bluuebunny/crossref_metadata_2025 huggingface dataset:
DIPG-30. ELUCIDATING DOWNSTREAM MEDIATORS OF ONCOGENESIS INFOXR2-EXPRESSING DIFFUSE MIDLINE GLIOMAS
Authors: Tsai Jessica W , Coppola Marissa , Arounleut Phonepasong , Collins Jared B , Hart Patrick , Keshishian Hasmik , Jones David T W , Bandopadhayay Pratiti , Phoenix Timothy N
Published: June 2024

BACKGROUND

Diffuse midline gliomas (DMGs) are universally fatal pediatric tumors with a median survival of less than one year. Forkhead Box R2 (FOXR2) is a forkhead family TF that we have found to be aberrantly expressed in DMGs. FOXR2 expression is sufficient to enhance glioma formation, and we have shown that regulation of FOXR2 occurs through a previously unrecognized epigenetic mechanism. FOXR2 is necessary for proliferation in FOXR2-expressing DMGs. It is also a potent oncogene, sufficient to enhance cell proliferation and in vivo tumor formation. However, the downstream mediators of FOXR2-mediated gliomagenesis are poorly understood.

METHODS

We applied an integrative approach using proteomics, transcriptomics, in vitro cancer models, and in vivo in utero electroporation mouse models to systematically evaluate how FOXR2 mediates gliomagenesis.

RESULTS

We have found that FOXR2 is aberrantly activated in DMGs. FOXR2 enhances MYC protein stability, even in the presence of cycloheximide. However, FOXR2 also exerts its oncogenic effects through MYC independent functions. FOXR2 is highly enriched at E26-transformation (ETS) motifs and specifically activates ETS transcriptional gene sets. To identify FOXR2 protein-protein interactions, we performed immunoprecipitation and mass spectrometry to identify FOXR2 protein interactors. Moreover, we have performed both proteomic and phospho-proteomic analyses of FOXR2-expressing human neural stem cells. These proteomic studies have allowed us to identify proteins, phospho-sites, and signaling pathways that are highly enriched in FOXR2-expressing cells. These pathways could be potential therapeutic targets in FOXR2-expressing DMGs.

CONCLUSIONS

Taken together, this study elucidates how FOXR2 protein interactors mediate oncogenesis in FOXR2-expressing diffuse midline gliomas.
DIPG-48. PRECISION GUIDED THERAPY PROVIDES CLINICAL BENEFIT IN H3K27-ALTERED DIFFUSE MIDLINE GLIOMA
Authors: McKay Campbell , Power Phoebe , Staunton Jordan , Sriharan Shampavi , Jessop Sophie , Zhukova Nataliya , Trinder Sarah , Govender Dinisha , Barahona Paulette , Gifford Andrew J , Mignone Cristina , Xie Angela , Tax Gabor , Tsoli Maria , Dolman Emmy , Mayoh Chelsea , Wong Marie , Cowley Mark , Marshall Glenn , Trahair Toby , Lock Richard B , Ekert Paul , Haber Michelle , Tyrell Vanessa , Lau Loretta , Manoharan* Neevika , Ziegler* David S , Khuong-Quang* Dong-Anh
Published: June 2024

BACKGROUND

The utility of precision-guided therapeutic approaches to H3K27-altered diffused midline glioma (DMG) remains uncertain. The Australian Zero Childhood Cancer (ZERO) program combines molecular profiling (whole-genome sequencing (WGS), whole-transcriptome sequencing (RNAseq), and DNA methylation profiling), with in vitro high-throughput drug screening (HTS) and patient-derived xenograft (PDX) drug-efficacy testing in patients with high-risk cancer.

METHODS

We report on the cohort of patients enrolled with a DMG in the ZERO clinical trial between 2017 and 2023.

RESULTS

68 patients were enrolled, predominantly at diagnosis (87%), with pontine lesions (66%) at a mean age of 8.7 years. 59 (87%) patients had WGS + RNAseq successfully performed. Most tumors harbored an H3F3A mutation (n=50), followed by HIST1H3B (n=11), HIST1H3C (n=2), HIST2H3C (n=1) and EZHIP overexpression (n=4). 37 samples were suitable for cell culture, with HTS successfully performed in 25 cases, and PDXs established in 7. Precision-guided therapy (PGT) was recommended by the ZERO multidisciplinary tumor board for 53 patients (78%), including 5 recommendations guided by HTS. PI3K/mTOR inhibitors and MEK inhibitors were the most recommended PGTs. 21 patients (31%), receiving 24 PGTs, were eligible for survival analysis. The clinical benefit rate (per RAPNO) was 52% for patients receiving PGT, with 5 patients exhibiting PR and 6 patients SD >6 months. Notably, the 5 PR included: a PR in a patient with BRAFV600E mutation to dabrafenib/trametinib, a near-CR in a patient with germline BRCA2 mutation to olaparib/durvalumab, a sustained PR in a patient with FGFR1 mutation to trametinib/bevacizumab and 2 patients with PIK3CA mutations who received PGT in the context of recent radiotherapy. Median overall survival of the PGT group was 21.2 months versus 11.8 months for the rest of the cohort (hazard ratio 0.67 [95%CI 0.39-1.1]).

CONCLUSIONS

These results, for the first time, highlight the potential clinical benefit of PGT in H3K27-altered DMG.
DIPG-53. AN EXCEPTIONALLY RARE CASE OF A DIFFUSE MIDLINE GLIOMA WITH CONCOMITANT H3.1 K27M AND G34R MUTATIONS IN THEHIST1H3C (H3C3) GENE
Authors: Reisz Zita , Pereira Rita , Nevis Smitha , Mackay Alan , Bhaw Leena , Grabovska Yura , Laxton Ross , Molinari Valeria , Burford Anna , Clark Barnaby , Bleil Cristina , Zebian Bassel , Weiser Annette , Carceller Fernando , Marshall Lynley , King Andrew , Bodi Istvan , Al-Sarraj Safa , Jones Chris , Clarke Matthew
Published: June 2024

BACKGROUND

Histone mutations (H3 K27M, H3 G34R/V) define subtypes of paediatric-type diffuse high-grade gliomas (HGG) (diffuse midline glioma (DMG), H3 K27-altered, diffuse hemispheric glioma (DHG), H3 G34-mutant). The WHO classification recognises exceptional cases where these mutations co-occur. We report one such case of a 2-year-old female presenting with neurological symptoms and lethargy.

