ALK Amplification and Rearrangements Are Recurrent Targetable Events in Congenital and Adult Glioblastoma.

PURPOSE: Anaplastic lymphoma kinase (ALK) aberrations have been identified in pediatric-type infant gliomas, but their occurrence across age groups, functional effects, and treatment response has not been broadly established. EXPERIMENTAL DESIGN: We performed a comprehensive analysis of ALK expression and genomic aberrations in both newly generated and retrospective data from 371 glioblastomas (156 adult, 205 infant/pediatric, and 10 congenital) with in vitro and in vivo validation of aberrations. RESULTS: ALK aberrations at the protein or genomic level were detected in 12% of gliomas (45/371) in a wide age range (0-80 years). Recurrent as well as novel ALK fusions (LRRFIP1-ALK, DCTN1-ALK, PRKD3-ALK) were present in 50% (5/10) of congenital/infant, 1.4% (3/205) of pediatric, and 1.9% (3/156) of adult GBMs. ALK fusions were present as the only candidate driver in congenital/infant GBMs and were sometimes focally amplified. In contrast, adult ALK fusions co-occurred with other oncogenic drivers. No activating ALK mutations were identified in any age group. Novel and recurrent ALK rearrangements promoted STAT3 and ERK1/2 pathways and transformation in vitro and in vivo. ALK-fused GBM cellular and mouse models were responsive to ALK inhibitors, including in patient cells derived from a congenital GBM. Relevant to the treatment of infant gliomas, we showed that ALK protein appears minimally expressed in the forebrain at perinatal stages, and no gross effects on perinatal brain development were seen in pregnant mice treated with the ALK inhibitor ceritinib. CONCLUSIONS: These findings support use of brain-penetrant ALK inhibitors in clinical trials across infant, pediatric, and adult GBMs. See related commentary by Mack and Bertrand, p. 2567.

Structural variants shape driver combinations and outcomes in pediatric high-grade glioma.

We analyzed the contributions of structural variants (SVs) to gliomagenesis across 179 pediatric high-grade gliomas (pHGGs). The most recurrent SVs targeted MYC isoforms and receptor tyrosine kinases (RTKs), including an SV amplifying a MYC enhancer in 12% of diffuse midline gliomas (DMG), indicating an underappreciated role for MYC in pHGG. SV signature analysis revealed that tumors with simple signatures were TP53 wild type (TP53WT) but showed alterations in TP53 pathway members PPM1D and MDM4. Complex signatures were associated with direct aberrations in TP53, CDKN2A and RB1 early in tumor evolution and with later-occurring extrachromosomal amplicons. All pHGGs exhibited at least one simple-SV signature, but complex-SV signatures were primarily restricted to subsets of H3.3K27M DMGs and hemispheric pHGGs. Importantly, DMGs with complex-SV signatures were associated with shorter overall survival independent of histone mutation and TP53 status. These data provide insight into the impact of SVs on gliomagenesis and the mechanisms that shape them.

Liquid biopsy detection of genomic alterations in pediatric brain tumors from cell-free DNA in peripheral blood, CSF, and urine.

BACKGROUND: The ability to identify genetic alterations in cancers is essential for precision medicine; however, surgical approaches to obtain brain tumor tissue are invasive. Profiling circulating tumor DNA (ctDNA) in liquid biopsies has emerged as a promising approach to avoid invasive procedures. Here, we systematically evaluated the feasibility of profiling pediatric brain tumors using ctDNA obtained from plasma, cerebrospinal fluid (CSF), and urine. METHODS: We prospectively collected 564 specimens (257 blood, 240 urine, and 67 CSF samples) from 258 patients across all histopathologies. We performed ultra-low-pass whole-genome sequencing (ULP-WGS) to assess copy number variations and estimate tumor fraction and developed a pediatric CNS tumor hybrid capture panel for deep sequencing of specific mutations and fusions. RESULTS: ULP-WGS detected copy number alterations in 9/46 (20%) CSF, 3/230 (1.3%) plasma, and 0/153 urine samples. Sequencing detected alterations in 3/10 (30%) CSF, 2/74 (2.7%) plasma, and 0/2 urine samples. The only positive results were in high-grade tumors. However, most samples had insufficient somatic mutations (median 1, range 0-39) discoverable by the sequencing panel to provide sufficient power to detect tumor fractions of greater than 0.1%. CONCLUSIONS: Children with brain tumors harbor very low levels of ctDNA in blood, CSF, and urine, with CSF having the most DNA detectable. Molecular profiling is feasible in a small subset of high-grade tumors. The level of clonal aberrations per genome is low in most of the tumors, posing a challenge for detection using whole-genome or even targeted sequencing methods. Substantial challenges therefore remain to genetically characterize pediatric brain tumors from liquid biopsies.

