Cynthia Hawkins

University of Toronto, Toronto, Ontario, Canada

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Publications (206)1465.11 Total impact

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    ABSTRACT: Myxopapillary ependymoma (MPE) is a distinct histological 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 on an overlapping cohort of 46 spinal ependymomas. Functional validation experiments were performed on tumour 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 findings are supported by specific copy number alterations occurring in each histological variant. Pathway analysis revealed that MPE are characterized by increased cellular metabolism, associated with up-regulation of HIF-1α. These findings were validated by western blot analysis demonstrating increased protein expression of HIF-1α, 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. Copyright © 2015, American Association for Cancer Research.
    Clinical Cancer Research 05/2015; DOI:10.1158/1078-0432.CCR-14-2650 · 8.19 Impact Factor
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    ABSTRACT: Pediatric gliomas are the most commonly diagnosed brain cancer in children, accounting for approximately 50% of all cases. Recently, we conducted genome-analysis of diffuse intrinsic pontine glioma (DIPG), which specifically arises in the brainstem. Through this, we identified a histone H3.3 mutation (a lysine-methionine substitution at position 27 [K27M]) in approximately 70% of cases. We then showed that H3.3K27M is a negative prognostic marker for DIPG patients independent of histology. We hypothesized a similar prognostic role for H3.3K27M in thalamic gliomas. Utilizing a newly optimized, ultra-sensitive digital droplet PCR assay, we analyzed 38 radiologically confirmed thalamic gliomas (13 low grade and 25 high grade gliomas). Median survival for patients with high grade thalamic gliomas was 1.35 years vs 8.71 years for low grade thalamic glioma patients. Three (23%) low grade and 11 (44%) high grade gliomas tested positive for the H3.3K27M mutation. 31 patients, clinically annotated for treatment, extent of resection, age and outcome were used to determine the prognostic implications of H3.3-K27M. Kaplan-Meier survival analysis revealed significantly worse overall survival of thalamic glioma patients harbouring the H3.3-K27M mutation versus wild type samples (log rank p < 0.001) with a median survival of 1.04 vs 5.81 years for H3.3K27M vs WT thalamic gliomas, respectively. Multivariate cox analysis demonstrated H3.3K27M mutation status to be independent of WHO grade as a predictor of overall survival with a hazard ratio of 6.5 (95% confidence intervals 1.78-24.4, p = 0.005). These findings provide the first evidence that H3.3K27M status is a negative prognostic indicator for thalamic pediatric glioma. Furthermore, we have optimized a digital droplet PCR assay to assess mutation status in small samples, including formalin-fixed paraffin embedded, with high sensitivity and specificity in a clinical setting.
    3rd Biennial Conference on Pediatric Neuro-Oncology Basic and Translational Research; 05/2015
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    ABSTRACT: Diffuse intrinsic pontine glioma (DIPG) is a fatal childhood cancer. We performed a chemical screen in patient-derived DIPG cultures along with RNA-seq analyses and integrated computational modeling to identify potentially effective therapeutic strategies. The multi-histone deacetylase inhibitor panobinostat demonstrated therapeutic efficacy both in vitro and in DIPG orthotopic xenograft models. Combination testing of panobinostat and the histone demethylase inhibitor GSK-J4 revealed that the two had synergistic effects. Together, these data suggest a promising therapeutic strategy for DIPG.