METHODS

MRI imaging identified a brainstem lesion; a stereotactic needle biopsy was undertaken, followed by standard diagnostic neuropathology workflows including histology review, panel immunohistochemistry, DNA methylation profiling (Illumina EPIC BeadArrays, brain tumour classifier (MNP v12.5 R package)) and WES/WGS. Patient-derived in vitro cell cultures were established allowing further characterisation using RNAseq and chromatin immunoprecipitation assays with sequencing (ChIP-seq).

RESULTS

Histology showed diffusely infiltrating pleomorphic astrocytes, multinucleated cells, and conspicuous mitotic activity; the diagnosis was DMG, H3 K27-altered (immunohistochemistry: H3K27me3 loss, H3K27M positivity). DNA methylation profiling classified the tumour as ‘DMG, H3 K27-altered’ (calibrated score=0.99). WES/WGS revealed concurrent H3.1 K27M and G34R mutations (clonal, in the same reads) of HIST1H3C (H3C3), somatic variants in FGF11 and PIK3CA, and a pathogenic germline NBN variant. The RNAseq profile of the primary tumour and cell cultures clustered with H3 K27M-mutant tumours. Unbiased in vitro drug screening showed no selective sensitivities. ChIP-seq (H3K27ac, H3K27me3, H3K36me3, RNApol2 marks) showed features in keeping with DMG H3 K27M-mutant tumours (H3K27ac loci including OLIG2, IRX1/2, PKDCC). The patient was treated with adjuvant radiotherapy and everolimus, but progressed and passed away 13 months post-diagnosis.

CONCLUSION

This case is an exceptionally rare, complex variant of histone-mutant paediatric HGG, and the first reported occurrence in HIST1H3C (H3C3). It illustrates that in cis, the H3.1 K27M mutation demonstrates a dominance over molecular and clinical profiles compared to G34R, and highlights the importance of broad molecular profiling to identify such examples for further study.
DIPG-63. RE-IRRADIATION FOR PROGRESSIVE DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG): THE SPANISH EXPERIENCE
Authors: Panizo Elena , Vazquez-Gomez Felisa , Perez-Somarriba Marta , Cruz Ofelia , Lopez-Ibor Blanca , Solano Palma , De las Heras Blanca Martinez- , Cortés-Hernandez Marta , Garcia-Ariza Miguel , Raynero-Mellado Roberto Carlos , Martinez-Merino Marta , De Lucio Ana , Tallón María , Garrido-Colino Carmen , Ortiz-Gonzalez Irene , Portugal Raquel , Baro Maria , Gonzalez-Sansegundo Carmen , Calvo Felipe , Lassaletta Alvaro
Published: June 2024

BACKGROUND

Despite advances in its biological understanding, current treatments for diffuse intrinsic pontine glioma (DIPG) have shown minimal impact on overall survival in this fatal disease. Radiotherapy (RT) is the only therapeutic intervention that has demonstrated efficacy in improving symptoms and prolonging progression-free survival. In addition, re-irradiation (rRT) is emerging as an alternative treatment for advanced disease, albeit palliative. This study presents the Spanish experience with re-irradiation in DIPG.

METHODS

We retrospectively reviewed demographic, clinical and RT data of patients with DIPG treated with rRT in Spain.

RESULTS

Between April 2015 and December 2023, 44 Pediatric patients with progressive DIPG underwent rRT in 16 Spanish institutions. Median time from diagnosis to progression was 10 months (range, 4.2-24.3). Median dose of rRT was 20 Gy (range, 18-40) in a median of 2 Gy fractions (range, 1.3-4). Twenty-one patients (47.7%) underwent additional treatments in addition to RT. Clinical and radiological improvements were observed in 77.3% and 60% of cases, respectively. Treatment was well tolerated with only 3 patients experiencing severe toxicity (one requiring a VP-shunt, and two finalizing rRT due to bronchoaspirations). Median overall survival was 15.1 months (range, 8.2-61.2), with a median time from rRT to death of 4.2 months (range, 0.6-10.3). Compared to patients who experienced earlier relapses, those who relapsed after 10 months exhibited superior overall survival (21.8 vs. 12.9 months; p < 0.001%), and a longer interval from rRT to death (6.2 vs. 3.8 months; p = 0.058). There was no survival benefit in patients receiving additional treatments.

CONCLUSIONS

rRT effectively improves symptoms and prolongs survival in many progressive DIPG patients. However, the ideal candidates for rRT remain undefined. The retrospective nature of the study makes it difficult to assess the true impact of additional treatments. We encourage prospective research into the combination of rRT with other therapies.
DIPG-78. OSSEOUS METASTASIS IN DIFFUSE MIDLINE GLIOMA: A CASE REPORT AND REVIEW OF LITERATURE
Authors: Agarwal Vibhuti , Nagasubramanian Ramamoorthy , Maxwell Rochelle , Douglas-Lindsay Dorothea , Ramakrishna Naren , Hayes Laura , Chandra Tushar
Published: June 2024

BACKGROUND

Diffuse midline glioma (DMG), H3K 27M-altered are uniformly fatal CNS tumors with 2-year overall survival of less than 10%. Neuroaxis dissemination with disease progression is well known. However, osseous metastasis is a rare occurrence.

METHODS

We report a patient with localized DMG at diagnosis with subsequent craniospinal and osseous metastasis. We also performed an updated literature review on DMG with extra-neural metastasis (ENM).