Novel predictive scoring system for morbid hypothalamic obesity in patients with pediatric craniopharyngioma.

PURPOSE: To identify the independent risk factors for developing morbid hypothalamic obesity, to propose a predictive scoring system for morbid hypothalamic obesity, and to propose an algorithm for management in order to minimize the risk of developing morbid hypothalamic obesity in patients with pediatric craniopharyngioma. METHODS: A retrospective analysis of all pediatric craniopharyngioma patients diagnosed and treated at Boston Children's Hospital (BCH) between 1985 and 2017. Analysis of the data was conducted using IBM SPSS Statistics. RESULTS: We identified 105 patients, 90 (47 males and 43 females) fulfilled the inclusion criteria. The median age of patients at time of diagnosis was 8.4 years. The median follow-up was 10.6 years. Morbid hypothalamic obesity was evident in 28 (31.1%) patients at the last follow-up visit. Age of patients at time of diagnosis > 10 years (P = 0.023), preoperative body mass index (BMI) > 95th percentile (P = 0.006), and preoperative papilledema (P < 0.001) were the independent risk factors for developing morbid hypothalamic obesity. CONCLUSION: We developed a unique predictive scoring system in order to differentiate between patients with and without high risk for developing morbid hypothalamic obesity.

A modified IRS-III chemotherapy regimen leads to prolonged survival in children with embryonal tumor with multilayer rosettes.

BACKGROUND: Embryonal tumor with multilayer rosettes (ETMR) is a rare CNS malignancy affecting young children that carries a very poor prognosis. Treatment with intensive surgical resection, radiotherapy, and high-dose chemotherapy is insufficient treatment in the vast majority of cases. Effective, biologically based therapies for this tumor are therefore desperately needed. The Dana-Farber Cancer Institute-modified IRS-III protocol incorporates preclinically active agents, such as doxorubicin and actinomycin D, into the treatment regimen for ETMR and may improve patient outcomes. METHODS: The authors present a case series of 5 children with ETMR treated with an IRS-III-based chemotherapy backbone. RESULTS: All 5 patients received a gross-total tumor resection. Patients received between 12 and 51 weeks of IRS-III therapy at the discretion of their treating physician. Four patients received focal radiation therapy, with the fifth patient instead receiving a cycle of high-dose chemotherapy with autologous stem cell rescue. Four patients have progression-free survival of more than 18 months. Chemotherapy treatment was reasonably tolerated by all 5 patients with one case of mild sinusoidal obstructive syndrome and one case of Grade 3 peripheral neuropathy. CONCLUSIONS: The patient outcomes in this small cohort are far better than would be expected based on the historical survival for this tumor. Given the tremendous need for effective therapy for ETMR, further investigation of this approach is warranted. An international consensus protocol based on the IRS-III regimen has been developed and will be available through a multicenter clinical trial and a global treatment registry.

Analysis of 2141 pediatric craniopharyngioma admissions in the USA utilizing the Kids' Inpatient Database (KID): predictors of discharge disposition.

