bluuebunny/crossref_metadata_2025 huggingface dataset:
LGG-14. INTEGRATED MULTI-OMICS EXPLORATION OF MAPK PATHWAY INHIBITION IN PEDIATRIC PILOCYTIC ASTROCYTOMA
Authors: Sigaud Romain , Stefanski Anja , Selt Florian , Usta Diren , Kocher Daniela , Picard Daniel , Büdenbender Isabel , Remke Marc , Pfister Stefan M , Jones David T W , Brummer Tilman , Witt Olaf , Milde Till
Published: June 2024

Pilocytic astrocytomas (PA), the most common pediatric brain tumors, exhibit MAPK pathway alterations leading to its constitutive activation. They are also associated with low proliferation index due to the oncogene-induced senescence (OIS), sustained by senescence-associated secretory phenotype (SASP) factors. Little is known about the downstream consequences of MAPK activation leading to OIS-SASP, and of the molecular implications of MAPK pathway inhibition in senescent PA cells. Senescent DKFZ-BT66 cells derived from a primary KIAA::BRAF-fusion positive PA were used to generate RNA-sequencing and phospho-/proteomic datasets, before and after treatment with the MEK inhibitor (MEKi) trametinib for different time-spans. A multi-omics factor analysis tool (MEFISTO) and single sample gene set enrichment analysis (ssGSEA) were used to identify key OIS effectors and differentially regulated pathways upon MAPK inhibition. Trametinib treatment inhibited OIS and SASP signatures across all omics levels in the senescent DKFZ-BT66 cells, associated with reduced sensitivity towards senolytics drugs, indicating inhibition of senescence features upon MEKi. MEFISTO analysis identified key effectors involved in MAPK-induced OIS in the senescent PA cells. We built a pathway network using a prior knowledge network approach allowing to map the direct downstream effectors of MAPK leading to OIS-SASP. We identified several parallel pathways (JAK/STAT, p38, GSK3B) potentially involved in OIS and under the control of the MAPK pathway. In addition, ssGSEA showed that pathways related to upstream MAPK activators (SOS1, CK2, several RTKs) were predicted to be upregulated upon treatment, highlighting putative targets to be further investigated. Our data suggest that MAPKi reverses OIS signaling in senescent PA cells, while inducing the activation of MAPK upstream regulators, identifying putative co-targets for the treatment of PA. Further validation of the targetability of these pathways is pending. Furthermore, the identification of the MAPK-related OIS-SASP genes provides insight into the regulation of OIS-SASP by the MAPK pathway.
LGG-18. BEVACIZUMAB: GOOD FOR EYES AND MRI’S! A NATIONAL UK ASSESSMENT OF VISUAL AND RADIOLOGICAL OUTCOMES OF BEVACIZUMAB THERAPY IN PAEDIATRIC LOW-GRADE GLIOMA (PLGG)
Authors: Green Katie L , Panagopoulou Paraskevi , D’Arco Felice , O’Hare Patricia , Bowman Richard , Walters Bronwen , Jorgensen Mette , Slater Olga , Ahmed Rehana , Bailey Simon , Carceller Fernando , Corley Elizabeth , English Martin , Hayden James , Kamal Ahmed , Kilday J P , Lowis Stephen , Lumb Blanche , Pace Erika , Picton Susan , Pizer Barry , Shafiq Ayad , Uzunova Lena , Wilson Shaun , Wayman Harriet , Hargrave Darren , Opocher Enrico
Published: June 2024

INTRODUCTION

Bevacizumab (BEV) is increasingly used for PLGGs in varying manners despite limited evidence. The potential for BEV to preserve or rescue vision in OPGs has not yet been explored. We performed a nationwide UK evaluation of BEV use for PLGG to provide large cohort safety & efficacy (radiological & visual) data.

METHODS

A retrospective UK multi-centre analysis of patients treated with BEV for PLGG 2009-2020. Clinical patient, tumour, treatment and toxicity data were analysed from medical records. Age-adjusted LOGMAR visual acuity and radiological MRI assessments (RANO) were reviewed from initiation of BEV until latest follow-up. Standardized radiological & visual criteria assessed efficacy and clinical–radiological correlation.

RESULTS

88 PLGG patients from 11 PTCs received BEV either 3rd-line with irinotecan (85%) or alongside 1st/2nd line chemotherapy (15%) at median age 6 years (0.65-17). Median duration from diagnosis to BEV was 38 months. PLGGs included:15% Non-OPGs, 85% OPGs. Cohort OS 92% at median follow-up 34 months(3-106). Toxicity was limited and minimal. 8% stopped BEV for CTCAE grade 2+ toxicities, & 3 patients had SAEs (2 intracranial haemorrhages, 1 thrombosis) after stopping BEV without obvious alternative cause. Overall radiological response (SD/PR/CR) was 88%; median duration to best response 3 months. Overall visual response (stable/improved) was 72%; median duration to best response 3-6 months. Superior visual outcomes were seen in NF1-OPGs (p=0.02). Concordance between visual and radiological responses was 36%; 48% using best eye only visual responses. 65% patients with treatment response had tumour progression (all-cause) within 8 months of BEV cessation. Visual responses endured significantly longer than radiological responses (p0.03).

CONCLUSIONS

BEV is a generally safe and effective treatment for PLGG. Most patients demonstrated on-treatment radiological and visual response. Preservation of response after BEV was limited, though visual responses endured better than radiological responses. BEV may have a unique role as a sight-saving strategy in OPG.
LGG-23. INHIBITORS IN THE TREATMENT OF LOW GRADE GLIOMAS- A SINGLE CENTER EXPERIENCE, BRATISLAVA, SLOVAKIA
Authors: Hederova Stanislava , Mocna Andrea , Slezakova Denisa , Bublakova Estera , Rychly Boris , Svajdler Marian , Kolenova Alexandra
Published: June 2024

BACKGROUND

Pediatric LGGs are the most common CNS tumors in children. They are a very heterogeneous group of tumors of different histological types, according to the WHO classification of grade 1- 2. The major molecular pathway affected in these tumors is the mitogen-activated protein kinase (MAPK) signaling cascade. The frequency of MAPK pathway activation makes this pathway an attractive candidate for targeted therapy, and direct inhibition via BRAF and/or MEK inhibitors is emerging as a clinically relevant strategy.