RESULTS

At 11 years of age, the patient presented with progressively worsening headache and vomiting and was found to have a tumor within the right thalamus with mild mass effect on the right lateral ventricle without hydrocephalus. The patient underwent stereotactic tumor biopsy with pathology consistent with DMG, H3K 27-altered. Whole exome sequencing revealed alterations in H3-3A, TP53 and PTPN11. Treatment consisted of upfront focal radiation therapy with subsequent stabilization of the thalamic lesion. However, within 1.5 months of completing radiotherapy, the patient developed drop metastasis, intracranial leptomeningeal dissemination, and diffuse osseous metastasis within the spine, bilateral iliac wings, and ribs. The patient died from disease progression within 2 months of metastatic progression, 6 months from initial diagnosis. Review of literature yielded 11 cases of ENM in pediatric patients with DMG, H3K 27M-altered. Four patients had ENM at diagnosis. The remaining seven patients developed extra CNS metastasis within 1-6 months of diagnosis. Eight patients received upfront radiotherapy with variation in adjuvant chemotherapy. All patients died with median overall survival of 9 months (range, 0.5-24) from diagnosis and 6 months (range, 0.5-22) from ENM occurrence.

CONCLUSION

ENM in DMG, H3K 27-altered is uncommon. Mechanisms for development of ENM in DMG is unclear. Biopsy and molecular testing for both primary site and ENM should be considered to help elucidate biologic mechanisms of ENM and potentially guide management.
DIPG-79. METTL16 AS A THERAPEUTIC VULNERABILITY IN H3K27M MUTANT DMG CELLS
Authors: Chilukuri Akanksha , Pomaville Monica , Halbert Matthew , He Chaun , Agnihotri Sameer
Published: June 2024

BACKGROUND

Diffuse Midline Glioma (DMG) is a highly aggressive (CNS WHO Grade IV) pediatric brain tumor characterized by the histone mutation H3K27M, resulting in global hypomethylation of histones. H3K27M mutant cells are highly dependent on methionine and methionine Adenosyltransferase 2A (MAT2A), a central regulator of the methionine cycle, representing a key vulnerability in H3K27M gliomas. MAT2A is upregulated by methyltransferase-like protein 16 (METTL16), which deposits N6-methyladenosine (m6A) on a subset of RNA residues to regulate gene expression. MAT2A is a sensor of methyl group donor S-adenosylmethionine (SAM) that, when placed, increases MAT2A intron splicing to compensate for a decrease in MAT2A function.

METHODS

To investigate our hypothesis, H3K27M histone mutation knockout cell lines were established using CRISPR Cas9 (Jabado lab) in DIPG4 cells. shRNA-mediated knockdown was used to attenuate METTL16 expression in DIPG4 H3K27M cells, and growth was assessed via sulforhodamine B (SRB) assay.

RESULTS

In silico analysis of normal brain tissue compared to low-grade glioma and high-grade glioma demonstrated increased METTL16 at both the RNA and protein levels (p=<0.0001). Therefore, we postulated that targeting METTL16 would affect H3K27M growth. Results showed increased cell death compared to control cells by day 4 (p=0.0034) and day 8 (p=<0.0001). Furthermore, knockdown of METTL16 in DMG cells with H3K27M decreased m6A levels on poly (A) RNA (p=0.049).

CONCLUSIONS

Our study highlights the vulnerability of H3K27M mutant cells to METTL16 modulation, elucidating underlying molecular mechanisms and paving the way for innovative therapeutic strategies targeting this axis.
DIPG-84. PHASE 1 DOSE-ESCALATION STUDY OF ACT001 IN PEDIATRIC PATIENTS WITH ADVANCED BRAIN AND SOLID TUMORS SHOWS ACTIVITY IN DIFFUSE MIDLINE GLIOMA (DMG)
Authors: Ziegler David S , Hassall Tim , Valvi Santosh , Cai Dongpo
Published: June 2024

BACKGROUND

ACT001, an oral parthenolide derivative targeting STAT3 and NF-κB pathways, has shown activity in preclinical models of DMG. We evaluated safety, toxicity and activity of ACT001 in this recently completed, first-in-child study of DMG and other relapsed/refractory brain and solid tumors.

METHODS

Eligible patients ≥ 1 and ≤ 21 years old were enrolled with dose escalation following a rolling 6 design and tumor lesions evaluated every 8 weeks per RANO/ RECIST criteria.

RESULTS

A total of 29 patients were enrolled across 5 cohorts, including 19 with DMG (13 with Diffuse Intrinsic Pontine Glioma (DIPG)). Median age was 11 years for the whole cohort and 7 years (3-17) for DMG patients. Safety was evaluated in escalating doses in 188, 533, 700, 875 and 1100 mg/m2,BID cohorts. No DLT nor grade 3 and above TRAE was identified. One SUSAR was noted for a grade 1 pain in extremity event. Peak ACT001 concentration for each dose cohort were estimated based on limited PK sampling time (cycle 1 day 1 at pre-dose, 2 and 4 hours post dose; cycle 1 day 15 and cycle 2 day 1 both at pre-dose). ACT001 peak concentration plateaued at the highest dose levels, fluctuating in the range of 6360, 5430 and 5980 mg/m2 for 700, 875 and 1100 mg/m2 cohorts respectively. The half-life was approximately 3 hours. 8/14 DMG patients treated at ≥ 700 mg/m2 exhibited objective response or stable disease (SD), including one patient with SD for 14 months, another patient with confirmed Partial Response who remained on study for 11-months before disease progression and five other patients with different degrees of tumor burden reduction.

CONCLUSION

ACT001 was well tolerated and showed preliminary evidence of anti-tumor activity in DMG/DIPG patients dosed at the highest dose levels. A Phase 2 trial is planned using 875 mg/m2 as the RP2D.
TRLS-01. INTRAVENTRICULAR B7-H3 CAR T CELLS FOR DIFFUSE INTRINSIC PONTINE GLIOMA: SAFETY AND EFFICACY REPORT FROM THE COMPLETED PHASE 1 TRIAL BRAINCHILD-03
Authors: Vitanza Nicholas A , Ronsley Rebecca , Huang Wenjuan , Seidel Kristy , Thomsen Alison , Gust Juliane , Hauptman Jason , Choe Michlle , Crotty Erin , Leary Sarah , Gustafson Joshua A , Gardner Rebecca A , Pattabhi Sowmya , Wendler Jason , Ho On , Annesley Colleen , Park Julie R , Jensen Michael C
Published: June 2024

BACKGROUND

BrainChild-03 is a first-in-human clinical trial that completed the phase 1 component of repeatedly dosed intraventricular B7-H3 CAR T cells to children with diffuse intrinsic pontine glioma (DIPG) without lymphodepleting chemotherapy.