OBJECTIVES: To recognize the national trends in management of pediatric craniopharyngioma and to address the significant predictors of discharge disposition. METHODS: We utilized the Kids' Inpatient Database (KID), a pediatric inpatient sample generated by the Healthcare Cost and Utilization Project (HCUP) triennially from 1997 to 2016. RESULTS: KID contains 2141 pediatric craniopharyngioma admissions. Patient demographics had no effect on discharge disposition. Based on the multivariable logistic regression analysis, we confirmed a significantly higher non-routine discharge rate among patients with hydrocephalus (P = 0.01). Patients who developed diabetes insipidus were at higher risk for non-routine discharge (P = 0.02). Admission of patients to a freestanding children's hospital increased the likelihood of routine discharge (P = 0.001). CONCLUSION: Hydrocephalus, diabetes insipidus, and admission to a freestanding children's hospital are significant independent predictors of discharge disposition.

Sixty years single institutional experience with pediatric craniopharyngioma: between the past and the future.

PURPOSE: To demonstrate the paradigm shift in management strategies of pediatric craniopharyngioma at our institution over the past six decades. METHODS: Retrospective analysis of all pediatric patients with craniopharyngioma treated at Boston Children's Hospital between 1960 and 2017. RESULTS: One hundred seventy-eight patients with craniopharyngioma were treated between 1960 and 2017; 135 (70 males and 65 females) fulfilled the inclusion criteria. Forty-five patients were treated in the old era (1960-1984) and 90 patients were treated in the new era (1985-2017). Gross total resection (GTR) was achieved in 4% and 43% of patients in old and new eras respectively. Sub-total resection (STR) and radiotherapy (XRT) were performed in 27% and 28% of patients in old and new eras respectively. STR without XRT was performed in 20% and 29% of patients in old and new era respectively. Cyst drainage and adjuvant radiotherapy were performed in 49% of patients in the old era while no patients in the new era underwent such conservative management. Aggressive surgical resection was associated with a higher risk of worsening visual outcomes (20% vs 16%), panhypopituitarism and diabetes insipidus (86% vs 53%), psycho-social impairment (42% vs 26%), and new-onset obesity (33% vs 22%). The mortality rate was higher in the old era in comparison with that of the new one (9% vs 2%). CONCLUSION: There was a paradigm shift in management strategies of pediatric craniopharyngioma over the past six decades which in turn affected the long-term outcomes and quality of life of patients.

Optimizing Postoperative Surveillance of Pediatric Low-Grade Glioma Using Tumor Behavior Patterns.

BACKGROUND: Pediatric low-grade gliomas are among the most common childhood neoplasms, yet their post-treatment surveillance remains nonstandardized, relying on arbitrarily chosen imaging intervals. OBJECTIVE: To optimize postoperative magnetic resonance imaging (MRI) surveillance protocols for pediatric low-grade gliomas. METHODS: Patients aged 0 to 21 yr with pediatric low-grade gliomas, treated between 1990 and 2016 were retrospectively analyzed. The timing of surveillance imaging and radiologic tumor outcomes were extracted, and the effect of patient age, tumor location, histology, and extent of resection as prognostic factors was studied. An algorithm was developed to analyze the detection efficacy and cost of all possible surveillance protocols. RESULTS: A total of 517 patients were included with a median follow-up of 7.7 yr (range: 2-25.1 yr) who underwent 8061 MRI scans (mean 15.6 scans per patient). Tumor recurrence was detected radiologically in 292 patients (56.5%), of whom, 143 underwent reoperation. The hazards ratio (HR) of recurrence was higher in patients who underwent biopsy (HR = 3.60; 95% confidence interval (CI): 2.45-5.30; P < .001), subtotal resection (HR = 2.97; 95% CI: 2.18-4.03; P < .001), and near-total resection (HR = 2.03; 95% CI: 1.16-3.54; P = .01), compared to patients with gross total resection (GTR). For all patients, an 8-image surveillance protocol at 0, 3, 6, 12, 24, 36, 60, and 72 mo (total cost: $13 672 per patient) yielded comparative detection rates to the current 15-image protocol ($25 635). For patients who underwent GTR, a 6-image protocol at 0, 3, 9, 24, 36, and 60 mo ($10 254) is sufficient. CONCLUSION: Our data suggest that postoperative surveillance of pediatric low-grade gliomas can be effectively performed using less frequent imaging compared to current practice, thereby improving adherence to follow-up, and quality-of-life, while reducing costs.

