Publications by authors named "Cynthia Hawkins"

294 Publications

Childhood head trauma and the risk of childhood brain tumours: a case-control study in Ontario, Canada.

Int J Cancer 2021 Sep 14. Epub 2021 Sep 14.

Prosserman Centre for Population Health Research, Lunenfeld-Tanenbaum Research Institute, Sinai Health, Toronto, ON, Canada.

Head trauma in early childhood has been hypothesized as a potential risk factor for childhood brain tumours (CBTs). However, head trauma has not been extensively studied in the context of CBTs and existing studies have yielded conflicting results. A population- and hospital-based case-control study of children 0-15 years with newly diagnosed CBTs from 1997-2003 recruited across Ontario through pediatric oncology centres was conducted. Controls were frequency-matched with cases by age, sex and geographical region. The association was assessed based on multivariable logistic regressions, accounting for child's age, sex, ethnicity, highest level of maternal education, and maternal pack-years of smoking during the pregnancy. Analyses were conducted separately based on age of first head trauma, sex and histology. A latency period analysis was conducted. Overall, based on 280 cases and 919 controls, CBTs were not significantly associated with previous history of head trauma (OR 1.34, 95% CI 0.96, 1.86), head trauma severity, number of head injuries, nor head or neck X-rays or computed tomography (CT) examinations. Results were consistent across sexes and histological subtypes. However, head trauma within the first year of life was significantly associated with CBTs (OR 2.00, 95% CI 1.01, 3.98), but the association diminished when adjusted for X-ray or CT occurring during the same time period (OR 1.62, 95% CI 0.75, 3.49), albeit limited sample size. Overall, no association was observed between head trauma and CBTs among all children, while head trauma occurring within first year of life may warrant further investigation in future research. This article is protected by copyright. All rights reserved.
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http://dx.doi.org/10.1002/ijc.33805DOI Listing
September 2021

The 2021 WHO Classification of Tumors of the Central Nervous System: a summary.

Neuro Oncol 2021 08;23(8):1231-1251

Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.

The fifth edition of the WHO Classification of Tumors of the Central Nervous System (CNS), published in 2021, is the sixth version of the international standard for the classification of brain and spinal cord tumors. Building on the 2016 updated fourth edition and the work of the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy, the 2021 fifth edition introduces major changes that advance the role of molecular diagnostics in CNS tumor classification. At the same time, it remains wedded to other established approaches to tumor diagnosis such as histology and immunohistochemistry. In doing so, the fifth edition establishes some different approaches to both CNS tumor nomenclature and grading and it emphasizes the importance of integrated diagnoses and layered reports. New tumor types and subtypes are introduced, some based on novel diagnostic technologies such as DNA methylome profiling. The present review summarizes the major general changes in the 2021 fifth edition classification and the specific changes in each taxonomic category. It is hoped that this summary provides an overview to facilitate more in-depth exploration of the entire fifth edition of the WHO Classification of Tumors of the Central Nervous System.
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http://dx.doi.org/10.1093/neuonc/noab106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8328013PMC
August 2021

Therapeutic implications of improved molecular diagnostics for rare CNS embryonal tumor entities: results of an international, retrospective study.

Neuro Oncol 2021 Sep;23(9):1597-1611

Department of Neurooncology, Russian Scientific Center of Radiology, Moscow, Russia.

Background: Only few data are available on treatment-associated behavior of distinct rare CNS embryonal tumor entities previously treated as "CNS-primitive neuroectodermal tumors" (CNS-PNET). Respective data on specific entities, including CNS neuroblastoma, FOXR2 activated (CNS NB-FOXR2), and embryonal tumors with multilayered rosettes (ETMR) are needed for development of differentiated treatment strategies.

Methods: Within this retrospective, international study, tumor samples of clinically well-annotated patients with the original diagnosis of CNS-PNET were analyzed using DNA methylation arrays (n = 307). Additional cases (n = 66) with DNA methylation pattern of CNS NB-FOXR2 were included irrespective of initial histological diagnosis. Pooled clinical data (n = 292) were descriptively analyzed.

Results: DNA methylation profiling of "CNS-PNET" classified 58 (19%) cases as ETMR, 57 (19%) as high-grade glioma (HGG), 36 (12%) as CNS NB-FOXR2, and 89(29%) cases were classified into 18 other entities. Sixty-seven (22%) cases did not show DNA methylation patterns similar to established CNS tumor reference classes. Best treatment results were achieved for CNS NB-FOXR2 patients (5-year PFS: 63% ± 7%, OS: 85% ± 5%, n = 63), with 35/42 progression-free survivors after upfront craniospinal irradiation (CSI) and chemotherapy. The worst outcome was seen for ETMR and HGG patients with 5-year PFS of 18% ± 6% and 22% ± 7%, and 5-year OS of 24% ± 6% and 25% ± 7%, respectively.

Conclusion: The historically reported poor outcome of CNS-PNET patients becomes highly variable when tumors are molecularly classified based on DNA methylation profiling. Patients with CNS NB-FOXR2 responded well to current treatments and a standard-risk CSI-based regimen may be prospectively evaluated. The poor outcome of ETMR across applied treatment strategies substantiates the necessity for evaluation of novel treatments.
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http://dx.doi.org/10.1093/neuonc/noab136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8408859PMC
September 2021

Survival Benefit for Individuals With Constitutional Mismatch Repair Deficiency Undergoing Surveillance.

J Clin Oncol 2021 Sep 4;39(25):2779-2790. Epub 2021 May 4.

Lebanese American University Medical Center-Rizk, Beirut, Lebanon.

