bluuebunny/crossref_metadata_2025 huggingface dataset:
DIPG-16. COMBINATION OF ARGININE DEPLETION AND POLYAMINE INHIBITION AS AN ANTICANCER STRATEGY FOR DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Khan Aaminah , Gamble Laura , Pandher Ruby , Burns Mark R , Mussai Francis , Norris Murray , Haber Michelle , Tsoli Maria , Ziegler David S
Published: December 2020

DIPG is an aggressive pediatric brainstem tumor, with a median survival below 12 months. Tumor cells are dependent upon arginine, a semi-essential amino acid, metabolised by arginase enzymes into ornithine, a pivotal precursor to the polyamine pathway. Polyamines, frequently upregulated in cancer, are intracellular polycations controlling key biological processes – the inhibition of which we have previously shown to be highly efficacious in preclinical DIPG models. Pegylated arginase (BCT-100) has recently been shown to significantly delay tumor development, prolonging survival of neuroblastoma-prone Th-MYCN mice. This study investigated the effects of arginine depletion therapy as a single agent and in combination with polyamine pathway inhibitors in DIPG. We found that ARG2, the gene encoding for arginase II, is expressed significantly more highly in DIPG tumors compared to normal brain. Arginine depletion via BCT-100 reduced DIPG cell proliferation and colony formation in patient-derived cell lines. Using orthotopic patient-derived xenograft models of DIPG, we found that frequent dosing of BCT-100 (4x/week) significantly delayed tumor development and increased the survival of the mice (p<0.0001). DFMO is an FDA-approved inhibitor of the enzyme ornithine decarboxylase, a key driver of polyamine synthesis. The combination of BCT-100 with DFMO led to significant enhancement in DIPG survival (p<0.005 compared to single agent treatments). Triple combination therapy with addition of the polyamine transport inhibitor AMXT-1501 led to a potent and profound improvement in survival. These data show that arginine depletion therapy using BCT-100 combined with dual polyamine inhibitory agents represents a potentially exciting new approach for the treatment of DIPG.
DIPG-19. TARGETING ATM MUTATION IN METASTATIC DIFFUSE MIDLINE GLIOMA – A CASE OF SUSTAINED RESPONSE USING PARP INHIBITOR
Authors: Tsui Karen , Law Andrew , Watson Michael K
Published: December 2020

Diffuse midline glioma (DMG) with H3.3K27M mutation is associated with an extremely poor prognosis, with a median survival of 10 to 12 months. Radiation remains the standard of care however there is no established curative therapy available. We describe a patient diagnosed with a diffuse intrinsic pontine glioma at 5 years of age by clinical and radiological criteria. He was treated with focal radiation 59Gy which resulted in reduction in size of the tumour, and partial improvement of T2 changes on MRI. At 18 months post diagnosis, the patient developed metastatic recurrence at the anterior fornix. This was biopsied and histopathology demonstrated a high grade glioma. Next generation sequencing revealed a H3F3A K27M mutation, and an ATM R3008H mutation. He received whole ventricular radiation 36Gy and boost to the lesion to 45Gy, followed by Olaparib 135mg/m2/day twice daily. He remains in radiological remission 20 months post metastatic relapse and has no organ toxicity to Olaparib. CONCLUSION: H3.3K27M and ATM co-segregating mutations are described in DMG. This is the first case report of targeting ATM mutation with a PARP inhibitor which resulted in prolonged remission of metastatic DMG. Olaparib was well tolerated.
DIPG-20. DETERMINATION AND MANAGEMENT OF HYDROCEPHALUS IN PATIENTS WITH DIPG, AN INSTITUTIONAL EXPERIENCE
Authors: Fonseca Adriana , Solano-Paez Palma , Zapotocky Michal , Bartels Ute , Bouffet Eric
Published: December 2020

BACKGROUND

The is no consensus in best practices for the management of hydrocephalus in patients with Diffuse Intrinsic Pontine Glioma (DIPG). To date, the impact on survival of hydrocephalus and Cerebro-Spinal Fluid (CSF) diversion in this population remains to be elucidated. Herein, we describe our institutional experience.

METHODS

Patients with a clinical and radiological diagnosis of DIPG were identified at the Hospital for Sick Children between 2000–2019. Images at diagnosis and at disease progression were assessed for hydrocephalus using the frontal-occipital ratio (FOR) method. Proportional hazard analyses were used to identify factors correlated with survival.

RESULTS

Eighty-nine consecutive patients diagnosed with DIPGs were treated at our institution. At diagnosis, 29% (n=26) of patients presented with hydrocephalus, seven patients underwent CSF diversion. Out of the remaining nineteen patients, n=6 had stable or improved hydrocephalus in follow-up scans, n=6 had persistent hydro and n=2 required CSF diversion at the time of disease progression. Seven did not undergo a follow-up scan. Out of sixty-five patients with imaging at the time of progression, fifty-five percent of patients (n=36) presented with hydrocephalus and ten of them required CSF diversion. On univariate analysis, the presence of hydrocephalus or CSF diversion at diagnosis and/or did not correlate with a survival advantage.