Natural History and Management of Incidentally Discovered Focal Brain Lesions Indeterminate for Tumor in Children.

BACKGROUND: The incidental discovery of brain lesions in children has increased due to greater utilization of neuroimaging. Standardized surveillance and management guidelines following the discovery of such lesions remain nonexistent. OBJECTIVE: To study the natural history and management of incidental brain lesions in children. METHODS: A retrospective analysis of pediatric patients who were treated at our institution between 2000 and 2016 with incidentally detected brain lesions that were indeterminate for neoplasm on MRI. RESULTS: We identified 445 patients with incidental brain abnormalities of whom 144 had lesions indeterminate for neoplasm. Average age at diagnosis was 11.2 (SD = 4.14) yr and average follow-up was 3.8 yr (range 1-13.2 yr). Lesions showed no progression in 112 patients (77.8%), whereas progression was detected in 31 patients (21.5%). Mean time to progression was 32.3 months (SD = 24.4). A change in management was made in 13/144 patients (9%), which included surgical resection (n = 11), biopsy (n = 1), and lumbar puncture (n = 1). Lesion size, location, multiplicity, new-onset symptoms, associated contrast enhancement, or edema were not predictive of radiologic progression. Larger lesions and those with contrast enhancement or edema were significantly more likely to undergo surgery (P < .001 each). Median geometric diameter of lesions that did not undergo surgery was 6.5 mm, whereas that of surgically resected lesions was 12.5 mm (P < .001). CONCLUSION: Most incidental brain lesions indeterminate for neoplasm have an indolent, benign course. For asymptomatic patients with radiologically stable lesions, we recommend conservative management with MRI and clinical surveillance at 6, 12, 24, 36, and 60 mo after detection.

Mitogenic and progenitor gene programmes in single pilocytic astrocytoma cells.

Pilocytic astrocytoma (PA), the most common childhood brain tumor, is a low-grade glioma with a single driver BRAF rearrangement. Here, we perform scRNAseq in six PAs using methods that enabled detection of the rearrangement. When compared to higher-grade gliomas, a strikingly higher proportion of the PA cancer cells exhibit a differentiated, astrocyte-like phenotype. A smaller proportion of cells exhibit a progenitor-like phenotype with evidence of proliferation. These express a mitogen-activated protein kinase (MAPK) programme that was absent from higher-grade gliomas. Immune cells, especially microglia, comprise 40% of all cells in the PAs and account for differences in bulk expression profiles between tumor locations and subtypes. These data indicate that MAPK signaling is restricted to relatively undifferentiated cancer cells in PA, with implications for investigational therapies directed at this pathway.

Resolving medulloblastoma cellular architecture by single-cell genomics.

Medulloblastoma is a malignant childhood cerebellar tumour type that comprises distinct molecular subgroups. Whereas genomic characteristics of these subgroups are well defined, the extent to which cellular diversity underlies their divergent biology and clinical behaviour remains largely unexplored. Here we used single-cell transcriptomics to investigate intra- and intertumoral heterogeneity in 25 medulloblastomas spanning all molecular subgroups. WNT, SHH and Group 3 tumours comprised subgroup-specific undifferentiated and differentiated neuronal-like malignant populations, whereas Group 4 tumours consisted exclusively of differentiated neuronal-like neoplastic cells. SHH tumours closely resembled granule neurons of varying differentiation states that correlated with patient age. Group 3 and Group 4 tumours exhibited a developmental trajectory from primitive progenitor-like to more mature neuronal-like cells, the relative proportions of which distinguished these subgroups. Cross-species transcriptomics defined distinct glutamatergic populations as putative cells-of-origin for SHH and Group 4 subtypes. Collectively, these data provide insights into the cellular and developmental states underlying subtype-specific medulloblastoma biology.

