-amplified PDCLs were 44 times more sensitive than TP53-mutated lines that showed complete resistance at therapeutically attainable concentrations (avg. IC50 of 0.52 μmol/L vs. 21.9 μmol/L). MDM4-amplified PDCLs were highly sensitive but showed intermediate response (avg. IC50 of 1.2 μmol/L),whereas response was heterogeneous in TP53 wild-type PDCLs with normal MDM2/4 levels (avg. IC50 of 7.7 μmol/L). In MDM2-amplified lines,RG7112 restored p53 activity inducing robust p21 expression and apoptosis. PK profiling of RG7112-treated PDCL intracranial xenografts demonstrated that the compound significantly crosses the blood-brain and the blood-tumor barriers. Most importantly,treatment of MDM2-amplified/TP53 wild-type PDCL-derived model (subcutaneous and orthotopic) reduced tumor growth,was cytotoxic,and significantly increased survival. CONCLUSIONS These data strongly support development of MDM2 inhibitors for clinical testing in MDM2-amplified GBM patients. Moreover,significant efficacy in a subset of non-MDM2-amplified models suggests that additional markers of response to MDM2 inhibitors must be identified. View Publication

Glioblastoma (GBM) is the most common and deadly malignant brain cancer,with a median survival of <2 years. GBM displays a cellular complexity that includes brain tumour-initiating cells (BTICs),which are considered as potential key targets for GBM therapies. Here we show that the transcription factors FOXG1 and Groucho/TLE are expressed in poorly differentiated astroglial cells in human GBM specimens and in primary cultures of GBM-derived BTICs,where they form a complex. FOXG1 knockdown in BTICs causes downregulation of neural stem/progenitor and proliferation markers,increased replicative senescence,upregulation of astroglial differentiation genes and decreased BTIC-initiated tumour growth after intracranial transplantation into host mice. These effects are phenocopied by Groucho/TLE knockdown or dominant inhibition of the FOXG1:Groucho/TLE complex. These results provide evidence that transcriptional programmes regulated by FOXG1 and Groucho/TLE are important for BTIC-initiated brain tumour growth,implicating FOXG1 and Groucho/TLE in GBM tumourigenesis. View Publication

BACKGROUND Alzheimer's disease (AD) is characterized by progressive memory loss and impaired cognitive function. Early-onset familial forms of the disease (FAD) are caused by inheritance of mutant genes encoding presenilin 1 (PS1) variants. We have demonstrated that prion promoter (PrP)-driven expression of human FAD-linked PS1 variants in mice leads to impairments in environmental enrichment (EE)-induced adult hippocampal neural progenitor cell (AHNPC) proliferation and neuronal differentiation,and have provided evidence that accessory cells in the hippocampal niche expressing PS1 variants may modulate AHNPC phenotypes,in vivo. While of significant interest,these latter studies relied on transgenic mice that express human PS1 variant transgenes ubiquitously and at high levels,and the consequences of wild type or mutant PS1 expressed under physiologically relevant levels on EE-mediated AHNPC phenotypes has not yet been tested. RESULTS To assess the impact of mutant PS1 on EE-induced AHNPC phenotypes when expressed under physiological levels,we exposed adult mice that constitutively express the PSEN1 M146V mutation driven by the endogenous PSEN1 promoter (PS1 M146V knock-in" (KI) mice) to standard or EE-housed conditions. We show that in comparison to wild type PS1 mice AHNPCs in mice carrying homozygous (PS1M146V/M146V) or heterozygous (PS1M146V/+) M146V mutant alleles fail to exhibit EE-induced proliferation and commitment towards neurogenic lineages. More importantly we report that the survival of newborn progenitors are diminished in PS1 M146V KI mice exposed to EE-conditions compared to respective EE wild type controls. CONCLUSIONS Our findings reveal that expression at physiological levels achieved by a single PS1 M146V allele is sufficient to impair EE-induced AHNPC proliferation survival and neuronal differentiation in vivo. These results and our finding that microglia expressing a single PS1 M146V allele impairs the proliferation of wild type AHNPCs in vitro argue that expression of mutant PS1 in the AHNPC niche impairs AHNPCs phenotypes in a dominant non-cell autonomous manner. View Publication

