bluuebunny/crossref_metadata_2025_split huggingface dataset:
LGG-02. Cardiac toxicity in patients receiving single-agent MEK inhibition
Authors: Cantor Evan , Shatara Margaret , Meyers Ashley , Ogle Andrea , McHugh Michele , Reiners Stephanie , Cluster Andrew , Abdelbaki Mohamed S , Navalkele Pournima , Brossier Nicole M 
Published: June 2022

Abstract
BACKGROUND: MEK inhibitor therapy is increasingly being utilized for the treatment of pediatric tumors, including low-grade glioma, plexiform neurofibroma and Langerhans cell histiocytosis. These drugs are well-tolerated but do have risk of toxicity, including cardiac toxicity. The purpose of this study is to better characterize MEK inhibitor-induced cardiac toxicity in pediatric patients. METHODS: Retrospective review of all patients who underwent MEK inhibitor mono-therapy for at least 3 months, 2015- 2021, age 25 years or less, at St. Louis Children’s hospital and Cardinal Glennon Children's hospital. RESULTS: We evaluated 31 patients, 19 (61%) with brain tumors and 12 (39%) without. Of the thirty-one, fifteen (48%) had NF1, 1 had Tuberous sclerosis. Cardiac toxicity consisted of asymptomatic sinus tachycardia, bradycardia, or decreased ejection fraction (EF). Thirteen patients (42%) experienced an asymptomatic decrease in left-ventricular ejection fraction (EF), Grade I-III. Time on therapy before decreased EF was 5 days to 21 months, median 2.8 months. Decreased EF developed in 5 of 13 patients receiving selumetinib and 8 of 18 receiving trametinib. Of the patients who developed decreased EF, 11 (85%) had brain tumors, 6 (46%) had NF1, and 89% had received prior systemic therapy. Out of the patients who had received no prior systemic therapy (6), 2 (33%) had decreased EF, while 11/25 (44%) of those who had received prior systemic therapy did. Drug was held temporarily for 6 patients, with dose limiting toxicity for 5 patients. Drug was discontinued for 1 patient after EF continued to decline despite dose reduction. Patients showed improvement in EF as early as 2 weeks after holding therapy. CONCLUSIONS: Cardiac toxicity in our patients was limited to asymptomatic reduction in ejection fraction, sinus bradycardia and tachycardia, reinforcing the need for appropriate monitoring via echocardiography. Prior systemic therapy was associated with decreased EF.
LGG-06. Selumetinib in pediatric patients with non-neurofibromatosis type 1-associated, non-optic pathway (OPG) and non-pilocytic recurrent/progressive low-grade glioma harboring BRAFV600E mutation or BRAF-KIAA1549 fusion: a multicenter prospective Pediatric Brain Tumor Consortium (PBTC) Phase 2 trial
Authors: Fangusaro Jason , Onar-Thomas Arzu , Poussaint Tina Young , Lensing Shelly , Wu Shengjie , Ligon Azra H , Lindeman Neal , Stewart Clinton F , Jones David T W , Pfister Stefan M , Smiley Natasha Pillay , Leach James , Packer Roger , Vezina Gilbert , Lenzen Alicia , Jaju Alok , Goldman Stewart , Doyle Laurence Austin , Smith Malcolm , Fouladi Maryam , Dunkel Ira 
Published: June 2022