METHODS

We performed a retrospective analysis of patients treated with inhibitors at the Department of Pediatric Hematology and Oncology in Bratislava since 03/2020. Currently 9 patients, 5 boys and 4 girls, are treated with inhibitors. They are pLGG patients, two of them with concomitant genetically confirmed neurofibromatosis type 1. Six patients are treated with the MEK inhibitor trametinib in monotherapy and three patients with BRAF V600-mutated LGG with a combination of the BRAF inhibitor dabrafenib and the MEK inhibitor trametinib. In our cohort with a small number of patients, with a median follow-up of 13 months, we did not observe disease progression in even one patient on inhibitor therapy. Tolerance to treatment is reasonable.

CONCLUSIONS

In recent years, our understanding of the molecular biology of pediatric brain tumors has improved significantly. Alterations in the mitogen-activated protein kinase (MAPK) pathway are generally the most common molecular alterations in cancer, and dysregulation of this pathway also dominates the development of pediatric LGGs. The introduction of targeted drugs not only allows to improve the disease prognosis and survival of children with CNS tumors, to improve their quality of life on treatment, but also to reduce toxicity caused by e.g. radiotherapy, and at the same time to reduce the incidence of late sequelae of treatment.
LGG-35. ROBUST TUMOR RESPONSE TO CHEMOTHERAPY IN THALAMIC PILOCYTIC ASTROCYTOMA WITH LARGE CYSTIC COMPONENT: A CASE REPORT
Authors: Rocco Abbey , Beck Mary , McHugh Michele , Lampe Ashley , Meyer Ashley , Ogle Andrea , Brossier Nicole M , Shatara Margaret , Abdelbaki Mohamed S , Cluster Andrew
Published: June 2024

BACKGROUND

Pilocytic astrocytoma (PA) is the most common glioma in children. Prognosis is excellent when complete resection is achievable. However, in central locations, such as optic pathway, thalamus, and brainstem, resection may lead to extensive morbidity, necessitating alternative treatment strategies. Chemo- and targeted therapy options have demonstrated efficacy in controlling tumor growth and providing clinical benefit; however, cystic portions are not typically responsive to either option.

METHODS

Case report, Retrospective chart review

RESULTS

A 4-year-old male presented with left sided weakness and ventriculomegaly. MRI of the brain revealed a 3.5 x 3.3 x 4.4 cm mixed solid and cystic enhancing mass extending from the right thalamus down to the right middle cerebellar peduncle. An endoscopic third ventriculostomy and tumor biopsy was performed. Histology confirmed PA, WHO Grade 1. Sequencing confirmed BRAF-KIAA1549 fusion. Chemotherapy was initiated with Carboplatin and Vincristine. Each subsequent MRI of the brain obtained during therapy and at the end of therapy demonstrated significant decrease in both solid and cystic portion of the tumor with complete resolution of symptoms and neurologic deficits. End of therapy MRI demonstrated 1.2 x 1.4 x 1.2 cm mixed solid and cystic mass.

CONCLUSIONS

The unique aspect of this case is the exceptional and robust response achieved in both solid and cystic components, challenging the historical notion of cystic lesions being less sensitive to chemotherapy. This observation can contribute valuable insights to the evolving understanding of treatment responses in these tumors.
LGG-38. UNRESECTABLE PEDIATRIC LOW-GRADE GLIOMAS OF THE BRAIN: TARGETED THERAPY COMPARED WITH STANDARD CHEMOTHERAPY AS FIRST-LINE TREATMENT
Authors: Molteni Marta , Verrico Antonio , Ramaglia Antonia , Rossi Andrea , Bagnasco Francesca , Fragola Martina , Piccolo Gianluca , Mercuri Claudia , Piatelli Gianluca , Gaggero Gabriele , De Marco Patrizia , Garrè Maria Luisa , Milanaccio Claudia
Published: June 2024

BACKGROUND

Pediatric low-grade gliomas (pLGG) frequently harbor MAPK-pathway mutations that determine poor response to standard chemotherapy (sCt). Targeted agents against BRAF-V600E mutation (MAPK-i) are emerging as molecularly driven treatments. Few studies have compared sCt with MAPK-i. We aimed to compare response and progression-free survival (PFS) of unresectable brain pLGG treated with sCt or MAPK-i. MAPK-i were used in first line or at relapse.

METHODS

We conducted a single-center observational retrospective study of all brain pLGG consecutively diagnosed and treated at Gaslini Children’s Hospital between January 2008 and December 2021. Treatment was assessed using RAPNO criteria at 6, 12-18 months, and at last follow-up. MRI studies were reviewed by two experienced neuroradiologists.

RESULTS

Seventy-one patients were enrolled: 66 received sCt and 10 MAPK-i (5 in first line, 5 after sCt failure). All patients who received MAPK-i were BRAF-V600E mutated. Groups were homogeneous for tumor location and dissemination. sCt group was enriched for pilocytic astrocytoma, MAPK-I group for ganglioglioma. sCt patients were younger. SCt lasted 12-18 months, MAPK-i were continuously given. Tumor size reduction was 19.5% at 6 months and 40.5% at 12-18 months for sCt group; 48% at 6 months and 43.5% at 12-18 months for MAPK-i group. SCt determined at least stable disease in 74.2% of patients; 60% of responders reached the best response at 6 months, 40% at 12-18 months. 5y-PFS was 40.3% (median time for progression: 2.5 years). MAPK-i determined at least stable disease in all patients at first evaluation with long-lasting response (median time of follow-up: 5.1 years).