METHODS

We report on BrainChild-03 Arm C, patients with DIPG receiving up to 10x10^7 B7-H3CAR T cells/dose. Primary endpoints were feasibility and safety. Secondary endpoints were disease response and correlatives of CAR T activity.

RESULTS

23 patients enrolled. All had successful CAR T manufacturing. 21 patients were treated; 17 received sufficient doses for safety evaluation (4 doses/8 weeks) without a dose limiting toxicity (DLT). 4 other treated patients include: 1 patient DLT (pontine hemorrhage 8 days post-initial dose) and 3 unevaluable patients (2 discontinued protocol therapy for rapid progression; 1 did not meet eligibility to begin treatment). Overall, patients received 224 doses (median: 7, range: 1-60). Common adverse events included headache, nausea/vomiting, and fever. Of 21 treated patients, 11 enrolled after progression and survived 9.7 months (range: 6-16.9) after initial CAR T cell infusion. Of the 10 patients enrolled prior to progression, the overall survival is 16.9 months (range: 7.6-40.5) with 5/10 patients still alive. Three patients are alive 3 years from diagnosis, including 2 patients still on protocol therapy. Patients were not allowed to receive other anti-tumor agents, radiation, or surgical debulking while on protocol therapy. Circulating CSF CAR T cells were identified in 18/21 (85.7%) of patients and elevations in chemokine/cytokines associated with T cell activation and migration, including CXCL10 and IFNy.

CONCLUSIONS

Repeated intraventricular B7-H3 CAR T cell dosing is feasible and tolerable for children with DIPG, even after progression, with evidence of local immune activation. Early signals of survival extension underscore the potential for clinical benefit and the consideration to advance to phase 2 multi-site clinical trials.
TRLS-15. “TAZNI”: A PHASE I/II COMBINATION TRIAL OF TAZEMETOSTAT WITH NIVOLUMAB AND IPILIMUMAB FOR CHILDREN WITH INI1-NEGATIVE OR SMARCA4-DEFICIENT TUMORS (NCT05407441)
Authors: Yi Joanna S , Czaplinski Jeffrey , Bhushan Ketki , Forrest Suzanne J , Shukla Neerav , Mack Stephen , Hong Andrew , Strachan Marylynne , Dubois Steven G , London Wendy B , Chi Susan N
Published: June 2024

BACKGROUND

Recent pediatric trials with EZH2 inhibitor tazemetostat monotherapy have demonstrated efficacy and disease stabilization in children with relapsed INI1/SMARCA4-deficient tumors: overall response rate (ORR) 14% in all patients (dose expansion cohort), and 24%, 33% and 22% response rates in ATRT, chordoma and epithelioid sarcoma, respectively (NCT02601937); and prolonged disease stabilization >6 months (NCT03213665). Leveraging the role of EZH2 in tumor immunity and increased immune signaling by tazemetostat, we hypothesized that combining this EZH2 inhibitor with checkpoint inhibitors may benefit pediatric patients with these rare cancers.

METHODS

“TAZNI” is a phase 1/2, multi-center trial of tazemetostat, nivolumab and ipilimumab for children with INI1/ SMARCA4-deficient tumors, administered either after standard upfront therapy or in the relapsed setting. All patients will receive standard nivolumab and ipilimumab doses/dosing schedule, with continuous tazemetostat dosing determined by disease strata: Stratum A- subjects with ATRT; Stratum B- all other (non-ATRT) tumors. Each stratum is subdivided by disease status: A1/B1- refractory disease; A2/B2- relapsed disease; and A3/B3- no evidence of disease. Part 1 of the study consists of two concurrent “rolling six” phase 1 studies to identify the recommended phase 2 dose (RP2D) by disease stratum. Two dose levels are planned, with one dose de-escalation. Part 2 will consist of two phase 2 studies to estimate the ORRs in substrata A1 and A2, in a Simon’s 2-stage design at the RP2D. All other substrata will have descriptive analyses. Patients may receive up to 26 cycles of therapy. Key inclusion/exclusion criteria include INI1 or SMARCA4 loss (by immunohistochemistry or molecular confirmation); age 6 mo - 21 yo; no prior immunotherapy; limited corticosteroid usage; and no concern for hematologic malignancy. This trial is currently ongoing and open to accrual. To date, four patients have enrolled and additional sites across the US are anticipated to open for enrollment (NCT05407441).
TRLS-17. INTERIM CLINICAL, PHARMACOKINETIC, AND TECHNICAL REPORT OF A PHASE 2 STUDY OF SONODYNAMIC THERAPY (SDT) USING SONALA-001 TOGETHER WITH MR-GUIDED LOW-INTENSITY FOCUSED ULTRASOUND (MRGFUS) IN CHILDREN WITH DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Syed Hasan R , Packer Roger J , Fonseca Adriana , Keating Robert F , Mueller Sabine , Narsinh Kazim , Ho Winson , Niazi Toba , Fenn Peter , Clanton Ryan , Henry Lenora , Potter Wyatt , Andresen Corina , Marcus Stuart , Benaim Ely , Kilburn Lindsay
Published: June 2024

BACKGROUND

Children with DIPG have limited treatment options and poor prognosis with median survival of 9-12 months. Preclinical studies reveal that sonodynamic therapy (SDT) via MR-guided focused ultrasound (MRgFUS) activates SONALA-001 (ALA) metabolite, protoporphyrin IX (PpIX), inducing tumor cell death and extending survival in glioma models.

METHODS

We present preliminary data from an ongoing first-in-child drug-device trial (NCT05123534) of SONALA-001 SDT in children with DIPG aged ≥ 5 years post-radiation therapy. The trial evaluates the safety of ALA-SDT, preliminary efficacy and pharmacokinetics (PK) of SONALA-001 at 5mg/kg administered 6-12 hours before SDT and establishes the RP2D. Each cohort involves three subjects: the first receiving half-pons treatment 30-days apart; the others receiving entire pons treatment. Single-treatment approach was amended to allow up to 12 monthly-treatments.