    Nature medicine 05/2015; DOI:10.1038/nm.3855 · 28.05 Impact Factor
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    ABSTRACT: OBJECT Choroid plexus carcinomas (CPCs) are rare brain tumors originating from the ventricular choroid plexus. They account for 2%-4% of all pediatric brain tumors and are most frequently seen in very young children. This pediatric proclivity, in combination with a marked vascularity, renders an aggressive resection a difficult and often dangerous endeavor. Blood losses of several total blood volumes in small children are not uncommon, sometimes forcing the neurosurgeon to abort the procedure, often leaving residual tumor. Great extent of tumor resection is an accepted beneficial factor for overall survival. Therefore, a second resection usually follows the administration of adjuvant chemotherapy. Second-look surgery appears to be associated with markedly decreased blood loss. Histological examination of specimens obtained at a second intervention shows decreased vascularity and fibrotic changes in tumor tissue. At the Hospital for Sick Children in Toronto, this empirical finding led to the strategy of neoadjuvant chemotherapy to minimize blood loss and maximize cytoreduction. The authors undertook this study to assess the potentially beneficial effect of neoadjuvant chemotherapy on blood loss during surgery for CPCs. METHODS In this retrospective cohort review, the demographic, clinical, and treatment parameters of 22 consecutive patients diagnosed with CPC are presented. All underwent surgical treatment at the Hospital for Sick Children from 1982 to 2013. Special attention was given to the impact of neoadjuvant chemotherapy on extent of resection and intraoperative blood loss. Extent of resection was calculated based on perioperative neuroimaging, and amount of blood loss was estimated based on transfusion parameters and perioperative changes in hematocrit. RESULTS Ten patients did not receive neoadjuvant chemotherapy, and 12 were treated with 2-5 cycles of ICE (ifosfamide, carboplatin, etoposide) chemotherapy in a neoadjuvant fashion. The 22 patients included in the study underwent a total of 37 tumor resection surgeries. In all of the cases in which neoadjuvant chemotherapy was used, at least a near-total resection (> 95% of tumor volume) was achieved. Patients who underwent gross-total resection had prolonged overall survival. Of the 37 resections, 18 were performed after chemotherapy. Mean blood loss in the neoadjuvant chemotherapy group was 22% of total estimated blood volume as opposed to 96% in patients without preoperative chemotherapy. CONCLUSIONS In children with CPC, the administration of neoadjuvant chemotherapy decreases intraoperative blood loss and increases extent of resection with a significant positive effect on overall survival.
    Journal of Neurosurgery Pediatrics 05/2015; DOI:10.3171/2014.12.PEDS14372 · 1.37 Impact Factor
  • Neuro-Oncology 04/2015; 17(suppl 3):iii13-iii13. DOI:10.1093/neuonc/nov061.51 · 5.29 Impact Factor
  • Neuro-Oncology 04/2015; 17(suppl 3):iii9-iii9. DOI:10.1093/neuonc/nov061.33 · 5.29 Impact Factor
  • Neuro-Oncology 04/2015; 17(suppl 3):iii18-iii19. DOI:10.1093/neuonc/nov061.72 · 5.29 Impact Factor
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    ABSTRACT: Lynch syndrome, the most common inherited colorectal cancer syndrome in adults, is an autosomal dominant condition caused by heterozygous germ-line mutations in DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2. Inheriting biallelic (homozygous) mutations in any of the MMR genes results in a different clinical syndrome termed biallelic mismatch repair deficiency (BMMR-D) that is characterised by gastrointestinal tumours, skin lesions, brain tumours and haematologic malignancies. This recently described and under-recognised syndrome can present with adenomatous polyps leading to early-onset small bowel and colorectal adenocarcinoma. An important clue in the family history that suggests underling BMMR-D is consanguinity. Interestingly, pedigrees of BMMR-D patients typically show a paucity of Lynch syndrome cancers and most parents are unaffected. Therefore, a family history of cancers is often non-contributory. Detection of BMMR-D can lead to more appropriate genetic counselling and the implementation of targeted surveillance protocols to achieve earlier tumour detection that will allow surgical resection. This review describes an approach for diagnosis and management of these patients and their families. Copyright © 2015 Elsevier Ltd. All rights reserved.