Purpose: Constitutional mismatch repair deficiency syndrome (CMMRD) is a lethal cancer predisposition syndrome characterized by early-onset synchronous and metachronous multiorgan tumors. We designed a surveillance protocol for early tumor detection in these individuals.

Patients And Methods: Data were collected from patients with confirmed CMMRD who were registered in the International Replication Repair Deficiency Consortium. Tumor spectrum, efficacy of the surveillance protocol, and malignant transformation of low-grade lesions were examined for the entire cohort. Survival outcomes were analyzed for patients followed prospectively from the time of surveillance implementation.

Results: A total of 193 malignant tumors in 110 patients were identified. Median age of first cancer diagnosis was 9.2 years (range: 1.7-39.5 years). For patients undergoing surveillance, all GI and other solid tumors, and 75% of brain cancers were detected asymptomatically. By contrast, only 16% of hematologic malignancies were detected asymptomatically ( < .001). Eighty-nine patients were followed prospectively and used for survival analysis. Five-year overall survival (OS) was 90% (95% CI, 78.6 to 100) and 50% (95% CI, 39.2 to 63.7) when cancer was detected asymptomatically and symptomatically, respectively ( = .001). Patient outcome measured by adherence to the surveillance protocol revealed 4-year OS of 79% (95% CI, 54.8 to 90.9) for patients undergoing full surveillance, 55% (95% CI, 28.5 to 74.5) for partial surveillance, and 15% (95% CI, 5.2 to 28.8) for those not under surveillance ( < .0001). Of the 64 low-grade tumors detected, the cumulative likelihood of transformation from low-to high-grade was 81% for GI cancers within 8 years and 100% for gliomas in 6 years.

Conclusion: Surveillance and early cancer detection are associated with improved OS for individuals with CMMRD.
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http://dx.doi.org/10.1200/JCO.20.02636DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8407605PMC
September 2021

MetaFusion: A high-confidence metacaller for filtering and prioritizing RNA-seq gene fusion candidates.

Bioinformatics 2021 May 3. Epub 2021 May 3.

Centre for Computational Medicine, The Hospital For Sick Children, Toronto, ON, Canada.

Motivation: Current fusion detection tools use diverse calling approaches and provide varying results, making selection of the appropriate tool challenging. Ensemble fusion calling techniques appear promising; however, current options have limited accessibility and function.

Results: MetaFusion is a flexible meta-calling tool that amalgamates outputs from any number of fusion callers. Individual caller results are standardized by conversion into the new file type Common Fusion Format (CFF). Calls are annotated, merged using graph clustering, filtered, and ranked to provide a final output of high confidence candidates. MetaFusion consistently achieves higher precision and recall than individual callers on real and simulated datasets, and reaches up to 100% precision, indicating that ensemble calling is imperative for high confidence results. MetaFusion uses FusionAnnotator to annotate calls with information from cancer fusion databases, and is provided with a benchmarking toolkit to calibrate new callers.

Availability: MetaFusion is freely available at https://github.com/ccmbioinfo/MetaFusion.

Supplementary Information: Supplementary data are available at Bioinformatics online.
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http://dx.doi.org/10.1093/bioinformatics/btab249DOI Listing
May 2021

A Practical Approach to the Evaluation and Diagnosis of Pediatric CNS Tumors.

Pediatr Dev Pathol 2021 Apr 19:10935266211007022. Epub 2021 Apr 19.

Children's Hospital Los Angeles, Department of Pathology and Laboratory Medicine, Keck School of Medicine of University of Southern California, Los Angeles, California.

Tumor classification in neuropathology is a dynamic and complex topic, with many changes emerging in the past 5 years, up to and including the 2021 publication of the 5th edition of the World Health Organization Classification of Tumours of the Central Nervous System (CNS). For pediatric pathologists who will encounter brain tumors with varying frequency, it is important to understand the principles of these classification updates, particularly the inclusion of molecular genetic features and development of a layered, or integrated, diagnosis. This issue of Perspectives in Pediatric Pathology is dedicated to the examination of pediatric brain tumors, and features articles on intraoperative diagnosis and updated information on molecular-based classification for pediatric glial, glioneuronal, ependymal, and embryonal tumors of the CNS.
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http://dx.doi.org/10.1177/10935266211007022DOI Listing
April 2021

Pediatric Glial Tumors.

Pediatr Dev Pathol 2021 Apr 19:10935266211009101. Epub 2021 Apr 19.

Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.

Pediatric glial tumors are unique from their adult counterparts. This important distinction is recognized and incorporated into the World Health Organization classification of central nervous system tumors and applies to both high- and low-grade gliomas, incorporating their specific molecular profiles. Molecular alterations in pediatric high-grade gliomas provide important prognostic information, for example in H3 K27M-mutant tumors. The integration of molecular information is also important for pediatric low-grade gliomas due to their overlapping morphologies and the prognostic and therapeutic implications of these molecular alterations. In this paper, we cover a variety of glial tumors, encompassing neoplasms with predominantly glial histology, astrocytic tumors, oligodendroglial tumors, and mixed glioneuronal tumors. Considering the complexity of this evolving field, the purpose of this article is to offer a practical approach to the diagnosis of pediatric gliomas, including the selection of the most appropriate molecular surrogate immunohistochemical stains, basic molecular studies, and more sophisticated techniques if needed. The goal is to reach a rapid, sound diagnosis, helping guide clinical decision-making regarding prognosis and potential therapies.
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http://dx.doi.org/10.1177/10935266211009101DOI Listing
April 2021

Local FK506 drug delivery enhances nerve regeneration through fresh, unprocessed peripheral nerve allografts.

