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Characterizing temporal genomic heterogeneity in pediatric high-grade gliomas.

ABSTRACT: Pediatric high-grade gliomas (pHGGs) are aggressive neoplasms representing approximately 20% of brain tumors in children. Current therapies offer limited disease control, and patients have a poor prognosis. Empiric use of targeted therapy, especially at progression, is increasingly practiced despite a paucity of data regarding temporal and therapy-driven genomic evolution in pHGGs. To study the genetic landscape of pHGGs at recurrence, we performed whole exome and methylation analyses on matched primary and recurrent pHGGs from 16 patients. Tumor mutational profiles identified three distinct subgroups. Group 1 (n?=?7) harbored known hotspot mutations in Histone 3 (H3) (K27M or G34V) or IDH1 (H3/IDH1 mutants) and co-occurring TP53 or ACVR1 mutations in tumor pairs across the disease course. Group 2 (n?=?7), H3/IDH1 wildtype tumor pairs, harbored novel mutations in chromatin modifiers (ZMYND11, EP300 n?=?2), all associated with TP53 alterations, or had BRAF V600E mutations (n?=?2) conserved across tumor pairs. Group 3 included 2 tumors with NF1 germline mutations. Pairs from primary and relapsed pHGG samples clustered within the same DNA methylation subgroup. ATRX mutations were clonal and retained in H3G34V and H3/IDH1 wildtype tumors, while different genetic alterations in this gene were observed at diagnosis and recurrence in IDH1 mutant tumors. Mutations in putative drug targets (EGFR, ERBB2, PDGFRA, PI3K) were not always shared between primary and recurrence samples, indicating evolution during progression. Our findings indicate that specific key driver mutations in pHGGs are conserved at recurrence and are prime targets for therapeutic development and clinical trials (e.g. H3 post-translational modifications, IDH1, BRAF V600E). Other actionable mutations are acquired or lost, indicating that re-biopsy at recurrence will provide better guidance for effective targeted therapy of pHGGs.

SUBMITTER: Salloum R

PROVIDER: S-EPMC5663045 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Characterizing temporal genomic heterogeneity in pediatric high-grade gliomas.

Salloum Ralph R McConechy Melissa K MK Mikael Leonie G LG Fuller Christine C Drissi Rachid R DeWire Mariko M Nikbakht Hamid H De Jay Nicolas N Yang Xiaodan X Boue Daniel D Chow Lionel M L LML Finlay Jonathan L JL Gayden Tenzin T Karamchandani Jason J Hummel Trent R TR Olshefski Randal R Osorio Diana S DS Stevenson Charles C Kleinman Claudia L CL Majewski Jacek J Fouladi Maryam M Jabado Nada N

Acta neuropathologica communications 20171030 1

Pediatric high-grade gliomas (pHGGs) are aggressive neoplasms representing approximately 20% of brain tumors in children. Current therapies offer limited disease control, and patients have a poor prognosis. Empiric use of targeted therapy, especially at progression, is increasingly practiced despite a paucity of data regarding temporal and therapy-driven genomic evolution in pHGGs. To study the genetic landscape of pHGGs at recurrence, we performed whole exome and methylation analyses on matched ...[more]

PMID: 29084603

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Project description:The outcome for children with high-grade gliomas (HGG) remains dismal, with a two-year survival rate of only 10-30%. Approximately half of pediatric HGGs are diffuse intrinsic pontine glioma (DIPG), a brainstem tumor that arises almost exclusively in children. Genome-wide analyses of copy number imbalances previously showed that platelet derived growth factor receptor alpha (PDGFRA) is the most frequent target of focal amplification in pediatric HGGs. To determine whether the PDGFRA is also targeted by more subtle mutations not detected by copy number analysis, we sequenced all PDGFRA coding exons from a cohort of pediatric HGGs. Somatic activating mutations were identified in 14.4% (13/90) of non-brainstem pediatric HGGs and 4.7% (2/43) of DIPGs, including missense mutations and in-frame deletions and insertions not previously described. 40% of tumors with mutation showed concurrent amplification, while 60% carried heterozygous mutations. Six different mutations impacting different domains all resulted in ligand-independent receptor activation that was blocked by small molecule inhibitors of PDGFR. Expression of mutants in p53-null primary mouse astrocytes conferred a proliferative advantage in vitro, and generated HGGs in vivo with complete penetrance when implanted into brain. The gene expression signatures reflected the spectrum of human diffuse HGGs. PDGFRA intragenic deletion of exons 8 and 9 were previously shown in adult HGG, but were not detected in 83 non-brainstem pediatric HGG and 57 DIPGs. Thus, a distinct spectrum of mutations confers constitutive receptor activation and oncogenic activity to PDGFR in childhood HGG. To better understand the consequence of PDGFRα mutation in pediatric gliomagenesis, retroviral constructs expressing wild-type PDGFRα or six selected PDGFRα mutants that affect different regions of the receptor were generated for functional studies. p53-null primary mouse astrocyte (PMA) cultures were chosen as a relevant cellular background to assess PDGFRα function.

Dataset Information

Characterizing temporal genomic heterogeneity in pediatric high-grade gliomas.

Publications

Characterizing temporal genomic heterogeneity in pediatric high-grade gliomas.

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