bluuebunny/crossref_metadata_2025 huggingface dataset:
LGG-07. MULTI-OMICS ANALYSIS IDENTIFIES MOLECULAR DRIVERS AND THERAPEUTIC TARGETS IN DIFFUSE LEPTOMENINGEAL GLIONEURONAL TUMOR WITH 1Q GAIN
Authors: Mikkelsen Margit , Li Xiaoyu , Yu Kaiwen , High Anthony , Tran Haiyan , Furtado Larissa V , Leelatian Nalin , Berry Julia D , Mobley Bret C , Dewan Michael C , May Adriana , Kofler Julia , Foster Jessica , Lazow Margot , Boué Daniel R , Qaddoumi Ibrahim , Robinson Giles W , Peng Junmin , Moreira Daniel C , Chiang Jason
Published: June 2024

BACKGROUND

Diffuse leptomeningeal glioneuronal tumors (DLGNT) with 1q gain (1q+) display aggressive clinical behavior. We sought to better describe the clinical characteristics of patients with DLGNT and identify molecular drivers and therapeutic vulnerabilities of DLGNT with 1q+.

METHODS

DLGNTs were collected from multiple institutions, sent for methylome array and if quantity-sufficient, were subjected to RNA-seq, proteome, and phosphoproteome profiling. Wherever available, clinical data was collected.

RESULTS

Twenty DLGNTs (13 with 1q+, 7 without 1q+) were collected. Clinical data was obtained on 15 patients (8 with 1q+, 7 without 1q+). The median progression-free survival (PFS) was 17.5 months for those with 1q+ tumors, compared to 51 months for those without (p=0.058). All with 1q+ tumors (n=4) that received CSI radiotherapy progressed (median 12 months), compared to none without (n=3) (p=0.12). There were no responses (complete or partial) in 1q+ tumors that received chemotherapy (n=8), with 2 progressions on therapy. In tumors without 1q+ that received chemotherapy (n=6), 2 responded (1 complete, 1 partial) and 1 progressed on therapy. For 1q+ tumors that received targeted therapy (n=6), there were no responses and 2 progressions on therapy, compared to 1 response and 1 progression for tumors without (n=3). Gene Set Enrichment Analysis of all differentially methylated regions demonstrated enrichment of genes acting in mRNA processing, transcriptional regulation, p53 signaling, TGF-β receptor signaling, and T cell receptor signaling in 1q+ tumors. It identified genes with transcription factor (TF) binding sites for TFs involved in MAPK, PI3K/AKT/mTOR, WNT, and p53 pathways. Consistent with these results, hypomethylated genes at chromosome 1q in 1q+ tumors are positive regulators of MAPK, PI3K/AKT/mTOR, WNT, and p53 signaling.

CONCLUSIONS

DLGNT with 1q+ were more refractory to current treatment options. We identified putative molecular drivers in 1q+ tumors. Our findings suggest therapy targeting the multiple affected pathways should be considered.
LGG-20. SELUMETINIB IN PEDIATRIC PATIENTS WITH RELAPSED/REFRACTORY OPTIC PATHWAY/HYPOTALAMIC LOW GRADE GLIOMA: A MONOINSTITUTIONAL EXPERIENCE
Authors: Schiavello Elisabetta , Biassoni Veronica , Nigro Olga , Gattuso Giovanna , Puma Nadia , Bergamaschi Luca , Colombo Valeria , Schiariti Marco Paolo , Carrabba Giorgio Giovanni , Massimino Maura Rita
Published: June 2024

BACKGROUND

Pediatric low-grade gliomas (pLGG) are the most common central nervous system tumors in children. The optic pathway and hypothalamic (OPH) frequent localizations are correlated with multiply relapses due to inoperability, thus emphasizing the need for alternative treatments. The results of activation of the BRAF oncogene through a tandem duplication resulting in a KIAA1549–BRAF fusion is the most common genetic aberration. Selumetinib is an oral mitogen-activated protein kinase (MEK) 1/2 inhibitor with promising efficacy and good tolerability on relapsed/refractory pLGG.

METHODS

From January 2021 to January 2024 three patients with refractory OPH-pLGG with KIIA1549-BRAF fusion were treated with Selumetinib 25 mg/sqm/day (compassionate use) all after two lines of chemotherapy. They were males, mean age at diagnosis 8 months, at starting Selumetinib 74 months. All had partial surgery at diagnosis and two of them other debulking surgeries during the treatment. All patients had numerous events of hydrocefalous with need of shunt revision.

RESULTS

Two patients experienced grade-3 stomatitis, one grade 3 nausea-vomiting, one grade 3 gastritis, one grade 1 increased level of CPK (CTCAE-V5.0). For grade 3 toxicity Selumetinib had to be stopped for a maximum of 7 days with clinical benefit. Two of them have completed treatment with Selumetinib, one is ongoing after 20 months, all with radiological stable disease at MRI. Median time of treatment is 26 months (range 20-30 months). All three experienced a trend in reduction of emergency room admission for ventricular-shunt problems. Median PFS at starting Selumetinib was 62 months, median OS is 97 months.

CONCLUSIONS

Selumetinib has a good profile of toxicity, allowing a good quality of life procrastinating radiotherapy and reducing surgery events in a context of heavily pretreated relapsed/refractory patients. Further data are needed on both visual and auxological parameters and late side effects.
LGG-33. NETWORK ANALYSIS INTEGRATING MICRORNAS AND CLINICAL DATA TO DETERMINE PROGNOSTIC OUTCOME IN PEDIATRIC LOW-GRADE GLIOMA PATIENTS
Authors: Catanzaro Giuseppina , Conte Federica , Besharat Zein Mersini , D’Antonio Federica , Spinello Zaira , Carai Andrea , Massimi Luca , Gessi Marco , Figarella-Branger Dominique , Paci Paola , Locatelli Franco , Mastronuzzi Angela , Ferretti Elisabetta
Published: June 2024

BACKGROUND

Low-grade pediatric gliomas (pLGGs) are the most common pediatric brain tumors. Surgical resection, when feasible, represents the standard of care. If complete resection cannot be achieved, disease progression occurs in about 30% of the cases, and these patients receive adjuvant therapy. The identification of predictive biomarkers to predict tumors that will progress after partial resection, requiring systemic treatment (Chemotherapy or target therapy), could support clinicians in the decision-making strategy. MicroRNAs have been related to tumorigenesis and tumor maintenance and can be used as important biomarkers. This study aims to develop a predictive model able to determine prognostic outcomes and to better stratify pLGG patients according to disease progression.