    European journal of cancer (Oxford, England: 1990) 04/2015; 51(8). DOI:10.1016/j.ejca.2015.02.008 · 4.82 Impact Factor
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    ABSTRACT: Rhabdoid brain tumours, also called atypical teratoid rhabdoid tumours, are lethal childhood cancers with characteristic genetic alterations of SMARCB1/hSNF5. Lack of biological understanding of the substantial clinical heterogeneity of these tumours restricts therapeutic advances. We integrated genomic and clinicopathological analyses of a cohort of patients with atypical teratoid rhabdoid tumours to find out the molecular basis for clinical heterogeneity in these tumours. We obtained 259 rhabdoid tumours from 37 international institutions and assessed transcriptional profiles in 43 primary tumours and copy number profiles in 38 primary tumours to discover molecular subgroups of atypical teratoid rhabdoid tumours. We used gene and pathway enrichment analyses to discover group-specific molecular markers and did immunohistochemical analyses on 125 primary tumours to evaluate clinicopathological significance of molecular subgroup and ASCL1-NOTCH signalling. Transcriptional analyses identified two atypical teratoid rhabdoid tumour subgroups with differential enrichment of genetic pathways, and distinct clinicopathological and survival features. Expression of ASCL1, a regulator of NOTCH signalling, correlated with supratentorial location (p=0·004) and superior 5-year overall survival (35%, 95% CI 13-57, and 20%, 6-34, for ASCL1-positive and ASCL1-negative tumours, respectively; p=0·033) in 70 patients who received multimodal treatment. ASCL1 expression also correlated with superior 5-year overall survival (34%, 7-61, and 9%, 0-21, for ASCL1-positive and ASCL1-negative tumours, respectively; p=0·001) in 39 patients who received only chemotherapy without radiation. Cox hazard ratios for overall survival in patients with differential ASCL1 enrichment treated with chemotherapy with or without radiation were 2·02 (95% CI 1·04-3·85; p=0·038) and 3·98 (1·71-9·26; p=0·001). Integrated analyses of molecular subgroupings with clinical prognostic factors showed three distinct clinical risk groups of tumours with different therapeutic outcomes. An integration of clinical risk factors and tumour molecular groups can be used to identify patients who are likely to have improved long-term radiation-free survival and might help therapeutic stratification of patients with atypical teratoid rhabdoid tumours. C17 Research Network, Genome Canada, b.r.a.i.n.child, Mitchell Duckman, Tal Doron and Suri Boon foundations. Copyright © 2015 Elsevier Ltd. All rights reserved.
    The Lancet Oncology 04/2015; DOI:10.1016/S1470-2045(15)70114-2 · 24.73 Impact Factor
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    ABSTRACT: Co-expression of ERBB2 and ERBB4, reported in 75 % of pediatric ependymomas, correlates with worse overall survival. Lapatinib, a selective ERBB1 and ERBB2 inhibitor has produced prolonged disease stabilization in patients with ependymoma in a phase I study. Bevacizumab exposure in ependymoma xenografts leads to ablation of tumor self-renewing cells, arresting growth. Thus, we conducted an open-label, phase II study of bevacizumab and lapatinib in children with recurrent ependymomas. Patients ≤21 years of age with recurrent ependymoma received lapatinib orally twice daily (900 mg/m(2)/dose to the first 10 patients, and then 700 mg/m(2)/dose) and bevacizumab 10 mg/kg intravenously on days 1 and 15 of a 28-day course. Lapatinib serum trough levels were analyzed prior to each course. Total and phosphorylated VEGFR2 expression was measured in peripheral blood mononuclear cells (PBMCs) before doses 1 and 2 of bevacizumab and 24-48 h following dose 2 of bevacizumab. Twenty-four patients with a median age of 10 years (range 2-21 years) were enrolled; 22 were eligible and 20 evaluable for response. Thirteen had anaplastic ependymoma. There were no objective responses; 4 patients had stable disease for ≥4 courses (range 4-14). Grade 3 toxicities included rash, elevated ALT, and diarrhea. Grade 4 toxicities included peri-tracheostomy hemorrhage (n = 1) and elevated creatinine phosphokinase (n = 1). The median lapatinib pre-dose trough concentration was 3.72 µM. Although the combination of bevacizumab and lapatinib was well tolerated in children with recurrent ependymoma, it proved ineffective.
