Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 21
Filter
1.
Sci Adv ; 8(39): eabq0593, 2022 Sep 30.
Article in English | MEDLINE | ID: mdl-36179034

ABSTRACT

The coronavirus disease 2019 (COVID-19) Exposure Assessment Tool (CEAT) allows users to compare respiratory relative risk to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for various scenarios, providing understanding of how combinations of protective measures affect risk. CEAT incorporates mechanistic, stochastic, and epidemiological factors including the (i) emission rate of virus, (ii) viral aerosol degradation and removal, (iii) duration of activity/exposure, (iv) inhalation rates, (v) ventilation rates (indoors/outdoors), (vi) volume of indoor space, (vii) filtration, (viii) mask use and effectiveness, (ix) distance between people (taking into account both near-field and far-field effects of proximity), (x) group size, (xi) current infection rates by variant, (xii) prevalence of infection and immunity in the community, (xiii) vaccination rates, and (xiv) implementation of COVID-19 testing procedures. CEAT applied to published studies of COVID-19 transmission events demonstrates the model's accuracy. We also show how health and safety professionals at NASA Ames Research Center used CEAT to manage potential risks posed by SARS-CoV-2 exposures.

2.
medRxiv ; 2022 Mar 16.
Article in English | MEDLINE | ID: mdl-35291295

ABSTRACT

The COVID-19 Exposure Assessment Tool (CEAT) allows users to compare respiratory relative risk to SARS-CoV-2 for various scenarios, providing understanding of how combinations of protective measures affect exposure, dose, and risk. CEAT incorporates mechanistic, stochastic and epidemiological factors including the: 1) emission rate of virus, 2) viral aerosol degradation and removal, 3) duration of activity/exposure, 4) inhalation rates, 5) ventilation rates (indoors/outdoors), 6) volume of indoor space, 7) filtration, 8) mask use and effectiveness, 9) distance between people, 10) group size, 11) current infection rates by variant, 12) prevalence of infection and immunity in the community, 13) vaccination rates of the community, and 14) implementation of COVID-19 testing procedures. Demonstration of CEAT, from published studies of COVID-19 transmission events, shows the model accurately predicts transmission. We also show how health and safety professionals at NASA Ames Research Center used CEAT to manage potential risks posed by SARS-CoV-2 exposures. Given its accuracy and flexibility, the wide use of CEAT will have a long lasting beneficial impact in managing both the current COVID-19 pandemic as well as a variety of other scenarios.

3.
Cancer Lett ; 504: 137-145, 2021 04 28.
Article in English | MEDLINE | ID: mdl-33571541

ABSTRACT

Medulloblastoma is the most common malignant pediatric brain tumor. Tumors having high levels of c-MYC have the worst clinical prognosis, with only a minority of patients surviving. To address this unmet clinical need, we generated a human neural stem cell model of medulloblastoma that recapitulated the most aggressive subtype phenotypically and by mRNA expression profiling. An in silico analysis of these cells identified mTOR inhibitors as potential therapeutic agents. We hypothesized that the orally bioavailable TORC1/2 kinase inhibitor TAK228 would have activity against MYC-driven medulloblastoma. TAK228 inhibited mTORC1/2, decreased cell growth and caused apoptosis in high-MYC medulloblastoma cell lines. Comprehensive metabolic profiling of medulloblastoma orthotopic xenografts showed upregulation of glutathione compared to matched normal brain. TAK228 suppressed glutathione production. Because glutathione is required to detoxify platinum-containing chemotherapy, we hypothesized that TAK228 would cooperate with carboplatin in medulloblastoma. TAK228 synergized with carboplatin to inhibit cell growth and induce apoptosis and extended survival in orthotopic xenografts of high-MYC medulloblastoma. Brain-penetrant TORC1/2 inhibitors and carboplatin may be an effective combination therapy for high-risk medulloblastoma.