METHODS

MicroRNAs levels have been assessed in 76 human tumor tissue samples. Clinical data have been collected for statistical and network-based analyses. Using a network-based approach, we integrated clinical data and tissue microRNA expression to identify a microRNA signature able to predict disease progression.

RESULTS

Our preliminary microRNA expression analysis displayed new promising signatures correlating with prognostic features, such as disease progression and embryological origin of the tumor.

CONCLUSION

The predictive model we developed integrating biomarkers and clinical data could be crucial to support clinicians in the decision-making strategy and in advancing personalized medicine.
LGG-40. TYPE II RAF INHIBITOR TOVORAFENIB IN RELAPSED/REFRACTORY PEDIATRIC LOW-GRADE GLIOMA (PLGG): REVERSIBLE DECREASES IN GROWTH VELOCITY IN THE PHASE 2 FIREFLY-1 TRIAL
Authors: Kline Cassie , Waanders Angela J , Ziegler David S , Kilburn Lindsay B , Nysom Karsten , van der Lugt Jasper , Hassall Timothy E , Gerber Nicolas U , Segal Devorah , Larouche Valérie , Khuong-Quang Dong-Anh , Hansford Jordan R , Leary Sarah E S , Driever Pablo Hernáiz , Bailey Simon , Perreault Sébastien , McCowage Geoffrey , Witt Olaf , Baxter Patricia A , Kang Hyoung Jin , Han Jung Woo , Hargrave Darren , Franson Andrea T , Oren Michal Yalon , Toledano Helen , Abdelbaki Mohamed S , Jabado Nada , Gottardo Nicholas G , Whipple Nicholas S , Chi Susan N , Oren Liat , Tan Enrica E K , Mueller Sabine , Wright Karen D , Blackman Samuel C , Qiu Jiaheng , Podesta Dolores , Walter Ashley , Da Costa Daniel , Manley Peter , McLeod Lisa , Landi Daniel B
Published: June 2024

BACKGROUND: Tovorafenib is an investigational, selective, CNS-penetrant, type II RAF inhibitor. The ongoing FIREFLY-1 (NCT04775485) phase 2 study (Kilburn LK, et al. Nat Med. 2023) of tovorafenib in BRAF-altered pLGG resulted in antitumor activity and manageable safety. Decreased growth velocity (GV) was observed; this is an update on GV changes in skeletally immature children receiving tovorafenib. Methods A planned safety analysis was completed on August 8, 2023 on 137 patients (Arm 1: 77 & Arm 2: 60). Additional follow-up on all cases of decreased GV (an AESI) reported to the global safety database (GSDB) as of January 19, 2024 is provided. Results Overall, 29% had decreased GV from baseline (BL); 19% had ≥50% decrease. Of the 40 with this AESI, 75% had pre-existing neuromuscular or endocrine comorbidities potentially affecting normal growth, including 6 on GnRH-analogues for precocious puberty and 9 with BL heights 2 SDs above/below average for age and sex. Nineteen had on-treatment bone age assessments; none showed bone age advancement from BL or premature growth plate closure. No osteopenia or abnormal fractures reported. All 10 who discontinued or interrupted tovorafenib for ≥3 months for any reason (mean follow-up: 5.8 months), with off-treatment growth measurements available, showed post-treatment annualized GV (AGV) recovery (average AGV: on-treatment, 1.1 cm/y; off-treatment, 8 cm/y), with some exceeding expected average AGV for age. A 4-year-old boy with 1.2 cm/y AGV on-treatment had 12.3 cm/y AGV off-treatment (follow-up: 2 months). Five additional events of decreased GV in patients not on study FIREFLY-1 were reported to the GSDB; 4 of 5 had ≥3 months of off-treatment follow-up, all 4 recovered GV. Conclusions Decreased GV has been observed in patients on tovorafenib. Preliminary follow-up data in those who interrupted treatment show consistent evidence of GV recovery and preservation of growth potential on bone age studies.
MDB-10. DIVERGENT MEDULLOBLASTOMA CHROMATIN STATES DISCLOSE KDM2B AS A NOVEL ONCOGENIC DEPENDENCY
Authors: Tao Ran , Erkek Serap , Matsui Yurika , Xu Beisi , Smith Kyle S , Gao Qingsong , Li Yiran , Djekidel Nadhir , Darrow Emily , Kumar Rahul , Paul Leena , Lin Hong , Hadley Jennifer , Batts Melissa , Bhanu Natarajan V , Kutscher Lena , Garcia Benjamin A , Zhou Xin , Orr Brent A , Robinson Giles W , Wu Gang , Korbel Jan O , Peng Jamy , Pfister Stefan M , Northcott Paul A
Published: June 2024

BACKGROUND

Medulloblastoma (MB) is a highly malignant childhood cerebellar tumor comprising a collection of molecularly and clinically distinct entities. Group 3 and Group 4-MB subgroups originate from overlapping progenitor pools of the developing rhombic lip when neuronal differentiation hierarchies are subverted through somatic alterations. Mutations suspected to deregulate the activity of chromatin-modifying genes are pervasive in Group 3 and Group 4-MB. However, the molecular consequences of these alterations remain largely undefined.

METHODS

We characterized the chromatin landscape of fifty-two primary MBs using chromatin immunoprecipitation followed by sequencing (ChIP-seq) for six histone modifications and performed multi-modal integration with sample-matched somatic lesions, genome-wide DNA methylation, and transcriptomic profiles.

RESULTS

Analysis of differential chromatin states across MB subgroups using a Hidden Markov Model revealed a significant enrichment of the bivalent enhancer state (EnhBiv; marked by coincident H3K4me1 and H3K27me3) in Group 4-MB which localized to promoters of neurodevelopmental genes and transcription factors. To functionally dissect the pathogenetic significance of the enriched EnhBiv state in Group 4-MB, we sought to identify key regulators that confer this state. Integrative bioinformatics coupled with CUT&RUN analysis revealed significant enrichment of KDM2B, a histone lysine demethylase overexpressed in Group 4-MB, in gene promoters marked by the EnhBiv state. CRISPR gene targeting or targeted protein degradation of KDM2B selectively suppressed growth of Group 3 and Group 4-MB models in vitro and in vivo. Mechanistically, inhibition of KDM2B disrupted chromatin bivalency by blocking PRC2 complex recruitment and reducing H3K27me3 deposition, profoundly derepressing PRC2 targets involved in neuronal differentiation.