RESULTS

Six patients (4M:2F, 5-12 years) in 2 cohorts received 22 SDT-treatments between August 2022 and February 2023. Sonication duration averaged 147 minutes. Five of 6 patients received repeated treatments. All were discharged post-procedure day 1 with no DLTs or related AE grade ≥ 3. For SONALA-001, the Cmax occurred at end of infusion, followed by rapid clearance (15.7 mL/min/kg); plasma half-life of < 1 hour, indicating rapid distribution. The PpIX-Cmax occurred 4-6 hours post-dose, declining with a longer mean half-life than SONALA-001 of 6 hours. Both Cmax and AUCall demonstrate circulating-PpIX and systemic exposure were significantly lower than for SONALA-001. Two of 6 patients achieved a partial response per RAPNO central-review, and 2 continue in the study treatment for 11 and 15 months, respectively.

CONCLUSION

SDT is an innovative and to-date well-tolerated strategy for children with DIPG post-initial radiotherapy. Sonications did not result in any adverse procedural effects. SONALA-001 exhibits rapid distribution and clearance, while PpIX PK align with metabolite formation. After dose escalation completion, dose-expansion at R2PD will offer insights into safety, PK, and efficacy.
ETMR-18. ADVANCING ETMR RESEARCH: NOVELIN VITRO ANDIN VIVO PRECLINICAL MODELS FOR DEVELOPING MORE EFFECTIVE TREATMENTS
Authors: Roosen Mieke , Krausert Sonja , Stathi Phylicia , Mack Norman , Schwalm Benjamin , Oehme Ina , Peterziel Heike , Meulenbroeks Chris , Kranendonk Mariëtte E G , Plasschaert Sabine L A , Hoving Eelco , Pfister Stefan M , Bunt Jens , van Tilburg Cornelis M , Witt Olaf , Kool Marcel
Published: June 2024

BACKGROUND

Embryonal Tumor with Multilayered Rosettes (ETMR) is a rare and aggressive tumor that occurs mainly in infants under three years of age. Genetically, ETMRs are characterized by amplification and fusion of a microRNA cluster on chromosome 19 (C19MC) with TTYH1, present in ~90% of the tumors. ETMR patients still have a poor prognosis without any recent advances in treatment. A major limitation to develop more effective treatment strategies is the lack of sufficient preclinical models.

METHODS

Establishment of ETMR patient-derived xenograft (PDX) models and tumoroid lines, molecular characterization, high throughput in vitro drug screens, targeted drug treatments in vitro and in vivo.

RESULTS

We have established four new tumoroid and five new PDX ETMR models. These models faithfully recapitulate ETMR patients’ tumors based on their histological, transcriptomic, and methylome signatures. The in vitro models were derived from two patients and two PDX models and included three C19MC-amplified cell lines, of which two were a primary-relapse pair, and one a primary C19MC non-amplified model. In vivo we established the same models as PDX models subcutaneously plus an additional C19MC-amplified relapse model. High-throughput drug screening assays, using drug libraries with 225 clinically approved drugs and other small molecules, were conducted across the panel of in vitro models. Potential therapeutic candidates with promising activity in ETMR tumoroid lines identified from these screens include FGFR, XPO1, MTOR, MDM2 and topoisomerase inhibitors.

CONCLUSIONS

The establishment of novel preclinical models represents a significant advancement in ETMR research, offering a platform that captures the molecular complexity of the disease. The identification of several inhibitors shows the potential of these models for drug discovery and preclinical testing. Ongoing in vitro and in vivo experiments with these drugs and combinations aim to further validate their activity, moving towards the development of more effective therapies for ETMR patients.
ETMR-23. CNS SARCOMAS WITHCIC- ORATXN1-ALTERATIONS — A META-ANALYSIS OF CLINICAL AND MOLECULAR FEATURES IN A LARGE SERIES OF PATIENTS
Authors: Geisemeyer Neal , Federico Aniello , Sill Martin , Rosenblum Marc , Bale Tejus , Mauermann Monika , Schrimpf Daniel , Johann Pascal , Pickles Jessica , Aldape Kenneth , Tauziède-Espariat Arnault , Hasselblatt Martin , Sturm Dominik , Tietze Anna , von Deimling Andreas , Sievers Philipp , Sahm Felix , Gojo Johannes , von Hoff Katja , Pfister Stefan M , Kool Marcel
Published: June 2024

BACKGROUND

In 2021, the 5th WHO classification of central nervous system (CNS) tumors acknowledged CNS sarcomas with CIC alterations as a distinct tumor type, which may also expand to non-CIC alterations including ATXN1. To tackle the lack of treatment protocols for these highly aggressive tumors, we conducted a meta-analysis to provide an overview of clinical and molecular characteristics, define clinically relevant subtypes, and ultimately advise on treatment guidelines.

METHODS

We collected molecular and clinical data for >200 patients with CIC- or ATXN1-altered CNS sarcomas by screening our in-house DNA methylation database (581 potential patients initially identified), publication databases (50 patients), and contacting centers worldwide (60 patients). Tumor tissue (FFPE and fresh frozen) for further molecular characterization was obtained from a subset of patients. DNA methylation-based clustering analyses (t-SNE, UMAP, consensus partitioning) were performed, integrating gene fusion details (RNAseq, FISH), copy-number variations, and clinical patient data to identify associations between (epi-)genetic and clinical parameters.

RESULTS

Most prominent fusion partners for CIC (n=47) and ATXN1 (n=9) were NUTM1 (n=18), LEUTX (n=17) and DUX4 (n=15). Clustering analyses of DNA methylation patterns indicated several epigenetic subtypes associated with different fusion types. Potential clinical implications are still under evaluation. Age distribution of patients at diagnosis in this cohort ranged from two months to 71 years (median=7.5 years). We observed no gender bias. Survival analyses are currently being performed, first results on survival and follow-up studies will be shown at the symposium.