Exp Neurol 2021 Jul 3;341:113680. Epub 2021 Mar 3.

Division of Plastic & Reconstructive Surgery, The Hospital for Sick Children, Toronto, Canada; Division of Plastic & Reconstructive Surgery, Department of Surgery, University of Toronto, Toronto, Canada; Institute of Biomaterials and Biomedical Engineering, Faculty of Applied Science and Engineering, University of Toronto, Toronto, Canada; Program in Neuroscience, SickKids Research Institute, The Hospital for Sick Children, Toronto, Canada. Electronic address:

Objective: Nerve allografts offer many advantages in the reconstruction of peripheral nerve gaps: they retain their native microstructure, contain pro-regenerative Schwann cells, are widely available, and avoid donor site morbidity. Unfortunately, clinical use of nerve allografts is limited by the need for systemic immunosuppression and its adverse effects. To eliminate the toxicity of the systemic immunosuppressant FK506, we developed a local FK506 drug delivery system (DDS) to provide drug release over 28 days. The study objective was to investigate if the local FK506 DDS enhances nerve regeneration in a rodent model of nerve gap defect reconstruction with immunologically-disparate nerve allografts.

Methods: In male Lewis rats, a common peroneal nerve gap defect was reconstructed with either a 20 mm nerve isograft from a donor Lewis rat or a 20 mm fresh, unprocessed nerve allograft from an immunologically incompatible donor ACI rat. After 4 weeks of survival, nerve regeneration was evaluated using retrograde neuronal labelling, quantitative histomorphometry, and serum cytokine profile.

Results: Treatment with both systemic FK506 and the local FK506 DDS significantly improved motor and sensory neuronal regeneration, as well as histomorphometric indices including myelinated axon number. Rats with nerve allografts treated with either systemic or local FK506 had significantly reduced serum concentrations of the pro-inflammatory cytokine IL-12 compared to untreated vehicle control rats with nerve allografts. Serum FK506 levels were undetectable in rats with local FK506 DDS.

Interpretation: The local FK506 DDS improved motor and sensory nerve regeneration through fresh nerve allografts to a level equal to that of either systemic FK506 or nerve isografting. This treatment may be clinically translatable in peripheral nerve reconstruction or vascularized composite allotransplantation.
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http://dx.doi.org/10.1016/j.expneurol.2021.113680DOI Listing
July 2021

Thrombospondin-1 mimetics are promising novel therapeutics for MYC-associated medulloblastoma.

Neurooncol Adv 2021 Jan-Dec;3(1):vdab002. Epub 2021 Feb 18.

Department of Pediatrics, Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.

Background: Medulloblastoma (MB) comprises four subtypes of which group 3 MB are the most aggressive. Although overall survival for MB has improved, the outcome of group 3 MB remains dismal. C- amplification or MYC overexpression which characterizes group 3 MB is a strong negative prognostic factor and is frequently associated with metastases and relapses. We previously reported that MYC expression alone promotes highly aggressive MB phenotypes, in part via repression of thrombospondin-1 (TSP-1), a potent tumor suppressor.

Methods: In this study, we examined the potential role of TSP-1 and TSP-1 peptidomimetic ABT-898 in amplified human MB cell lines and two distinct murine models of MYC-driven group 3 MBs.

Results: We found that TSP-1 reconstitution diminished metastases and prolonged survival in orthotopic xenografts and promoted chemo- and radio-sensitivity via AKT signaling. Furthermore, we demonstrate that ABT-898 can recapitulate the effects of TSP-1 expression in MB cells in vitro and specifically induced apoptosis in murine group 3 MB tumor cells.

Conclusion: Our data underscore the importance of TSP-1 as a critical tumor suppressor in MB and highlight TSP-1 peptidomimetics as promising novel therapeutics for the most lethal subtype of MB.
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http://dx.doi.org/10.1093/noajnl/vdab002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7890793PMC
February 2021

Clinical and molecular heterogeneity of pineal parenchymal tumors: a consensus study.

Acta Neuropathol 2021 05 22;141(5):771-785. Epub 2021 Feb 22.

Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA.

Recent genomic studies have shed light on the biology and inter-tumoral heterogeneity underlying pineal parenchymal tumors, in particular pineoblastomas (PBs) and pineal parenchymal tumors of intermediate differentiation (PPTIDs). Previous reports, however, had modest sample sizes and lacked the power to integrate molecular and clinical findings. The different proposed molecular group structures also highlighted a need to reach consensus on a robust and relevant classification system. We performed a meta-analysis on 221 patients with molecularly characterized PBs and PPTIDs. DNA methylation profiles were analyzed through complementary bioinformatic approaches and molecular subgrouping was harmonized. Demographic, clinical, and genomic features of patients and samples from these pineal tumor groups were annotated. Four clinically and biologically relevant consensus PB groups were defined: PB-miRNA1 (n = 96), PB-miRNA2 (n = 23), PB-MYC/FOXR2 (n = 34), and PB-RB1 (n = 25). A final molecularly distinct group, designated PPTID (n = 43), comprised histological PPTID and PBs. Genomic and transcriptomic profiling allowed the characterization of oncogenic drivers for individual tumor groups, specifically, alterations in the microRNA processing pathway in PB-miRNA1/2, MYC amplification and FOXR2 overexpression in PB-MYC/FOXR2, RB1 alteration in PB-RB1, and KBTBD4 insertion in PPTID. Age at diagnosis, sex predilection, and metastatic status varied significantly among tumor groups. While patients with PB-miRNA2 and PPTID had superior outcome, survival was intermediate for patients with PB-miRNA1, and dismal for those with PB-MYC/FOXR2 or PB-RB1. Reduced-dose CSI was adequate for patients with average-risk, PB-miRNA1/2 disease. We systematically interrogated the clinical and molecular heterogeneity within pineal parenchymal tumors and proposed a consensus nomenclature for disease groups, laying the groundwork for future studies as well as routine use in tumor diagnostic classification and clinical trial stratification.
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http://dx.doi.org/10.1007/s00401-021-02284-5DOI Listing
May 2021

Mutations in the RAS/MAPK Pathway Drive Replication Repair-Deficient Hypermutated Tumors and Confer Sensitivity to MEK Inhibition.

