title: Spatial genomic heterogeneity in diffuse intrinsic pontine and midline high-grade glioma: implications for diagnostic biopsy and targeted therapeutics.
abstract: BACKGROUND
  Diffuse intrinsic pontine glioma (DIPG) and midline high-grade glioma (mHGG) are lethal childhood brain tumors. Spatial genomic heterogeneity has been well-described in adult HGG but has not been comprehensively characterized in pediatric HGG. We performed whole exome sequencing on 38-matched primary, contiguous, and metastatic tumor sites from eight children with DIPG (n = 7) or mHGG (n = 1) collected using a unique MRI-guided autopsy protocol. Validation was performed using Sanger sequencing, Droplet Digital polymerase-chain reaction, immunohistochemistry, and fluorescent in-situ hybridization.
  
  
  RESULTS
  Median age at diagnosis was 6.1 years (range: 2.9-23.3 years). Median overall survival was 13.2 months (range: 11.2-32.2 months). Contiguous tumor infiltration and distant metastases were observed in seven and six patients, respectively, including leptomeningeal dissemination in three DIPGs. Histopathological heterogeneity was evident in seven patients, including intra-pontine heterogeneity in two DIPGs, ranging from World Health Organization grade II to IV astrocytoma. We found conservation of heterozygous K27M mutations in H3F3A (n = 4) or HIST1H3B (n = 3) across all primary, contiguous, and metastatic tumor sites in all DIPGs. ACVR1 (n = 2), PIK3CA (n = 2), FGFR1 (n = 2), and MET (n = 1) were also intra-tumorally conserved. ACVR1 was co-mutated with HIST1H3B (n = 2). In contrast, PDGFRA amplification and mutation were spatially heterogeneous, as were mutations in BCOR (n = 1), ATRX (n = 2), and MYC (n = 1). TP53 aberrations (n = 3 patients) varied by type and location between primary and metastatic tumors sites but were intra-tumorally conserved.
  
  
  CONCLUSIONS
  Spatial conservation of prognostically-relevant and therapeutically-targetable somatic mutations in DIPG and mHGG contrasts the significant heterogeneity of driver mutations seen in adult HGG and supports uniform implementation of diagnostic biopsy in DIPG and mHGG to classify molecular risk groups and guide therapeutic strategy.
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. Lindsey.hoffman@cchmc.org.
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Hoffman
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. mariko.dewire@cchmc.org.
authors.forename: Mariko
authors.initials: M
authors.lastname: DeWire
authors.affiliation: The Hospital for Sick Children, Toronto, Canada. Scott.ryall@sickkids.ca.
authors.forename: Scott
authors.initials: S
authors.lastname: Ryall
authors.affiliation: The Hospital for Sick Children, Toronto, Canada. Pawel.buczkowicz@sickkids.ca.
authors.forename: Pawel
authors.initials: P
authors.lastname: Buczkowicz
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. james.leach@cchmc.org.
authors.forename: James
authors.initials: J
authors.lastname: Leach
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. lili.miles@nemours.org.
authors.forename: Lili
authors.initials: L
authors.lastname: Miles
authors.affiliation: The Hospital for Sick Children, Toronto, Canada. arun.ramani@sickkids.ca.
authors.forename: Arun
authors.initials: A
authors.lastname: Ramani
authors.affiliation: The Hospital for Sick Children, Toronto, Canada. Michael.brudno@sickkids.ca.
authors.forename: Michael
authors.initials: M
authors.lastname: Brudno
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. shiva.kumar@cchmc.org.
authors.forename: Shiva Senthil
authors.initials: SS
authors.lastname: Kumar
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. rachid.drissi@cchmc.org.
authors.forename: Rachid
authors.initials: R
authors.lastname: Drissi
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. phillip.dexheimer@cchmc.org.
authors.forename: Phillip
authors.initials: P
authors.lastname: Dexheimer
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. ralph.salloum@cchmc.org.
authors.forename: Ralph
authors.initials: R
authors.lastname: Salloum
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. lionel.chow@cchmc.org.
authors.forename: Lionel
authors.initials: L
authors.lastname: Chow
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. trent.hummel@cchmc.org.
authors.forename: Trent
authors.initials: T
authors.lastname: Hummel
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. Charles.stevenson@cchmc.org.
authors.forename: Charles
authors.initials: C
authors.lastname: Stevenson
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. Richard.lu@cchmc.org.
authors.forename: Q Richard
authors.initials: QR
authors.lastname: Lu
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. blaise.jones@cchmc.org.
authors.forename: Blaise
authors.initials: B
authors.lastname: Jones
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. david.witte@cchmc.org.
authors.forename: David
authors.initials: D
authors.lastname: Witte
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. bruce.aronow@cchmc.org.
authors.forename: Bruce
authors.initials: B
authors.lastname: Aronow
authors.affiliation: The Hospital for Sick Children, Toronto, Canada. Cynthia.hawkins@sickkids.ca.
authors.forename: Cynthia E
authors.initials: CE
authors.lastname: Hawkins
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. Maryam.fouladi@cchmc.org.
authors.forename: Maryam
authors.initials: M
authors.lastname: Fouladi
mesh_terms: D000293:Adolescent; D001706:Biopsy; D020295:Brain Stem Neoplasms / Q000175:diagnosis* / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D005260:Female; D020869:Gene Expression Profiling; D005910:Glioma / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009154:Mutation / Q000235:genetics*; D012720:Severity of Illness Index; D055815:Young Adult