CONCLUSIONS

CSF diversion for the management of hydrocephalus in patients with DIPG does not impact survival and in some cases resolves spontaneously after the initiation of radiotherapy and steroids. This observation needs to be validated in a prospective cohort.
DIPG-21. INDUCTION OF MITOTIC ABNORMALITIES AND BMI-1 MODULATION TO TREAT DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Kumar Shiva Senthil , Sengupta Satarupa , Zhu Xiaoting , Mishra Deepak Kumar , Fuller Christine , Fouladi Maryam , Drissi Rachid
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) is a poor-prognosis pediatric brain tumor with a median survival of less than one year. No effective therapy is currently available, and no therapeutic advances have been made in several decades. BMI-1 is a member of the multimeric protein complex Polycomb repressor complex 1 (PRC1). It has been implicated in self-renewal of normal and cancer cells, and in DNA damage signaling. We have previously identified BMI-1 as a potential therapeutic target in DIPG and have shown that BMI-1 is highly expressed in DIPG tumors regardless of histone 3 subtype. In the present study, we show that the modulation of BMI-1 leads to DNA damage, M phase cell cycle arrest, chromosome abnormalities and cell death. Furthermore, modulation of BMI-1 sensitizes DIPG patient-derived stem-like cells to ionizing radiation (IR). Treatment of DIPG stem-like cells with PTC596, a BMI-1 modulator, and IR, impairs the kinetics of DNA damage response (DDR). Both DDR foci formation and resolution were delayed, resulting in further reduction in cell viability compared with either treatment alone. In vivo, treatment of mice bearing DIPG xenografts with PTC596 leads to decreased tumor volume and growth kinetics, increased in-tumor apoptosis and sustained animal survival benefit. Gene expression analysis indicates that BMI-1 expression correlates positively with DIPG stemness and BMI-1 signature. Together our findings indicate that BMI-1 modulation is associated with mitotic abnormalities, impaired DDR and cell death, supporting the combination of BMI-1 modulation and radiation as a promising novel therapy to treat children with DIPG.
DIPG-23. SINGLE CASE REPORT OF LOW DOSE RADIOTHERAPY AND CHEMOTHERAPY IN THE TREATMENT OF DIPG
Authors: Tseng Chen Kan , Chou I-Jun
Published: December 2020

A 3 year-old girl, was noted to have progressive gait problem since Nov. 2017 and brought to hospital for checkup. Brain MRI on Jan. 2018 showed T2 hyperintensity infiltrative pontine lesion, favoring diffuse infiltrative pontine glioma and mild obstructive hydrocephalus, received VP-shunting on Jan. 15, 2018. Due to the refusal of surgical biopsy for tissue proof, we started the radiotherapy from Jan. 24, 2018, using Rapidarc technique with 6MV photon energy to treat the brain stem lesion, ended on Feb. 24, 2018 with total dose of 25.5Gy in 17 fractions as our usual practice. Following the completion of radiotherapy, we started the adjuvant chemotherapy using 1-week on, 1-week off regimen of temozolomide using dosage of 75 mg/sq-m/day, and this patient’s general condition returned back to nearly normal. Serial follow-up images of brain MRI on 04/30/2018, 08/01/2018, 11/30/2018, 02/26/2019, 05/30/2019, 08/28/2019 showed slow progression of the pontine lesion, without the development of contrast enhanced new lesion. She maintained the functional independent until Sep. 2019, she was noted to have symptoms of ataxic gait, esotropia and choking on drinking liquid. We started the retreatment of radiotherapy from Oct.7, 2019, using same technique, ended on Nov. 5, 2019 with total dose of 30Gy in 20 fractions. The symptoms improved partially after the treatment, with residual weakness over left extremity. We are still treating the patient with adjuvant temozolomide, and she has survived most of time functionally independent in these 2 years.
DIPG-29. PHOSPHATIDYLINOSITOL-4,5-BISPHOSPHATE 3-KINASE (PI3K) INHIBITION DRIVES PROTEIN KINASE C ACTIVATION (PKC) IN DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Duchatel Ryan J , Mannan Abdul , Jackson Evangeline R , Staudt Dilana , Skerrett-Byrne David A , Jamaluddin M Fairuz B , Woldu Ameha S , Douglas Alicia , Hulleman Esther , Carcaboso Angel M , Monje Michelle , Alvaro Frank , Tsoli Maria , Ziegler David S , Dun Matthew D
Published: December 2020

Recurring somatic mutations and gene amplifications to members of the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) signaling axis are overarching contributors to the aggressive growth and survival of diffuse intrinsic pontine gliomas (DIPG). However, targeting PI3K has thus far failed to improve outcomes for patients in the clinic. To identify the mechanisms underpinning PI3K/AKT/mTOR treatment failure in DIPG, we have employed high-resolution quantitative phosphoproteomic profiling in patient-derived DIPG cell lines harboring H3K27M and PI3K mutations, +/- the blood-brain barrier permeable PI3K inhibitor, paxalisib (previously “GDC-0084”, currently in Phase I trials - NCT03696355) and rapamycin. Paxalisib was significantly more potent than rapamycin at inducing PI3K/AKT/mTOR inhibition, however, both simultaneously activated protein kinase C signaling (pT500PKCβ +8.2 and +4.5 fold, respectively). PKC lies directly upstream of myristoylated alanine-rich C-kinase substrate (MARCKs), which was phosphorylated at Ser170 by +9.4 and +4.7 fold, respectively; promoting actin cytoskeletal remodeling and cellular migration. Indeed, activation of PKC signaling using phorbol 12-myristate 13-acetate (PMA), increased DIPG cell growth and migration by >3 fold. Targeting PKC using midostaurin (FDA-approved for acute myeloid leukemia), and enzastaurin (blood-brain barrier penetrant inhibitor of PKCβ), in combination with paxalisib was highly synergistic (CI=<0.9), reducing proliferation and driving apoptosis. Mechanistically, compensatory activation of PKC signaling following PI3K inhibition was regulated by the accumulation of Ca+2 ions, as chelation using BAPTA-AM significantly reduced PKC activity following PI3K inhibition. These data highlight the power of phosphoproteomic profiling for the rational design of drug combination strategies, which need to be tested in vivo prior to clinical trials for DIPG.
DIPG-34. SUPER ELONGATION COMPLEX AS A TARGETABLE DEPENDENCY IN H3K27M+ DIFFUSE MIDLINE GLIOMA
Authors: Dahl Nathan , Danis Etienne , Balakrishnan Ilango , Wang Dong , Pierce Angela , Walker Faye , Gilani Ahmed , Serkova Natalie , Madhaven Krishna , Fosmire Susan , Green Adam , Foreman Nicholas , Venkataraman Sujatha , Vibhakar Rajeev
Published: December 2020