CONCLUSION

We show first-of-its-kind data describing a large cohort of CNS sarcomas with CIC or ATXN1 alterations, outlining molecular and clinical characteristics, which may facilitate the development of guidelines for optimal treatment of these tumors based on retrospective response data. New molecular insights may also open up an avenue for targeted therapeutic approaches.
EPEN-04. OVERWHELMING ZFTA-RELA NUCLEAR LOCALIZATION AS A THERAPEUTIC STRATEGY AGAINST EPENDYMOMA
Authors: Arabzade Amir , Ippagunta Siri , Kardian Alisha , Emanus Erik , Varadharajan Srinidhi , Shirnecki Hazheen , Venere Monica , Kriwacki Richard , Deneen Benjamin , Mack Stephen C , Bertrand Kelsey C
Published: June 2024

BACKGROUND

Pediatric ependymoma is a malignant brain tumor without targeted therapies. The 10-year survival is close to 50%, as this relentless tumor often relapses years following initial diagnosis. Over two thirds of supratentorial ependymomas harbor a gene fusion between ZFTA and RELA (ZFTA-RELA). Despite evidence that ZFTA-RELA drives tumorigenicity, mechanistic details remain elusive, hindering efforts to uncover therapeutic vulnerabilities. Since direct targeting of ZFTA-RELA is not currently possible, we hypothesized that ZFTA-RELA fusion binding partners would represent vulnerabilities amenable to therapeutic targeting.

METHODS

We investigated the biochemical basis of ZFTA-RELA, with the goal of identifying key members of the protein interaction landscape. This was performed in our in utero electroporation mouse model of ZFTA-RELA ependymoma. A series of sucrose gradient and immuno-precipitation experiments were performed, coupled with mass spectrometry. ZFTA-RELA interaction proteins were functionalized using focused CRIPSR-Cas9 library screens in cell cultures. Critically, these revealed novel dependencies and druggable targets, with XPO1 emerging as a lead candidate. In vitro and in vivo studies were conducted to evaluate targeting XPO1 in ZFTA-RELA ependymoma.

RESULTS

ZFTA-RELA regulates XPO1 gene transcription, and elevated gene expression is associated with poor survival in these patients. While expression of ZFTA-RELA is necessary for oncogenic transcription, extremely elevated nuclear localization is associated with reduced growth. This suggests a ‘goldilocks’ model in which XPO1 titrates precise levels of nuclear ZFTA-RELA protein. We reveal that a potential therapeutic vulnerability emerges through modulation of ZFTA-RELA nuclear localization. Supporting this, chemical inhibition of XPO1 using Selinexor, has a direct effect on ZFTA-RELA cellular localization patterns. Critically, in patient derived orthotopic xenograft models, XPO1 inhibition exerts anti-tumor effects both in vitro and in vivo.

CONCLUSION

Our findings reveal a novel therapeutic strategy in ependymoma, and provide the mechanistic and pre-clinical data needed to develop a clinical trial for patients with ZFTA-RELA ependymoma.
EPEN-09. TARGETING EPHB2/ABL1 RESTORES ANTI-TUMOR IMMUNITY IN A PRECLINICAL MODEL OF EPENDYMOMA
Authors: Ren Jun , Amoozgar Zohreh , Uccello Taylor P , Zhao Yuhui , Lei Pinji , Ho William W , Roberge Sylvie , Huang Peigen , Duda Dan G , Xu Lei , Jain Rakesh K
Published: June 2024

BACKGROUND

Ependymoma (EPN) is a childhood brain cancer that is often resistant to cytotoxic therapies. Molecular profiling has led to a better understanding of unique EPN subtypes and revealed a critical role of EPHB2 in driving disease. With this in mind, new treatments for EPN are desperately needed and should be developed in a molecular subtype-specific fashion.

METHODS

We developed a syngeneic mouse model of EPHB2-driven genetically engineered EPN tumor cells. We performed transcriptomic profiling and analysis of EPHB2-driven murine EPN tumors and human EPN datasets to reveal multiple protein kinases as potential druggable targets. After identifying the tyrosine kinase inhibitor, Dasatinib, as a potentially effective FDA-approved agent, we measured changes in the murine microenvironment during EPN growth and after Dasatinib treatment.

RESULTS

We determined that Dasatinib inhibited the growth of EPN both in vitro and in vivo, through blocking EPHB2 and ABL1 signaling. Furthermore, we identified an increased frequency of immunosuppressive M2-like tumor- associated macrophages (TAMs), which proportionally increased with tumor size during tumor progression. However, treatment with Dasatinib reprogrammed the EPN immune microenvironment by polarizing TAMs toward an anti-tumor M1-like phenotype and increasing CD8 T cell activation. In addition, Dasatinib treatment induced complete regression of established EPN tumors in 78% of the animals and protected survivors against tumor recurrence. Depletion of CD8 T cells compromised the durability of response and reduced overall survival.

CONCLUSION

In conclusion, these data indicate that Dasatinib may be an effective therapy for EPHB2-driven molecular subgroup of EPN by activating the anti-tumor immune response and support further investigation of Dasatinib in clinical trials.
EPEN-10. INDUCING A SENESCENCE PHENOTYPE BY BROMODOMAIN INHIBITION IN HIGH-RISK EPENDYMOMA
Authors: Jaunecker Carola N , Freund Julia , Laemmerer Anna , Roosen Mieke , Kirchhofer Dominik , Otto Antonia , Madlener Sybille , Mager Leah , Bruckner Katharina , Stepien Natalia , Pirker Christine , Gabler Lisa , Senfter Daniel , Jenseit Anne , Kuess Peter , Eckert Franziska , Spiegl-Kreinecker Sabine , Dorfer Cristian , Filbin Mariella , Kool Marcel , Gojo Johannes , Berger Walter , Loetsch-Gojo Daniela
Published: June 2024

BACKGROUND

Ependymomas (EPN) constitute 10% of pediatric brain tumors. WHO classification identified 10 molecular subtypes, with ZFTA fusion-driven supratentorial tumors (ST-ZFTA) and posterior fossa group A (PFA) being amongst the most aggressive ones. Current therapeutic success relies on local treatments, emphasizing the urgent need for novel targets. Epigenetic dysregulation is a major contributor to EPN aggressiveness. Bromodomain and extra-terminal domain (BET) proteins are transcriptional mediators involved in proto-oncogene transcription, thereby representing promising targets in cancer therapy. As the BET protein BRD4 co-regulates ZFTA-RELA fusion-mediated aberrant transcription, BET inhibitors emerge as novel targeted therapy approach in ST-ZFTA.