CONCLUSIONS

Our comprehensive characterization of the MB chromatin landscape in a large cohort of primary tumors provides unprecedented insights into the epigenetic basis of MB subgroups, implicating novel mechanisms of tumorigenesis, and nominating KDM2B as a selective dependency in Group 3/4-MB that should be prioritized as an attractive therapeutic target.
MDB-25. ESTABLISHING A NOVEL CEREBELLAR ORGANOID MODEL FOR INVESTIGATING HEREDITARY PREDISPOSITION TO CHILDHOOD BRAIN CANCER
Authors: Manz Frederik , Bianchini Luca , Atamian Alexander , Northcott Paul , Quadrato Giorgia , Kutscher Lena
Published: June 2024

During the development of the central nervous system, pools of progenitor cells undergo proliferation and subsequent differentiation into mature neurons, establishing a functional neuronal network. However, an imbalance in these processes, characterized by excessive proliferation and loss of differentiation, can lead to tumor formation in pediatric patients. In the developing cerebellum, medulloblastomas of the Sonic Hedgehog (SHH) group arise from excessive proliferation of granule neuron progenitor cells (GNPs) driven by SHH signaling, accompanied by hindered differentiation into mature granule neurons. Genetic predisposition accounts for nearly 40% of all pediatric SHH-medulloblastomas, but the development of humanized models to study these predisposition genes has been lacking. To address this gap, we created an ATOH1-driven EGFP reporter iPSC line to generate reliable cerebellar organoids focused on the development of the granule cell lineage. Our cerebellar organoid protocol yielded homogeneous organoids with robust activation of the ATOH1-EGFP reporter around day 30. Through bulk transcriptomics analysis at day 30, we observed pronounced expression of GNP markers, followed by increased expression of markers associated with mature granule neurons by day 60. Furthermore, by aligning the single-nuclei RNA sequencing (snRNAseq) data of day 60 cerebellar organoids with our human cerebellar development snRNAseq atlas, we identified various cerebellar cell types, including GNPs, mature granule neurons, Purkinje cells, interneurons, as well as glutamatergic and GABAergic neurons. Using this protocol, we examined the development of cerebellar organoids in models of hereditary predisposition to childhood cancer. Using a Gorlin syndrome model, we found that PTCH1HET organoids are larger in size than their isogenic control counterparts, while a model for ELP1HET hereditary predisposition showed no change in size compared with control organoids. These organoid models will allow us to uncover novel molecular mechanisms of hereditary predisposition using human cells.
MDB-33. SIOPE-MB6 – THE RATIONALE FOR THE NEXT EUROPEAN STANDARD RISK MEDULLOBLASTOMA PHASE II/III TRIAL
Authors: Mynarek Martin , Doz Francois , Clifford Steve C , Bailey Simon , Rutkowski Stefan , Padovani Laeticia , Bouchoucha Yassine , Partanen Marita , Verity Sarah , Sehested Astrid , Puhr Anita , Rossius Anne , Chevignard Mathilde , Dorfer Christian , Damaty Ahmed El , Beccaria Kevin , Aquilina Kristian , Hoving Eelco W , Schuhmann Martin U , Thomale Ulrich W , Milde Till
Published: June 2024

BACKGROUND

Neurocognitive impairment is one of the key late effects of childhood medulloblastoma and is potentially influenced by surgical resection, chemotherapy and/or radiotherapy. Still, reduction of therapy to reduce neurotoxicity may be associated with a higher risk of relapses.

METHODS

SIOP-MB6 is a European, prospective, randomized phase II/III trial, aiming to reduce late effects of neurosurgery, radiotherapy and chemotherapy using an improved clinico-molecular risk stratification. Four different interventional questions will be assessed.

RESULTS

Patients with clinically and biologically standard risk medulloblastoma (non-metastatic, no large cell/anaplastic histology, no MYC/MYCN amplification, SHH-medulloblastoma only if TP53 wildtype) are eligible for this trial. Surgical arm: The aim of surgery is randomized to be maximal safe resection (standard) or safe subtotal/near total resection, i.e. sparing critical structures, intending to leave small residual tumor behind (experimental), with systematic treatment of hydrocephalus. The primary endpoint is neurocognitive functioning. Risk-stratified adjuvant therapy: All patients receive one or two blocks of carboplatin/etoposide chemotherapy depending on degree of resection, risk stratification and randomization, followed by re-resection in case of residual tumor. Very favorable risk: Single arm Phase II trial for WNT-activated medulloblastoma. Intervention: reduction of radiotherapy and chemotherapy. Favorable risk: Single arm phase II trial for SHH medulloblastoma (TP53 wildtype) or non-WNT/non-SHH medulloblastoma (subtype VII or favourable whole chromosomal abberations phenotype). Intervention: reduction of radiotherapy and chemotherapy. Standard risk: Randomized phase III trial for non-WNT/non-SHH medulloblastoma not eligible for the favourable risk arm. Randomization in standard therapy (23.4Gy CSI, 4 cycles of cyclophosphamide/cisplatin based chemotherapy) or experimental tandem high-dose thiotepa with stem cell support, radiotherapy (23.4Gy CSI) and temozolomid maintenance. The primary endpoint of all three arms will be progression-free survival, with neurocognitive functioning among secondary endpoints.

DISCUSSION

Detailed rationales for this design will be presented during the presentation.
MDB-44. MIR-106B-5P DEPLETION IN GROUP 4 METASTATIC MEDULLOBLASTOMA SEVS FINE-TUNES MMP-2 ACTIVATION VIA DIFFERENTIAL TIMP-2 PROTEIN ABUNDANCE
Authors: Levers Connor T , Jackson Hannah K , Kerr Ian D , Dajas-Bailador Federico , Coyle Beth
Published: June 2024

BACKGROUND

Small Extracellular Vesicles (sEVs) are major intercellular communicators, with growing evidence of a role in establishing favourable metastatic niches during cancer progression. We have shown that, relative to their paired primary counterpart, Group 4 (Grp4) metastatic Medulloblastoma (MB) cell-lines release significantly more sEVs with increased functionally active MMP-2 on their surface, resulting in enhanced extracellular matrix degradation and subsequently increased cell invasiveness.