Mutations in the histone 3 gene (H3K27M) are the eponymous driver in diffuse intrinsic pontine gliomas (DIPGs) and other diffuse midline gliomas (DMGs), aggressive pediatric brain tumors for which no curative therapy currently exists. To identify specific epigenetic dependencies within the context of the H3K27M mutation, we performed an shRNA screen targeting 408 genes classified as epigenetic/chromatin-associated molecules in patient-derived DMG cultures. This identified AFF4, a component of the super elongation complex (SEC), as necessary for DMG cells to maintain growth and self-renewal. We hypothesized that aberrant SEC expression occurs as a consequence of the H3K27M mutation and that this dysregulated SEC signaling overcomes repressive transcriptional regulation in order to suppresses differentiation and promote self-renewal of DMG tumor stem cells. We interrogated the role of AFF4 in DMG using an shRNA lentiviral approach. We demonstrate a significant decrease in in vitro clonogenicity and stem cell maintenance following AFF4 depletion. We employed RNA-seq-based gene set enrichment analysis to delineate differentiation programs under SEC regulatory control. Finally, we sought to determine whether CDK9, the catalytic subunit of the SEC, represents a therapeutic vulnerability in DMG. Using RNA polymerase II ChIP-seq, we demonstrate that CDK9 pharmacologic inhibition restores regulatory Pol II pausing, promotes cellular differentiation, and leads to potent anti-tumor effect both in vitro and in patient-derived xenograft models. These studies present a biologic rationale for the translational exploration of CDK9 inhibition as a promising therapeutic approach.
DIPG-40. TARGETING MASTER REGULATOR DEPENDENCIES IN DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Pavisic Jovana , Sethi Chankrit , Jones Chris , Zacharoulis Stergios , Califano Andrea
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) remains a fatal disease with no effective drugs to date. Mutation-based precision oncology approaches are limited by lack of targetable mutations and genetic heterogeneity. We leveraged systems biology methodologies to discover common targetable disease drivers—master regulator proteins (MRs)—in DIPG to expand treatment options. Using the metaVIPER algorithm, we interrogated an integrated low grade glioma and GBM gene regulatory network with 31 DIPG-gene expression signatures to identify tumor-specific MRs by differential expression of their transcriptional targets. Unsupervised clustering identified MR signatures of upregulated activity in RRM2/TOP2A in 13 patients, CD3D in 5 patients, and MMP7, TACSTD2, RAC2 and SLC15A1/SLC34A2 in individual patients, all of which can be targeted. Notably, intratumoral administration of etoposide by convection enhanced delivery was effective in murine proneural gliomas in which TOP2 was identified as a MR while RRM2—targetable by drugs such as cladribine—has been shown to be a positive regulator of glioma progression whose knock-down inhibits tumor growth. We also prioritized drugs by their ability to reverse MR-activity signatures using a large drug-perturbation database. Patients clustered by predicted drug sensitivities with distinct groups of tumors predicted to respond to proteasome inhibitors, Thiotepa or Volasertib all of which have early evidence in treating gliomas. We will refine this analysis in a multi-institutional study of >100 patient gene expression profiles to define MR signatures driving known biological/molecular disease subtypes, use DIPG cell lines recapitulating common MR architectures to optimize therapy prioritization, and validate our findings in vivo.
DIPG-49. BRAINSTEM AND PONTINE VOLUMETRIC ANALYSIS AS A SURROGATE MEASURE OF LOCAL DISEASE CONTROL IN CHILDREN WITH DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Bander Evan D , Freret Morgan E , Wembacher-Schroeder Eva , Wolden Suzanne L , Souweidane Mark M
Published: December 2020

INTRODUCTION

Response-assessment in pediatric neuro-oncology (RAPNO) criteria designed to describe treatment outcomes are poorly implemented in diffuse intrinsic pontine glioma (DIPG), due to inter-observer variability in measurement of tumor volume, lack of tumor enhancement, and undefined relationships between radiographic parameters and survival. Given these issues, this study assessed whether anatomically defined brainstem and pontine volumes can serve as surrogate measures of local disease burden and response to therapy in DIPG.

METHODS

Thirty-two consecutive patients with newly diagnosed DIPG were treated with standard definitive radiation therapy (RT) between 2010 and 2016 at a single institution. MRI brain scans throughout treatment course were analyzed using iPlan® Flow software (Brainlab AG, Munich, Germany). Semi-automated 3D measurements of the brainstem and pons were calculated using a built-in knowledge-based segmentation approach and manually adjusted.

RESULTS

Mean age at diagnosis was 6.5+/-0.5 years (range 2–12 years). Median follow up time was 317 days. Average brainstem volume at diagnosis (Vdiag) was 52.7+/-2.1mL with subsequent decrease at first post-RT MRI to 41.4+/-2.0mL (p < 0.0001). By time of last follow up, brainstem volume increased to 51.9+/-3.3, no longer significantly different as compared to Vdiag (p=0.61). The same relationships were found for pontine volume.

CONCLUSIONS

Volumetric changes in the brainstem and pons occur in response to treatment and correlate with local disease burden and response to therapy. This surrogate may be a useful standardized measure in ongoing and future trials involving localized delivery of therapeutics in DIPG that require evaluation of local-regional disease control in addition to survival.
DIPG-51. ACVR1 MUTATIONS PROMOTE TUMOR GROWTH IN MODELS OF DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Adorno Jennifer Ocasio , Hover Laura , He Chen , Zhu Xiaoyan , Goldhamer David , Carcaboso Angel , Yadavilli Sridevi , Nazarian Javad , Baker Suzanne
Published: December 2020

Mutations in the gene encoding activin A receptor type 1 (ACVR1) are found in approximately 25% of diffuse intrinsic pontine gliomas (DIPGs), a pediatric glioma with 2-year survival rate of less than 10%. ACVR1mutations frequently coincide with activating PIK3CA or PIK3R1 mutations, indicating a potential cooperative effect of BMP and PI3K signaling in gliomagenesis. We used genetically engineered mice with inducible knock-in of Acvr1R206H or Pik3caE545K alleles, such that cre-mediated recombination resulted in expression of the gain of function mutated genes from their endogenous promoters at physiological levels. Cre-mediated deletion in GFAP-CreER;Pik3caE545K/+;p53cKO mice (Pik3ca;p53) mediated Trp53 deletion and expression of Pik3caE545K in glial progenitors, and spontaneously induced high-grade glioma (HGG) in mice with complete penetrance. Heterozygous knock-in of the Acvr1R206H allele accelerated tumorigenesis and impaired survival in Pik3ca;p53 mice (Acvr1;Pik3ca;p53). Transcriptomic analysis of Acvr1;Pik3ca;p53 tumors compared to Pik3ca;p53 littermate controls, as in patient-derived tumors, revealed broad molecular signatures associated with cell fate commitment and chromosome maintenance. Pharmacologic inhibition of ACVR1 was sufficient to impair growth in human patient-derived DIPG cell lines. Together, our studies show that ACVR1 activation promotes tumor growth in spontaneous mouse HGG and patient-derived DIPG cells, suggesting that ACVR1 inhibition may produce a clinically significant therapeutic effect in DIPG.
DIPG-56. EXPLORATION OF TUMOR/STROMA INTERACTIONS IN DIPG XENOGRAFT BY SPECIES-SPECIFIC RNA-SEQ DECONVOLUTION INDICATES A ROLE OF MICROGLIA CELL IN DIPG DEVELOPMENT
Authors: Merlevede Jane , Plessier Alexandre , Felix Arthur , Philippe Cathy , Dret Ludivine Le , Hardy David , Beccaria Kevin , Grill Jacques , Castel David , Varlet Pascale , Debily Marie-Anne
Published: December 2020