BACKGROUND Epigenetic modifications,particularly DNA methylation and posttranslational histone modifications regulate heritable changes in transcription without changes in the DNA sequence. Despite a number of studies showing clear links between environmental factors and DNA methylation,little is known about the effect of environmental factors on the recently identified histone lysine methylation. Since their identification numerous studies have establish critical role played by these enzymes in mammalian development. OBJECTIVES Identification of the Jumonji (Jmj) domain containing histone lysine demethylase have added a new dimension to epigenetic control of gene expression by dynamic regulation of histone methylation marks. The objective of our study was to evaluate the effect of prohexadione and trinexapac,widely used plant growth regulators of the acylcyclohexanediones class,on the enzymatic activity of histone lysine demethylases and histone modifications during the neural stem/progenitor cell differentiation. METHODS Here we show that prohexadione,but not trinexapac,directly inhibits non-heme iron (II),2-oxoglutarate-dependent histone lysine demethylase such as Jmjd2a. We used molecular modeling to show binding of prohexadione to Jmjd2a. We also performed in vitro demethylation assays to show the inhibitory effect of prohexadione on Jmjd2a. Further we tested this molecule in cell culture model of mouse hippocampal neural stem/progenitor cells to demonstrate its effect toward neuronal proliferation and differentiation. RESULTS Molecular modeling studies suggest that prohexadione binds to the 2-oxoglutarate binding site of Jmjd2a demethylase. Treatment of primary neural stem/progenitor cells with prohexadione showed a concentration dependent reduction in their proliferation. Further,the prohexadione treated neurospheres were induced toward neurogenic lineage upon differentiation. CONCLUSIONS Our results describe an important chemico-biological interaction of prohexadione,in light of critical roles played by histone lysine demethylases in human health and diseases. View Publication

Cell culture is one of the most common methods used to recapitulate a human disease environment in a laboratory setting. Cell culture techniques are used to grow and maintain cells of various types including those derived from primary tissues,such as stem cells and cancer tumors. However,a major confounding factor with cell culture is the use of serum and animal (xeno) products in the media. The addition of animal products introduces batch and lot variations that lead to experimental variability,confounds studies with therapeutic outcomes for cultured cells,and represents a major cost associated with cell culture. Here we report a commercially available serum-free,albumin-free,and xeno free (XF) media (Neuro-Pure(TM)) that is more cost-effective than other commercial medias. Neuro-Pure was used to maintain and differentiate various cells of neuronal lineages,fibroblasts,as well as specific cancer cell lines; without the use of contaminants such serum,albumin,and animal products. Neuro-Pure allows for a controlled and reproducible cell culture environment that is applicable to translational medicine and general tissue culture. View Publication

Specific neuronal types derived from embryonic stem cells (ESCs) can facilitate mechanistic studies and potentially aid in regenerative medicine. Existing induction methods,however,mostly rely on the effects of the combined action of multiple added growth factors,which generally tend to result in mixed populations of neurons. Here,we report that overexpression of specific transcription factors (TFs) in ESCs can rather guide the differentiation of ESCs towards specific neuron lineages. Analysis of data on gene expression changes 2 d after induction of each of 185 TFs implicated candidate TFs for further ESC differentiation studies. Induction of 23 TFs (out of 49 TFs tested) for 6 d facilitated neural differentiation of ESCs as inferred from increased proportion of cells with neural progenitor marker PSA-NCAM. We identified early activation of the Notch signaling pathway as a common feature of most potent inducers of neural differentiation. The majority of neuron-like cells generated by induction of Ascl1,Smad7,Nr2f1,Dlx2,Dlx4,Nr2f2,Barhl2,and Lhx1 were GABA-positive and expressed other markers of GABAergic neurons. In the same way,we identified Lmx1a and Nr4a2 as inducers for neurons bearing dopaminergic markers and Isl1,Fezf2,and St18 for cholinergic motor neurons. A time-course experiment with induction of Ascl1 showed early upregulation of most neural-specific messenger RNA (mRNA) and microRNAs (miRNAs). Sets of Ascl1-induced mRNAs and miRNAs were enriched in Ascl1 targets. In further studies,enrichment of cells obtained with the induction of Ascl1,Smad7,and Nr2f1 using microbeads resulted in essentially pure population of neuron-like cells with expression profiles similar to neural tissues and expressed markers of GABAergic neurons. In summary,this study indicates that induction of transcription factors is a promising approach to generate cultures that show the transcription profiles characteristic of specific neural cell types. View Publication

MicroRNA-10b (miR-10b) is a unique oncogenic miRNA that is highly expressed in all GBM subtypes,while absent in normal neuroglial cells of the brain. miR-10b inhibition strongly impairs proliferation and survival of cultured glioma cells,including glioma-initiating stem-like cells (GSC). Although several miR-10b targets have been identified previously,the common mechanism conferring the miR-10b-sustained viability of GSC is unknown. Here,we demonstrate that in heterogeneous GSC,miR-10b regulates cell cycle and alternative splicing,often through the non-canonical targeting via 5'UTRs of its target genes,including MBNL1-3,SART3,and RSRC1. We have further assessed the inhibition of miR-10b in intracranial human GSC-derived xenograft and murine GL261 allograft models in athymic and immunocompetent mice. Three delivery routes for the miR-10b antisense oligonucleotide inhibitors (ASO),direct intratumoral injections,continuous osmotic delivery,and systemic intravenous injections,have been explored. In all cases,the treatment with miR-10b ASO led to targets' derepression,and attenuated growth and progression of established intracranial GBM. No significant systemic toxicity was observed upon ASO administration by local or systemic routes. Our results indicate that miR-10b is a promising candidate for the development of targeted therapies against all GBM subtypes. View Publication