Cancer Discov 2021 Jun 9;11(6):1454-1467. Epub 2021 Feb 9.

Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.

The RAS/MAPK pathway is an emerging targeted pathway across a spectrum of both adult and pediatric cancers. Typically, this is associated with a single, well-characterized point mutation in an oncogene. Hypermutant tumors that harbor many somatic mutations may obscure the interpretation of such targetable genomic events. We find that replication repair-deficient (RRD) cancers, which are universally hypermutant and affect children born with RRD cancer predisposition, are enriched for mutations ( = 10). These mutations are not random, exist in subclones, and increase in allelic frequency over time. The RAS/MAPK pathway is activated both transcriptionally and at the protein level in patient-derived RRD tumors, and these tumors responded to MEK inhibition and . Treatment of patients with RAS/MAPK hypermutant gliomas reveals durable responses to MEK inhibition. Our observations suggest that hypermutant tumors may be addicted to oncogenic pathways, resulting in favorable response to targeted therapies. SIGNIFICANCE: Tumors harboring a single driver mutation are targeted individually for therapeutic purposes. We find that in RRD hypermutant cancers, mutations in the RAS/MAPK pathway are enriched, highly expressed, and result in sensitivity to MEK inhibitors. Targeting an oncogenic pathway may provide therapeutic options for these hypermutant polyclonal cancers..
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http://dx.doi.org/10.1158/2159-8290.CD-20-1050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8406556PMC
June 2021

Clinical Outcomes and Patient-Matched Molecular Composition of Relapsed Medulloblastoma.

J Clin Oncol 2021 03 27;39(7):807-821. Epub 2021 Jan 27.

Division of Pediatric Hematology and Oncology, University of Texas Southwestern Medical Center, Dallas, TX.

Purpose: We sought to investigate clinical outcomes of relapsed medulloblastoma and to compare molecular features between patient-matched diagnostic and relapsed tumors.

Methods: Children and infants enrolled on either SJMB03 (NCT00085202) or SJYC07 (NCT00602667) trials who experienced medulloblastoma relapse were analyzed for clinical outcomes, including anatomic and temporal patterns of relapse and postrelapse survival. A largely independent, paired molecular cohort was analyzed by DNA methylation array and next-generation sequencing.

Results: A total of 72 of 329 (22%) SJMB03 and 52 of 79 (66%) SJYC07 patients experienced relapse with significant representation of Group 3 and wingless tumors. Although most patients exhibited some distal disease (79%), 38% of patients with sonic hedgehog tumors experienced isolated local relapse. Time to relapse and postrelapse survival varied by molecular subgroup with longer latencies for patients with Group 4 tumors. Postrelapse radiation therapy among previously nonirradiated SJYC07 patients was associated with long-term survival. Reirradiation was only temporizing for SJMB03 patients. Among 127 patients with patient-matched tumor pairs, 9 (7%) experienced subsequent nonmedulloblastoma CNS malignancies. Subgroup (96%) and subtype (80%) stabilities were largely maintained among the remainder. Rare subgroup divergence was observed from Group 4 to Group 3 tumors, which is coincident with genetic alterations involving , , and . Subgroup-specific patterns of alteration were identified for driver genes and chromosome arms.

Conclusion: Clinical behavior of relapsed medulloblastoma must be contextualized in terms of up-front therapies and molecular classifications. Group 4 tumors exhibit slower biological progression. Utility of radiation at relapse is dependent on patient age and prior treatments. Degree and patterns of molecular conservation at relapse vary by subgroup. Relapse tissue enables verification of molecular targets and identification of occult secondary malignancies.
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http://dx.doi.org/10.1200/JCO.20.01359DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8078396PMC
March 2021

DNA Polymerase and Mismatch Repair Exert Distinct Microsatellite Instability Signatures in Normal and Malignant Human Cells.

Cancer Discov 2021 May 18;11(5):1176-1191. Epub 2020 Dec 18.

Department of Pediatric Hematology-Oncology, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania.

Although replication repair deficiency, either by mismatch repair deficiency (MMRD) and/or loss of DNA polymerase proofreading, can cause hypermutation in cancer, microsatellite instability (MSI) is considered a hallmark of MMRD alone. By genome-wide analysis of tumors with germline and somatic deficiencies in replication repair, we reveal a novel association between loss of polymerase proofreading and MSI, especially when both components are lost. Analysis of indels in microsatellites (MS-indels) identified five distinct signatures (MS-sigs). MMRD MS-sigs are dominated by multibase losses, whereas mutant-polymerase MS-sigs contain primarily single-base gains. MS deletions in MMRD tumors depend on the original size of the MS and converge to a preferred length, providing mechanistic insight. Finally, we demonstrate that MS-sigs can be a powerful clinical tool for managing individuals with germline MMRD and replication repair-deficient cancers, as they can detect the replication repair deficiency in normal cells and predict their response to immunotherapy. SIGNIFICANCE: Exome- and genome-wide MSI analysis reveals novel signatures that are uniquely attributed to mismatch repair and DNA polymerase. This provides new mechanistic insight into MS maintenance and can be applied clinically for diagnosis of replication repair deficiency and immunotherapy response prediction..
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http://dx.doi.org/10.1158/2159-8290.CD-20-0790DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8223607PMC
May 2021

Epigenetic activation of a RAS/MYC axis in H3.3K27M-driven cancer.