METHODS

Transcriptomic analysis of sEV microRNA cargoes derived from metastatic/recurrent and primary cell-line and patient CSF samples, followed by microRNA target prediction of differentially abundant microRNAs using TargetScan and miRDB was conducted. Patient dataset analysis was used to confirm microRNA target mRNA expression levels. Finally, microRNA inhibition followed by RT-qPCR or invasion assays were used to quantify changes at the gene and functional level.

RESULTS

Transcriptomic analysis demonstrated >75% miR-106b-5p depletion in Grp4 MB metastatic sEVs compared to their primary sEV counterparts derived from cell-line and patient CSF samples. This microRNA is predicted to target TIMP-2, which plays a crucial role in MMP-2 activation. We confirmed TIMP-2 to be upregulated in paired metastatic Grp4 tumours relative to their primary counterpart using a publicly available patient dataset. Following miR-106b-5p inhibition in the primary cell-line, RT-qPCR analysis and invasion assays determined the existence of a complex functional response, with increasing TIMP-2 gene expression leading to decreasing invasiveness. This suggests a delicately balanced process where TIMP-2 overabundance can ultimately impede MMP-2 activation. In support of this, analysis of patient datasets showed intermediate TIMP-2 gene expression amongst Grp3/4 patients compared to less frequently metastatic subgroups.

CONCLUSIONS

Our data support the hypothesis that sEV-derived miR-106b-5p regulates enhanced ECM degradation through fine-tuning MMP-2 activation via differential TIMP-2 abundance. Future work will quantify changes in cell/sEV surface-bound TIMP-2 and MMP-2 alongside MMP-2 activation via flow cytometry and gelatin zymography respectively.
MDB-55. LYMPHOID ENHANCER-BINDING FACTOR 1 (LEF1): AN IMMUNOHISTOCHEMICAL PREDICTIVE MARKER FOR WNT-ACTIVATED MEDULLOBLASTOMA
Authors: Ranade Manali , Naik Khushi , Bapat Prachi , Gurav Mamta , Shetty Omshree , Shah Aekta , Sahay Ayushi , Prasad Maya , Singh Vikash , Shetty Prakash , Moiyadi Aliasgar , Dasgupta Archya , Chatterjee Abhishek , Chinnaswamy Girish , Gupta Tejpal , Epari Sridhar
Published: June 2024

AIM

To evaluate lymphoid enhancer-binding factor 1 (LEF1) immunohistochemical expression in various molecular subtypes of medulloblastoma.

MATERIALS AND METHODS

Molecular subtyping of medulloblastomas was based on real-time PCR target 12 gene panel. LEF1 immunohistochemistry was performed and its expression was correlated with histological and molecular subtypes.

RESULTS

The study cohort included 65 cases; comprising 17 WNT-activated, 20 SHH-activated, and 28 non-WNT/non-SHH [group 3: 11, group 4: 10, non-WNT/non-SHH NOS: 7] medulloblastomas. The age range was 1-40 years (≤18 years=54 [WNTa:15, SHHa:13, non-WNT/non-SHH:26], 19-40 years=11) with a median age of 9, and an interquartile range (IQR) of 5-14.5. Forty-one were males and 24 were females (M:F=1.7:1). LEF1 immunostaining was diffuse (≥50% tumour cells) in 13 cases, focal (5-49% tumour cells) in 11 cases, and negative in 41 cases. All cases with diffuse LEF1 immunostaining (n=13) were WNT-activated with classic histology. Twelve of the 13 cases had CTNNB1 mutation on Sanger sequencing and monosomy 6 by fluorescence in-situ hybridization (FISH) while 1 case was uninterpretable for CTNNB1 Sanger sequencing and chromosome 6 FISH. LEF1 staining intensity was strong in 9 cases while heterogenous in 4 cases. No differential staining pattern was observed for paediatric and adult cases. Diffuse LEF1 immunostaining was significantly associated with the WNT-activated subtype of medulloblastoma (p=<0.01). Of 11 focal LEF1 positive cases, 4 were WNT-activated (all having classic histology and CTNNB1 mutation) and 7 were SHH-activated, TP53-wildtype (classic: 2 and desmoplastic nodular [D/N]: 5). None of the WNT-activated, 12 SHH-activated, TP53-wildtype (6 classic, 6 D/N), 1 SHH-activated, TP53-mutant (large-cell/Anaplastic [LC/A]) and all (n=28) non-WNT/non-SHH (classic: 25, LC/A: 3) were LEF1 negative.

CONCLUSION

Classic histology with diffuse (≥50% tumor cells; including heterogeneous intensity) LEF1 immunostaining is a good predictive marker for the WNT-activated molecular group of medulloblastoma, however focal staining is not.
MDB-60. CDK7 INHIBITION DISRUPTS ACQUIRED RESISTANCE MECHANISMS IN MYC-MB
Authors: Veo Bethany , Wang Dong , Michlin Joshua , Wimsatt Genevieve , Vibhakar Rajeev
Published: June 2024

