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  • Hawkins, Cynthia  (41)
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  • 1
    In: Neuro-Oncology, 2014, Vol. 16(suppl5), pp.v214-v214
    Description: Aggressive cancer cells are characterized by high rates glycolysis and lactate production, a metabolic reprogramming event known as the Warburg effect. This ultimately provides tumor cells including GBM the most malignant and common primary brain tumor with intermediate metabolites for anabolic processes, cell proliferation and invasion. However, these biological processes generate oxidative stress that must be balanced through detoxification of reactive oxygen species (ROS). Using an unbiased retroviral loss of function screen in pre-disposed but non-transformed astrocytes, we demonstrate that PTEN Induced Kinase 1 (PINK1), a mitochondrial kinase is a crucial regulator of the Warburg effect. Mechanistically, loss of PINK1 mediates metabolic reprogramming in normal human astrocytes through ROS dependent hypoxia-inducible factor-1α (HIF1α) stabilization, a transcription factor that controls expression of several aerobic glycolysis genes. Overexpression of PINK1 in GBM cells suppresses ROS, HIF1a and the Warburg effect in vitro and in vivo. Surprisingly, loss of PINK1 in GBM cells that retain PINK1 expression increases oxidative stress and reduces cell viability suggesting ROS balance and maintenance is critical in tumor cells and can be therapeutically exploited. PINK1 loss was observed in GBM and correlated with poor patient survival. Collectively, we demonstrate that PINK1 is a negative regulator of the Warburg effect.
    Keywords: Detoxification ; Glioblastoma ; Astrocytes ; Pten-Induced Putative Kinase ; Mitochondria ; Oncology ; Metabolites ; Pten Protein ; Tumor Cells ; Cancer ; Brain Tumors ; Reactive Oxygen Species ; Oxidative Stress ; Transcription Factors ; Lactic Acid ; Cell Proliferation ; Glycolysis ; Neurobiology;
    ISSN: 1522-8517
    E-ISSN: 1523-5866
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  • 2
    Language: English
    In: Pediatric Blood & Cancer, July, 2014, Vol.61(7), p.1190(5)
    Keywords: Medulloblastoma -- Diagnosis ; Children'S Hospitals
    ISSN: 1545-5009
    ISSN: 20450907
    E-ISSN: 20450915
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  • 3
    Language: English
    In: Cancer Research, 04/15/2013, Vol.73(8 Supplement), pp.3552-3552
    ISSN: 0008-5472
    E-ISSN: 1538-7445
    Source: CrossRef
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  • 4
    Language: English
    In: Cancer Research, 08/01/2015, Vol.75(15 Supplement), pp.3551-3551
    ISSN: 0008-5472
    E-ISSN: 1538-7445
    Source: CrossRef
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  • 5
    Language: English
    In: Clinical cancer research : an official journal of the American Association for Cancer Research, 15 August 2015, Vol.21(16), pp.3750-8
    Description: Myxopapillary ependymoma (MPE) is a distinct histologic variant of ependymoma arising commonly in the spinal cord. Despite an overall favorable prognosis, distant metastases, subarachnoid dissemination, and late recurrences have been reported. Currently, the only effective treatment for MPE is gross-total resection. We characterized the genomic and transcriptional landscape of spinal ependymomas in an effort to delineate the genetic basis of this disease and identify new leads for therapy. Gene expression profiling was performed on 35 spinal ependymomas, and copy number profiling was done on an overlapping cohort of 46 spinal ependymomas. Functional validation experiments were performed on tumor lysates consisting of assays measuring pyruvate kinase M activity (PKM), hexokinase activity (HK), and lactate production. At a gene expression level, we demonstrate that spinal grade II and MPE are molecularly and biologically distinct. These are supported by specific copy number alterations occurring in each histologic variant. Pathway analysis revealed that MPE are characterized by increased cellular metabolism, associated with upregulation of HIF1α. These findings were validated by Western blot analysis demonstrating increased protein expression of HIF1α, HK2, PDK1, and phosphorylation of PDHE1A. Functional assays were performed on MPE lysates, which demonstrated decreased PKM activity, increased HK activity, and elevated lactate production. Our findings suggest that MPE may be driven by a Warburg metabolic phenotype. The key enzymes promoting the Warburg phenotype: HK2, PKM2, and PDK are targetable by small-molecule inhibitors/activators, and should be considered for evaluation in future clinical trials for MPE.