Nat Commun 2020 12 4;11(1):6216. Epub 2020 Dec 4.

Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, ON, Canada.

Histone H3 lysine 27 (H3K27M) mutations represent the canonical oncohistone, occurring frequently in midline gliomas but also identified in haematopoietic malignancies and carcinomas. H3K27M functions, at least in part, through widespread changes in H3K27 trimethylation but its role in tumour initiation remains obscure. To address this, we created a transgenic mouse expressing H3.3K27M in diverse progenitor cell populations. H3.3K27M expression drives tumorigenesis in multiple tissues, which is further enhanced by Trp53 deletion. We find that H3.3K27M epigenetically activates a transcriptome, enriched for PRC2 and SOX10 targets, that overrides developmental and tissue specificity and is conserved between H3.3K27M-mutant mouse and human tumours. A key feature of the H3K27M transcriptome is activation of a RAS/MYC axis, which we find can be targeted therapeutically in isogenic and primary DIPG cell lines with H3.3K27M mutations, providing an explanation for the common co-occurrence of alterations in these pathways in human H3.3K27M-driven cancer. Taken together, these results show how H3.3K27M-driven transcriptome remodelling promotes tumorigenesis and will be critical for targeting cancers with these mutations.
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http://dx.doi.org/10.1038/s41467-020-19972-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718276PMC
December 2020

Re-irradiation with concurrent BRAF and MEK inhibitor therapy.

Pediatr Blood Cancer 2021 May 30;68(5):e28838. Epub 2020 Nov 30.

Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada.

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http://dx.doi.org/10.1002/pbc.28838DOI Listing
May 2021

Senescence Induced by BMI1 Inhibition Is a Therapeutic Vulnerability in H3K27M-Mutant DIPG.

Cell Rep 2020 10;33(3):108286

Department of Pediatrics and Section of Pediatric Hematology/Oncology/BMT, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; The Morgan Adams Foundation Pediatric Brain Tumor Research Program, Children's Hospital Colorado, Aurora, CO, USA.

Diffuse intrinsic pontine glioma (DIPG) is an incurable brain tumor of childhood characterized by histone mutations at lysine 27, which results in epigenomic dysregulation. There has been a failure to develop effective treatment for this tumor. Using a combined RNAi and chemical screen targeting epigenomic regulators, we identify the polycomb repressive complex 1 (PRC1) component BMI1 as a critical factor for DIPG tumor maintenance in vivo. BMI1 chromatin occupancy is enriched at genes associated with differentiation and tumor suppressors in DIPG cells. Inhibition of BMI1 decreases cell self-renewal and attenuates tumor growth due to induction of senescence. Prolonged BMI1 inhibition induces a senescence-associated secretory phenotype, which promotes tumor recurrence. Clearance of senescent cells using BH3 protein mimetics co-operates with BMI1 inhibition to enhance tumor cell killing in vivo.
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http://dx.doi.org/10.1016/j.celrep.2020.108286DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7574900PMC
October 2020

Clinical and molecular characterization of a multi-institutional cohort of pediatric spinal cord low-grade gliomas.

Neurooncol Adv 2020 Jan-Dec;2(1):vdaa103. Epub 2020 Aug 24.

Department of Pediatrics, University of Colorado Denver, Aurora, Colorado, USA.

Background: The mitogen-activated protein kinases/extracelluar signal-regulated kinases pathway is involved in cell growth and proliferation, and mutations in have made it an oncogene of interest in pediatric cancer. Previous studies found that mutations as well as fusions are common in intracranial low-grade gliomas (LGGs). Fewer studies have tested for the presence of these genetic changes in spinal LGGs. The aim of this study was to better understand the prevalence of BRAF and other genetic aberrations in spinal LGG.

Methods: We retrospectively analyzed 46 spinal gliomas from patients aged 1-25 years from Children's Hospital Colorado (CHCO) and The Hospital for Sick Children (SickKids). CHCO utilized a 67-gene panel that assessed and additionally screened for other possible genetic abnormalities of interest. At SickKids, was assessed by droplet digital polymerase chain reaction and immunohistochemistry. BRAF fusions were detected by fluorescence in situ hybridization, reverse transcription polymerase chain reaction, or NanoString platform. Data were correlated with clinical information.

Results: Of 31 samples with complete fusion analysis, 13 (42%) harbored . All 13 (100%) patients with confirmed survived the entirety of the study period (median [interquartile range] follow-up time: 47 months [27-85 months]) and 15 (83.3%) fusion-negative patients survived (follow-up time: 37.5 months [19.8-69.5 months]). Other mutations of interest were also identified in this patient cohort including , , , , , and deletion.

Conclusion: was seen in higher frequency than or other genetic aberrations in pediatric spinal LGGs and experienced lower death rates compared to negative patients, although this was not statistically significant.
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http://dx.doi.org/10.1093/noajnl/vdaa103DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7542983PMC
August 2020

Giant choroid plexus cysts with calvarial erosion: a case report and literature review.

Childs Nerv Syst 2021 07 15;37(7):2381-2385. Epub 2020 Oct 15.

Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.

Choroid plexus cysts rarely grow to be symptomatic. Few large choroid plexus cysts have been reported in the pediatric population. The authors report a 15-month-old boy with increased head circumference and a bony deformity in the left parietal region due to mass effect from a giant choroid plexus cyst. The child had a craniotomy for open resection of the cyst, and made an excellent recovery. The differential diagnosis for intraventricular cysts and the literature surrounding choroid plexus cysts are discussed.
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http://dx.doi.org/10.1007/s00381-020-04930-xDOI Listing
July 2021

Advances and Challenges in Pediatric and Childhood Cancers.

Cancer Cell 2020 10;38(4):429-432

As we continue to learn about the unique biology of pediatric and childhood cancers and as new therapies are being developed, we asked some experts to highlight the most notable advances in our understanding of these diseases and in the development of treatments in the past decade, and to point out current challenges that still need to be addressed.
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http://dx.doi.org/10.1016/j.ccell.2020.09.013DOI Listing
October 2020

Cancers from Novel -Mutant Mouse Models Provide Insights into Polymerase-Mediated Hypermutagenesis and Immune Checkpoint Blockade.

Cancer Res 2020 12 16;80(24):5606-5618. Epub 2020 Sep 16.

Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada.

mutations are a major cause of hypermutant cancers, yet questions remain regarding mechanisms of tumorigenesis, genotype-phenotype correlation, and therapeutic considerations. In this study, we establish mouse models harboring cancer-associated mutations P286R and S459F, which cause rapid albeit distinct time to cancer initiation , independent of their exonuclease activity. Mouse and human correlates enabled novel stratification of mutations into three groups based on clinical phenotype and mutagenicity. Cancers driven by these mutations displayed striking resemblance to the human ultrahypermutation and specific signatures. Furthermore, -driven cancers exhibited a continuous and stochastic mutagenesis mechanism, resulting in intertumoral and intratumoral heterogeneity. Checkpoint blockade did not prevent lymphomas, but rather likely promoted lymphomagenesis as observed in humans. These observations provide insights into the carcinogenesis of -driven tumors and valuable information for genetic counseling, surveillance, and immunotherapy for patients. SIGNIFICANCE: Two mouse models of polymerase exonuclease deficiency shed light on mechanisms of mutation accumulation and considerations for immunotherapy..
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http://dx.doi.org/10.1158/0008-5472.CAN-20-0624DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8218238PMC
December 2020

Outcomes of BRAF V600E Pediatric Gliomas Treated With Targeted BRAF Inhibition.

JCO Precis Oncol 2020 20;4. Epub 2020 May 20.

Semmelweis University, Budapest, Hungary.

Purpose: Children with pediatric gliomas harboring a BRAF V600E mutation have poor outcomes with current chemoradiotherapy strategies. Our aim was to study the role of targeted BRAF inhibition in these tumors.

Patients And Methods: We collected clinical, imaging, molecular, and outcome information from patients with BRAF V600E-mutated glioma treated with BRAF inhibition across 29 centers from multiple countries.

Results: Sixty-seven patients were treated with BRAF inhibition (pediatric low-grade gliomas [PLGGs], n = 56; pediatric high-grade gliomas [PHGGs], n = 11) for up to 5.6 years. Objective responses were observed in 80% of PLGGs, compared with 28% observed with conventional chemotherapy ( < .001). These responses were rapid (median, 4 months) and sustained in 86% of tumors up to 5 years while receiving therapy. After discontinuation of BRAF inhibition, 76.5% (13 of 17) of patients with PLGG experienced rapid progression (median, 2.3 months). However, upon rechallenge with BRAF inhibition, 90% achieved an objective response. Poor prognostic factors in conventional therapies, such as concomitant homozygous deletion of , were not associated with lack of response to BRAF inhibition. In contrast, only 36% of those with PHGG responded to BRAF inhibition, with all but one tumor progressing within 18 months. In PLGG, responses translated to 3-year progression-free survival of 49.6% (95% CI, 35.3% to 69.5%) versus 29.8% (95% CI, 20% to 44.4%) for BRAF inhibition versus chemotherapy, respectively ( = .02).

Conclusion: Use of BRAF inhibition results in robust and durable responses in BRAF V600E-mutated PLGG. Prospective studies are required to determine long-term survival and functional outcomes with BRAF inhibitor therapy in childhood gliomas.
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http://dx.doi.org/10.1200/PO.19.00298DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7446502PMC
May 2020

Cancer proteome and metabolite changes linked to SHMT2.

PLoS One 2020 9;15(9):e0237981. Epub 2020 Sep 9.

Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada.

Serine hydroxymethyltransferase 2 (SHMT2) converts serine plus tetrahydrofolate (THF) into glycine plus methylene-THF and is upregulated at the protein level in lung and other cancers. In order to better understand the role of SHMT2 in cancer a model system of HeLa cells engineered for inducible over-expression or knock-down of SHMT2 was characterized for cell proliferation and changes in metabolites and proteome as a function of SHMT2. Ectopic over-expression of SHMT2 increased cell proliferation in vitro and tumor growth in vivo. Knockdown of SHMT2 expression in vitro caused a state of glycine auxotrophy and accumulation of phosphoribosylaminoimidazolecarboxamide (AICAR), an intermediate of folate/1-carbon-pathway-dependent de novo purine nucleotide synthesis. Decreased glycine in the HeLa cell-based xenograft tumors with knocked down SHMT2 was potentiated by administration of the anti-hyperglycinemia agent benzoate. However, tumor growth was not affected by SHMT2 knockdown with or without benzoate treatment. Benzoate inhibited cell proliferation in vitro, but this was independent of SHMT2 modulation. The abundance of proteins of mitochondrial respiration complexes 1 and 3 was inversely correlated with SHMT2 levels. Proximity biotinylation in vivo (BioID) identified 48 mostly mitochondrial proteins associated with SHMT2 including the mitochondrial enzymes Acyl-CoA thioesterase (ACOT2) and glutamate dehydrogenase (GLUD1) along with more than 20 proteins from mitochondrial respiration complexes 1 and 3. These data provide insights into possible mechanisms through which elevated SHMT2 in cancers may be linked to changes in metabolism and mitochondrial function.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237981PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7480864PMC
October 2020