CONCLUSIONS

In our study sCt was effective in inducing response but prolonged disease control is not always achieved. BRAF-V600E mutated patients upon MAPK-i start gained a rapid disease control with long-lasting response, also if they have been pretreated. Acknowledgement: this study was supported by ARTUCEBA ONLUS.
LGG-46. MEKI WITH MIRDAMETINIB: EXPLORING ADAPTIVE SIGNALING PATHWAY DYNAMICS AND IMMUNE MODULATION IN PEDIATRIC GLIOMAS
Authors: Pensabene Juliana M , Perez Natalia Muñoz , Yazejian Rita M , Moziak Kirsten , Martin Allison M
Published: June 2024

INTRODUCTION

Glial neoplasms are among the most common types of solid tumors in children. The mitogen-activated protein kinase (MAPK) pathway is implicated in glioma tumorigenesis. Drugs targeting this pathway hold promise as novel therapy for this disease. Vertical inhibition of the MAPK pathway has been linked to increased inflammation in several other cancers but similar exploration in pediatric brain tumors is limited. Within the MAPK pathway, MEK plays a significant role as a modulator of ERK phosphorylation. This study investigates the therapeutic potential of the MEK inhibitor, Mirdametinib, and evaluates the drugs’ capacity to induce tumor-intrinsic inflammation by characterizing changes in PD-L1 expression and proliferation in a panel of pediatric glial neoplasms.

METHODS

Three cell lines were included in the panel (Res186, Res259, SF188) and were treated with Mirdametinib for 3, 5, or 7 days. P-ERK expression, analyzed by western blot, verified successful inhibition of MEK by Mirdametinib. The CCK8 cytotoxic assay was utilized to determine the drug’s 50% inhibitory concentration as well as its direct effects on cell viability. Changes in Ki67 expression assessed by flow cytometry further characterized Mirdametinib’s effects on cell proliferation. Flow cytometry was also utilized to measure changes in PD-L1 expression following treatment.

RESULTS

Despite minimal effects on proliferation as measured by Ki67 and CCK8, expression of P-ERK verifies successful inhibition of MEK. Western blot data also reveals increased Pi3K/AKT pathway activity in SF188 groups treated with Mirdametinib. FACS data for SF188 also demonstrates increased PD-L1 expression in response to treatment.

CONCLUSIONS

Data suggests that, in response to MEKi, gliomas utilize compensatory growth mechanisms through Pi3K/AKT signaling. Findings also point to immune-modulatory effects of MEKi. Supporting results in ongoing experiments are expected to further our understanding of these mechanisms and may help inform effective combination treatment strategies for pediatric gliomas.
MDB-05. PERSONALIZED, RISK ADAPTED THERAPY FOR PEDIATRIC PATIENTS WITH MEDULLOBLASTOMA – A SINGLE CENTER 8-YEAR RETROSPECTIVE REVIEW
Authors: Martinez Devin Antonio , Fragoso Ruben , Zwienenberg Marike , Sharma Julia , Sadegh Cameron , Lee Han Sung , Patel Vihar , Beckham Melinda , Johnson Anita Rochelle , Antony Reuben
Published: June 2024

BACKGROUND

Clinically relevant risk stratification and optimal therapies for pediatric medulloblastoma molecular subgroups are still being investigated.

METHODS

We reviewed host/disease characteristics, patient/tumor specific risk adapted therapy and outcomes of patients treated for medulloblastoma at UC Davis since 2016.

RESULTS

Fifteen patients (age 1-19 years, 12 male, 3 with Li Fraumeni Syndrome (LFS), 2 with spinal cord disease) were included in our review. Tumor histologies included: Classic (n=8), Desmoplastic-Nodular (n=6), Anaplastic (n=1). Tumor genomic profiles were SHHP53WT(n=5), SHHP53 mutated (n=4), Group4 (n=3), NWNSHH (n=2), WNT (n=1). Gross total resection was achieved in 9 patients. Patients with post resection residual tumor, high risk genomic features or disseminated disease were stratified as high risk. We treated all radiation eligible patients (n=13) per COG ACNS0332 maintenance chemotherapy regardless of risk group with 12/13 receiving radiosensitization (Vincristine/Carboplatin) and either 23.4 Gy/36 Gy CSI (two patients treated per Headstart3D2 and ACNS0334 respectively). 2 patients with spinal cord disease were treated with intrathecal topotecan and liposomal cytarabine respectively. During ACNS0332 maintenance bacteremia, weight loss and hypomagnesemia were frequent complications. 5 patients required chemotherapy dose reductions (4 Vincristine/1 Cisplatin). Two patients with LFS developed glioblastoma/undifferentiated pleomorphic sarcoma following ACNS0332 therapy. Two patients (with WNT and NWNSHH subgroup tumors) experienced medulloblastoma relapse. These patients were treated using LITT/Intrathecal chemotherapy and ACNS0821 chemotherapy. Both are alive and one patient is NED off therapy. All patients who have not developed secondary malignancies (n=13) are alive. (follow up 7-72 months). All attend school with support, 10 have hearing impairment and 5 receive endocrine supplements.

CONCLUSIONS

Utilizing patient specific risk adapted therapy we have achieved favorable clinical outcomes in our patient cohort. Therapy deintensification for patients with WNT medulloblastomas should be approached with caution. Patients with LFS might require radiation sparing therapeutic protocols for longer term benefit.
MDB-06. ALTERNATIVE SPLICING MEDIATED BY OTX2 DRIVES THE DEVELOPMENT OF GROUP 3 MEDULLOBLASTOMA
Authors: Saulnier Olivier , Zagozewski Jamie , Liang Lisa , Hendrikse Liam D , Layug Paul , Gordon Victor , Aldinger Kimberly A , Haldipur Parthiv , Borlase Stephanie , Coudière-Morrison Ludivine , Cai Ting , Martell Emma , Palidwor Gareth , Porter Christopher J , Richard Stephane , Sharif Tanveer , Doble Brad W , Millen Kathleen J , Taylor Michael D , Werbowetski-Ogilvie Tamra E
Published: June 2024

BACKGROUND

OTX2 is a transcription factor and known molecular hallmark of Group 3 medulloblastoma (MB). While previous studies have focused on its association with active enhancer elements to modulate the chromatin landscape, here, we demonstrate an unexpected role for OTX2 in regulating Group 3 MB alternative splicing (AS).