Subject(s)
Antineoplastic Agents/therapeutic use , Carboplatin/therapeutic use , Cell Proliferation/physiology , Cerebellar Neoplasms/pathology , Glutathione/metabolism , Mechanistic Target of Rapamycin Complex 1/antagonists & inhibitors , Mechanistic Target of Rapamycin Complex 2/antagonists & inhibitors , Medulloblastoma/pathology , Protein Kinase Inhibitors/therapeutic use , Proto-Oncogene Proteins c-myc/physiology , Animals , Antineoplastic Agents/pharmacology , Cerebellar Neoplasms/drug therapy , Cerebellar Neoplasms/enzymology , Cerebellar Neoplasms/metabolism , Female , Humans , Medulloblastoma/drug therapy , Medulloblastoma/enzymology , Medulloblastoma/metabolism , Mice , Protein Kinase Inhibitors/pharmacology , Xenograft Model Antitumor Assays
4.
Cancer Cell ; 34(3): 396-410.e8, 2018 09 10.
Article in English | MEDLINE | ID: mdl-30205044

ABSTRACT

There is a pressing need to identify therapeutic targets in tumors with low mutation rates such as the malignant pediatric brain tumor medulloblastoma. To address this challenge, we quantitatively profiled global proteomes and phospho-proteomes of 45 medulloblastoma samples. Integrated analyses revealed that tumors with similar RNA expression vary extensively at the post-transcriptional and post-translational levels. We identified distinct pathways associated with two subsets of SHH tumors, and found post-translational modifications of MYC that are associated with poor outcomes in group 3 tumors. We found kinases associated with subtypes and showed that inhibiting PRKDC sensitizes MYC-driven cells to radiation. Our study shows that proteomics enables a more comprehensive, functional readout, providing a foundation for future therapeutic strategies.


Subject(s)
Biomarkers, Tumor/metabolism , Brain Neoplasms/pathology , Medulloblastoma/pathology , Protein Processing, Post-Translational , Adolescent , Adult , Cell Line, Tumor , Child , Child, Preschool , DNA Methylation , DNA-Activated Protein Kinase/metabolism , Female , Gene Expression Profiling , Hedgehog Proteins/metabolism , Humans , Infant , Male , Nuclear Proteins/metabolism , Proteome/metabolism , Proteomics , Proto-Oncogene Proteins c-myc/metabolism , Sequence Analysis, RNA , Young Adult
5.
Handb Clin Neurol ; 148: 785-797, 2018.
Article in English | MEDLINE | ID: mdl-29478614

ABSTRACT

Classically, brain cancers have been graded and diagnosed based on histology and risk stratified by clinical criteria. Recent advances in genomics and epigenomics have ushered in an era of defining cancers based on molecular criteria. These advances have increased our precision of identifying oncogenic driving events and, most importantly, increased our precision at predicting clinical outcome. For the first time in its history, the 2016 revision of the WHO Classification of Tumors of the Central Nervous System included molecular features as tumor classification criteria. Brain tumors can develop in the context of genetic cancer predisposition syndromes, such as Li-Fraumeni or Gorlin syndrome, but by far most commonly arise through the acquisition of somatic mutations and chromosome changes in the malignant cells. By taking a survey across this cancer landscape, certain themes emerge as being common events to drive cancer: DNA damage repair, genomic instability, mechanistic target of rapamycin pathway, sonic hedgehog pathway, hypoxia, and epigenetic dysfunction. Understanding these mechanisms is of paramount importance for improving targeted therapies, and for identifying the right patients for those therapies.


Subject(s)
Brain Neoplasms/diagnosis , Brain Neoplasms/genetics , Genetic Predisposition to Disease , Genomics/methods , Humans
6.
Neurotherapeutics ; 14(2): 265-273, 2017 04.
Article in English | MEDLINE | ID: mdl-28386677

ABSTRACT

Recent advances in cancer genomics have revealed 4 distinct subgroups of medulloblastomas, each with unique transcription profiles, DNA alterations and clinical outcome. Molecular classification of medulloblastomas improves predictions of clinical outcome, allowing more accurate matching of intensity of conventional treatments with chemotherapy and radiation to overall prognosis and setting the stage for the introduction of targeted therapies.