Germline-driven replication repair-deficient high-grade gliomas exhibit unique hypomethylation patterns.

Acta Neuropathol 2020 11 8;140(5):765-776. Epub 2020 Sep 8.

The Royal Children's Hospital, 50 Flemington Rd, Parkville, VIC, 3052, Australia.

Replication repair deficiency (RRD) leading to hypermutation is an important driving mechanism of high-grade glioma (HGG) occurring predominantly in the context of germline mutations in RRD-associated genes. Although HGG presents specific patterns of DNA methylation corresponding to oncogenic mutations, this has not been well studied in replication repair-deficient tumors. We analyzed 51 HGG arising in the background of gene mutations in RRD utilizing either 450 k or 850 k methylation arrays. These were compared with HGG not known to be from patients with RRD. RRD HGG harboring secondary mutations in glioma genes such as IDH1 and H3F3A displayed a methylation pattern corresponding to these methylation subgroups. Strikingly, RRD HGG lacking these known secondary mutations clustered together with an incompletely described group of HGG previously labeled "Wild type-C" or "Paediatric RTK 1". Independent analysis of two comparator HGG cohorts showed that other RRD/hypermutant tumors clustered within these subgroups, suggesting that undiagnosed RRD may be driving some HGG clustering in this location. RRD HGG displayed a unique CpG Island Demethylator Phenotype in contrast to the CpG Island Methylator Phenotype described in other cancers. Hypomethylation was enriched at gene promoters with prominent demethylation in genes and pathways critical to cellular survival including cell cycle, gene expression, cellular metabolism, and organization. These data suggest that methylation arrays may provide diagnostic information for the detection of RRD HGG. Furthermore, our findings highlight the unique natural selection pressures in these highly dysregulated, hypermutant cancers and provide the novel impact of hypermutation and RRD on the cancer epigenome.
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http://dx.doi.org/10.1007/s00401-020-02209-8DOI Listing
November 2020

Diffuse midline glioma: review of epigenetics.

J Neurooncol 2020 Oct 17;150(1):27-34. Epub 2020 Aug 17.

University of California, San Francisco, CA, USA.

Purpose: Our understanding of diffuse midline glioma (DMG) biology inclusive of diffuse intrinsic pontine glioma has been revolutionized by the discovery of novel mutations on the tails of histone 3, leading to the reclassification in 2016 of 'diffuse midline glioma, H3 K27M-mutant.' Given the abundance of basic, translational, and clinical information put forth in recent years, a review of the epigenetics of diffuse midline glioma is warranted.

Methods: Literature for the epigenetics of diffuse midline glioma published from 1989 to 2019 was reviewed by searching PubMed using the terms "diffuse intrinsic pontine glioma", "pontine glioma", or "midline glioma". The final references list was generated on the basis of originality and relevance to the broad scope of our review.

Results: The effects of H3K27M-mutation, while better understood, suggest multiple consequences on the chromatin landscape and DNA modification states, contributed to the progression of DMG. A rapid pace of translational development is occurring for epigenetic modifiers, and several classes of inhibitors have already made their way into clinical trial testing. As more agents become clinically accessible, immense effort is underway to understand the target effects, tumor penetration, and immune microenvironmental changes of epigenetic modification.

Conclusion: We continue to seek a comprehensive understanding of the mechanisms that govern chromatin dysregulation and DNA modification in DMG, and in parallel we forge ahead with clinical testing of epigenetic modifiers. The determined efforts from bench to bedside, along with collaborative mindset and unified mission, will ultimately result in improved outcomes for DMG.
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http://dx.doi.org/10.1007/s11060-020-03553-1DOI Listing
October 2020

Pattern of Relapse and Treatment Response in WNT-Activated Medulloblastoma.

Cell Rep Med 2020 Jun;1(3)

Departments of Pediatrics, Anatomy, and Neurobiology, Washington University School of Medicine, St. Louis, MO, USA.

Over the past decade, wingless-activated (WNT) medulloblastoma has been identified as a candidate for therapy de-escalation based on excellent survival; however, a paucity of relapses has precluded additional analyses of markers of relapse. To address this gap in knowledge, an international cohort of 93 molecularly confirmed WNT MB was assembled, where 5-year progression-free survival is 0.84 (95%, 0.763-0.925) with 15 relapsed individuals identified. Maintenance chemotherapy is identified as a strong predictor of relapse, with individuals receiving high doses of cyclophosphamide or ifosphamide having only one very late molecularly confirmed relapse (p = 0.032). The anatomical location of recurrence is metastatic in 12 of 15 relapses, with 8 of 12 metastatic relapses in the lateral ventricles. Maintenance chemotherapy, specifically cumulative cyclophosphamide doses, is a significant predictor of relapse across WNT MB. Future efforts to de-escalate therapy need to carefully consider not only the radiation dose but also the chemotherapy regimen and the propensity for metastatic relapses.
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http://dx.doi.org/10.1016/j.xcrm.2020.100038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7394286PMC
June 2020

An OTX2-PAX3 signaling axis regulates Group 3 medulloblastoma cell fate.