METHODS

We used TurboID to broadly interrogate the Group 3 MB OTX2 protein interactome and identify associations with splicing regulators. RNA-sequencing was performed to identify OTX2-driven AS events, a subset of which were validated in Group 3 and Group 4 MB patient tumors and the developing human cerebellar rhombic lip (RL). Splice blocking morpholinos were used to mimic OTX2-regulated splicing events and to determine their role in MB cell fate decisions both in vitro and in vivo.

RESULTS

OTX2 associates with the Large Assembly of Splicing Regulators (LASR) complex through protein-protein interactions and modulates the localization of a LASR protein to help stabilize the complex and sustain a Group 3 MB splicing program. Motif enrichment analysis demonstrates that members of the LASR complex are also significantly enriched near OTX2-regulated alternatively spliced exons. OTX2 is found on nascent mRNA, and its role in AS is independent of DNA-regulatory functions. OTX2 controls a pro-tumorigenic splicing program that is mirrored in the human cerebellar RL origins. Among the OTX2-regulated spliced genes, PPHLN1 is expressed in the most primitive rhombic lip stem cells, and targeting PPHLN1 splicing reduces tumor growth, while enhancing differentiation and survival in vivo.

CONCLUSIONS

While splicing defects are commonly observed in adult cancers, the functional role of AS in the most aggressive MBs has never been explored. These findings identify OTX2-mediated AS as a major determinant of cell fate decisions and highlight AS events as novel therapeutic targets to drive Group 3 MB differentiation.
MDB-11. DOES THE INTRAOPERATIVE ASSESSMENT OF SITE OF ORIGIN OF MEDULLOBLASTOMA ALLOW FOR A TAILORING OF THE NEUROSURGICAL STRATEGY? DATA FROM A RETROSPECTIVE SINGLE-CENTER ASSESSMENT AND PROPOSAL OF A PROSPECTIVE MULTICENTER STUDY
Authors: Ciobanu-Caraus Olga , Czech Thomas , Peyrl Andreas , Haberler Christine , Kasprian Gregor , Furtner Julia , Kool Marcel , Sill Martin , Frischer Josa , Cho Anna , Slavc Irene , Rössler Karl , Gojo Johannes , Dorfer Christian
Published: June 2024

BACKGROUND

Developmental gene expression data from medulloblastoma (MB) suggest that WNT-MB originate from the region of the embryonic lower rhombic lip (LRL), whereas SHH-MB and non-WNT/non-SHH MB arise from cerebellar precursor matrix regions. This study aims to analyze detailed intraoperative data with regard to the site of origin (STO) and compare these findings with the hypothesized regions of origin associated with the molecular group.

METHODS

A review of the institutional database identified 58 out of 72 pediatric patients who were operated on a MB at our department between 1996 and 2020 that had a detailed operative report, surgical video as well as clinical and genetic classification data available for analysis. The STO was assessed based on intraoperative findings.

RESULTS

Using the intraoperatively defined STO, “correct” prediction of molecular groups was feasible in 20% of WNT-MB, 60% of SHH-MB and 71% of non-WNT/non-SHH MB. The positive predictive values of the neurosurgical inspection to detect the molecular group were 0.21 (95% CI 0.08–0.48) for WNT-MB, 0.86 (95% CI 0.49–0.97) for SHH-MB and 0.73 (95% CI 0.57–0.85) for non-WNT/non-SHH MB.

CONCLUSION

In our series of 58 well-documented cases, the intraoperative assessment of the STO could not reliably predict the molecular group. Thus, the current evidence does still not allow for intraoperative group-specific risk stratification that would enable tailoring the neurosurgical strategy to the prognostic and predictive profile of the patient. Prospective multicenter assessments are necessary to systematically evaluate the growth pattern and site of origin of medulloblastoma. Accordingly, a study protocol of an international cohort study will be presented.
MDB-13. GERMLINEELP1 DEFICIENCY SENSITIZES CEREBELLAR GRANULE NEURON PROGENITORS TO SHH MEDULLOBLASTOMA
Authors: Ahmad Shiekh Tanveer , Garcia-Lopez Jesus , Li Yiran , Gudenas Brian , Hadley Jennifer , Paul Leena , Batts Melissa , Soliman Taha , Kojic Marija , Pitre Aaron , Manz Frederik , Zindy Frederique , Jones Alun , Mayasundari Anand , Bianski Brandon , Tinkle Christopher , Shirinifard Abbas , Janke Laura , Lu Meifen , Pfister Stefan M , Gajjar Amar , Baker Suzanne J , Roussel Martine F , Rankovic Zoran , Waszak Sebastian M , Robinson Giles W , Orr Brent A , Wainwright Brandon , Kutscher Lena M , Lin Hong , Northcott Paul A
Published: June 2024

BACKGROUND

Germline loss-of-function (LOF) variants in Elongator complex protein 1 (ELP1) are the most prevalent predisposing genetic events observed in medulloblastoma (MB), accounting for 30% of the Sonic Hedgehog 3 subtype (SHH-3). Molecularly, ELP1-associated SHH-MBs acquire somatic PTCH1 mutations in >80% of cases, and universal loss-of-heterozygosity of the wild-type ELP1 and PTCH1 alleles through loss of chromosome-arm 9q, resulting in their biallelic inactivation. Notably, germline ELP1 LOF occurs mutually exclusive with somatic/germline TP53 mutations in the SHH-3 subtype, suggesting that genetic perturbation of either ELP1 or TP53 may promote similar tumorigenic consequences in cerebellar granule neuron progenitors (GNPs), the accepted cellular origin of SHH-MB. Despite these findings, the molecular, biochemical, and cellular mechanism(s) by which ELP1-deficiency provokes malignant pathogenesis remain unknown. In this study, we sought to close this knowledge gap and functionally determine why children harboring pathogenic ELP1 germline variants are at an increased risk of developing SHH-MB.