Medulloblastoma (MB) is the most common malignant brain tumor in children, accounting for 20% of all pediatric brain tumors. Medulloblastoma manifests as a clinically heterogeneous tumor with varying prognoses depending on the molecular subgroup. Group 3 tumors have the worst overall prognosis, and are associated with MYC gene amplification, higher rates of metastasis, and increased likelihood of recurrence. Our prior work demonstrated that WEE1 is upregulated in all MB subtypes and is a critical mediator of MB cell viability. We have established that Myc-driven MB is particularly sensitive to the WEE1 inhibitor AZD1775. Although AZD1775 showed promising results in combination with other genotoxic agents, tumor cells frequently acquire resistance to small molecule inhibitors. Thus, to identify regulators of resistance in Myc-MB we performed a Kinome scale RNAi screen in isogenic parental and resistant cells and identified CDK7 as a key mediator of AZD1775 resistance that restored sensitivity to WEE1 inhibition when depleted. CDK7 controls transcriptional initiation by phosphorylating the c-terminal domain of RNA Pol II. CDK7 has been implicated in several Myc-associated malignancies and is frequently enriched at Super Enhancers. Enhancer-promoter interactions (EPIs) are dynamic and can facilitate resistance mechanisms by inducing additional enhancer elements to promote transcription. Here, we investigated 3D chromatin interactions by HiChIP and further assessed CTCF and H3K27ac patterns after treatment with the CDK7 inhibitor, THZ1, by Cut and Run. Our analysis suggests that AZD1775-resistant cells are reorganized to establish alternate cis-acting elements that reinforce transcription of DNA repair and proliferation genes, circumventing AZD1775 treatment. We further examine cisplatin-resistant MB cells to determine if the mechanism is consistent in Myc-MB cell lines or therapy specific. Overall, we suggest that reorganized chromatin structure aids resistance development and that inhibition of CDK7 intervenes in this process, restoring sensitivity to standard therapies.
MDB-66. HIGH-THROUGHPUT SMALL MOLECULE DRUG SCREENING, TRANSCRIPTOMICS AND INTEGRATIVE AI IDENTIFY TARGETABLE MYC-DEPENDENT THERAPEUTIC VULNERABILITIES IN HIGH-RISK MEDULLOBLASTOMA
Authors: Llargués-Sistac Gemma , Taylor Louisa , Lindsey Janet , Buttigieg Marie Claire , Morcavallo Alaide , Bowers Chantelle , Che Harvey , Kwok Colin , Williamson Daniel , Anderson John , Donovan Laura K , Hill Rebecca M , Al-Lazikani Bissan , Chesler Louis , Clifford Steven C
Published: June 2024

INTRODUCTION

MYC-amplified Group 3 medulloblastomas (MBGroup3-MYC) do not respond to conventional up-front therapies and are almost universally fatal (<5% survival). MYC is not directly targetable. Thus, the systematic development of therapies which target complementary MYC-dependencies offers clear potential to rationally re-design effective therapeutic strategies.

METHODS

Isogenic cell-based models with regulable shRNA MYC-knockdown were developed in three independent MYC-amplified backgrounds (D283Med; D425Med; HD-MB03). These were utilised to i) define the MYC-dependent transcriptome/proteome in MBGroup3, through analysis in conjunction with our primary tumour cohort, and ii) as the basis of an automated MYC-dependent high-throughput drug screen (HTS; >500 clinically-actionable compounds). Bespoke integrative AI tools and bioinformatic analysis, and subsequent siRNA/pharmacodynamic validation, identified and validated candidate MYC-dependent therapeutic vulnerabilities. Prioritised drugs were advanced to pre-clinical trials across two in vivo MBGroup3 models (GTML/Trp53KI/KI (GEMM; MYCN-driven) and GMYC (GEMM-derived allografts; MYC-driven)) to evaluate candidate efficacy and toxicity.

RESULTS

shRNA-mediated MYC knockdown could be maintained for 28 days without escape in all models and, as anticipated, was associated with cell cycle abrogation and elevated caspase-3/-7 activity. HTS across all models revealed that MYC expression confers differential dependencies to small molecule inhibitors, with 82 compounds spanning 11 major drug classes demonstrating MYC-dependent activity. AI-based integration of HTS data with model and primary patient MYC-dependent transcriptome data shortlisted multiple druggable molecular targets which, in turn, were independently validated. To date, we have progressed alisertib (AURKAi), volasertib (PLK1i) and prexasertib (CHK1i) to in vivo pre-clinical trials. Promisingly, both alisertib and prexasertib demonstrated efficacy within MBGroup3-MYC models.

CONCLUSIONS

Integrated human tumour and model-based screening approaches have enabled identification and validation of critical MYC co-dependencies, targetable using established small-molecules, to inhibit MBGroup3 tumour growth. Their further evaluation, including integration into established and/or rationally-designed combinations, will be essential next steps in their (pre-)clinical development.
MDB-69. RADIOLOGICAL PATTERNS OF RECURRENCE IN MEDULLOBLASTOMA SUBGROUPS AND CORRELATION WITH SURVIVAL
Authors: Sahu Arpita , Nair Swetha M , Dasgupta Archya , Mynalli Soujanya , Jain Ayushi , Sridhar Epari , Chatterji Abhishek , Choudhari Amitkumar , Bhattacharya Kajari , Prasad Maya , Chinnaswamy Girish , Menon Nandini , Singh Vikas , Shetty Prakash , Moiyadi Ali Asgar , Gupta Tejpal
Published: June 2024

BACKGROUND

Medulloblastomas can recur in up to one-third of the patients despite optimal therapy. The knowledge of the molecular group can provide clues to the possible pattern of relapse and the course of disease, with therapeutic implications. In the present study, we have identified anatomical locations and radiological patterns of relapse.

METHODS AND MATERIALS

Patients with a histopathological diagnosis and available subgroups of medulloblastoma with first relapse, treated in a single tertiary care center during 2005-2021 with available magnetic resonance imaging of brain and spine were included in the retrospective study. Statistical analysis was done using Pearson chi-square test and Fisher’s exact test.

RESULTS

127 patients were included in the final analysis. Median age at diagnosis was 12 years and time to first recurrence was 21 months. Tumor bed relapse was seen in 49% cases, maximum in SHH subgroup, p<0.01. Involvement of the ventricular system (including cisterns and ventricles) was seen in 37% of cases, and was significantly associated (p:<0.01) with non-WNT, non-SHH tumours. Leptomeningeal metastasis was seen in 36% of cases, with significant association (p<0.01) in group 3 (75% of all group 3 cases) and group 4 tumors (50% of all group 4 cases). Disease in spine was most common in group 3 (65%) and group 4 tumours (71%), p<0.01. Hippocampus was involved in 19 cases (15%), mostly in non-WNT, non-SHH (14 cases). Significant difference in survival after recurrence was seen with ventricular, extraventricular metastases with one year survival 83% and 73% respectively, p=0.02. Hippocampal involvement showed significantly decreased survival, one year survival of 37%, p<0.01.