Hypoxia-enhanced Blood-Brain Barrier Chip recapitulates human barrier function and shuttling of drugs and antibodies.

The high selectivity of the human blood-brain barrier (BBB) restricts delivery of many pharmaceuticals and therapeutic antibodies to the central nervous system. Here, we describe an in vitro microfluidic organ-on-a-chip BBB model lined by induced pluripotent stem cell-derived human brain microvascular endothelium interfaced with primary human brain astrocytes and pericytes that recapitulates the high level of barrier function of the in vivo human BBB for at least one week in culture. The endothelium expresses high levels of tight junction proteins and functional efflux pumps, and it displays selective transcytosis of peptides and antibodies previously observed in vivo. Increased barrier functionality was accomplished using a developmentally-inspired induction protocol that includes a period of differentiation under hypoxic conditions. This enhanced BBB Chip may therefore represent a new in vitro tool for development and validation of delivery systems that transport drugs and therapeutic antibodies across the human BBB.

Correction to: Iatrogenic obstructive hydrocephalus resulting from Gelfoam accumulation within the cerebral aqueduct: a case report.

The original version of this article unfortunately contained an error. The authors apologize to have miss looked a typo of author name "Joseph Diver". The correct name is "Joseph Driver".

Phase I study of gene-mediated cytotoxic immunotherapy with AdV-tk as adjuvant to surgery and radiation for pediatric malignant glioma and recurrent ependymoma.

BACKGROUND: Gene-mediated cytotoxic immunotherapy (GMCI) is a tumor-specific immune stimulatory strategy implemented through local delivery of aglatimagene besadenovec (AdV-tk) followed by anti-herpetic prodrug. GMCI induces T-cell dependent tumor immunity and synergizes with radiotherapy. Clinical trials in adult malignant gliomas demonstrated safety and potential efficacy. This is the first trial of GMCI in pediatric brain tumors. METHODS: This phase I dose escalation study was conducted to evaluate GMCI in patients 3 years of age or older with malignant glioma or recurrent ependymoma. AdV-tk at doses of 1 × 1011 and 3 × 1011 vector particles (vp) was injected into the tumor bed at the time of surgery followed by 14 days of valacyclovir. Radiation started within 8 days of surgery, and if indicated, chemotherapy began after completion of valacyclovir. RESULTS: Eight patients (6 glioblastoma, 1 anaplastic astrocytoma, 1 recurrent ependymoma) were enrolled and completed therapy: 3 on dose level 1 and 5 on dose level 2. Median age was 12.5 years (range 7-17) and Lansky/Karnofsky performance scores were 60-100. Five patients had multifocal/extensive tumors that could not be resected completely and 3 had gross total resection. There were no dose-limiting toxicities. The most common possibly GMCI-related adverse events included Common Terminology Criteria for Adverse Events grade 1-2 fever, fatigue, and nausea/vomiting. Three patients, in dose level 2, lived more than 24 months, with 2 alive without progression 37.3 and 47.7 months after AdV-tk injection. CONCLUSIONS: GMCI can be safely combined with radiation therapy with or without temozolomide in pediatric patients with brain tumors and the present results strongly support further investigation. CLINICAL TRIAL REGISTRY: ClinicalTrials.gov NCT00634231.

Noninvasive Thermal Evaluation of Ventriculoperitoneal Shunt Patency and Cerebrospinal Fluid Flow Using a Flow Enhancing Device.