Diffuse Intrinsic Pontine Glioma (DIPG) and more largely Diffuse Midline Gliomas H3 K27M-mutant (DMG) harbor a unique property of infiltration. Our objective is to elucidate/describe the cellular and molecular determinants of micro-environmental modifications resulting from the tumour/stroma dialogue as it might provide pro-invasive conditions that favour the development of the disease. To this end, we performed RNA-seq analyses to characterize exhaustively the bidirectional molecular modifications of the stroma/tumour in DIPG xenograft models. Gene expression changes in murine microenvironment compartment were investigated as continuous or semi-continuous traits of tumor load by measuring transcriptome in zone with high vs. low infiltration. We observed substantial modulations in gene expression in the microenvironment associated with increasing tumor cell content, pointing to a modification of the macrophage/microglial infiltrate. The expression or overexpression of several modulated genes was validated by IHC in the stroma of DMG primary tumors. Among them, overexpression of the cytokine CCL3 was confirmed, reflecting the activation status of microglial cells. Moreover, we observed in patients that the density of IBA-1 positive microglial cells increases according to the extent of tumor infiltration and that a significant part of them harbor a mitotic status, supporting their interaction with DMG cells. The involvement of this interaction in DMG development needs further evaluation and might represent opportunity to slow down DIPG extension.
DIPG-60. PILOT STUDY OF CIRCULATING TUMOR CELLS IN PEDIATRIC HIGH GRADE BRAIN TUMORS
Authors: Zaky Wafik , Dao Long , Ragoonanan Dristhi , Bath Izhar , Yi Sofia , Gill Jonathan , Khatua Soumen , Li Shulin
Published: December 2020

BACKGROUND

Despite its increasing use, circulating tumor cells (CTCs) have not been studied in pediatric brain tumors.

METHODS

Cell surface vimentin (CSV) is a marker for CTC detection. We developed an automated CSV-based CTC capture method for pediatric brain tumor using the Abnova Cytoquest platform. PBMCs isolated from blood samples from 52 brain tumor patients were processed to isolate CSV+ CTCs. Captured cells were then stained for CSV and CD45 and scanned to determine the number of CTCs. DIPG samples were additionally examined for H3K27M expression on CSV+ cells. Long term cancer survivors were used as a control cohort.

RESULTS

86.4% of all the samples exhibited between 1–13 CSV+ CTCs, with a median of 2 CSV+ CTCs per sample. Using a value of ≥ 1 CTC as a positive result, the sensitivity and specificity of this test was 83.05% and 60.0% respectively. 19 DIPG samples were analyzed and 70% (13 samples) were positive for 1–5 CTCs. Five of these 7 positive CSV+ CTCs DIPG samples were also positive for H3K27M mutations by immunohistochemistry (71%). Mean survival in days for the CTC positive and negative DIPG samples were 114 and 211 days, respectively (p= 0.13).

CONCLUSION

This is the first study of CTCs in pediatric CNS tumors using an automated approach. Patients with brain tumors can exhibit CSV+ CTCs within peripheral blood. The use of specific molecular markers such as H3K27M can improve the diagnostic capability of liquid biopsies and may enable future disease assessment for personalized therapy.
DIPG-61. RESCUE REGIMENS AFTER BIOMEDE: POSSIBLE INFLUENCE ON OS ASSESSMENT
Authors: Carlo Daniela Di , Pommier Bertille , Teuff Gwenael Le , Abbou Samuel , Berlanga Pablo , Geoerger Birgit , Puget Stephanie , Beccaria Kevin , Blauwblomme Thomas , Debily Marie-Anne , Castel David , Lechapt Emmanuelle , Varlet Pascale , Dangouloff-Ros Volodia , Boddaert Nathalie , Vassal Gilles , Deley Marie-Cécile Le , Grill Jacques
Published: December 2020

BIOMEDE is a multicentric randomized phase II trial to evaluate in DIPG the OS of patients treated with dasatinib, erlotinib or everolimus. The OS is the result of the first line treatment but it could also be affected by re-irradiation and the second line treatment received after progression, especially in case of a possible crossover outside of the trial. This preliminary analysis focuses on the first patients enrolled at Gustave Roussy (n=37). The median age at diagnosis was 7 years, median interval from diagnosis to progression and median survival after progression were 7 (1–20) and 2 (0–13) months respectively. Initial treatment was everolimus for 13, dasatinib for 20, erlotinib for 4 patients. The most frequent targetable molecular alterations were mTOR pathway in 6, PDGRFA in 4, ACVR1 in 3 patients. Out of the 31 patients who relapsed and were evaluable, 18 and 13 had a median survival < 3 and > 3 months respectively. At relapse patients have received different types of therapies, in 6 cases matching the molecular profile of the tumour obtained by sequencing. At progression, seven patients switched from dasatinib to mTOR inhibitors and 2 patients switched from everolimus to dasatinib. Patients with OS after progression > 3 months had higher rate of reirradiation (77% vs 5%), steroid weaning (69% vs 33%) and Lansky/Karnowsky > 50% (85 vs 67%). Extended results on the entire cohort will be presented. It will be important to consider the distribution of reirradiation to interpret the results of the randomisation on OS.
DIPG-66. FEASIBILITY AND APPLICABILITY OF MOLECULAR GUIDED THERAPY IN HIGH GRADE GLIOMA/DIFFUSE MIDLINE GLIOMA: RESULTS FROM BEAT CHILDHOOD CANCER NMTRC-009 MOLECULAR GUIDED THERAPY STUDY
Authors: Harrod Virginia , Nagulapally Abhinav , Lewis Elizabeth , Sholler Giselle
Published: December 2020