Abstract
BACKGROUND: A greater understanding of the Ras-MAP kinase pathway in pediatric low-grade glioma (LGG) paired with the availability of selective inhibitors has enhanced the ability to target this pathway with therapeutic intent. METHODS: The PBTC conducted a multi-institutional phase II study (NCT01089101) evaluating selumetinib (AZD6244, ARRY-142886), a MEK I/II inhibitor, in children with recurrent/progressive LGG assigned to 6 strata and treated at a dose of 25 mg/m2/dose PO BID for up to two years. Here we present stratum 5 which enrolled children without NF1, non-OPG and non-pilocytic LGG harboring either a BRAFV600E mutation or BRAF-KIAA1549 fusion. RESULTS: Twenty-four of 25 children enrolled were eligible; 23 were evaluable for the primary radiologic response endpoint. Enrollment stopped early due to slow accrual and initiation of COG ACNS1931. The most common histologies were ganglioglioma (42%) and astrocytoma NOS (33%). Thirteen tumors (54%) had BRAF-KIAA1549 fusion; 11 (46%) had the BRAFV600E mutation. Five of 23 (22%) evaluable patients achieved a centrally confirmed partial response (PR), 12 (52%) had stable disease and 6 (26%) had progression with a 2-year progression-free survival of 75 + 9%. Four of 11 (36%) patients with a BRAFV600E mutation and 1/12 (8%) with a BRAF-KIAA1549 fusion achieved a PR. The 2-year PFS did not significantly differ between tumors with BRAFV600E mutation (82 + 12%) versus BRAF-KIAA1549 fusion (68 + 13%) (n=24, p=0.548). No patient remains on therapy. The most common attributable toxicities were grade 1/2 ALT/AST elevation, dry skin and leukopenia. Rare grade 3/4 toxicities included elevated CPK, rash, paronychia, fever, weight gain and sinus tachycardia. CONCLUSIONS: Despite lower than planned accrual, selumetinib met the design threshold for success in treating children with recurrent/progressive non-pilocytic, non-OPG LGG without NF1 that harbored the common BRAF aberrations. Ongoing phase 3 prospective studies will better determine the role of this agent in this population.
LGG-17. Preventing recurrence: targeting molecular mechanisms driving tumor growth rebound after MAPKi withdrawal in pediatric low-grade glioma
Authors: Kocher Daniela , Selt Florian , Valinciute Gintvile , Zaman Julia , Vonhören David , Pusch Stefan , Guiho Romain , Martinez-Barbera Juan Pedro , von Deimling Andreas , Pfister Stefan M , Jones David T W , Brummer Tilman , Witt Olaf , Milde Till , Sigaud Romain 
Published: June 2022

Abstract
Pediatric low-grade gliomas, a diverse group of WHO grade 1 and 2 glial or glioneural tumors, comprise the most common category of primary brain tumors in children. The majority of these tumors are driven by alterations in the MAPK pathway, making them in principle susceptible to MAPKi therapy. While patients often benefit from MAPKi during treatment, tumor rebound may occur once treatment is stopped, constituting a significant clinical challenge. BT-40, patient-derived cells with molecular features of pleomorphic xanthoastrocytoma (BRAFV600E, CDKN2Adel), were used to model the rebound growth in vitro, based on viable cell counts in response to treatment and withdrawal of the clinically relevant BRAFV600E specific inhibitor dabrafenib. Standard-of-care chemotherapy (vincristine and carboplatin) was used as a reference. MAPK pathway reactivation upon withdrawal was assessed by WB and qPCR analysis. Based on the observed cell-regrowth and MAPK-reactivation pattern, key-timepoints during withdrawal were identified, which are currently being further analyzed through RNAseq and phospho-/proteomics. BT-40 cells started to proliferate again two days after dabrafenib withdrawal, and earliest five days after chemotherapy withdrawal. MAPK pathway activity, based on Mek and Erk phosphorylation, reached baseline levels three hours after dabrafenib withdrawal, this was associated with 2.5-fold increased c-Fos gene expression two hours after withdrawal. The earlier cell regrowth after dabrafenib withdrawal compared to chemotherapy withdrawal matches clinical observations, making the model suitable to study the rebound. The observed MAPK overactivation suggests the growth rebound might not only be caused by a fast reactivation of the pathway but also by other mechanisms, e.g. accumulation of upstream activators due to loss of negative feedback or parallel pathways. To investigate this, key-timepoints during treatment withdrawal will be analyzed using a multi-omics approach. Based on these findings, possible rebound-driving mechanisms will be identified and further validated using BT-40 and additional PXA models in vitro and in vivo.
LGG-55. Autophagy sensitizes CNS tumors to targeted therapy by lowering their apoptotic threshold
Authors: Crespo Michele , Zahedi Shadi , Morin Andrew , Wodetzki Darya , Caino Cecilia , Levy Jean Mulcahy 
Published: June 2022