    Keywords: DNA Copy Number Variations -- Genetics ; Ependymoma -- Genetics ; Spinal Neoplasms -- Genetics ; Transcriptome -- Genetics
    ISSN: 1078-0432
    E-ISSN: 15573265
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  • 6
    Language: English
    In: Acta Neuropathologica, 2012, Vol.123(4), pp.615-626
    Description: The diagnosis of medulloblastoma likely encompasses several distinct entities, with recent evidence for the existence of at least four unique molecular subgroups that exhibit distinct genetic, transcriptional, demographic, and clinical features. Assignment of molecular subgroup through routine profiling of high-quality RNA on expression microarrays is likely impractical in the clinical setting. The planning and execution of medulloblastoma clinical trials that stratify by subgroup, or which are targeted to a specific subgroup requires technologies that can be economically, rapidly, reliably, and reproducibly applied to formalin-fixed paraffin embedded (FFPE) specimens. In the current study, we have developed an assay that accurately measures the expression level of 22 medulloblastoma subgroup-specific signature genes (CodeSet) using nanoString nCounter Technology. Comparison of the nanoString assay with Affymetrix expression array data on a training series of 101 medulloblastomas of known subgroup demonstrated a high concordance (Pearson correlation r  = 0.86). The assay was validated on a second set of 130 non-overlapping medulloblastomas of known subgroup, correctly assigning 98% (127/130) of tumors to the appropriate subgroup. Reproducibility was demonstrated by repeating the assay in three independent laboratories in Canada, the United States, and Switzerland. Finally, the nanoString assay could confidently predict subgroup in 88% of recent FFPE cases, of which 100% had accurate subgroup assignment. We present an assay based on nanoString technology that is capable of rapidly, reliably, and reproducibly assigning clinical FFPE medulloblastoma samples to their molecular subgroup, and which is highly suited for future medulloblastoma clinical trials.
    Keywords: Medulloblastoma ; Molecular classification ; Clinical trials ; NanoString
    ISSN: 0001-6322
    E-ISSN: 1432-0533
    Source: Springer Science & Business Media B.V.
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  • 7
    In: Nature, 2012, Vol.488(7409), p.49
    Description: Medulloblastoma, the most common malignant paediatric brain tumour, is currently treated with nonspecific cytotoxic therapies including surgery, whole-brain radiation, and aggressive chemotherapy. As medulloblastoma exhibits marked intertumoural heterogeneity, with at least four distinct molecular variants, previous attempts to identify targets for therapy have been underpowered because of small samples sizes. Here we report somatic copy number aberrations (SCNAs) in 1,087 unique medulloblastomas. SCNAs are common in medulloblastoma, and are predominantly subgroup-enriched. The most common region of focal copy number gain is a tandem duplication of SNCAIP, a gene associated with Parkinson's disease, which is exquisitely restricted to Group 4a. Recurrent translocations of PVT1, including PVT1-MYC and PVT1-NDRG1, that arise through chromothripsis are restricted to Group 3. Numerous targetable SCNAs, including recurrent events targeting TGF-[beta] signalling in Group 3, and NF-[kappa]B signalling in Group 4, suggest future avenues for rational, targeted therapy.
    Keywords: Medulloblastoma – Physiological Aspects ; Medulloblastoma – Genetic Aspects ; Genetic Variation – Research ; Cancer Genetics – Research ; Cancer Metastasis – Research;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 8
    Language: English
    In: Journal of neurosurgery. Pediatrics, March 2015, Vol.15(3), pp.236-42
    Description: While medulloblastoma was initially thought to comprise a single homogeneous entity, it is now accepted that it in fact comprises 4 discrete subgroups, each with its own distinct demographics, clinical presentation, transcriptomics, genetics, and outcome. Hydrocephalus is a common complication of medulloblastoma and not infrequently requires CSF diversion. The authors report the incidence of CSF diversion surgery in each of the subgroups of medulloblastoma (Wnt, Shh, Group 3, and Group 4). The medical and imaging records for patients who underwent surgery for medulloblastoma at The Hospital for Sick Children were retrospectively reviewed. The primary outcome was the requirement for CSF diversion surgery either before or within 60 days of tumor resection. The modified Canadian Preoperative Prediction Rule for Hydrocephalus (mCPPRH) was compared among subgroups. Of 143 medulloblastoma patients, treated from 1991 to 2013, sufficient data were available for 130 patients (15 with Wnt, 30 with Shh, 30 with Group 3, and 55 with Group 4 medulloblastomas). Of these, 28 patients (22%) ultimately underwent CSF diversion surgery: 0% with Wnt, 29% with Shh, 29% with Group 3, and 43% with Group 4 tumors. Patients in the Wnt subgroup had a lower incidence of CSF diversion than all other patients combined (p = 0.04). Wnt patients had a lower mCPPRH score (lower risk of CSF diversion, p = 0.045), were older, had smaller ventricles at diagnosis, and had no leptomeningeal metastases. The overall rate of CSF diversion surgery for Shh, Group 3, and Group 4 medulloblastomas is around 30%, but no patients in the present series with a Wnt medulloblastoma required shunting. The low incidence of hydrocephalus in patients with Wnt medulloblastoma likely reflects both host factors (age) and disease factors (lack of metastases). The absence of hydrocephalus in patients with Wnt medulloblastomas likely contributes to their excellent rate of survival and may also contribute to a higher quality of life than for patients in other subgroups.