CONCLUSIONS

Leptomeningeal dissemination and diffuse disease were mostly seen in group 3 tumours, indicating their aggressive nature. The lower rates of ventricular relapse and around hippocampus in SHH medulloblastoma provide the opportunity to explore hippocampal avoidance-craniospinal irradiation.
MDB-76. ONC201 INHIBITS THE CHARACTERISTICS OF CANCER STEM CELLS IN GROUP 3 MEDULLOBLASTOMA
Authors: Abballe Luana , Antonacci Celeste , Gianesello Matteo , Lago Chiara , Mastronuzzi Angela , Catanzaro Giuseppina , Giannatale Angela Di , Tiberi Luca , Locatelli Franco , Miele Evelina
Published: June 2024

BACKGROUND

Medulloblastoma (MB), the most frequent childhood brain tumor, originates in the cerebellum. Despite treatment advances, recurrence affects 40%, with a mortality rate of 30%. Cancer stem cells drive tumor initiation, maintenance, and therapy resistance, in several tumors including MB (MBSC). In response to stress, stem cells activate mechanisms like the unfolded protein response (UPR) to maintain homeostasis and survive adverse conditions. The UPR restores endoplasmic reticulum balance, supporting cell function and survival. Recent studies have shown that the UPR plays an important role in tumorigenesis, however, its function in MBSC remains unknown.

METHODS

To understand the involvement of the UPR in stem cell maintenance, we have investigated the biological effects of its pharmacological inhibition on Group 3 (G3) MBSC. We selected three G3 MB cell lines (D283-Med, D341-Med and Med411), for in vitro studies. Cell line selection was based on their fidelity to the expected methylation class, corresponding to the subgroup of the parental tumors, and were grown in “stem-like” conditions as neurospheres. We evaluated drugs targeting the UPR stress program, identifying ONC201 as the most effective against MBSC. ONC201 is an imipridone compound that activates p53-independent apoptosis causing changes in gene expression similar to those caused by UPR.

RESULTS

Our findings revealed that ONC201 modulates protein synthesis via ATF4, a pivotal UPR molecule, with stronger induction observed in MB cells cultured under “stem-like” conditions. This ATF4 upregulation triggers the activation of pro-apoptotic programs. Additionaly, ONC201 was effective on reducing the stem-like features of MBSC, including self-renewal, stem cell markers expression, migration, and invasion potential. Notably, ONC201 demonstrates synergy with vincristine and methotrexate chemotherapy.

CONCLUSIONS

These results propose ONC201 as a promising agent for targeting G3 medulloblastoma by compromising the stem cell compartment. Further investigation is warranted to confirm its efficacy and potential clinical application.
MDB-92. EFFECT OF REDUCED-DOSE CRANIOSPINAL IRRADIATION AND REDUCED-DOSE ADJUVANT CHEMOTHERAPY ON CHILDREN AND ADOLESCENTS WITH WNT MEDULLOBLASTOMA WITHOUT RESIDUAL OR METASTATIC DISEASE: RESULTS FROM THE SJMB12 CLINICAL TRIAL
Authors: Robinson Giles W , Merchant Thomas E , Orr Brent A , Bass Johnnie K , Conklin Heather M , Bag Asim , Dhanda Sandeep K , Pinto Soniya , Delaney Angela , Mikkelsen Margit , Reddick Wilburn , Huang Jie , Ashford Jason , Edwards Angela , Christy Leigh Ann , Soans Eroica , Clarke Molly , Strother Doug , Fisher Michael J , Bendel Anne , Hwang Eugene I , Zhao Sibo , Smith Amy , Gottardo Nicholas G , Hassall Timothy E G , Elster Jennifer , Perreault Sebastien , Ramaswamy Vijay , Partap Sonia , Laughton Stephen , Cohn Richard , Chintagumpala Murali , McCowage Geoffrey , Sullivan Michael , Sayour Elias , Bowers Daniel , Marks Asher , Lucas John , Tinkle Christopher , Sabin Noah D , Klimo Paul , Ellison David W , Northcott Paul A , Onar-Thomas Arzu , Gajjar Amar
Published: June 2024

BACKGROUND

In response to studies showing medulloblastoma (MB) survival is not only contingent on clinical factors (e.g. metastases, residual disease) but also on molecular factors (e.g. molecular group, gene aberrations), we launched the SJMB12 (NCT01878617) trial to stratify treatment using both clinical and molecular risk factors. Specifically, we sought to evaluate if patients with WNT-group MB, without metastatic (M0) or residual disease (R0), treated with reduced-dose craniospinal irradiation (CSI) and reduced-dose cyclophosphamide-based chemotherapy could maintain a high survival with fewer treatment-related side effects.

METHODS

Tumors were molecularly stratified via immunohistochemistry and fluorescence in-situ hybridization. Patients with WNT tumors were grouped into 3 strata: W1 (M0, R0, classic histology, monosomy of chromosome 6); W2 (M0, R0, without monosomy 6 or classic histology); W3 [metastatic (M+), residual disease (R+), or MYC/MYCN amplification]. Treatment of W1 consisted of 15-Gy CSI/51-Gy primary site (0.5cm CTV margin) followed by 4 cycles of chemotherapy resulting in cumulative doses of 8 mg/m2 vincristine, 300 mg/m2 cisplatin, 12 gm/m2 cyclophosphamide. Serial audiology, neurocognitive, and endocrine evaluations were conducted over a six-year follow-up period.

RESULTS

From 2013-2022, 72 patients enrolled onto the W1 stratum: median age was 10.3 years (4.9-22.0); 62.5% female; median time of follow-up was 4.5 years (1.1-10.1). 5-year progression-free survival (PFS) and overall survival were 90.4 ± 5.1% and 98.6 ± 2.1%, respectively. Five patients had PFS events: 4 relapses and 1 accidental death. Relapsed disease was local in 2, distant in 1, and mixed in 1. Time to relapse was > 2 years from enrollment for 3 patients. Severe ototoxicity (SIOP grade ≥ 3) at the end of therapy occurred in 14.4 ± 4.5%. Neurocognitive, endocrine, and detailed molecular data are forthcoming.