Abstract
Autophagy inhibition improves the effectiveness and overcomes RAF pathway inhibition (RAFi) resistance across multiple CNS tumors and molecularly distinct resistance mechanisms. Mechanistic links between autophagy and apoptotic cell death may explain this ability to improve RAFi response and reverse resistance. RAFi sensitive (MAF 794, AM38) and resistant (MAF 794R, MAF 905-3, AM38R, B76) BRAFV600E CNS tumor cell lines were analyzed at baseline, following RAFi (vemurafenib), autophagy inhibition (chloroquine or shRNAs), and combination therapy. Growth assays and caspase activation were monitored by Incucyte Zoom. qRT-PCR evaluated key pro-apoptotic BH3-only members of the BCL-2 family. Broad BH-3 profiling was completed using the Letai JC-1 Plate-Based protocol. Western blot analysis assessed protein levels. Combination pharmacologic treatment caused alterations in key pro-apoptotic BH3-only proteins including an increase in BNIP3L and PUMA. Genetically inhibiting autophagy with shRNAs for ATG5 and ATG7 (proteins required for formation of the autophagosome) produced similar results with increases in both protein and mRNA levels of BNIP3L and PUMA following RAFi treatment. This suggested autophagy-mediated regulation of BH3 proteins functions to determine cellular apoptotic threshold. Caspase activation demonstrated increased effectiveness of combined RAFi and autophagy inhibition overcoming the apoptotic threshold compared to single drug treatment. BH3 profiling demonstrated a dependence on BCL-2 to inhibit apoptosis. BH3 mimetics competitively bind to pro-survival BCL-2 family members, blocking their protective effects and pushing tumor cells towards apoptosis. Autophagy inhibition can also improve treatment response by overcoming the apoptotic threshold in RAFi resistant cells and magnifying the apoptotic response in sensitive cells. BH3 profiling reveals CNS BRAFV600E are BCL-2 dependent cells, unprimed for apoptosis, which may be good candidates for additional treatment with BH3 mimetics such as venetoclax. This presents an attractive treatment for MAPK activated CNS tumors by enhancing apoptotic cell death by targeting the MAPK pathway, autophagy and BH3.
MEDB-23. Targeting epigenetic dysregulation in medulloblastoma with poor prognosis
Authors: Badodi Sara , Pomella Nicola , Zhang Xinyu , Zabet Nicolae Radu , Basson M Albert , Marino Silvia 
Published: June 2022

Abstract
Medulloblastoma (MB) is the most common paediatric malignant brain tumour and is classified into four distinct molecular subgroups (WNT, SHH, G3 and G4), each of them further subdivided into subtypes with different prognosis and responses to therapy. Deregulation of chromatin modifier genes play an essential role in MB, particularly in the G4 subgroup. A BMI1High;CHD7Low molecular signature identifies patients with poor survival within this subgroup. We show that BMI1High;CHD7Low sustains MB growth through regulation of MAPK/ERK signalling and via a novel epigenetic regulation of inositol metabolism in both G4 MB cells and patients. These tumours display over-activation of MAPK/ERK signalling, sustaining tumour proliferation, and of AKT/mTOR pathway which leads to energetic rewiring characterised by enhanced glycolytic capacity and reduced mitochondrial function. We demonstrate that inositol administration counteracts this metabolic alteration, impairs proliferation and significantly extends survival in a pre-clinical model. Moreover, inositol synergises with cisplatin, a chemotherapy agent currently used in MB treatment, enhancing its therapeutic effect in vivo. Additionally, we identify a synergistic vulnerability of BMI1High;CHD7Low MB to a combination treatment with BMI1 and MAPK/ERK inhibitors that overcomes acquired resistance to single-drug therapy. Mechanistically, we observe a CHD7-dependent binding of BMI1 to MAPK-regulated genes underpinning the CHD7-BMI1-MAPK regulatory axis that is critical for the anti-tumour effect of the inhibitors in vitro and in a pre-clinical model. Moreover, we demonstrate that the BMI1High;CHD7Low molecular signature defines G4 MB patients with an enhanced ERK1-ERK2 phosphorylation activity. Importantly, cerebellar neural stem cells modelling the BMI1High;CHD7Low signature are not affected by BMI1 and MAPK/ERK inhibitors and do not show metabolic adaptation hence are resistant to the proposed treatments. In summary, we have identified two actionable vulnerabilities in a pre-clinical setting modelling a molecularly defined group of MB patients, paving the way for the design of signature-matched clinical trials.
MEDB-25. Do extracellular vesicles transfer a multidrug resistant phenotype via ABC transporters in medulloblastoma?
Authors: Wade Philippa , Jackson Hannah , Taylor Louisa , Hume Alistair , Kerr Ian , Coyle Beth 
Published: June 2022