    Journal of Neuro-Oncology 04/2015; DOI:10.1007/s11060-015-1764-7 · 2.79 Impact Factor
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    ABSTRACT: OBJECT Intravenous fluorescein sodium has been used during resection of high-grade gliomas to help the surgeon visualize tumor margins. Several studies have reported improved rates of gross-total resection (GTR) using high doses of fluorescein sodium under white light. The recent introduction of a fluorescein-specific camera that allows for high-quality intraoperative imaging and use of very low dose fluorescein has drawn new attention to this fluorophore. However, the ability of fluorescein to specifically stain glioma cells is not yet well understood. METHODS The authors designed an in vitro model to assess fluorescein uptake in normal human astrocytes and U251 malignant glioma cells. An in vivo experiment was also subsequently designed to study fluorescein uptake by intracranial U87 malignant glioma xenografts in male nonobese diabetic/severe combined immunodeficient mice. A genetically induced mouse glioma model was used to adjust for the possible confounding effect of an inflammatory response in the xenograft model. To assess the intraoperative application of this technology, the authors prospectively enrolled 12 patients who underwent fluorescein-guided resection of their high-grade gliomas using low-dose intravenous fluorescein and a microscope-integrated fluorescence module. Intraoperative fluorescent and nonfluorescent specimens at the tumor margins were randomly analyzed for histopathological correlation. RESULTS The in vitro and in vivo models suggest that fluorescein demarcation of glioma-invaded brain is the result of distribution of fluorescein into the extracellular space, most likely as a result of an abnormal blood-brain barrier. Glioblastoma tumor cell-specific uptake of fluorescein was not observed, and tumor cells appeared to mostly exclude fluorescein. For the 12 patients who underwent resection of their high-grade gliomas, the histopathological analysis of the resected specimens at the tumor margin confirmed the intraoperative fluorescent findings. Fluorescein fluorescence was highly specific (up to 90.9%) while its sensitivity was 82.2%. False negatives occurred due to lack of fluorescence in areas of diffuse, low-density cellular infiltration. Margins of contrast enhancement based on intraoperative MRI-guided StealthStation neuronavigation correlated well with fluorescent tumor margins. GTR of the contrast-enhancing area as guided by the fluorescent signal was achieved in 100% of cases based on postoperative MRI. CONCLUSIONS Fluorescein sodium does not appear to selectively accumulate in astrocytoma cells but in extracellular tumor cell-rich locations, suggesting that fluorescein is a marker for areas of compromised blood-brain barrier within high-grade astrocytoma. Fluorescein fluorescence appears to correlate intraoperatively with the areas of MR enhancement, thus representing a practical tool to help the surgeon achieve GTR of the enhancing tumor regions.
    Journal of Neurosurgery 04/2015; DOI:10.3171/2015.2.JNS132507 · 3.15 Impact Factor
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    ABSTRACT: Solid tumors arising from malignant transformation of glial cells are one of the leading causes of central nervous system tumor-related death in children. Recurrence in spite of rigorous surgical and chemoradiation therapies remains a major hurdle in management of these tumors. Here, we investigate the efficacy of the second-generation receptor tyrosine kinase inhibitor nilotinib as a therapeutic option for the management of pediatric gliomas. We have utilized two independent pediatric high-grade glioma cell lines with either high platelet-derived growth factor receptor alpha (PDGFRα) or high PDGFRβ expression in in vitro assays to investigate the specific downstream effects of nilotinib treatment. Using in vitro cell-based assays we show that nilotinib inhibits PDGF-BB-dependent activation of PDGFRα. We further show that nilotinib is able to decrease cell proliferation and anchorage-independent growth via suppression of AKT and ERK1/2 signaling pathways. Our results suggest that nilotinib may be effective for management of a PDGFRα-dependent group of pediatric gliomas.