Subject(s)
Cerebellar Neoplasms/classification , Cerebellar Neoplasms/genetics , Medulloblastoma/classification , Medulloblastoma/genetics , Precision Medicine , Signal Transduction , Cerebellar Neoplasms/metabolism , Genomics , Hedgehog Proteins , Humans , Medulloblastoma/metabolism , Mutation , Wnt Signaling Pathway
7.
Cancer Discov ; 7(3): 288-301, 2017 03.
Article in English | MEDLINE | ID: mdl-28213356

ABSTRACT

Medulloblastoma is the most frequent malignant pediatric brain tumor and is divided into at least four subgroups known as WNT, SHH, Group 3, and Group 4. Here, we characterized gene regulation mechanisms in the most aggressive subtype, Group 3 tumors, through genome-wide chromatin and expression profiling. Our results show that most active distal sites in these tumors are occupied by the transcription factor OTX2. Highly active OTX2-bound enhancers are often arranged as clusters of adjacent peaks and are also bound by the transcription factor NEUROD1. These sites are responsive to OTX2 and NEUROD1 knockdown and could also be generated de novo upon ectopic OTX2 expression in primary cells, showing that OTX2 cooperates with NEUROD1 and plays a major role in maintaining and possibly establishing regulatory elements as a pioneer factor. Among OTX2 target genes, we identified the kinase NEK2, whose knockdown and pharmacologic inhibition decreased cell viability. Our studies thus show that OTX2 controls the regulatory landscape of Group 3 medulloblastoma through cooperative activity at enhancer elements and contributes to the expression of critical target genes.Significance: The gene regulation mechanisms that drive medulloblastoma are not well understood. Using chromatin profiling, we find that the transcription factor OTX2 acts as a pioneer factor and, in cooperation with NEUROD1, controls the Group 3 medulloblastoma active enhancer landscape. OTX2 itself or its target genes, including the mitotic kinase NEK2, represent attractive targets for future therapies. Cancer Discov; 7(3); 288-301. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 235.


Subject(s)
Cerebellar Neoplasms/genetics , Chromatin/metabolism , Medulloblastoma/genetics , Otx Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cell Line, Tumor , Cell Survival/genetics , Cerebellar Neoplasms/pathology , Chromatin/genetics , Enhancer Elements, Genetic , Gene Expression Regulation, Neoplastic , Humans , Medulloblastoma/pathology , Mesenchymal Stem Cells/physiology , NIMA-Related Kinases/genetics , NIMA-Related Kinases/metabolism , Otx Transcription Factors/metabolism
8.
Nat Genet ; 49(2): 289-295, 2017 Feb.
Article in English | MEDLINE | ID: mdl-27941797

ABSTRACT

SMARCB1 (also known as SNF5, INI1, and BAF47), a core subunit of the SWI/SNF (BAF) chromatin-remodeling complex, is inactivated in nearly all pediatric rhabdoid tumors. These aggressive cancers are among the most genomically stable, suggesting an epigenetic mechanism by which SMARCB1 loss drives transformation. Here we show that, despite having indistinguishable mutational landscapes, human rhabdoid tumors exhibit distinct enhancer H3K27ac signatures, which identify remnants of differentiation programs. We show that SMARCB1 is required for the integrity of SWI/SNF complexes and that its loss alters enhancer targeting-markedly impairing SWI/SNF binding to typical enhancers, particularly those required for differentiation, while maintaining SWI/SNF binding at super-enhancers. We show that these retained super-enhancers are essential for rhabdoid tumor survival, including some that are shared by all subtypes, such as SPRY1, and other lineage-specific super-enhancers, such as SOX2 in brain-derived rhabdoid tumors. Taken together, our findings identify a new chromatin-based epigenetic mechanism underlying the tumor-suppressive activity of SMARCB1.