High grade gliomas/diffuse midline gliomas (HGG/DMG) historically have a poor prognosis with an overall survival of less than 20% at 5 years. The pathophysiology is under close investigation across the world in efforts to understand this tumor type with aims of increasing effective treatment options. We present our results on the feasibility and outcomes of patients treated on our Molecular Guided Therapy study. Tumor samples were analyzed with whole exome (DNA) and RNA sequencing. Three drug matching algorithms were utilized to generate a report that was reviewed at a multi-institutional tumor board meeting, culminating in a proposed treatment protocol. Eleven patients enrolled, but one did not complete cycle 1 of therapy due to progression of disease, thus ten patients (6-HGG, 4-DMG) were evaluable and received at least 2 cycles of therapy. Time to reports generated and tumor board assembly was (median) 18 and 24 days, respectively. Secondary goals included evaluation of efficacy. Responses showed 50% of patients with stable disease or better at 2 cycles of therapy, but these were temporary with median time to progression of 81 days. In conclusion, we determined that it is feasible to collect individual biological DNA and RNA sequencing information to offer patients individualized treatment plans for this devastating group of diseases. Though data is not statistically significant, we show that there is a suggestion of efficacy in this approach to treatment for patients, indicating a need to expand on this treatment approach with individualized medicine.
DIPG-68. ALPHA-THALASSEMIA X-LINKED MENTAL RETARDATION PROTEIN (ATRX) LOSS-OF-FUNCTION IN A MOUSE MODEL OF DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Shen Chen , Picketts David , Becher Oren
Published: December 2020

Diffuse Intrinsic Potine Glioma (DIPG) is a rare pediatric brain tumor for which no cure or efficacious therapies exist. Previous discoveries have revealed that, DIPG harbors distinct genetic alterations, when compared with adult high-grade glioma (HGG) or even with non-DIPG pediatric HGGs. ATRX alteration is found in 9% of clinical cases of DIPG, and significantly overlaps with H3.3K27M mutation and p53 loss, the two most common genetic changes in DIPG, found in 80% and 77% clinical cases, respectively. Here we developed genetically engineered mouse model of brainstem glioma using the RCAS-Tv-a system by targeting PDGF-B overexpression, p53 loss, H3.3K27M mutation and ATRX loss-of function to Nestin-expression brainstem progenitor cells of the neonatal mouse. Specifically, we used Nestin-Tv-a; p53 floxed; ATRX heterozygous female and Nestin-Tv-a; p53 floxed; ATRX floxed male breeders, generated offsprings with ATRX loss of function (n=18), ATRX heterozygous females (n=6), and ATRX WT (n=10). Median survial of the three groups are 65 days, 88 days and 51 days, respectively. Also, ATRX null mice is lower in tumor incidence (44.4%), compared with ATRX WT (80%). We evaluated the pathological features of DIPG with or without ATRX alteration, RNA-seq is performed to identify differentially expressed genes between ATRX WT and loss-of-function. In conclution, this study generated the first genetically modified mouse model studying ATRX loss-of-function in DIPG, and suggested that ATRX loss-of-function in DIPG may slow down tumorigenesis and decrease tumor incidence.
DIPG-71. SELECTIVE HDAC INHIBITOR RG2833 INDUCES DIPG CELL DEATH VIA DOWNREGULATION OF THE NFĸB PATHWAY
Authors: Barnett Katherine , Novak Orlandi , Eberhart Charles , Raabe Eric
Published: December 2020

Histone deacetylase (HDAC) inhibitor panobinostat demonstrated activity against diffuse intrinsic pontine glioma (DIPG) in vitro, but its efficacy in vivo was limited by toxicity and poor blood brain barrier penetration. RG2833 (RGFP109) is a selective HDAC1/3 inhibitor that has established brain penetration. In clinical trials, the Cmax (plasma) of RG2833 was 32uM. RG2833 demonstrated cytotoxicity against temozolomide-resistant glioblastoma and downregulated the NFĸB pathway. Because this pathway is overexpressed in DIPG and may play a role in DIPG cell growth and survival, we hypothesized that RG2833 would kill DIPG cells. Treatment of DIPG cell lines with RG2833 as a single agent suppresses cell proliferation in the 5–10μM range (MTS assay for HSJD007 p=0.0004 10μM vs DMSO, JHH-DIPG1 p=0.001 10μM vs DMSO, SF-7761 p=0.04 10μM vs DMSO, SU-DIPG13 p=0.01 10μM vs DMSO by t-test). RG2833 induces apoptosis by 48 hours as measured by Western blot for cPARP and cleaved caspase 3 immunofluorescence (HSJD007 p<0.003 8μM vs DMSO, JHH-DIPG1 p=0.0026 10μM vs DMSO by t-test). RG2833 also slows cell proliferation as measured by Western blot for pRb and immunofluorescence for BrdU (HSJD007 p=0.008 8μM vs DMSO, JHH-DIPG1 p=0.0002 10μM vs DMSO by t-test). Western blot confirmed a dose-dependent increase in histone 3 acetylation with RG2833 treatment at 5 hours. We detected increased acetylated p65 and decreased expression of the NFĸB regulated pro-survival genes BCL2, BCL-xL, and XIAP with RG2833 treatment. Together, this data shows that HDAC inhibitor RG2833 may be a promising therapeutic candidate for DIPG via downregulation of the NFĸB pathway.
EPCT-09. CLR 131 IN PATIENTS WITH RELAPSED OR REFRACTORY PEDIATRIC MALIGNANCIES
Authors: Puccetti Diane , Otto Mario , Morgenstern Daniel , DeSantes Kenneth , Cho Steven , Hall Lance , Oliver Kate , Longcor Jarrod
Published: December 2020

BACKGROUND

CLR 131 is a novel targeted radiotherapeutic that exploits the selective uptake and retention of phospholipid ethers by malignant cells. CLR 131 selectively delivers radiation to malignant tumor cells, thus minimizing radiation exposure to normal tissues.