METHODS

Initial assessments encompassed primary, patient-derived (n=9) cell models representing ST-ZFTA and PFA EPN. RNA sequencing of two ZFTA-RELA models was performed, using DGE and GSEA analyses to discern altered pathways following BET-inhibition. On functional level, we investigated sensitivity towards BET-inhibition using cell viability, clone- and sphere formation assays, as well as Western blot and qPCR after treatment. Additionally, anti-tumor effects in genetically engineered cerebral organoids were assessed.

RESULTS

First investigations showed elevated BRD2 and BRD4 levels in ST-ZFTA compared to PFA models. Accordingly, treatment with BET inhibitors resulted in reduced survival and cell cycle arrest, evidenced by cell viability and clone formation assays, along with increased p21 and cleaved PARP levels in Western blot analyses. RNA sequencing revealed altered pathways associated with cell-cycle regulation and senescence following BET inhibition, supported by downregulation of the telomerase subunit TERT and genes of the senescence-associated secretory phenotype. Additionally, BET inhibitors exhibited synergistic effects with EZH2- and PARP inhibitors primarily in ZFTA-RELA cell lines, as well as decreased tumor volumes in ZFTA-RELA-driven cerebral organoids.

CONCLUSIONS

Summarizing, we show drastic effects of BET-inhibition in ZFTA-RELA EPN. Subsequently, the influence of Bromodomain inhibition on stemness and senescence, particularly combined with radio- and chemotherapy will be investigated.
EPEN-11. CHARACTERIZING EPIGENETIC MODULATIONS AND EZHIP DOWNSTREAM TARGETS IN PFA EPENDYMOMA
Authors: Wang Shanzheng , Jenseit Anne , Hübner Jens-Martin , Mauermann Monika , Okonechnikov Konstantin , Pfister Stefan M , Kool Marcel
Published: June 2024

BACKGROUND

Ependymomas can arise from all compartments of the central nervous system and ten distinct molecular groups have been identified in children and adults. In children, the most aggressive group is posterior fossa group A ependymoma (PFA). In PFA ependymomas, the aberrant overexpression of EZHIP (EZH inhibitory protein) has been implicated as a relevant driver of the disease. EZHIP suppresses the installing and spreading of the repressive epigenetic mark H3K27me3 via disturbing PRC2 (polycomb repressive complex 2) activity through inhibiting EZH2 (enhancer of zeste 2), which causes overall low levels of H3K27me3 in PFA.

METHODS

To get a better understanding how EZHIP may drive the disease, how it affects the epigenetic landscape and what the downstream targets of EZHIP are, we performed DNA sequencing, RNA expression profiling and ChIP-seq experiments of H3K27me3, H3K27ac, EZH2, and EZHIP in PFA, PFB, and ST-ZFTA ependymomas (n = 3 tumor cases each).

RESULTS

After validating the high levels of EZHIP and global reduction of H3K27me3 in PFA, we characterized the epigenetic landscape and EZHIP chromatin binding characteristics in PFA compared to PFB and ST-ZFTA ependymoma. Transcriptome analysis showed that overall more genes are up-regulated in PFA compared with PFB and ZFTA, which might be caused by its relatively high accessibility with a global loss of H3K27me3. EZHIP knockdown experiments confirmed direct changes on H3K27me3, H3K27ac and gene expression. We also found that PLAG1 (pleomorphic adenoma gene 1) expression linearly correlated with EZHIP expression in PFA tumors. ChIP-seq data indeed showed the PLAG1 locus to be bound by EZHIP and marked with increased H3K27ac and decreased H3K27me3 signals in PFA.

CONCLUSIONS

We identified PLAG1 as a potential downstream target of EZHIP in PFA tumors. Currently, more experiments on PLAG1 are being performed to further explore its role as a potential vulnerability in PFA ependymoma.
EPEN-21. EXPLORATION OF TUMOR SUPPRESSOR LATS1 LOSS IN POSTERIOR FOSSA GROUP A EPENDYMOMA WITH LOSS OF CHROMOSOME 6Q
Authors: Donson Andrew M , Griesinger Andrea M , Calzadilla Annaliese , Amani Vladimir , Grimaldo Enrique , Foreman Nicholas K
Published: June 2024

INTRODUCTION

Chromosome 6q loss (6q-) has recently been identified as an ultra-high-risk factor in posterior fossa group A ependymoma (PFA). This study seeks to pinpoint the biological mechanism underlying the aggressive biology of PFA 6q-. We hypothesize that loss of chromosome 6q gene large tumor suppressor kinase 1 (LATS1) in PFA 6q- results in increased Hippo pathway activity that drives malignant tumor progression. LATS1 is a key negative regulator of the Hippo pathway which may represent a novel therapeutic vulnerability in 6q- PFA.

METHODS

We are testing this hypothesis using genomic and transcriptomic analysis of PFA patient samples, and by gene knock-in and pharmaceutical interventions of LATS1 and Hippo pathway components in PFA 6q- models.

RESULTS

Tumor suppressor LATS1 shows reduced expression in PFA 6q- patient samples. Although complete loss of the entire 6q arm is common in PFA 6q-, partial loss of chromosome 6q is also observed, and in all cases this partial loss encompasses the LATS1 locus on chromosome 6q. We used lentiviral transduction to knock-in LATS1 in PFA 6q- cell lines to determine the effect on tumor growth. This demonstrated loss of viability that was specific for 6q- PFA cell lines versus 6q WT control cell lines.

DISCUSSION

Data point to LATS1 loss being a key driver of the aggressive phenotype of PFA6q-, implicating the Hippo pathway in PFA 6q- and potential for novel therapeutic strategies.
EPEN-24. 5FU SENSITIVITY IS MEDIATED THROUGH TRISOMY UCK2 EXPRESSION IN 1Q+ PFA EPN
Authors: Griesingr Andrea Marie , Calzadilla Annaliese J , Grimaldo Enrique , Donson Andrew M , Amani Vladimir , Pierce Angela M , Steiner Jena , Kargar Soudabeh , Serkova Natalie J , Bertrand Kelsey C , Wright Karen D , Vibhakar Rajeev , Hankinson Todd , Handler Michael , Lindsay Holly B , Foreman Nicholas K , Dorris Kathleen
Published: June 2024

BACKGROUND

Nearly all children with gain of chromosome 1q (1q+) PFA ependymoma (EPN) will die, highlighting the urgent need to develop new treatment strategies for these patients. It has recently been shown that 1q+ creates a p53 mutant-like phenotype through trisomy expression of MDM4, a repressor of p53 signaling. This same study found toxic uracil analogs could reverse trisomy MDM4 effect on p53 and this was mediated through another 1q-trisomy gene UCK2. We and other have previously identified 5-fluorouracil (5FU) as an ependymoma specific inhibitor. In this study, we present the mechanism for 5FU sensitivity.