Subject(s)
Chromatin Assembly and Disassembly/genetics , Enhancer Elements, Genetic/genetics , SMARCB1 Protein/genetics , Cell Line, Tumor , Chromatin/genetics , DNA-Binding Proteins/genetics , Epigenesis, Genetic/genetics , Humans , Mutation/genetics , Nuclear Proteins/genetics , Rhabdoid Tumor/genetics
9.
Cancer Res ; 76(23): 6774-6777, 2016 12 01.
Article in English | MEDLINE | ID: mdl-27864348

ABSTRACT

Cancer systems biology aims to understand cancer as an integrated system of genes, proteins, networks, and interactions rather than an entity of isolated molecular and cellular components. The inaugural Systems Approaches to Cancer Biology Conference, cosponsored by the Association of Early Career Cancer Systems Biologists and the National Cancer Institute of the NIH, focused on the interdisciplinary field of cancer systems biology and the challenging cancer questions that are best addressed through the combination of experimental and computational analyses. Attendees found that elucidating the many molecular features of cancer inevitably reveals new forms of complexity and concluded that ensuring the reproducibility and impact of cancer systems biology studies will require widespread method and data sharing and, ultimately, the translation of important findings to the clinic. Cancer Res; 76(23); 6774-7. ©2016 AACR.


Subject(s)
Neoplasms , Systems Biology/methods , Humans
10.
Clin Cancer Res ; 22(15): 3903-14, 2016 08 01.
Article in English | MEDLINE | ID: mdl-27012813

ABSTRACT

PURPOSE: We used human stem and progenitor cells to develop a genetically accurate novel model of MYC-driven Group 3 medulloblastoma. We also developed a new informatics method, Disease-model Signature versus Compound-Variety Enriched Response ("DiSCoVER"), to identify novel therapeutics that target this specific disease subtype. EXPERIMENTAL DESIGN: Human neural stem and progenitor cells derived from the cerebellar anlage were transduced with oncogenic elements associated with aggressive medulloblastoma. An in silico analysis method for screening drug sensitivity databases (DiSCoVER) was used in multiple drug sensitivity datasets. We validated the top hits from this analysis in vitro and in vivo RESULTS: Human neural stem and progenitor cells transformed with c-MYC, dominant-negative p53, constitutively active AKT and hTERT formed tumors in mice that recapitulated Group 3 medulloblastoma in terms of pathology and expression profile. DiSCoVER analysis predicted that aggressive MYC-driven Group 3 medulloblastoma would be sensitive to cyclin-dependent kinase (CDK) inhibitors. The CDK 4/6 inhibitor palbociclib decreased proliferation, increased apoptosis, and significantly extended the survival of mice with orthotopic medulloblastoma xenografts. CONCLUSIONS: We present a new method to generate genetically accurate models of rare tumors, and a companion computational methodology to find therapeutic interventions that target them. We validated our human neural stem cell model of MYC-driven Group 3 medulloblastoma and showed that CDK 4/6 inhibitors are active against this subgroup. Our results suggest that palbociclib is a potential effective treatment for poor prognosis MYC-driven Group 3 medulloblastoma tumors in carefully selected patients. Clin Cancer Res; 22(15); 3903-14. ©2016 AACR.