CONCLUSIONS

Patients with low-risk WNT-MB maintained a high PFS (>90%) when treated with reduced-dose CSI and reduced-dose cyclophosphamide-based chemotherapy. Preliminary data suggests fewer treatment-related side effects.
NFS-03. MEDULLOBLASTOMA IN CHILDREN WITH FANCONI ANEMIA: ASSOCIATION WITH FA-D1/FA-N, SHH TYPE AND POOR SURVIVAL INDEPENDENT OF TREATMENT STRATEGIES
Authors: Sönksen Marthe , Obrecht-Sturm Denise , Driever Pablo Hernáiz , Sauerbrey Axel , Graf Norbert , Kontny Udo , Reimann Christian , Kordes Uwe , Schwarz Rudolf , Obser Tobias , Boschann Felix , Schüller Ulrich , Altendorf Lea , Goschzik Tobias , Pietsch Torsten , Mynarek Martin , Rutkowski Stefan
Published: June 2024

BACKGROUND

Outcome of children with medulloblastoma (MB) and Fanconi Anemia (FA), an inherited DNA repair deficiency, has not systematically been described. Treatment is complicated by high vulnerability to treatment-associated side effects, yet structured data are lacking. This study provides a comprehensive overview about clinical and molecular characteristics of pediatric FA MB patients.

METHODS

Clinical data including detailed information on treatment and toxicities of six previously unreported FA MB patients were supplemented with data of 16 published cases.

RESULTS

We identified 22 cases of children with FA and MB with clinical data available. Biological subgroup was SHH in all cases with data available (n=9), confirmed by methylation profiling in five patients. FA MB patients exclusively belonged to complementation groups FA-D1 (n=16) or FA-N (n=3). Patients were treated with postoperative chemotherapy only (50%) or radiotherapy (RT)±chemotherapy (27%). 23% did not receive adjuvant therapy. Excessive treatment-related toxicities were frequent. Severe hematological toxicity occurred in 91% of patients treated with alkylating chemotherapy, while non-alkylating agents and RT were less toxic. 14 patients (63.6%) developed 20 other malignancies, of which ten occurred before, five simultaneously with and five after MB diagnosis. Median overall survival (OS) was 1 year (95%CI 0.3-1.9). 1-year-progression-free-survival (PFS) was 26.3±10.1% and 1-year-OS was 42.1±11.3%. Adjuvant therapy prolonged survival (1y-OS/1y-PFS 0%/0% without adjuvant therapy vs. 53.3±12.9%/33.3±12.2% with adjuvant therapy, p=0.006/p=0.086), with no difference whether the patient had received chemotherapy only or RT±chemotherapy.

CONCLUSIONS

MB in FA patients is strongly associated with SHH activation and FA-D1/FA-N. Despite the dismal prognosis, adjuvant therapy may improve survival. Non-alkylating chemotherapy and RT are feasible in selected patients with careful monitoring of toxicities and dose adjustments. Unlike in standard MB protocols, focal RT may be considered in FA MB patients. Curative therapy for FA MB-SHH remains an unmet medical need.
NFS-06. MANAGEMENT TRENDS OF MEK INHIBITOR DERMATOLOGIC ADVERSE EVENTS FOR NEUROFIBROMATOSIS PATIENTS
Authors: Parisi Rose , Dhulipalla Sanjana , Widemann Brigitte , Pichard Dominique C , Gross Andrea , Weintraub Lauren
Published: June 2024

BACKGROUND

Selumetinib, a MEK inhibitor (MEKi), is approved for the treatment of plexiform neurofibromas (PN) in pediatric neurofibromatosis (NF) patients. In pivotal trials, nearly 70% of participants had PN shrinkage; however, 93% experienced a rash. This is the first study to characterize management trends of MEKi induced dermatologic adverse events (DAEs).

METHODS

Physicians treating NF patients were surveyed to assess MEKi DAE frequency, treatment, and effect on MEKi therapy. The survey was distributed using the Children’s Tumor Foundation listserv.

RESULTS

The survey was completed by MD/DOs (n=15) who were pediatric hematologists/oncologists (n=13) and pediatric neurologists (n=2). Physicians treated pediatric patients (n=8), adult patients (n=2), or both (n=5). Common DAEs included folliculitis (range:10-50% of treated patients; n=11), xerosis (range:1-80%;n=8), acneiform eruptions (range: 20-80%;n=10), eczematous dermatitis (range: 10-80%;n=12), paronychia (range: 10-80%;n=12), and seborrheic dermatitis (range:1-60%;n=8). Approximately half of physicians (n=8) used prophylactic DAE treatment. Prophylaxis for pre-pubertal patients included emollients (n=4), bleach baths (n=2), topical clindamycin (n=1), and doxycycline (n=1). Post-pubertal prophylaxis included emollients (n=5), doxycycline (n=5), topical clindamycin (n=4), bleach baths (n=1), and topical hydrocortisone (n=1). Almost all physicians modified MEKi treatment at least once because of a DAE (n=14), including dose hold (range: 1-25%;n=10), dose reduction (range:1-25%;n=10), and MEKi discontinuation (range:1-25%;n=8). Of the 10 physicians who reported dose holds, 6 were from physicians utilizing prophylactic therapy. Of the 8 physicians who reported MEKi discontinuations, only 3 were reported by physicians utilizing prophylactic therapy.

CONCLUSIONS

Most physicians modified MEKi treatment for DAEs, and many started prophylactic DAE therapy. The benefit of prophylactic treatment cannot yet be determined. Given the low response rate, future research will be aimed at collecting more data. There is a need for more studies to establish standardized treatment guidelines to reduce the frequency of MEKi modifications secondary to DAEs.
NFS-20. DECIPHERING CELLULAR CROSSTALK IN PERIPHERAL NERVOUS SYSTEM TUMORS ASSOCIATED WITH NEUROFIBROMATOSIS TYPE 1 THROUGH SINGLE-CELL RNA SEQUENCING
Authors: Freund Julia , Robl Bernhard , Gabler Lisa , Machreich Sarah , Madlener Sibylle , Baumgartner Alicia , Lötsch-Gojo Daniela , Azizi Amedeo , Gojo Johannes
Published: June 2024

BACKGROUND

Neurofibromatosis Type 1 (NF1) is a genetic disorder characterized by mutations and dysfunctional expression of neurofibromin 1 gene, a critical tumor-suppressor gene. NF1’s complex pathophysiology involves dysregulation of the RAS-MAPK signaling pathway, resulting in sustained MAPK signaling. Among others, the spectrum of clinical features includes low-grade tumors (e.g. plexiform neurofibromas (pNFs)) and malignant peripheral nerve sheath tumors (MPNST). While surgical removal of peripheral nerve tumors is common, total resection is often unattainable. Additionally, approved therapies comprising MEK inhibitors fail to prevent malignization, highlighting the urgent need for novel targets for effective therapies.