METHODS

Mice were genetically engineered to mimic heterozygous Elp1 LOF (Elp1HET). We studied the effect of Elp1 LOF in GNPs using a combination of molecular profiling, immunophenotyping, and cellular assays.

RESULTS

GNPs from Elp1HET mice exhibited a spectrum of molecular and biochemical hallmarks of malignant transformation including increased DNA replication stress, DNA damage, accelerated cell cycle progression, and stalled differentiation. Orthotopic transplantation of Elp1HET GNPs engineered to harbor somatic Ptch1 inactivation yielded SHH-MB-like tumors with compromised p53 signaling, providing an explanation for the specificity of ELP1-associated tumors in SHH-3, and their exclusivity with TP53-mutant tumors. Treatment of ELP1-mutant patient-derived xenografts with an FDA-approved MDM2 inhibitor reactivated p53-dependent apoptosis and extended survival.

CONCLUSIONS

Collectively, our findings functionally substantiate the role of ELP1 deficiency in predisposition to SHH-3 MB and nominate therapeutic strategies to overcome p53 inhibition as a rational treatment option.
MDB-14. TREATMENT AND OUTCOMES OF MEDULLOBLASTOMA: FIRST REPORT FROM ARMENIA
Authors: Hoveyan Julieta , Bardakhchyan Samvel , Asatryan Eduard , Papyan Ruzanna , Hovhannisyan Saten , Grigoryan Henrik , Hovsepyan Shushan , Lalazaryan Nara , Sujyan Paylak , Lazaryan Armine , Mkhitharyan Armen , Hakobyan Lusine , Sargsyan Lilit , Sargsyan Samvel , Salman Zeena , Qaddoumi Ibrahim , Tamamyan Gevorg , Amayiri Nisreen , Bailey Simon
Published: June 2024

BACKGROUND

Medulloblastoma accounts for approximately 20% of all primary CNS tumors. Although advanced diagnostic tools and risk-adjusted treatment regimens produce a more than 70% five-year overall survival in HICs the data from LMICs is scarce. This study analyzed the outcome of children with medulloblastoma treated in Armenia.

METHODS

Demographic and treatment data was collected from medical records of pediatric and young adult patients (≤ 25 years) treated in four major centers in Armenia from 1995-2023. Event-free survival and overall survival were estimated using Kaplan-Meier method.

RESULTS

During the study period 41 patients with medulloblastoma were registered (20.7% of primary CNS tumors), male-to-female ratio 1.73:1. The median age at diagnosis was 8 years (range: 0.83-25 years). Most common presenting symptoms were nausea and vomiting (82.5%), headache (75%) and ataxia (50%). Metastatic status was evaluated (spinal MRI and CSF cytology) in 48.8% of patients (25% M+ disease). Risk assessment was available for 30 patients (12 standard-risk and 18 high-risk). All patients underwent surgery, gross-total or near-total resection was achieved in 53.7% of cases. Radiation therapy and chemotherapy given to 63.4% and 58.5% of cases, respectively. Of 8 infants included in this study 4 were treated with chemotherapy only, 3 died without further treatment. Median time from surgery to RT/chemotherapy was 6 weeks. Five-year EFS and OS were estimated 58.3% (95% CI 37.5-71%) and 62.5% (95% CI 43.75-77.1%), respectively. Patients with GTR/NTR had a higher OS than patients with STR (83.3% vs 33.3%, p=0.005). No statistically significant difference in EFS/OS was detected based on risk group, metastatic status, or completion of the protocol.

CONCLUSIONS

OS was lower than expected in this study. Accurate risk assessment and risk-stratified treatment were often lacking during the study period. Compliance to the standardized treatment protocols and multidisciplinary care are needed for improving outcomes of medulloblastoma.
MDB-15. INHIBITING THE IRON-SULFUR CLUSTER TRANSPORTER ABCB7 CAN POTENTIATE CISPLATIN RESPONSE IN PEDIATRIC GROUP 3 MEDULLOBLASTOMAS BY TRIGGERING FERROPTOSIS
Authors: Mahapatra Sidharth , Kanchan Ranjana K , Doss David , Khan Parvez , Nasser Mohd Wasim , Batra Surinder K
Published: June 2024

BACKGROUND

Medulloblastoma (MB) is the most common malignant pediatric brain tumor, with group 3 tumors (G3MB) being the most aggressive. Uniquely, their aggressiveness is inversely proportional to ferroptosis activation. Intracellularly, these tumors activate iron-sulfur (Fe-S) cluster export and upregulate the expression of glutathione peroxidase 4 (GPX4), the central regulator of ferroptosis. Our main objective was to investigate whether ferroptosis evasion was a targetable driver of aggressiveness in G3MBs that can be inhibited to potentiate classical chemotherapy. We hypothesized that inhibiting Fe-S cluster export would trigger ferroptosis and potentiate cisplatin cytotoxicity in G3MBs.

METHODS

We repressed ABCB7 expression (si-/sh-/KO) in classic G3MB cell lines (HDMB03 and D425) and studied its impact on cancer cell growth, ferroptosis activation, mitochondrial function, and cisplatin cytotoxicity. We further investigated the impact of artesunate, an FDA-approved anti-malarial agent capable of inhibiting ABCB7, on cisplatin action and tumor burden. To rescue cells from iron overload and ferroptosis, we used deferoxamine and ferrostatin-1, respectively.

RESULTS

Silencing ABCB7 resulted in cytoplasmic and mitochondrial iron overload, oxidative stress, and lipid ROS, culminating in ferroptosis and growth retardation. Seahorse studies revealed a switch from oxidative phosphorylation to glycolysis, and TMRM staining revealed loss of mitochondrial membrane potential in ABCB7-silenced cells. Notably, silencing ABCB7 abrogated GPX4 expression and reduced GSH levels. Moreover, ABCB7 silencing reduced the IC50 of cisplatin 2-fold, and ABCB7-silenced cells treated with cisplatin experienced a heightened index of ferroptosis. In vivo, silencing ABCB7 resulted in smaller tumors, dramatically prolonged survival, and potentiated cisplatin action. Artesunate recapitulated ABCB7 silencing by potentiating cisplatin action, reducing tumor burden, and prolonging survival in vivo.