Subject(s)
Cerebellar Neoplasms/genetics , Computational Biology/methods , Genetic Predisposition to Disease , Medulloblastoma/genetics , Models, Biological , Animals , Apoptosis/drug effects , Biomarkers , Cell Line, Tumor , Computer Simulation , Cyclin-Dependent Kinases/antagonists & inhibitors , Cyclin-Dependent Kinases/metabolism , Disease Models, Animal , Drug Discovery , Gene Expression Profiling , Humans , Medulloblastoma/drug therapy , Medulloblastoma/metabolism , Medulloblastoma/pathology , Mice , Neural Stem Cells/metabolism , Phosphorylation , Piperazines/pharmacology , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins c-myc/genetics , Pyridines/pharmacology , Transcriptome , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , Xenograft Model Antitumor Assays
11.
Cancer Cell ; 27(5): 613-5, 2015 May 11.
Article in English | MEDLINE | ID: mdl-25965568

ABSTRACT

Ependymomas have a variable prognosis. In this issue of Cancer Cell, Pajtler and colleagues identify nine subgroups of ependymoma using DNA methylation profiles. Two subgroups, predominately pediatric, are responsible for most of the mortality, with all others having nearly 100% overall survival after 5 years.


Subject(s)
Age Factors , Central Nervous System Neoplasms/pathology , Ependymoma/pathology , Female , Humans , Male
12.
Acta Neuropathol ; 127(4): 593-603, 2014 Apr.
Article in English | MEDLINE | ID: mdl-24196163

ABSTRACT

Neural tumors often express neurotransmitter receptors as markers of their developmental lineage. Although these receptors have been well characterized in electrophysiological, developmental and pharmacological settings, their importance in the maintenance and progression of brain tumors and, importantly, the effect of their targeting in brain cancers remains obscure. Here, we demonstrate high levels of GABRA5, which encodes the α5-subunit of the GABAA receptor complex, in aggressive MYC-driven, "Group 3" medulloblastomas. We hypothesized that modulation of α5-GABAA receptors alters medulloblastoma cell survival and monitored biological and electrophysiological responses of GABRA5-expressing medulloblastoma cells upon pharmacological targeting of the GABAA receptor. While antagonists, inverse agonists and non-specific positive allosteric modulators had limited effects on medulloblastoma cells, a highly specific and potent α5-GABAA receptor agonist, QHii066, resulted in marked membrane depolarization and a significant decrease in cell survival. This effect was GABRA5 dependent and mediated through the induction of apoptosis as well as accumulation of cells in S and G2 phases of the cell cycle. Chemical genomic profiling of QHii066-treated medulloblastoma cells confirmed inhibition of MYC-related transcriptional activity and revealed an enrichment of HOXA5 target gene expression. siRNA-mediated knockdown of HOXA5 markedly blunted the response of medulloblastoma cells to QHii066. Furthermore, QHii066 sensitized GABRA5 positive medulloblastoma cells to radiation and chemotherapy consistent with the role of HOXA5 in directly regulating p53 expression and inducing apoptosis. Thus, our results provide novel insights into the synthetic lethal nature of α5-GABAA receptor activation in MYC-driven/Group 3 medulloblastomas and propose its targeting as a novel strategy for the management of this highly aggressive tumor.


Subject(s)
Cerebellar Neoplasms/metabolism , Gene Expression Regulation, Neoplastic/physiology , Medulloblastoma/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Receptors, Nicotinic/metabolism , Animals , Benzodiazepines/pharmacology , Cell Cycle/genetics , Cell Line, Tumor , Cell Proliferation , Cerebellar Neoplasms/pathology , Cisplatin/pharmacology , Colony-Forming Units Assay , GABA Agonists/pharmacology , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Humans , Medulloblastoma/pathology , Membrane Potentials/drug effects , Membrane Potentials/genetics , Mice , Patch-Clamp Techniques , Receptors, Nicotinic/genetics , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , Xenograft Model Antitumor Assays , gamma-Aminobutyric Acid/pharmacology
13.
Nat Genet ; 46(1): 2-3, 2014 Jan.
Article in English | MEDLINE | ID: mdl-24370739

ABSTRACT

Embryonal tumors with multilayered rosettes (ETMRs) are primitive neuroectodermal tumors arising in infants. A new study shows that these tumors are universally driven by fusion of the promoter of a gene with brain-specific expression, TTYH1, to C19MC, the largest human microRNA cluster, activating a fetal neural development program.