OBJECTIVE

CLR 131 is being examined in a Phase 1 trial, CLOVER-2 (NCT03478462), to determine the safety, tolerability, and initial efficacy of CLR 131 in children and adolescents with relapsed/refractory malignancies.

METHODS

Eligibility criteria include children with relapsed or refractory solid tumors or malignant brain tumors for which there are no standard treatment options with curative potential. Subjects must be between ages 2 and 21 with no limit to the number of prior therapies. CLR 131 is administered as a single infusion in escalating doses beginning at 15 mCi/m2. Adverse events (AEs) are graded by NCI-CTCAE v5.

RESULTS

As of 10Jan2020, four subjects with brain tumors have received CLR 131; one at 15 mCi/m2 and three at 30 mCi/m2. Diagnoses included DIPG (2), glioblastoma (1), and medulloblastoma (1). Median age is 13 years (range 10–15) and patients received a median of two prior therapies (range 1 to 8). There were no treatment emergent AEs at the 15 mCi/m2 dose level attributed to CLR 131 by the investigator. Assessment of the 30 mCi/m2 dose level is ongoing.

CONCLUSIONS

CLR 131 is a unique, first in class targeted radiotherapeutic for pediatric malignancies. Preliminary data shows an acceptable and expected safety profile in this patient population. Dose escalation to determine the highest tolerated dose is ongoing.
EPCT-11. PHASE 1 STUDY OF FLUVASTATIN-CELECOXIB COMBINATION IN CHILDREN WITH RELAPSING/REFRACTORY OPTICO-CHIASMATIC LOW-GRADE GLIOMA OR HIGH-GRADE GLIOMAS (FLUVABREX): FINAL RESULTS
Authors: Andrew Nicolas , Sterin Arthur , Solas Caroline , Deley Marie-Cécile Le , Probst Alicia , Aerts Isabelle , Faure-Conter Cécile , Bertozzi Anne-Isabelle , Chastagner Pascal , Entz-Werle Natacha , De Carli Emilie , Dory-Lautrec Philippe , Bouche Gauthier , Leblond Pierre
Published: December 2020

BACKGROUND

Preclinical data support the activity of celecoxib and fluvastatin in high grade (HGG) and low grade gliomas (LGG). A Phase I study was designed to evaluate this combination in children with refractory/relapsed glioma. AIM: To assess the safety, pharmacokinetics (PK), maximum tolerated dose, Recommended Dose for Phase II (RDP2). METHOD: Multicenter phase I trial, including patients aged 6 to 21 year old. Fluvastatin starting dose was 2 mg/kg/day, 14/28 days, with fixed dose of celecoxib (200–800 mg /day). Four dose levels of fluvastatin (2, 4, 6, 8 mg/kg/day) were evaluated. A Continual Reassessment Method was used for dose escalation. Dose-limiting toxicities (DLT) were determined on the 1st cycle. PK samples were obtained at D1 and D14 of cycle 1, pre-dose of cycle 2.

RESULTS

20 patients were enrolled with a median age of 12 years (5.9–19). They previously received a median of 3 (1–7) lines of treatment. Ten patients were treated for LGG and 10 for HGG, receiving a median of 3.5 cycles (1–21). Patients with LGG received a median of 9 cycles (1–21). Among the 17 patients evaluable for DLT, 2 DLTs were reported: 1 grade 3 maculo-papular rash (4 mg/kg), and 1 grade 4 increase of CPK (6 mg/kg). The RP2D of fluvastatin is 6 mg/kg/day.

CONCLUSION

In children with refractory/relapsed glioma, the RDP2 of fluvastatin associated with celecoxib is 6 mg/kg/day. This combination is well tolerated encouraging a phase 2 study in LGG.
EPEN-03. LONG-TERM FOLLOW-UP OF AIEOP 2ND SERIES OF CHILDREN AND ADOLESCENT WITH PRIMARY INTRACRANIAL (ST:SUPRATENTORIAL; PF: POSTERIOR FOSSA) EPENDYMOMA AND METHYLATION GROUPS RE-ANALYSES
Authors: Massimino Maura , Buttarelli Francesca Romana , Witt Hendrik , Johann Pascal , Minasi Simone , Pfister Stefan M , Pajtler Kristian W , Antonelli Manila , Barretta Francesco , Modena Piergiorgio , Gandola Lorenza , Garrè Maria Luisa , Bertin Daniele , Mastronuzzi Angela , Mascarin Maurizio , Quaglietta Lucia , Viscardi Elisabetta , Sardi Iacopo , Ruggiero Antonio , Pollo Bianca , Buccoliero Annamaria , Boschetti Luna , Biassoni Veronica , Schiavello Elisabetta , Chiapparini Luisa , Erbetta Alessandra , Giangaspero Felice
Published: December 2020

BACKGROUND

This 2002–2014 Italian prospective study stratified 160 patients by surgical resection (complete=NED/incomplete=ED) and centrally-reviewed grade. Grade2/NED patients received focal radiotherapy (RT) up to 59.4Gy, Grade3/NED received 4 courses of VEC(vincristine,etoposide,cyclophosphamide) after RT.ED patients received 1–4 VEC courses, second-look surgery, 59.4 Gy+8Gy boost on measurable residue.

METHODS

We re-analyzed data at 115 months follow-up including methylation profile on available samples.

RESULTS

Global PFS/OS at 5/10 years were 66/59% and 80/74%, respectively. Of the 64 relapsers at median 20 months, 53 died at median 37/18 months after diagnosis/relapse, respectively.10/64 relapsed after 5 years (66–126 months); 4 died, relapse was local in 8/10, metastatic 1, combined 1;5/10 patients were below age 3, 5 females, 8 PF tumors. Their survival post-relapse was not longer than earlier relapsers’. At univariable analysis, age over 3 years, female sex, complete surgery, grade 2, no shunt confirmed better PFS/OS. 66/95 analyzed tumors received a score >0.80 through the DNA methylation-based central nervous system tumor classifier: 41/8 as PFA/PFB, respectively,14/17 ST as RELA-positive (3 scored for other molecular entities i.e. anaplastic PXA, LGG MYB, HGNET). Prognostic factors were equally distributed among PFA/PFB groups,1 only group B patient relapsed locally at 96 months.