    Journal of Neuro-Oncology 03/2015; DOI:10.1007/s11060-015-1744-y · 2.79 Impact Factor
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    ABSTRACT: Medulloblastoma comprises four distinct molecular variants with distinct genetics, transcriptomes, and outcomes. Subgroup affiliation has been previously shown to remain stable at the time of recurrence, which likely reflects their distinct cells of origin. However, a therapeutically relevant question that remains unanswered is subgroup stability in the metastatic compartment. We assembled a cohort of 12-paired primary-metastatic tumors collected in the MAGIC consortium, and established their molecular subgroup affiliation by performing integrative gene expression and DNA methylation analysis. Frozen tissues were collected and profiled using Affymetrix gene expression arrays and Illumina methylation arrays. Class prediction and hierarchical clustering were performed using existing published datasets. Our molecular analysis, using consensus integrative genomic data, establishes the unequivocal maintenance of molecular subgroup affiliation in metastatic medulloblastoma. We further validated these findings by interrogating a non-overlapping cohort of 19 pairs of primary-metastatic tumors from the Burdenko Neurosurgical Institute using an orthogonal technique of immunohistochemical staining. This investigation represents the largest reported primary-metastatic paired cohort profiled to date and provides a unique opportunity to evaluate subgroup-specific molecular aberrations within the metastatic compartment. Our findings further support the hypothesis that medulloblastoma subgroups arise from distinct cells of origin, which are carried forward from ontogeny to oncology.
    Acta Neuropathologica 03/2015; 129(3):449-57. DOI:10.1007/s00401-015-1389-0 · 9.78 Impact Factor
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    ABSTRACT: To uncover the genetic events leading to transformation of pediatric low-grade glioma (PLGG) to secondary high-grade glioma (sHGG). We retrospectively identified patients with sHGG from a population-based cohort of 886 patients with PLGG with long clinical follow-up. Exome sequencing and array CGH were performed on available samples followed by detailed genetic analysis of the entire sHGG cohort. Clinical and outcome data of genetically distinct subgroups were obtained. sHGG was observed in 2.9% of PLGGs (26 of 886 patients). Patients with sHGG had a high frequency of nonsilent somatic mutations compared with patients with primary pediatric high-grade glioma (HGG; median, 25 mutations per exome; P = .0042). Alterations in chromatin modifying genes and telomere-maintenance pathways were commonly observed, whereas no sHGG harbored the BRAF-KIAA1549 fusion. The most recurrent alterations were BRAF V600E and CDKN2A deletion in 39% and 57% of sHGGs, respectively. Importantly, all BRAF V600E and 80% of CDKN2A alterations could be traced back to their PLGG counterparts. BRAF V600E distinguished sHGG from primary HGG (P = .0023), whereas BRAF and CDKN2A alterations were less commonly observed in PLGG that did not transform (P <.001 and P < .001 respectively). PLGGs with BRAF mutations had longer latency to transformation than wild-type PLGG (median, 6.65 years [range, 3.5 to 20.3 years] v 1.59 years [range, 0.32 to 15.9 years], respectively; P = .0389). Furthermore, 5-year overall survival was 75% ± 15% and 29% ± 12% for children with BRAF mutant and wild-type tumors, respectively (P = .024). BRAF V600E mutations and CDKN2A deletions constitute a clinically distinct subtype of sHGG. The prolonged course to transformation for BRAF V600E PLGGs provides an opportunity for surgical interventions, surveillance, and targeted therapies to mitigate the outcome of sHGG.