Subject(s)
Brain Neoplasms/genetics , Chromosomes, Human, Pair 19 , DNA (Cytosine-5-)-Methyltransferases/genetics , Membrane Proteins/genetics , MicroRNAs/genetics , Neoplasms, Germ Cell and Embryonal/genetics , Humans , Male , DNA Methyltransferase 3B
14.
Future Oncol ; 8(12): 1597-604, 2012 Dec.
Article in English | MEDLINE | ID: mdl-23231521

ABSTRACT

Medulloblastomas, the most common malignant pediatric brain tumors, are comprised of four molecularly distinct subtypes. However, treatment has yet to exploit these molecular vulnerabilities. Three recent studies sequenced a total of 310 primary tumors and identified that two of the four medulloblastoma subtypes are concomitantly associated with subtype-specific mutations as previously characterized. In contrast, the overwhelming majority of mutations occurred only once in the entire cohort and just 12 genes were recurrently mutated with statistical significance. Perturbations in epigenetic regulation are emerging as a unifying theme in cancer and similarly recurring mutations in epigenetic mechanisms were distributed across all subtypes in medulloblastoma. Designing targeted therapies to such a molecularly diverse disease in the post-genomic era presents new challenges. This will require novel methods to link these nonrecurrent mutations into pathways, and preclinical models that faithfully recapitulate patient driver events. Presently, medulloblastoma reinforces epigenetic mechanisms as a tantalizing therapeutic target in cancers.


Subject(s)
Antineoplastic Agents/pharmacology , Cerebellar Neoplasms/genetics , Epigenesis, Genetic , Medulloblastoma/genetics , Animals , Cerebellar Neoplasms/pathology , Child , Disease Models, Animal , Drug Design , Genomic Instability , Humans , Medulloblastoma/pathology , Mutation
15.
Nature ; 488(7409): 106-10, 2012 Aug 02.
Article in English | MEDLINE | ID: mdl-22820256

ABSTRACT

Medulloblastomas are the most common malignant brain tumours in children. Identifying and understanding the genetic events that drive these tumours is critical for the development of more effective diagnostic, prognostic and therapeutic strategies. Recently, our group and others described distinct molecular subtypes of medulloblastoma on the basis of transcriptional and copy number profiles. Here we use whole-exome hybrid capture and deep sequencing to identify somatic mutations across the coding regions of 92 primary medulloblastoma/normal pairs. Overall, medulloblastomas have low mutation rates consistent with other paediatric tumours, with a median of 0.35 non-silent mutations per megabase. We identified twelve genes mutated at statistically significant frequencies, including previously known mutated genes in medulloblastoma such as CTNNB1, PTCH1, MLL2, SMARCA4 and TP53. Recurrent somatic mutations were newly identified in an RNA helicase gene, DDX3X, often concurrent with CTNNB1 mutations, and in the nuclear co-repressor (N-CoR) complex genes GPS2, BCOR and LDB1. We show that mutant DDX3X potentiates transactivation of a TCF promoter and enhances cell viability in combination with mutant, but not wild-type, ß-catenin. Together, our study reveals the alteration of WNT, hedgehog, histone methyltransferase and now N-CoR pathways across medulloblastomas and within specific subtypes of this disease, and nominates the RNA helicase DDX3X as a component of pathogenic ß-catenin signalling in medulloblastoma.