Abstract
INTRODUCTION: Medulloblastoma is the most common malignant paediatric brain tumour accounting for 20% of all childhood tumours; approximately one-third of patients present with metastatic disease at diagnosis and the outcome for these patients remains very poor. The high frequency of recurrence and metastatic relapse in medulloblastoma supports the idea of intrinsic drug resistance within cells. This work looks at the ATP-binding cassette (ABC) transporters, known to be upregulated in several cancers, and we hypothesise that extracellular vesicles may transfer ABC transporters to surrounding cells, promoting multidrug resistance within tumours. METHODS: The Cavalli dataset, made up of 763 patient samples, was used to assess the gene expression of a number of ABC transporters across medulloblastoma subgroups. ABC transporter gene and protein expression was then further assessed in medulloblastoma cell lines, including drug-tolerant lines, using qPCR and western blot. Cell viability analysis was used to assess changes in drug response. Matched cell and EV protein samples were used for proteomic analysis. RESULTS: Patient gene expression data showed that high expression of two ABC transporters correlated with reduced patient survival in high-risk subgroups. qPCR analysis of medulloblastoma cell lines showed differential subgroup expression patterns. Additionally, qPCR analysis of drug-tolerant cell lines showed significant increases in the expression of specific drug transporters across the subgroups. RNA-seq confirmed the presence of ABC transporter mRNA in exosomes isolated from high-risk medulloblastoma cell lines. Functional studies of EV transference of ABC transporters are ongoing. CONCLUSIONS: Data to date supports the hypothesis that multidrug transporter carrying extracellular vesicles may transfer their multidrug resistant phenotype to surrounding cells in medulloblastoma, promoting drug resistance. Future work will test this hypothesis by knocking down candidate ABC transporters and assessing the effect on transference of drug resistance by extracellular vesicles.
MEDB-44. Transcriptomic resolution of subgroup-specific medulloblastoma architecture
Authors: Willard Nicholas , Riemondy Kent , Griesinger Andrea , Kaufman Michael , Venkataraman Sujatha , Foreman Nicholas , Vibhakar Rajeev , Donson Andrew 
Published: June 2022

Abstract
Despite a growing understanding and stratification of medulloblastoma, it remains an aggressive childhood brain tumor with high morbidity and mortality. Multimodal genomic and epigenomic analysis has permitted the classification of medulloblastoma into four subgroups with varying biology and clinical behavior: WNT, Sonic-Hedgehog (SHH), Group 3, and Group 4. In our previously published work, Single-cell RNA sequencing (scRNAseq) identified distinct tumor cell subpopulations in specific medulloblastoma groups. However, this technology is limited by its lack of architectural information. Spatial transcriptomics is a relatively new technology that permits the analysis of gene expression as it occurs within organized tissue. In our ongoing study, we utilized Visium spatial transcriptomics, integrated with scRNAseq data and immunohistochemistry, to analyze frozen samples of medulloblastomas (SHH, Group 4, and Group 3 with and without MYC amplification). In SHH in particular, we were able to identify scRNAseq populations within the geographically constricted Visium data, including SHH-C2, a population located in histologic nodules, the predominant neuronal-differentiated population SHH-C1, and progenitor populations (SHH-B1 and B2). In addition, we were able to visualize clusters not detectable by scRNAseq – a cluster lining nodules with expression of vascular endothelium marker, reticulin and M2-macrophage genes, and a novel DNA-repair cluster. In addition, Visium data permits the spatial constraint of proliferating cells, which is frequently problematic in scRNAseq, as dividing cells cluster independently. The proliferation is highest in the SHH-B2 minor progenitor population, absent in the SHH-C1 major differentiated population, and is moderate in other population including the SHH-C2 nodules. Group 3 and 4 medulloblastoma are more complex but show preliminary corroboration with scRNAseq data. In summary, Visium allows us to map subpopulations identified by scRNAseq to tumor architecture more definitively and rapidly than IHC. These novel insights advance our understanding of medulloblastoma, a critical step in improving treatment options for children with this disease.
MEDB-56. POx NPs mediated delivery of (TLR7/8) agonist resiquimod improves treatment outcomes in SHH medulloblastoma by targeting tumor associated macrophages
Authors: Hwang Duhyeong , Alicea Coral del Mar , Lim Chaemin , Park Christopher , Gershon Timothy , Sokolsky-Papkov Marina 
Published: June 2022