METHODS

In this study we utilize 1q+ PFA in vitro models to test the efficacy of combination radiation and 5FU in a preclinical setting. We measured p53 signaling through proteomic array and qRT-PCR for p21, a p53 response gene.

RESULTS

5FU enhances radiotherapy in 1q+ PFA cell lines. Specifically, 5FU increases p53 activity mediated by the extra copy of UCK2 located on chromosome 1q in 1q+ PFA. Experimental down regulation of UCK2 resulted in decreased 5FU sensitivity in 1q+ PFA cells. Though not statistically significant, we did see prolong survival and decreased tumor burden in 1q+ PFA orthotopic patient-derived xenograft models treated with focal 2Gyx5days radiation and 5FU.

CONCLUSION

These results are the first to identify a 1q+ specific therapy approach in PFA EPN. Existing phase 1 studies in pediatrics have already established safety and dose of 5FU, providing a rapid translation into phase 2 trials for children both up front and at recurrence for 1q+ PFA.
EPEN-25. “CONCERNING EPENDYMOMAS, A FURTHER SUBDIVISION IS NEITHER MORPHOLOGICALLY NOR BIOLOGICALLY NECESSARY”: A NARRATIVE REVIEW OF RESEARCH ON EPENDYMOMAS BETWEEN 1865 AND 2024
Authors: Ghasemi David R
Published: June 2024

BACKGROUND

The history of research on ependymomas dates back to the nineteenth century. However, ependymomas have received much less attention than other neuro-oncological diseases. This narrative review investigates the history of ependymoma as a distinct tumour entity.

METHODS

A comprehensive literature search in German, English and French was carried out for publications from 1850 to 2024 in PubMed, the Internet Archive, and the library of Heidelberg University. Additionally, the evolution of the classification of ependymoma throughout the editions of the WHO classification of CNS tumours was analysed.

RESULTS

The first major systematic description of ependymal tumours was published in 1865 by Rudolf Virchow, who hypothesized that ependymomas originated from chronic irritations to the ependyma. In 1899, perivascular (pseudo-)rosettes were described for the first time. Subsequently, Percival Bailey and Harvey Cushing’s systematic classification efforts laid the groundwork for new advancements. Debates about the classification of ependymomas can already be found in publications by Percival Bailey or Gustave Roussy in 1924, with a major focus on the definition of ependymoblastoma as an independent entity, which was only resolved in 2016 with the introduction of the new diagnosis ETMR. Klaus Joachim Zülch’s important mid-20th-century work highlighted clinical variations within ependymomas but deemed no further stratification necessary. The WHO’s classifications in 1979, 1993, 2000 and 2007 relied on histopathology, with only minor details being adapted over the years. A new era began in 2016 with the recognition of C11orf95-RELA (ZFTA-RELA) as a defining hallmark of supratentorial ependymomas. The latest WHO classification in 2021 adopted a molecular-anatomical approach, incorporating new subgroups and abandoning histomorphological subtypes due to limited prognostic value. Tumor grading became mostly optional.

CONCLUSIONS

This review summarises the significant evolution in ependymoma research, particularly in the 2010s. Strikingly, many of the questions that Virchow, Bailey or Roussy investigated, remain unanswered in 2024.
EPID-07. INCIDENCE OF PAEDIATRIC BRAIN TUMORS IN AN ITALIAN REGIONAL COHORT: AN EPIDEMIOLOGICAL STUDY FROM 2012 TO 2023
Authors: Toniutti Maristella , Pilotto Chiara , Pedicini Sara , Pegolo Enrico , Mascarin Maurizio , Coassin Elisa , Kiren Valentina , Rabusin Marco , Tuniz Francesco , Vindigni Marco , D’Agostini Serena , De Colle Maria Cristina , Cogo Paola Elisa , Liguoro Ilaria
Published: June 2024

BACKGROUND

Central nervous system (CNS) tumors are the most common solid cancer in children, second only to leukaemia.

METHODS

We conducted a retrospective epidemiological study of primary CNS tumors diagnosed in children up to 16 years of age between 2012 and 2023, in order to estimate the incidence in a regional cohort of 1,2 million inhabitants (Northeastern Italy). Only primitive lesions were enrolled, relapses were excluded.

RESULTS

Over a period of twelve years, 100 new diagnoses were made (44% Female, 56% Male) with a mean age of 8,92 years (range 0-16 years) at time of onset. In terms of location, we recorded an equal number of supratentorial and subtentorial diagnoses (50% vs 50%). A time-series analysis was performed to verify possible variations in the incidence rate of brain tumors over years, and no significant change was described (R2 0.301, p=0.06). However, after 2017 a significant increase was noted (R2 0.725, p=0.015), as the incidence of new diagnosis quite doubled, from 3.16 in 2018 (95%CI 3.15-3.17) to 5.59 in 2023 (95%CI 5.57-5,61). Data were therefore divided in two groups: 2012-2017 (group 1), and 2018-2023 (group 2). There were no differences in terms of gender or age. The number of low-grade (LG) and high-grade (HG) diagnosis were compared: HG tumors, including high grade glioma, ependymoma and medulloblastoma, were significantly higher in the group 2 than group 1 (27/50, 54% vs 6/43, 14%, p<0.001).

CONCLUSIONS

In childhood, CNS tumors incidence has been fairly stable in the last twelve years in our regional cohort, but a recent concern of an increased rate of high-grade diseases emerged according to our data. In case of a confirmation of this trend, further analysis will be required in order to understand the reason.