CONCLUSION

The current study illustrates how targeting mitochondrial Fe-S cluster transport can trigger ferroptosis and potentiate cisplatin in G3MBs. Our study also provides evidence for using an FDA-approved drug with the same mechanism of action to treat G3MB tumors.
MDB-18. SYNERGISTIC TARGETING OF CDK8 AND MTOR FOR MYC-DRIVEN MEDULLOBLASTOMA
Authors: Wang Dong , Ritz Caitlin , Luo Yuhuan , Veo Bethany , Pierce Angela , Vibhakar Rajeev
Published: June 2024

MYC-driven medulloblastoma represents a highly aggressive subgroup with poor prognosis and limited treatment options. CRISPR-Cas9 screening across MB cell lines revealed cyclin-dependent kinase 8 (CDK8) as a top dependency for MB growth. Loss of CDK8 significantly decreased both MYC expression and MB growth. Mechanistically, our RNA-Seq analysis demonstrated that CDK8 depletion suppressed ribosome biogenesis and mRNA translation. We found dual role of CDK8 in regulating protein synthesis. Firstly, CDK8-mediated phosphorylation of 4EBP1 was essential for initiating eIF4E-dependent translation and maintaining the typical function of medulloblastoma cells. Secondly, the inhibition of CDK8 led to a reduction in Pol II phosphorylation, resulting in the suppression of gene expression, particularly genes associated with ribosomal function. Targeting CDK8 effectively suppressed cancer stem and progenitor cells characterized by increased ribosome biogenesis activity. We revealed the synergistic effects of the combination inhibition of CDK8 and mTOR in MYC-driven MB cell lines and in xenograft models. Our findings suggest a promising therapeutic approach for MYC-driven MB by targeting CDK8 and mTOR to improve patient outcomes.
MDB-20. TOXICITY PROFILE OF TWO CHEMOTHERAPEUTIC REGIMENS ADOPTED FROM COG A9961 AND ACNS0331 FOR STANDARD-RISK MEDULLOBLASTOMA, A COMPARATIVE STUDY
Authors: Elayadi Moatasem Mohamed Hatem , Elsayed Sarah Magdy , Maher Eslam , sidhom Iman Abdelmokhales , Aboulnaga Sherif Aboulnaga
Published: June 2024

BACKGROUND

Medulloblastoma (MB) is classically treated with surgery, irradiation, and chemotherapy (CTH). Cisplatin-based CTH regimens for standard-risk (SR) MB entail significant toxicities particularly ototoxicity which adversely affect patients’ quality of life. We compared the toxicity profile of two regimens in terms of grade 3 or 4 ototoxicity, hematologic toxicity, hepatotoxicity, nephrotoxicity, and neurotoxicity.

METHODS

SR-MB patients enrolled at Children Cancer Hospital-Egypt (57357) between January 2016 and December 2019 (cohort A) received adjuvant CTH adopted from COG-A9961 protocol (regimen A; 8 cycles of vincristine, cisplatin, and CCNU; cumulative cisplatin dose 600 mg/m2). Starting from January 2020 (cohort B), patients received CTH adopted from ACNS0331 protocol (9 cycles; 2 cycles of vincristine, cisplatin, CCNU followed by 1 cycle of cyclophosphamide and vincristine, for 3 rounds; cumulative cisplatin dose 450 mg/m2). Toxicity grading was done using Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.

RESULTS

enrolled patients (n=168; cohort A = 112; 67% and cohort B = 56; 33%). Cohort A had significantly higher rate of grade ≥3 ototoxicity at some point during treatment (27% vs 3.6%, p <0.001). Similarly, cohort A had higher grade ≥3 neurotoxicity (26% vs 12%, p =0.046), anaemia and thrombocytopenia (72% vs 56%, p =0.04). Cumulative rate of leukopenia was very high in both cohorts, 98% of all patients, while the rate of febrile neutropenia was much lower in cohort A (38% vs 67%, p <0.001). No toxic deaths were observed in both cohorts. There was no difference in grade ≥3 nephrotoxicity nor hepatotoxicity between the 2 cohorts. The 2-year OS for cohort A and B were 96.4% and 86.6%, respectively, p=0.11. Similarly, the 2-year EFS were 92.9% and 86.8%, p=0.29.

CONCLUSION

adjuvant CTH from ACNS0331 protocol showed a better toxicity profile particularly for ototoxicity compared to A9961 CTH regimen, while maintaining comparable survival.
MDB-22. DECIPHERING MEDULLOBLASTOMA’S MOSAIC: UNVEILING SUBGROUP CLASSIFICATION THROUGH METHYLATION PROFILING
Authors: Ashraf Nader , Kofide Amani Al , Arabi Tarek , Sabbah Belal , Aboian Mariam , Ouban Abderrahman
Published: June 2024

BACKGROUND

Medulloblastoma represents the most prevalent malignant brain tumor in children, posing significant treatment challenges despite advances in multimodal therapies. The heterogeneity of medulloblastomas necessitates precise classification to improve therapeutic outcomes. This study explores the utility of genome-wide DNA methylation profiling in categorizing medulloblastomas into molecular subgroups, aiming to refine diagnostic and treatment strategies.

METHODS

This investigation involved the analysis of medulloblastoma samples from pediatric patients at the King Faisal Hospital and Research Centre. We employed the Illumina Infinium 850K EPIC assay to assess the CpG methylation status in six medulloblastoma cases. The methylation data were then compared with immunohistochemical findings to validate the methylation-based subgroup classification.