Subject(s)
Cerebellar Neoplasms/genetics , Exome/genetics , Genome, Human/genetics , Medulloblastoma/genetics , Mutation/genetics , Cerebellar Neoplasms/classification , Child , DEAD-box RNA Helicases/chemistry , DEAD-box RNA Helicases/genetics , DEAD-box RNA Helicases/metabolism , DNA Helicases/chemistry , DNA Helicases/genetics , DNA-Binding Proteins/genetics , Hedgehog Proteins/metabolism , Histone Methyltransferases , Histone-Lysine N-Methyltransferase/genetics , Histone-Lysine N-Methyltransferase/metabolism , Humans , Intracellular Signaling Peptides and Proteins/genetics , LIM Domain Proteins/genetics , Medulloblastoma/classification , Models, Molecular , Neoplasm Proteins/genetics , Nuclear Proteins/chemistry , Nuclear Proteins/genetics , Patched Receptors , Patched-1 Receptor , Promoter Regions, Genetic/genetics , Protein Structure, Tertiary/genetics , Proto-Oncogene Proteins/genetics , Receptors, Cell Surface/genetics , Repressor Proteins/genetics , Signal Transduction , TCF Transcription Factors/metabolism , Transcription Factors/chemistry , Transcription Factors/genetics , Tumor Suppressor Protein p53/genetics , Wnt Proteins/metabolism , beta Catenin/genetics , beta Catenin/metabolism
17.
Acta Neuropathol ; 123(4): 539-52, 2012 Apr.
Article in English | MEDLINE | ID: mdl-22402744

ABSTRACT

Medulloblastomas are the most common malignant brain tumors in children. Several large-scale genomic studies have detailed their heterogeneity, defining multiple subtypes with unique molecular profiles and clinical behavior. Increased expression of the miR-183~96~182 cluster of microRNAs has been noted in several subgroups, including the most clinically aggressive subgroup associated with genetic amplification of MYC. To understand the contribution of miR-183~96~182 to the pathogenesis of this aggressive subtype of medulloblastoma, we analyzed global gene expression and proteomic changes that occur upon modulation of miRNAs in this cluster individually and as a group in MYC-amplified medulloblastoma cells. Knockdown of the full miR-183~96~182 cluster results in enrichment of genes associated with apoptosis and dysregulation of the PI3K/AKT/mTOR signaling axis. Conversely, there is a relative enrichment of pathways associated with migration, metastasis and epithelial to mesenchymal transition, as well as pathways associated with dysfunction of DNA repair in cells with preserved miR-183 cluster expression. Immunocytochemistry and FACS analysis confirm induction of apoptosis upon knockdown of the miR-183 cluster. Importantly, cell-based migration and invasion assays verify the positive regulation of cell motility/migration by the miR-183 cluster, which is largely mediated by miR-182. We show that the effects on cell migration induced by the miR-183 cluster are coupled to the PI3K/AKT/mTOR pathway through differential regulation of AKT1 and AKT2 isoforms. Furthermore, we show that rapamycin inhibits cell motility/migration in medulloblastoma cells and phenocopies miR-183 cluster knockdown. Thus, the miR-183 cluster regulates multiple biological programs that converge to support the maintenance and metastatic potential of medulloblastoma.


Subject(s)
Apoptosis/genetics , Cell Movement/genetics , Cell Proliferation , MicroRNAs/genetics , Signal Transduction/genetics , Cell Cycle/genetics , Cell Line, Tumor , Cell Migration Assays , Cerebellar Neoplasms/pathology , Comet Assay , Computational Biology , Gene Expression Regulation, Neoplastic/genetics , Gene Knockdown Techniques , Humans , Medulloblastoma/pathology , Proteomics , Proto-Oncogene Proteins c-myc/genetics , Transfection
18.
Cancer Cell ; 20(2): 133-4, 2011 Aug 16.
Article in English | MEDLINE | ID: mdl-21840477

ABSTRACT

Ependymomas are common childhood brain tumors, but little is known about their underlying biology. In this issue of Cancer Cell, Witt et al. present that posterior fossa ependymomas comprise two distinct molecular subtypes, each with unique gene expression signatures, different levels of genomic instability, and different prognosis.