    Journal of Clinical Oncology 02/2015; DOI:10.1200/JCO.2014.58.3922 · 17.88 Impact Factor
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    ABSTRACT: The advent of integrated genomics has fundamentally changed our understanding of medulloblastoma. Although survival differences exist among the 4 principal subgroups, this has yet to be elucidated in a North American cohort of irradiated patients. Ninety-two consecutive patients between the ages of 3 and 17 treated with surgery, craniospinal irradiation, and chemotherapy were identified at the Hospital for Sick Children. Molecular subgrouping was performed using nanoString. Two treatment periods were identified: prior to 2006 as per the protocols of the Children's Oncology Group, and after 2006 per the St Jude Medulloblastoma 03 protocol. Five-year progression-free survival (PFS) over the entire cohort was 0.801 (95% CI: 0.692-0.875) with no significant difference between treatment protocols. Strikingly, we found that Group 4 patients had excellent 5-year PFS of 0.959 (95% CI: 0.744-0.994) for average risk and 0.887 (95% CI: 0.727-0.956) across all Group 4 patients. Group 3 patients had 5-year PFS of 0.733 (95% CI: 0.436-0.891). Sonic hedgehog patients did poorly across both treatment protocols, with 5-year PFS of 0.613 (95% CI: 0.333-0.804), likely owing to a high proportion of TP53 mutated patients in this age group. In a cohort of irradiated patients over 3 years of age, PFS for Group 4 patients was significantly improved compared with initial reports. The impact of subgroup affiliation in these children needs to be assessed in large prospectively treated cooperative protocols to determine if more than just WNT patients can be safely selected for de-escalation of therapy. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
    Neuro-Oncology 01/2015; DOI:10.1093/neuonc/nou357 · 5.29 Impact Factor
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    ABSTRACT: Limb Girdle Muscular Dystrophy (LGMD) is a heterogeneous group of genetic disorders leading to progressive muscle degeneration and often associated with cardiac complications. We present two adult siblings with childhood-onset of weakness progressing to a severe quadriparesis with the additional features of triangular tongues and biventricular cardiac dysfunction. Whole exome sequencing identified compound heterozygous missense mutations that are predicted to be pathogenic in LIMS2. Biopsy of skeletal muscle demonstrated disrupted immunostaining of LIMS2. This is the first report of mutations in LIMS2 and resulting disruption of the ILK-LIMS-Parvin complex associated with LGMD. This article is protected by copyright. All rights reserved.
    Clinical Genetics 01/2015; DOI:10.1111/cge.12561 · 3.65 Impact Factor
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    ABSTRACT: The cure rate for childhood intracranial ependymoma is approximately 70% in the setting of a gross total resection followed by radiation, but management remains challenging in patients with residual disease. Therefore, robust biomarkers are needed to guide the development of new targeted therapy. The authors evaluated the expression of several biomarkers in pediatric intracranial ependymoma and observed that the expression of enhancer of zeste homolog 2 (EZH2), a polycomb complex protein involved in epigenetic regulation of gene expression, was independently associated with poor survival. Tissue microarray immunostaining was performed on 180 ependymoma samples from 12 of 16 Canadian pediatric centers. Expression levels of EZH2, Ki-67, B lymphoma Moloney-murine leukemia virus insertion region 1 homolog, tumor protein 16 (P16), Y-box binding protein 1, phosphorylated protein kinase B (pAKT), and epidermal growth factor receptor were evaluated. Cox regression analyses were performed, and the Kaplan-Meier method was used to construct survival curves. EZH2 expressed in 16% of tumors was associated with inferior 5-year overall survival. Ki-67 and pAKT levels were associated with a poor outcome in patients with posterior fossa ependymoma, and the absence of P16 was associated with a poor outcome in patients with supratentorial ependymoma. Multivariate analysis revealed that younger age and EZH2 expression (95% confidence interval, 1.1-36.0) were independent markers of a poor prognosis. EZH2 is a novel, independent marker of a poor prognosis in patients with ependymoma, especially in those who have tumors located in the posterior fossa. EZH2, pAKT, and P16 are potential therapeutic targets, particularly for patients who have tumors in which standard gross total resection plus fractionated radiotherapy is not feasible. Cancer 2015. © 2015 American Cancer Society. © 2015 American Cancer Society.