CONCLUSIONS

Already published prognostic factors remained at long-term follow-up;6.2% patients had late relapses. OS after relapse was not better in late relapsers. Group B confirmed better prognosis but all patients had received «at least» adjuvant RT. Modern ependymoma trials need long follow-up to draw firm conclusions.
EPEN-05. CLINICAL AND GENETIC EVOLUTION OF EPENDYMOMA EXPOSED FROM A MULTI-RECURRENCE GIRL CASE
Authors: Chen Zhong-ping , Wang Jing , Xi Shao-yan , Zhao Qi , Xia Yun-fei , Guo Cheng-cheng , Yang Qun-ying , Li Zhao-jie , Li Zhi , Han Fu , Wang Fang , Sai Ke , Cai Hai-ping , Zhang Xiang-heng , Ke Chao , Wang Jian
Published: December 2020

Ependymomas are glial brain tumors accounting for approximately 2~3% of all primary tumors of the central nervous system (CNS), and 12% of all pediatric intracranial tumors. To better understand the evolution process of ependymomas, we studied the clinical, pathological and genetic development of a rare girl case with repeatedly recurrent ependymoma. This girl was diagnosed as ependymoma at age of 9 years old, and experienced 7 times tumor relapse and received 9 times surgeries but finally ceased at 19 years old with multiregional recurrences. The pathological characteristics, radiographic images and therapeutic strategies of the patient were all retrieved. Molecular markers confirmed the diagnosis of anaplastic ependymoma based on the updated WHO guideline for CNS tumors. Whole-genome sequencing (WGS) was performed to elucidate the landscape of mutation signatures and to identify potential driver mutations along the tumor progression. The seven tumor specimens showed a highly branched evolutionary pattern. There were six gene mutations found in 5 of the 7 specimens (PCDHA4, PCDHA8, SEC14L6, SETD2, RIOK2, and SLCO2A1) and three in 6 of 7 the samples (RYR1, SNX25, DSC2). Strikingly, there was one gene, ADGRL3, which was found to be consistently mutated in the entire disease progression process. Our findings therefore suggest that ADGRL3 might play roles in the disease progression of ependymoma patient.
EPEN-07. PATTERNS OF EXTRANEURAL METASTASES IN PEDIATRIC SUPRATENTORIAL EPENDYMOMA: CASE SERIES AND REVIEW OF THE LITERATURE
Authors: Chan Priya P , Whipple Nicholas S , Perry Arie , Solomon David A , Zhou Holly , Linscott Luke L , Kestle John R W , Bruggers Carol
Published: December 2020

BACKGROUND

Ependymomas account for 10% of all malignant pediatric intracranial tumors. Standard therapy includes maximal safe surgical resection followed by involved-field radiation. Up to 50% of localized pediatric ependymomas recur. Extraneural metastases at time of recurrence are rarely reported.

OBJECTIVE

To describe extraneural metastases of pediatric ependymomas.

METHODS

Retrospective review of patients’ medical records and literature review.

RESULTS

Three patients with history of locally recurrent, supratentorial ependymoma developed extraneural metastases: one in a cervical lymph node, one with a scalp nodule, and one with a dural lesion. Each extraneural recurrence had similar histologic and molecular features as the initial diagnosis. The cervical lymph node recurrence was treated with multimodal therapy; she is without disease four years later. The isolated scalp nodule occurred at the exit site of a subgaleal drain placed during prior resection. Following nodule resection, he developed additional scalp and lymph node disease and is receiving palliative care. The isolated dural recurrence occurred at the exit site of a ventriculoperitoneal shunt placed following a previous resection. She died of progressive disease 18 months after dural lesion resection. Reports of lymph node, scalp, and dural metastases of ependymomas are exceedingly rare, and outcomes are poor.

CONCLUSIONS

Extraneural manifestations of ependymoma are rare. Regional seeding from prior surgical procedures may play a role in metastatic spread. Extraneural metastases should be considered in children previously treated for ependymoma who develop local findings even in the absence of CNS relapse. Salvage therapy with curative intent should be considered using a multimodal approach.
EPEN-11. ONGOING RESPONSE IN A MULTIPLY RELAPSED METASTATIC POSTERIOR FOSSA EPENDYMOMA A AFTER VORINOSTAT AND CONCOMITANT IRRADIATION
Authors: Gorsi Hamza S , Toll Stephanie , Yankelevich Maxim
Published: December 2020

BACKGROUND

Among the nine molecular subgroups of ependymoma identified, posterior fossa ependymoma A (PF-EPN-A) confers the worst prognosis. These tumors often relapse despite aggressive resection and irradiation, resulting in limited therapeutic options. Although the genomic profile of PF-EPN-A does not typically show any recurrent alterations; they demonstrate distinct epigenetic changes which can be targeted with modulators such as histone deacetylase (HDAC) inhibitors. These inhibitors have shown efficacy in pre-clinical studies in both their anticancer and radio-sensitizing properties. CASE: We describe a male diagnosed with a posterior fossa ependymoma at 3 years of age. After initial therapy with resection and focal irradiation, he went on to have a number of recurrences requiring multimodal therapy. Most recently, he developed diffuse intraventricular and leptomeningeal disease not amenable to surgical intervention. Genetic evaluation demonstrated a BCOR mutation and methylation profile was consistent with PF-EPN-A. He received 23.4 Gray craniospinal irradiation with a 30.6 Gray boost to the nodular lesions. Vorinostat was given concomitantly for radio-sensitization in 2 week intervals for a total of 6 weeks. Serial imaging after irradiation revealed decreased tumor burden with almost complete resolution of disease at 15 months. Unfortunately, MRI at 18 months exhibited mild interval growth of 2 lesions.