RESULTS

The Infinium 850K EPIC assay successfully classified all six medulloblastoma cases into the recognized subgroups: WNT, SHH, Group 3, and Group 4. This classification was further supported by immunohistochemical analysis, demonstrating the assay’s robustness in accurately identifying the molecular subtypes. Notably, the assay also distinguished a control case within the cohort, illustrating its potential for widespread clinical application. The study highlights the feasibility of using formalin-fixed, paraffin-embedded (FFPE) tissues, which offers a practical advantage by eliminating the need for fresh tissue samples.

CONCLUSIONS

Genome-wide methylation profiling emerges as a superior method for the classification of pediatric medulloblastomas, facilitating the identification of molecular subgroups with distinct prognostic and therapeutic implications. The ability to utilize FFPE tissues broadens the applicability of this approach, particularly in settings where fresh samples are not readily available. This advancement holds significant promise for enhancing the clinical management of medulloblastoma in pediatric populations.
MDB-28. THE CYTOSKELETON REGULATORS FORMINS CONTROL THE SHH PATHWAY AND ARE INVOLVED IN MEDULLOBLASTOMA TUMORIGENESIS
Authors: Infante Paola , Conenna Marilisa , Adabbo Gennaro , Bufalieri Francesca , Bottero Marta , Severini Ludovica Lospinoso , Bartolini Francesca , Marcotullio Lucia Di
Published: June 2024

BACKGROUND

Medulloblastoma (MB) is a lethal pediatric malignancy of the cerebellum. Among MB’s molecular subgroups, Sonic Hedgehog (SHH) is the most abundant and it is characterized by alterations of key components of the SHH development pathway. However, the molecular mechanisms driving SHH-MB require to further be unveiled to design more effective therapies. Recently, we identified formins, well-known players of cytoskeletal dynamics, as regulators of SHH signaling able to affect SHH-MB growth.

METHODS

Luciferase functional assays, western-blot and RT-qPCR have been performed to analyze the effect of formins on GLI1 (the final effector of SHH signaling) transcriptional activity and expression. Proliferation assays and Brillouin microscopy have been carried out on primary murine SHH-MB cells to test the effect of formins on SHH-MB growth and stiffness.

RESULTS

We demonstrated that formins have a dual role in the regulation of SHH signaling, either positive or negative. The modulation of formins expression in SHH-dependent cell models affect GLI1 transcriptional activity and expression. Moreover, formins show opposite protein expression levels during the development of murine cerebellum, and their modulation impair the proliferation of granule cell progenitors (GCPs), the cells of origin of MB. Interestingly, formins protein levels are highly altered in SHH-MB samples. Notably, the overexpression or the genetic silencing of formins in SHH-MB primary cells from Math1-Cre/Ptc1fl/fl mice significantly impact on the cell proliferation as consequence of modulated GLI1 expression levels and the stiffness of primary SHH-MB cells, thus suggesting that formins could affect tumor cell motility and invasiveness.

CONCLUSIONS

Our findings identify formins as regulators of SHH signaling and illuminate on the role of cytoskeleton in SHH-MB for the design of innovative interventions.
MDB-34. LITHIUM AND RADIATION REDUCE TUMOUR GROWTH IN GROUP 3 MEDULLOBLASTOMA
Authors: Ruchiy Yana , Nunes Daniela , Salinas Casandra , Kanatani Shigeaki , Rosen Gabriela , Zhao Miao , Swartling Fredrik J , Rodrigues Carlos F D , Blomgren Klas , Carlson Lena-Maria
Published: June 2024

Medulloblastoma (MB) is the most common high-grade paediatric brain tumour, accounting for ~20 % of all childhood CNS tumours. It is comprised of 4 distinct molecular subtypes, with Group 3 MB having the worst prognosis with an overall survival of around 50 %. Additionally, current treatments, especially radiotherapy (RT), come at a very high cost for the developing brain and result in permanent complications, including lower IQ, slower processing speed, as well as social problems and lifelong dependency. Lithium has been shown to protect neurogenesis and cognitive functions from the negative effects of RT on the juvenile brain in vivo and can therefore be hypothesised as a preventive treatment strategy to ameliorate these side effects. However, the effects and mechanisms of action of lithium on MB tumours remain largely unknown. In this study, we used GMYC GFP Group 3 MB cells (Mainwaring et al., 2023) to study the effects of lithium and RT in vitro, as well as creating a syngeneic model of Group 3 MB to study those effects in vivo. By using a whole brain immunostaining technique (iDISCO+) and light sheet microscopy, we created a 3D model of every tumour and quantified the tumour volume under different treatment conditions. Our results show that lithium – alone and in combination with radiation – significantly decreases Group 3 MB tumour growth both in vitro and in vivo. Additionally, we studied the transcriptomic changes induced by lithium, validating them through protein analysis that identified Klf4 as a potential effector of its underlying mechanism of action.
MDB-36. 22-HDOHE, A PREDICTIVE MARKER IN CSF OF PATIENTS WITH RECURRENT MEDULLOBLASTOMA TREATED WITH MEMMAT
Authors: Peyrl Andreas , Hagn Gerhard , Stepien Natalia , Senfter Daniel , Madlener Sibylle , Sterba Jaroslav , Lassaletta Alvaro , Leblond Pierre , Nysom Karsten , Haberler Christine , Bileck Andrea , Azizi Amedeo A , Mayr Lisa , Gojo Johannes , Slavc Irene , Gerner Christopher
Published: June 2024

BACKGROUND

With the antiangiogenic metronomic MEMMAT combinatorial regimen, we could achieve sustained responses in a quarter of the patients with previously irradiated recurrent medulloblastoma. There are currently no molecular biomarkers predicting response to MEMMAT treatment for recurrent medulloblastoma. Lipid mediators, including classical arachidonic acid-derived eicosanoids and docosanoids, are locally acting bioactive signaling lipids that regulate a diverse set of homeostatic and inflammatory processes. Before initiation of MEMMAT treatment for relapsed medulloblastoma, we examined the bioactive lipid mediator profile in the cerebrospinal fluid (CSF) of patients and compared it with samples from patients with different neurological disorders, but without cancer.