METHODS

To explore novel potential targets across a broad spectrum, we analyzed published scRNA-seq datasets (Kershner et al. 2021, Wu et al. 2022) from human patients, including pNFs and MPNSTs. We further investigated key pathways in vitro with patient-derived cell culture models.

RESULTS

ScRNA-seq provides insight into complex networks of cell-to-cell interactions that drive the malignant phenotype of cancerous tissues. Due to the rich presence of ECM in NF1 tumors we aimed to investigate cell types contributing to key extracellular matrix (ECM) components and associated signaling pathways. Analysis of 19 NF1 tumor samples revealed consistent presence of Schwann cells (SCs), fibroblasts, endothelial cells, and immune cells. Proliferating cells were found in MPNSTs, while pericytes were exclusive to pNFs. We compared secreted and ECM signaling between the cell types of both tumors. Our analysis discovered, among other findings, collagen signaling, highlighting fibroblasts as emitters and SCs as receivers. We further confirmed these findings through culturing of NF1-derived cells in vitro with and without collagen, observing increased cell proliferation in the presence of collagen. Further experiments and analyses are ongoing.

CONCLUSIONS

The emphasis on ECM and signaling adds depth to our understanding of NF1 pathogenesis and suggests potential therapeutic targets.
NFS-29. DEVELOPMENTAL SCREENING AND MONITORING IN NEUROFIBROMATOSIS-1
Authors: Janke Kelly , Lawler Danielle , Kearns Zoe
Published: June 2024

BACKGROUND

Pilot data showed developmental screening at Neurofibromatosis-1 (NF1) appointments is feasible to identify those needing neuropsychology or other referrals. Outcomes for this larger sample, many re-screened and/or seen for a neuropsychology visit, allow us to describe evolving clinical management.

METHODS

Screenings are offered annually (ages 2-17) at NF1 clinic appointments by the psychosocial team. Forty-eight early childhood patients (ages 2-5) were screened (54% male, 66.7% White,) while 35 were ineligible (e.g., recent neuropsychology visit) or experienced logistical barriers to screening. These groups did not differ in race/ethnicity, sex, glioma status, or childhood opportunity index. Parents completed well-validated measures including the PEDS: Developmental Milestones – Assessment Level (PEDS:DM), Modified Checklist for Autism in Toddlers, and/or an ADHD Rating for preschoolers.

RESULTS

On initial screens, 73.9% showed a delay of 25% or more on at least one PEDS:DM domain. Measures often aligned with clinical impressions (81.3%); however, when findings were contextualized with record review, there were false positives (8.3%) and negatives (10.4%). Screening identified emerging concerns in attention, fine-motor, and academic skills. Nearly half (47.9%) of patients had services at the time of screening, and new/modified recommendations were offered for 70.8%. One third were referred to our Education Coordinator or Social Worker for educational advocacy, support through Early Intervention/school evaluation, or outpatient referrals. Twenty-two (45.8%) were referred to Neuropsychology and 18 have now been seen (consultation, targeted testing, or comprehensive evaluation) to confirm or rule-out neurodevelopmental diagnoses (e.g., autism, ADHD, language or global delay) and further guide educational or intervention management. Follow-up screens (N = 21) have monitored developmental progress, previously subclinical symptoms rising to a significant level, and need for re-evaluation or additional services.

CONCLUSIONS

Multipronged systematic screening results in referrals for diagnostic clarity, guides transition from Early Intervention to school services, and supports dynamic management of changing concerns.
QOL-02. PREDICTING NEUROCOGNITIVE OUTCOMES AMONG CHILDREN EXPERIENCING VARYING DEGREES OF POSTOPERATIVE POSTERIOR FOSSA SYNDROME
Authors: Conklin Heather M , Raches Darcy , Khan Raja B , Ashford Jason M , Lin Tong , Onar-Thomas Arzu , Potter Brian S , Klimo, Jr Paul , Gajjar Amar , Robinson Giles W
Published: June 2024

BACKGROUND

Postoperative posterior fossa syndrome (PFS) has historically been diagnosed as present vs. absent despite a continuum of severity in presentations. We recently demonstrated categorizing children into PFS1 (complete mutism) and PFS2 (diminished speech) has prognostic utility for neurological recovery. Given children who experience PFS are also at increased risk for neurocognitive impairments, we investigated whether these PFS variants predict neurocognitive outcomes while considering well-established risk factors (i.e., age and treatment intensity).

METHODS

Children treated for medulloblastoma at St. Jude on a prospective, risk-stratified protocol (SJMB12; NCT 01878617) were study eligible if they had at least two neurocognitive evaluations. SJMB12 participants received neurological and neurocognitive evaluations prior to irradiation and annually for 5 years. Neurocognitive outcomes included intellectual functioning (Wechsler Intelligence Scale for Children [WISC-IV] estimated IQ [EIQ]), processing speed (WISC-IV Processing Speed Index [PSI]), working memory (WISC-IV Working Memory Index [WMI]), and adaptive functioning (Behavior Assessment System for Children [BASC2] Activities of Daily Living [ADL]).

RESULTS

149 patients (age at diagnosis= 10.7±5.6; 64% male; 9% 15Gy, 40% 23.4Gy, 51% ≥36Gy) were included. No significant differences between PFS1 (n=34) or PFS2 (n=16) compared to NonPFS (n=99) were identified in age, sex, or irradiation dose (ps>.05). Multivariable linear mixed models indicate NonPFS have better EIQ than PFS1 and PFS2 (p<.03), with EIQ improving over time (p=.01). NonPFS have better PSI than PFS1 and PFS2 (p<.001). PSI declines over time irrespective of age (p>.05); however, PSI declines for those receiving 36Gy while improving for those receiving 15Gy (p<.001). NonPFS have better WMI than PFS1 and PFS2 (p<.05); older age at diagnosis is associated with improvement in WMI over time (p<.0005). ADL declines only in PFS1 patients (p<.05).

CONCLUSIONS

PFS variants add value beyond established risk factors in predicting neurocognition. Severity of PFS, in addition to treatment intensity, predicts worse outcomes.