BACKGROUND: While a noninvasive flow determination would be desirable in the diagnosis of cerebrospinal fluid shunt malfunction, existing studies have not yet defined a role for thermal flow detection. OBJECTIVE: To evaluate a revised test protocol using a micropumper designed to transiently enhance flow during thermal testing to determine whether thermal detection of flow is associated with progression to shunt revision surgery. METHODS: Eighty-two unique tests were performed in 71 shunts. The primary outcome, need for revision within 7 d of testing, was compared with results of micropumper-augmented thermal flow detection. Statistical analysis was based on blind interpretation of test results and raw temperature data recorded during testing. RESULTS: The test was sensitive (73%) and specific (68%) in predicting need for revision, with 5.6-fold higher probability of revision when flow was not detected. Negative predictive value in our sample was 94.2%. The probability of not requiring revision increased with increasing total temperature drop. Analysis of various possible thresholds showed that the optimal temperature cutoff may be lower than suggested by the manufacturer (0.125°C vs 0.2°C). CONCLUSION: This is the first study to report a strong association between thermal flow evaluation and a clinical impression that a shunt is not malfunctioning. The current recommended threshold may increase the false positive rate unnecessarily, and as clinicians gain experience with the method, they may find value in examining the temperature curves themselves. Multicenter studies are suggested to further define a role for this diagnostic test.

The Impact of Intraoperative Electrocorticography on Seizure Outcome After Resection of Pediatric Brain Tumors: A Cohort Study.

BACKGROUND: Intraoperative electrocorticography (ECoG) has been utilized in patients with tumor-associated seizures; however, its effectiveness for seizure control remains controversial. OBJECTIVE: To evaluate clinical outcomes in pediatric patients undergoing lesionectomy with or without ECoG. METHODS: Patients undergoing brain tumor resection at Boston Children's Hospital were examined retrospectively (2005-2014). Inclusion criteria involved diagnosis of a supratentorial tumor, ≥2 unequivocal seizures, and ≥6 mo follow-up. Patients with isolated cortical dysplasia or posterior fossa tumors were excluded. Logistic regression models evaluated predictors of ECoG use, and the impact of ECoG, gross total resection, and focal cortical dysplasia with tumors on seizure freedom by Engel Class and anti-epileptic drug use (AED). RESULTS: A total of 119 pediatric patients were included (n = 69 males, 58%; median age, 11.3 yr). Forty-one patients (34.5%) had ECoG-guided surgery. Preoperative seizure duration and number and duration of AED use were significant predictors for undergoing ECoG. There were no differences in seizure freedom (Engel Class I) or improved Engel Score (Class I-II vs III-IV) in patients who did or did not have ECoG at 30 d, 6 mo, and 1, 2, or 5 yr. Patients undergoing ECoG required a greater number of AEDs at 6 mo (P = .01), although this difference disappeared at subsequent time intervals. Gross total resection predicted seizure freedom at 30 d and 6 mo postsurgery (P = .045). CONCLUSION: This retrospective study, one of the largest evaluating the use of ECoG during tumor resection, suggests that ECoG does not provide improved seizure freedom compared to lesionectomy alone for children.

Tumor dissemination through surgical tracts in diffuse intrinsic pontine glioma.

OBJECTIVEDiffuse intrinsic pontine glioma (DIPG) is a highly aggressive and lethal brainstem tumor in children. In the 1980s, routine biopsy at presentation was abandoned since it was claimed "unnecessary" for diagnosis. In the last decade, however, several groups have reincorporated this procedure as standard of care or in the context of clinical trials. Expert neurosurgical teams report no mortality and acceptable morbidity, and no relevant complications have been previously described. The aim of this study was to review needle tract dissemination as a potential complication in DIPG.METHODSThe authors retrospectively analyzed the incidence of dissemination through surgical tracts in DIPG patients who underwent biopsy procedures at diagnosis in 3 dedicated centers. Clinical records and images as well as radiation dosimetry from diagnosis to relapse were reviewed.RESULTSFour patients (2 boys and 2 girls, age range 6-12 years) had surgical tract dissemination: in 3 cases in the needle tract and in 1 case in the Ommaya catheter tract. The median time from biopsy to identification of dissemination was 5 months (range 4-6 months). The median overall survival was 11 months (range 7-12 months). Disseminated lesions were in the marginal radiotherapy field (n = 2), out of the field (n = 1), and in the radiotherapy field (n = 1).CONCLUSIONSAlthough surgical tract dissemination in DIPG is a rare complication (associated with 2.4% of procedures in this study), it should be mentioned to patients and family when procedures involving a surgical tract are proposed. The inclusion of the needle tract in the radiotherapy field may have only limited benefit. Future studies are warranted to explore the benefit of larger radiotherapy fields in patients with DIPG.