METHODS

We analyzed CSF samples from 23 patients with relapsed MBL before initiation of MEMMAT treatment and from 12 controls. Lipid mediators were enriched via solid phase extraction and analyzed using liquid chromatography coupled to a high resolution orbitrap Exploris 480 mass spectrometer.

RESULTS

Mass spectrometry-based untargeted oxylipin analysis led to the identification of 98 lipid mediators. Several molecules were downregulated in medulloblastoma samples versus control, such as lipoxin A4 and 14(15)-DiHETE. Non-responders had lower levels of these molecules than responders. Glycodeoxycholic acid and deoxycholic acid were up-regulated in medulloblastoma patients, again with higher levels in non-responders. Remarkably, the docosahexaenoic acid (DHA)-derived 22-HDoHE was specifically identified in the CSF samples of medulloblastoma patients but not in control samples.

CONCLUSION

An oxylipin pattern in CSF might serve as a predictive biomarker signature for response in patients with recurrent medulloblastoma treated with the antiangiogenic metronomic MEMMAT regimen. Our findings advocate for the prospective assessment of CSF-derived lipid markers in future trials for recurrent medulloblastoma.
MDB-42. RADIOMIC TEXTURAL AND MORPHOLOGICAL-BASED FEATURES TO RISK-STRATIFY PEDIATRIC MEDULLOBLASTOMA PATIENTS
Authors: Ismail Marwa , Um Hyemin , Salloum Ralph , de Blank Peter , Tiwari Pallavi
Published: June 2024

BACKGROUND

One key determinate in the treatment pathway for pediatric medulloblastoma (MB), the most frequent malignant brain tumor in children, is accurate risk-stratification. MB tumors are classified as standard- or high-risk based on current approaches (Chang’s/molecular stratification). However, there is still a need for additional attributes towards reliable risk-stratification. This work presents a radiomic-based approach that combines textural- and morphological-based attributes to risk-stratify MB patients. Our rationale is that coupling texture and morphology attributes from the intra-tumoral regions that quantify the heterogeneity and disorderly nature of aggressive tumors can transcend the current clinical approaches in accurately stratifying tumors into high- and standard-risk.

METHODS

T1-weighted MRI scans of 119 MB patients (2–18 years) were collected from Cincinnati Children’s Hospital Medical Center (Site1-n=42), Children’s Hospital Los Angeles (Site2-n=47), and Children’s Hospital of Philadelphia (Site3-n=30), used interchangeably for training and testing. Following preprocessing and performing annotations for the enhancing lesion and edema sub-compartments, 232 textural and morphological features were extracted from each sub-compartment. Namely, 214 textural (gradient, Haralick, intensity, Gabor, Laws, entropy) as well as 34 morphological (4 surface-based (e.g., curvedness and sharpness), 18 global (e.g., roundness, elongation, compactness, flatness)) features were extracted. Features were then fed into Elastic-Net regression models for survival analysis.

RESULTS

Our analysis revealed that texture and morphology features, combined, yielded Concordance index (CI) and p-value of 0.52, 0.0001, respectively, for the enhancing lesion, using Sites1,3 for training, and CI=0.61, p=0.0065 using Site3 for testing. Additionally, for edema, CI and p-value of 0.514, 0.0001 were obtained when employing Sites2,3 for training and CI=0.61, p=0.00096 using Site1 for testing. Results were not significant when using Chang’s or molecular stratification alone for survival analysis.

CONCLUSIONS

Our study shows that radiomic-based morphological and textural features show promise towards reliable MB risk-stratification.
MDB-61. STARVING TUMORS OF POLYAMINES: A NOVEL APPROACH IN TREATING AGGRESSIVE PEDIATRIC MEDULLOBLASTOMA
Authors: Khan Aaminah , Gopalakrishnan Anjana , Liu Jie , Burns Mark R , Tsoli Maria , Ziegler David S
Published: June 2024

BACKGROUND

Polyamines, essential intracellular polycations, govern fundamental cell processes and drive oncogenesis. Our research unveiled the dependency of pediatric Diffuse Midline Gliomas (DMG) on the polyamine pathway (Khan et al.,2021). Disruption of this pathway with the synthesis inhibitor DFMO, and the transport inhibitor AMXT1501, potently inhibited DMG tumors, yielding unprecedented survival in-vivo. We hypothesized that dual polyamine pathway targeting could similarly suppress growth in other aggressive pediatric brain tumors.

METHODS/RESULTS

We analyzed the expression of polyamine pathway regulators in high-risk pediatric brain cancers ZERO precision medicine platform and found elevated expression in medulloblastoma. ODC1, a polyamine synthesis driver, was found to have significant correlation in high-grade gliomas with four key functional tumor states—stemness, cell cycle, hypoxia, and angiogenesis. Medulloblastoma cells were sensitive to treatment with DFMO but showed a compensatory increase in polyamine transporter expression. Conversely, treatment with AMXT1501 increased ODC1 expression. Dual targeting of the polyamine pathway potently and synergistically inhibited cell proliferation and clonogenic potential in Group-3 medulloblastoma cells. Flow cytometric analysis of Annexin V-stained cells showed that treatment with DFMO and AMXT1501 in combination led to induction of apoptosis. Critically, dual polyamine inhibition potently sensitized medulloblastoma cells to the topoisomerase-I inhibitor, SN-38, leading to complete eradication of medulloblastoma cell proliferation and colony formation at nanomolar chemotherapeutic concentrations, with the effect most pronounced in Group-3 medulloblastoma. In triple combination-treated cells, over-representation analysis revealed heightened mitotic DNA damage, macroautophagy, and apoptosis, coupled with diminished neuron/synapse development, glycosylation, and cellular signaling pathways. We are currently testing this treatment strategy in aggressive orthotopic medulloblastoma models.

CONCLUSION

These findings suggest targeting the polyamine pathway as a promising strategy to sensitize aggressive pediatric medulloblastoma tumors to chemotherapy. DFMO/AMXT1501 is in Phase I evaluation for adults (NCT05500508) and advancing to a Phase I/II trial for children through the CONNECT consortium.