Nat Commun 2020 07 20;11(1):3627. Epub 2020 Jul 20.

Regenerative Medicine Program, Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, Canada.

OTX2 is a potent oncogene that promotes tumor growth in Group 3 medulloblastoma. However, the mechanisms by which OTX2 represses neural differentiation are not well characterized. Here, we perform extensive multiomic analyses to identify an OTX2 regulatory network that controls Group 3 medulloblastoma cell fate. OTX2 silencing modulates the repressive chromatin landscape, decreases levels of PRC2 complex genes and increases the expression of neurodevelopmental transcription factors including PAX3 and PAX6. Expression of PAX3 and PAX6 is significantly lower in Group 3 medulloblastoma patients and is correlated with reduced survival, yet only PAX3 inhibits self-renewal in vitro and increases survival in vivo. Single cell RNA sequencing of Group 3 medulloblastoma tumorspheres demonstrates expression of an undifferentiated progenitor program observed in primary tumors and characterized by translation/elongation factor genes. Identification of mTORC1 signaling as a downstream effector of OTX2-PAX3 reveals roles for protein synthesis pathways in regulating Group 3 medulloblastoma pathogenesis.
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http://dx.doi.org/10.1038/s41467-020-17357-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7371715PMC
July 2020

Salvage chemotherapy after failure of targeted therapy in a child with BRAF V600E low-grade glioma.

Pediatr Blood Cancer 2021 01 18;68(1):e28561. Epub 2020 Jul 18.

Division of Haematology/Oncology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.

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http://dx.doi.org/10.1002/pbc.28561DOI Listing
January 2021

Pontine gliomas a 10-year population-based study: a report from The Canadian Paediatric Brain Tumour Consortium (CPBTC).

J Neurooncol 2020 Aug 7;149(1):45-54. Epub 2020 Jul 7.

Division of Haematology Oncology, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, M5G 1X8, Canada.

Background: Diffuse intrinsic pontine gliomas (DIPG) are midline gliomas that arise from the pons and the majority are lethal within a few months after diagnosis. Due to the lack of histological diagnosis the epidemiology of DIPG is not completely understood. The aim of this report is to provide population-based data to characterize the descriptive epidemiology of this condition in Canadian children.

Patients And Methods: A national retrospective study of children and adolescents diagnosed with DIPG between 2000 and 2010 was undertaken. All cases underwent central review to determine clinical and radiological diagnostic characteristics. Crude incidence figures were calculated using age-adjusted (0-17 year) population data from Statistics Canada. Survival analyses were performed using the Kaplan-Meier method.

Results: A total of 163 patients with pontine lesions were identified. Central review determined one-hundred and forty-three patients who met clinical, radiological and/or histological criteria for diagnosis. We estimate an incidence rate of 1.9 DIPG/1,000,000 children/year in the Canadian population over a 10 years period. Median age at diagnosis was 6.8 years and 50.3% of patients were female. Most patients presented with cranial nerve palsies (76%) and ataxia (66%). Despite typical clinical and radiological characteristics, histological confirmation reported three lesions to be low-grade gliomas and three were diagnosed as CNS embryonal tumor not otherwise specified (NOS).

Conclusions: Our study highlights the challenges associated with epidemiology studies on DIPG and the importance of central review for incidence rate estimations. It emphasizes that tissue biopsies are required for accurate histological and molecular diagnosis in patients presenting with pontine lesions and reinforces the limitations of radiological and clinical diagnosis in DIPG. Likewise, it underscores the urgent need to increase the availability and accessibility to clinical trials.
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http://dx.doi.org/10.1007/s11060-020-03568-8DOI Listing
August 2020

MR imaging features of diffuse intrinsic pontine glioma and relationship to overall survival: report from the International DIPG Registry.

Neuro Oncol 2020 11;22(11):1647-1657

Department of Radiology and Medical Imaging, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.

Background: This study describes imaging features of diffuse intrinsic pontine glioma (DIPG) and correlates with overall survival (OS) and histone mutation status in the International DIPG Registry (IDIPGR).

Methods: Four hundred cases submitted to the IDIPGR with a local diagnosis of DIPG and baseline MRI were evaluated by consensus review of 2 neuroradiologists; 43 cases were excluded (inadequate imaging or alternative diagnoses). Agreement between reviewers, association with histone status, and univariable and multivariable analyses relative to OS were assessed.

Results: On univariable analysis imaging features significantly associated with worse OS included: extrapontine extension, larger size, enhancement, necrosis, diffusion restriction, and distant disease. On central review, 9.5% of patients were considered not to have DIPG. There was moderate mean agreement of MRI features between reviewers. On multivariable analysis, chemotherapy, age, and distant disease were predictors of OS. There was no difference in OS between wild-type and H3 mutated cases. The only imaging feature associated with histone status was the presence of ill-defined signal infiltrating pontine fibers.

Conclusions: Baseline imaging features are assessed in the IDIPGR. There was a 9.5% discordance in DIPG diagnosis between local and central review, demonstrating need for central imaging confirmation for prospective trials. Although several imaging features were significantly associated with OS (univariable), only age and distant disease were significant on multivariable analyses. There was limited association of imaging features with histone mutation status, although numbers are small and evaluation exploratory.
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http://dx.doi.org/10.1093/neuonc/noaa140DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7690352PMC
November 2020
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