Iatrogenic obstructive hydrocephalus resulting from Gelfoam accumulation within the cerebral aqueduct: a case report.

The authors present the case of a previously healthy 12-year-old male with intractable seizures localized to a right frontal area of encephalomalacia and porencephalic cyst who underwent resection of the seizure focus. The surgical resection cavity extended into the right lateral ventricle, and due to encountered hemorrhage, Gelfoam was used for optimal hemostasis. The patient did well following the procedure, but presented 5 months later with headaches and emesis and was discovered to have obstructive hydrocephalus on imaging studies. Endoscopic third ventriculostomy (ETV) was performed, where Gelfoam was encountered in the third ventricle, obstructing the cerebral aqueduct. After the completion of the ETV, the patient did well and continues to be asymptomatic 1 year following the procedure.

Prospective feasibility and safety assessment of surgical biopsy for patients with newly diagnosed diffuse intrinsic pontine glioma.

Background: Diagnosis of diffuse intrinsic pontine glioma (DIPG) has relied on imaging studies, since the appearance is pathognomonic, and surgical risk was felt to be high and unlikely to affect therapy. The DIPG Biology and Treatment Study (DIPG-BATS) reported here incorporated a surgical biopsy at presentation and stratified subjects to receive FDA-approved agents chosen on the basis of specific biologic targets. Methods: Subjects were eligible for the trial if the clinical features and imaging appearance of a newly diagnosed tumor were consistent with a DIPG. Surgical biopsies were performed after enrollment and prior to definitive treatment. All subjects were treated with conventional external beam radiotherapy with bevacizumab, and then stratified to receive bevacizumab with erlotinib or temozolomide, both agents, or neither agent, based on O6-methylguanine-DNA methyltransferase status and epidermal growth factor receptor expression. Whole-genome sequencing and RNA sequencing were performed but not used for treatment assignment. Results: Fifty-three patients were enrolled at 23 institutions, and 50 underwent biopsy. The median age was 6.4 years, with 24 male and 29 female subjects. Surgical biopsies were performed with a specified technique and no deaths were attributed to the procedure. Two subjects experienced grade 3 toxicities during the procedure (apnea, n = 1; hypertension, n = 1). One subject experienced a neurologic deficit (left hemiparesis) that did not fully recover. Of the 50 tumors biopsied, 46 provided sufficient tissue to perform the study assays (92%, two-stage exact binomial 90% CI: 83%-97%). Conclusions: Surgical biopsy of DIPGs is technically feasible, associated with acceptable risks, and can provide biologic data that can inform treatment decisions.

Developmental and oncogenic programs in H3K27M gliomas dissected by single-cell RNA-seq.

Gliomas with histone H3 lysine27-to-methionine mutations (H3K27M-glioma) arise primarily in the midline of the central nervous system of young children, suggesting a cooperation between genetics and cellular context in tumorigenesis. Although the genetics of H3K27M-glioma are well characterized, their cellular architecture remains uncharted. We performed single-cell RNA sequencing in 3321 cells from six primary H3K27M-glioma and matched models. We found that H3K27M-glioma primarily contain cells that resemble oligodendrocyte precursor cells (OPC-like), whereas more differentiated malignant cells are a minority. OPC-like cells exhibit greater proliferation and tumor-propagating potential than their more differentiated counterparts and are at least in part sustained by PDGFRA signaling. Our study characterizes oncogenic and developmental programs in H3K27M-glioma at single-cell resolution and across genetic subclones, suggesting potential therapeutic targets in this disease.