CONCLUSIONS

To our knowledge, this is the first report of a clinical response in a pediatric patient with PF-EPN-A following irradiation administered concomitantly with vorinostat therapy. This response highlights the importance of further studies evaluating this combination therapy and its potential use in this population.
EPEN-16. TRANSCRIPTIONAL REGULATORY CIRCUITRIES AS MOLECULAR TARGETS IN EPENDYMOMA
Authors: Bertrand Kelsey , Mack Stephen , Parsons Donald W
Published: December 2020

Genomic sequencing has driven precision-based oncology therapy; however, genetic drivers remain unknown or non-targetable for many malignancies, demanding alternative approaches to identify therapeutic leads. Ependymomas comprise histologically similar tumor entities driven by distinct molecular mechanisms, such as fusion oncoproteins, genome-wide chromosomal instability, or disruption of DNA methylation patterns. Despite these differences, ependymomas resist chemotherapy and lack available targeted agents for clinical trial development. Based on our previous findings, we hypothesized that mapping chromatin landscapes and super enhancers (SE) could uncover transcriptional dependencies as targets for therapy (Mack, Pajtler, Chavez et al., Nature, 2018). To functionally test the requirement of these SE genes for ependymoma cellular growth, we designed a pooled RNA interference screen against 267 SE associated genes. Our screen was performed in one C11ORF95-RELA-fusion model and two PF-EPN-A models as controls in biological triplicates. As an indication that our screen was successful, positive controls scored among lead hits including KIF11, BUB1B, PHF5A and MYC. Importantly, we identified many subtype specific dependencies in both C11ORF95-RELA-fusion and PF-EPN-A models, thus revealing novel pathways that potentially govern subgroup-specific ependymoma cell growth. Further, several candidates detected across all ependymoma lines were also identified as pan-cancer dependencies or glioma/glioblastoma specific essential genes from the DepMap Cancer Dependency Gene Resource. Our findings reveal novel targets and pathways that are essential for ependymoma cell growth, which may provide new insight into therapeutic strategies against these aggressive brain tumors.
EPEN-26. NON-CANONICAL NF-κB SIGNALING DRIVES MESENCHYMAL EPENDYMAL CELL SUBPOPULATION IN PFA EPENDYMOMA
Authors: Griesinger Andrea , Harris Faith , Donson Andrew , Gillen Austin , Riemondy Kent , Venkataraman Sujatha , Amani Vladimir , Handler Michael , Hankinson Todd , Foreman Nicholas
Published: December 2020

NF-κB signaling is a hallmark of PFA1 ependymoma. Loss of LDOC1, through epigenetic silencing, leads to constitutively active NF-κB signaling and chronic IL-6 secretion. In this study, we investigate the loss of LDOC1 within the PFA tumor clusters. Using our PFA scRNAseq database, in which there are 5 clusters within the tumor cell compartment: mesenchymal (MEC), ciliated (CEC), transportive (TEC), and undifferentiated (UEC). LDOC1 expression was significantly reduced and had an inverse correlation with genes defining the unfavorable MEC subpopulation, predominate in PFA1. This is consistent with our findings that MEC was defined by an NF-κB2 signaling profile. In contrast, LDOC1 expression was higher and positively correlated with genes defining the favorable CEC subpopulation, mostly seen in PFA2. RELA expression, which we studied as a target of LDOC1, was not localized to MEC and was wide-spread throughout the PFA compartment. RELB, part of non-conical NF-κB signaling, was expressed only the MEC subpopulation correlating with IL-6 gene expression found only in this subpopulation. In MAF-811, a PFA cell line with more CEC-like gene phenotype, RELB co-immunoprecipates with the active form of NF-κB2 in both the nucleus and cytoplasm. IL-6 gene expression is almost completely lost when NF-κB2 is knock-down using shRNA. Additionally, loss of LDOC1 leads to over 3 fold increase in NF-κB2 expression. Combined with our previous work, this would suggest that NF-κB2 drives IL-6 expression by binding with RELB in MEC subpopulation and targeting loss of LDOC1 may shift the MEC subpopulation toward the more favorable CEC subpopulation.
EPEN-27. CDKN2A DELETION IN SUPRATENTORIAL EPENDYMOMA WITH RELA ALTERATION INDICATES A DISMAL PROGNOSIS – A RETROSPECTIVE ANALYSIS OF THE HIT EPENDYMOMA TRIAL COHORT
Authors: Jünger Stephanie T , Andreiuolo Felipe , Mynarek Martin , Dörner Evelyn , zur Mühlen Anja , Velez-Char Natalia , von Hoff Katja , Rutkowski Stefan , Warmuth-Metz Monika , Kortmann Rolf-Dieter , Timmermann Beate , von Bueren Andre O , Pietsch Torsten
Published: December 2020

INTRODUCTION

Since supratentorial RELA-fusion positive ependymomas are considered a biologically distinct disease, we aimed to identify histological and genetic predictors of outcome in a defined cohort of pediatric patients.

MATERIALS AND METHODS

We analyzed 54 RELA ependymomas in pediatric patients treated according to HIT2000-E protocols. All cases underwent central neuropathological review. Genome-wide copy number alterations were assessed by molecular inversion probe or SNP array. RELA alterations were detected by RT-PCR, sequencing and assessment of nuclear p65-RelA protein. Copy number alteration of the CDKN2A (cyclin dependent kinase inhibitor 2A) locus and concordant p16 protein expression were analyzed.

RESULTS

Fifty-two tumors were classified as WHO-grade III (96.3%) with high mitotic activity in 39 cases (72.2%), vascular proliferation in 47 (87.0%), necrosis in 43 (79.6%) and clear cell morphology in 19 (35.2%). All tumors harbored RELA alterations. Homo- or heterozygous CDKN2A deletions were detected in 9 (16.7%) and 14 (25.9%) cases, respectively. p16 protein expression was lost in all cases with homozygous deletion. Median follow-up was 5.4 years with 5-years EFS and OS of 74.1% and 92.6%. In Kaplan-Meier analysis high mitotic activity was related to shorter EFS (p=0.016) and clear cell morphology to longer OS (p=0.039); CDKN2A deletion was associated with shorter OS (homozygous deletion, p=0.009; homo-or heterozygous deletion, p=0.034). No correlation between CDKN2A deletion and high mitotic activity was found but with higher age at diagnosis (p=0.001).

CONCLUSION

Deletion of CDKN2A occurred in 42.6% of supratentorial ependymomas with RELA alteration and represented a genetic predictor of worse overall outcome in pediatric patients.