    Keywords: Etv = Endoscopic Third Ventriculostomy ; FOR = Frontal and Occipital Horn Ratio ; Endoscopic Third Ventriculostomy ; Hydrocephalus ; Mcpprh ; Mcpprh = Modified Canadian Preoperative Prediction Rule for Hydrocephalus ; Medulloblastoma ; Molecular Subgroups ; Oncology ; Pediatric ; Posterior Fossa ; Shunt ; Biomarkers, Tumor -- Analysis ; Cerebellar Neoplasms -- Complications ; Hedgehog Proteins -- Analysis ; Hydrocephalus -- Surgery ; Medulloblastoma -- Complications ; Ventriculostomy -- Statistics & Numerical Data ; Wnt Proteins -- Analysis
    ISSN: 19330707
    E-ISSN: 1933-0715
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  • 9
    Language: English
    In: Cell, 20 January 2012, Vol.148(1-2), pp.59-71
    Description: Genomic rearrangements are thought to occur progressively during tumor development. Recent findings, however, suggest an alternative mechanism, involving massive chromosome rearrangements in a one-step catastrophic event termed chromothripsis. We report the whole-genome sequencing-based analysis of a Sonic-Hedgehog medulloblastoma (SHH-MB) brain tumor from a patient with a germline mutation (Li-Fraumeni syndrome), uncovering massive, complex chromosome rearrangements. Integrating status with microarray and deep sequencing-based DNA rearrangement data in additional patients reveals a striking association between mutation and chromothripsis in SHH-MBs. Analysis of additional tumor entities substantiates a link between mutation and chromothripsis, and indicates a context-specific role for p53 in catastrophic DNA rearrangements. Among these, we observed a strong association between somatic mutations and chromothripsis in acute myeloid leukemia. These findings connect p53 status and chromothripsis in specific tumor types, providing a genetic basis for understanding particularly aggressive subtypes of cancer. ► Complex chromosomal alterations (chromothripsis) observed in medulloblastomas ► Cancers with such alterations harbor TP53 mutations ► Context-specific link between the status of p53 and likelihood of chromothripsis ► p53 status and chromothripsis also correlate with aggressive acute myeloid leukemia Connecting p53 status and chromothripsis in specific types of cancer provides a genetic basis for the more aggressive forms of medulloblastoma and leukemia.
    Keywords: Biology
    ISSN: 0092-8674
    E-ISSN: 1097-4172
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  • 10
    In: Nature Genetics, 2015
    Description: DNA replication-associated mutations are repaired by two components: polymerase proofreading and mismatch repair. The mutation consequences of disruption to both repair components in humans are not well studied. We sequenced cancer genomes from children with inherited biallelic mismatch repair deficiency (bMMRD). High-grade bMMRD brain tumors exhibited massive numbers of substitution mutations (〉250/Mb), which was greater than all childhood and most cancers (〉7,000 analyzed). All ultra-hypermutated bMMRD cancers acquired early somatic driver mutations in DNA polymerase ɛ or δ. The ensuing mutation signatures and numbers are unique and diagnostic of childhood germ-line bMMRD (P 〈 10(-13)). Sequential tumor biopsy analysis revealed that bMMRD/polymerase-mutant cancers rapidly amass an excess of simultaneous mutations (∼600 mutations/cell division), reaching but not exceeding ∼20,000 exonic mutations in 〈6 months. This implies a threshold compatible with cancer-cell survival. We suggest a new mechanism of cancer progression in which mutations develop in a rapid burst after ablation of replication repair.
    Keywords: Base Pair Mismatch ; DNA Mismatch Repair ; Brain Neoplasms -- Genetics ; DNA Replication -- Genetics;
    ISSN: 1061-4036
    E-ISSN: 15461718
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