19.
Dev Biol ; 350(2): 429-40, 2011 Feb 15.
Article in English | MEDLINE | ID: mdl-21147085

ABSTRACT

Sox1, Sox2 and Sox3, the three members of the SoxB1 subgroup of transcription factors, have similar sequences, expression patterns and overexpression phenotypes. Thus, it has been suggested that they have redundant roles in the maintenance of neural stem cells in development. However, the long-term effect of overexpression or their function in combination with their putative co-factor Oct4 has not been tested. Here, we show that overexpression of sox1, sox2, sox3 or oct91, the Xenopus homologue of Oct4, results in the same phenotype: an expanded neural plate at the expense of epidermis and delayed neurogenesis. However, each of these proteins induced a unique profile of neural markers and the combination of Oct91 with each SoxB1 protein had different effects, as did continuous misexpression of the proteins. Overexpression studies indicate that Oct91 preferentially cooperates with Sox2 to maintain neural progenitor marker expression, while knockdown of Oct91 inhibits neural induction driven by either Sox2 or Sox3. Continuous expression of Sox1 and Sox2 in transgenic embryos represses neuron differentiation and inhibits anterior development while increasing cell proliferation. Constitutively active Sox3, however, leads to increased apoptosis suggesting that it functions as a tumor suppressor. While the SoxB1s have overlapping functions, they are not strictly redundant as they induce different sets of genes and are likely to partner with different proteins to maintain progenitor identity.


Subject(s)
Neurogenesis , Octamer Transcription Factor-3/physiology , SOXB1 Transcription Factors/physiology , Xenopus Proteins/physiology , Xenopus laevis/embryology , Animals
20.
Mech Dev ; 126(1-2): 42-55, 2009.
Article in English | MEDLINE | ID: mdl-18992330

ABSTRACT

The SRY-related, HMG box SoxB1 transcription factors are highly homologous, evolutionarily conserved proteins that are expressed in neuroepithelial cells throughout neural development. SoxB1 genes are down-regulated as cells exit the cell-cycle to differentiate and are considered functionally redundant in maintaining neural precursor populations. However, little is known about Sox3 function and its mode of action during primary neurogenesis. Using gain and loss-of-function studies, we analyzed Sox3 function in detail in Xenopus early neural development and compared it to that of Sox2. Through these studies we identified the first targets of a SoxB1 protein during primary neurogenesis. Sox3 functions as an activator to induce expression of the early neural genes, sox2 and geminin in the absence of protein synthesis and to indirectly inhibit the Bmp target Xvent2. As a result, Sox3 increases cell proliferation, delays neurogenesis and inhibits epidermal and neural crest formation to expand the neural plate. Our studies indicate that Sox3 and 2 have many similar functions in this process including the ability to activate expression of geminin in naïve ectodermal explants. However, there are some differences; Sox3 activates the expression of sox2, while Sox2 does not activate expression of sox3 and sox3 is uniquely expressed throughout the ectoderm prior to neural induction suggesting a role in neural competence. With morpholino-mediated knockdown of Sox3, we demonstrate that it is required for induction of neural tissue by BMP inhibition. Together these data indicate that Sox3 has multiple roles in early neural development including as a factor required for nogginmediated neural induction.


Subject(s)
Ectoderm/metabolism , Neurons/metabolism , Stem Cells/metabolism , Transcription Factors/metabolism , Xenopus laevis/embryology , Xenopus laevis/metabolism , Animals , Biomarkers/metabolism , Bone Morphogenetic Proteins/metabolism , Carrier Proteins/genetics , Carrier Proteins/metabolism , Cell Differentiation , Cell Proliferation , Ectoderm/embryology , Embryo, Nonmammalian/cytology , Embryo, Nonmammalian/embryology , Embryo, Nonmammalian/metabolism , Gene Expression Regulation, Developmental , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Neurons/cytology , SOXB1 Transcription Factors/genetics , SOXB1 Transcription Factors/metabolism , Signal Transduction , Stem Cells/cytology , Transcription Factors/genetics , Xenopus Proteins/genetics , Xenopus Proteins/metabolism , Xenopus laevis/genetics
SELECTION OF CITATIONS
SEARCH DETAIL
...