Abstract
Cancer immunotherapy, the utilization of the patients’ own immune system to treat cancer, has emerged as a powerful new strategy in cancer treatment. Recent clinical data has demonstrated immunotherapy to be effective in a wide range of cancers, including lung, bladder, renal cell, colorectal, gastro-esophageal, and head and neck cancers5-11. However, clinical reports of immune-based treatments for medulloblastomas are scarce and preliminary. Therefore, there is a need in developing strategies to improve medulloblastoma immunotherapy. Our recent studies have confirmed that SHH medulloblastomas are enriched in Tumor Associated Macrophages (TAMs) and unlike other tumors, TAMs are associated with positive outcomes and play a positive role by impairing tumor growth. Overall, analysis of TME in medulloblastomas reveals TAMs as a potential therapeutic target. Resiquimod is a synthetic small molecule agonist of Toll-like receptors 7 and 8 (TLR7/8) that modulates innate immune cells. We have loaded resiquimod into ultra-high-capacity polyoxazoline (POx) block copolymers forming small, homogeneous nanoparticles (POx-resiquimod). Our recent study shows that loading into POx nanoparticles improves drug delivery to tumors and treatment with 3 injections of POx-res as the single-agent treatment results in a profound anti-tumor effect G-Smo mice while treatment with free drug shows no therapeutic benefit. Our data also shows that that the tumors of G-Smo mice are enriched with the mixed populations of anti-inflammatory and pro-inflammatory macrophages and the treatment with POx-resiquimod have enhanced infiltration of macrophages into the tumors, enhanced the repolarization of macrophages to M1 subtype and decreased tumor cells viability. These studies show for the first time that targeting the medulloblastoma TME with POx-resiquimod can produce a significant anti-tumor effect. Furthermore, combination of POx-resiquimod with radiation resulted in long term survivals, showing potential therapeutic combination. The expression of TLR7/8 on TAMs in patient-derived medulloblastoma samples suggests that resiquimod may produce similar anti-medulloblastoma effects in humans.
MEDB-57.GNAS inactivation as a driver for sonic hedgehog-activated medulloblastoma
Authors: Goode Erin , Montoya Liliana , Graham Eric , Pruniski Brianna , Simmons Curtis , Ngwube Alexander , Hoffman Lindsey M , Tiwari Nishant , Aldape Kenneth , Price Harper N , Paulson Vera , Mangum Ross 
Published: June 2022

Abstract
INTRODUCTION: Sonic hedgehog (SHH)-activated medulloblastoma is one of the four consensus molecular subgroups of medulloblastoma and is typically associated with PTCH1, SUFU, and/or SMO mutations. GNAS inactivating mutations are a less commonly recognized tumorigenic driver for SHH pathway activation.
CASE PRESENTATION: We report the case of an 11-month-old male who presented with a large posterior fossa mass, cerebellar tonsillar herniation, and obstructive hydrocephalus. Following a successful gross total resection, pathology was consistent with desmoplastic/nodular medulloblastoma. Tumor molecular profiling using a DNA-based, next-generation sequencing platform detected a pathogenic frameshift mutation in the GNAS gene (p.D189Mfs*14, NM_000516.4:c.565_568del) at a variant allele frequency of 81%, suggestive of biallelic GNAS inactivation. The same mutation was detected from a buccal swab sample, confirming germline GNAS inactivation. Whole genome methylation profiling was consistent with medulloblastoma subclass SHH B (infant). Concurrent with this brain tumor evaluation, a skin biopsy was performed of scattered subcutaneous, plate-like nodules distributed over the patient’s back and extremities. This revealed metaplastic-appearing cancellous bone within the dermis and subcutaneous tissue consistent with plate-like osteoma cutis. He was treated with high-dose chemotherapy followed by autologous stem cell rescue and remains disease-free 15 months from diagnosis.
DISCUSSION: There have been scattered case reports describing germline loss-of-function GNAS mutations acting as tumorigenic drivers of SHH medulloblastoma. However, GNAS alterations are not covered by most standard diagnostic molecular sequencing panels for medulloblastoma. Other phenotypic manifestations of germline inactivating GNAS mutations include pseudohypoparathyroidism, pseudopseudohypoparathyroidism, progressive osseous heteroplasia, and osteoma cutis.
CONCLUSION: Knowledge of the possible association between germline GNAS inactivating mutations and the development of childhood SHH-activated medulloblastoma is essential for prompt diagnosis and treatment initiation. As such, consideration should be given for inclusion of GNAS alterations in diagnostic medulloblastoma sequencing panels, especially in the setting of osteoma cutis or other endocrinopathies.