    Cancer 01/2015; 121(9). DOI:10.1002/cncr.29198 · 4.90 Impact Factor
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    ABSTRACT: TP53 mutations confer subgroup specific poor survival for children with medulloblastoma. We hypothesized that WNT activation which is associated with improved survival for such children abrogates TP53 related radioresistance and can be used to sensitize TP53 mutant tumors for radiation. We examined the subgroup-specific role of TP53 mutations in a cohort of 314 patients treated with radiation. TP53 wild-type or mutant human medulloblastoma cell-lines and normal neural stem cells were used to test radioresistance of TP53 mutations and the radiosensitizing effect of WNT activation on tumors and the developing brain. Children with WNT/TP53 mutant medulloblastoma had higher 5-year survival than those with SHH/TP53 mutant tumours (100% and 36.6%¿±¿8.7%, respectively (p¿<¿0.001)). Introduction of TP53 mutation into medulloblastoma cells induced radioresistance (survival fractions at 2Gy (SF2) of 89%¿±¿2% vs. 57.4%¿±¿1.8% (p¿<¿0.01)). In contrast, ß-catenin mutation sensitized TP53 mutant cells to radiation (p¿<¿0.05). Lithium, an activator of the WNT pathway, sensitized TP53 mutant medulloblastoma to radiation (SF2 of 43.5%¿±¿1.5% in lithium treated cells vs. 56.6¿±¿3% (p¿<¿0.01)) accompanied by increased number of ¿H2AX foci. Normal neural stem cells were protected from lithium induced radiation damage (SF2 of 33%¿±¿8% for lithium treated cells vs. 27%¿±¿3% for untreated controls (p¿=¿0.05). Poor survival of patients with TP53 mutant medulloblastoma may be related to radiation resistance. Since constitutive activation of the WNT pathway by lithium sensitizes TP53 mutant medulloblastoma cells and protect normal neural stem cells from radiation, this oral drug may represent an attractive novel therapy for high-risk medulloblastomas.
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    ABSTRACT: OBJECT 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). METHODS 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. RESULTS 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. CONCLUSIONS 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.
    Journal of Neurosurgery Pediatrics 12/2014; 15(3):1-7. DOI:10.3171/2014.9.PEDS14280 · 1.37 Impact Factor
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    ABSTRACT: Over-expression of PDGF receptors (PDGFRs) has been previously implicated in high-risk medulloblastoma (MB) pathogenesis. However, the exact biological functions of PDGFRα and PDGFRβ signaling in MB biology remain poorly understood. Here, we report the subgroup specific expression of PDGFRα and PDGFRβ and their associated biological pathways in MB tumors. c-MYC, a downstream target of PDGFRβ but not PDGFRα, is involved in PDGFRβ signaling associated with cell proliferation, cell death, and invasion. Concurrent inhibition of PDGFRβ and c-MYC blocks MB cell proliferation and migration synergistically. Integrated analysis of miRNA and miRNA targets regulated by both PDGFRβ and c-MYC reveals that increased expression of JAG2, a target of miR-1280, is associated with high metastatic dissemination at diagnosis and a poor outcome in MB patients. Our study may resolve the controversy on the role of PDGFRs in MB and unveils JAG2 as a key downstream effector of a PDGFRβ-driven signaling cascade and a potential therapeutic target.
    Oncotarget 12/2014; · 6.63 Impact Factor

Publication Stats

9k Citations
1,465.11 Total Impact Points

Institutions

  • 2004–2015
    • University of Toronto
      • • Laboratory Medicine Program
      • • Department of Medical Biophysics
      • • Hospital for Sick Children
      Toronto, Ontario, Canada
  • 2003–2015
    • SickKids
      • • Arthur and Sonia Labatt Brain Tumour Research Centre (BTRC)
      • • Department of Paediatric Laboratory Medicine (DPLM)
      • • Division of Pathology
      • • Division of Neurology
      • • Division of Hematology/Oncology
      • • Division of Neurosurgery
      Toronto, Ontario, Canada
  • 2013
    • Ludwig-Maximilians-University of Munich
      München, Bavaria, Germany
  • 2011
    • Erasmus Universiteit Rotterdam
      Rotterdam, South Holland, Netherlands
  • 2009
    • McMaster University
      • Division of Hematology/Oncology
      Hamilton, Ontario, Canada