bluuebunny/crossref_metadata_2025_split huggingface dataset:
EMBR-13. NOVEL SYNERGISTIC APPROACHES FOR TARGETED THERAPY OF MYC-DRIVEN MEDULLOBLASTOMA USING CRISPR/CAS9 GENE EDITING
Authors: Qin Nan , Picard Daniel , Rickert Daniel , Meyer Frauke-Dorothee , Blümel Lena , Göbbels Sarah , Bartl Jasmin , Pauck David , Fischer Ute , Borkhardt Arndt , Reifenberger Guido , Remke Marc 
Published: June 2021

Abstract

Introduction
Resistance to chemotherapy is a common cause of treatment failure in cancer patients and a major problem facing current cancer research. Targeted modulation of oncogenic signaling pathways may be used to systematically characterize drug resistance mechanisms across tumor entities and may help to identify new therapeutic strategies. Since the transcription factor MYC is aberrantly activated in many cancers including pediatric malignant brain tumors, like medulloblastoma (MB), our study focused on MYC-related drug resistance.

Methods and Results
We performed high-throughput drug screening using our in-house semi-automated platform and identified the HDAC inhibitor Entinostat as a drug that shows promising effects in MYC-driven MB. Investigating genome-wide dCas9-based transcriptional activation screening, potential drug response modulators, mainly TGFB1/Erk/MKNK1 signaling including neural EGFL like 2 (NELL2), were discovered. For further validation, we stably overexpressed NELL2 in MYC-driven MB cells and treated overexpressing cells and the corresponding control cells with Entinostat. Using PI staining, cell cycle status was tracked. Entinostat treatment led to modest induction of cell death in MYC-driven MB control cells but only slightly increased cell death rate in MYC-driven MB cells with NELL2-overexpression.

Conclusion
We report that the combination of genetic and pharmacological approaches is a powerful approach to study drug resistance. Our data suggest that activation of the TGFB1/Erk/MKNK1 signaling pathway desensitizes MYC-driven MB cells to Entinostat. Synergistic targeting of TGFB1/Erk/MKNK1 signaling and MYC could therefore provide a novel therapeutic option in this aggressive MB subtype.
EMBR-18. LASER INTERSTITIAL THERMAL THERAPY FOR RECURRENT MEDULLOBLASTOMA
Authors: Xu Jordan , Pathare Jodi , Hoerig Clay , Goldberg Aaron , Abongwa Chenue , Plant Ashley , Olaya Joffre 
Published: June 2021

Abstract

Background
Medulloblastoma is one of the most common malignant childhood brain tumors and is managed by maximal surgical resection followed by cranio-spinal irradiation and adjuvant chemotherapy. The estimates for survival have not significantly improved over the last two decades, and survivors have an increased risk of poor quality of life. Disease relapse occurs in around 30% of children and survival is less than 20%. Laser interstitial thermal therapy (LITT) is a minimally invasive approach that has been increasingly used to treat brain lesions, particularly for high-risk surgeries. While LITT has been described in a variety of primary brain tumors, including glioblastoma multiforme and metastatic brain tumors, there have been few reports of LITT for recurrent medulloblastoma.

Case Description
We describe a case of an 11-year-old female with recurrent medulloblastoma first treated at age 5. She initially underwent gross total resection complicated by severe posterior fossa syndrome followed by chemotherapy and radiation (per ACNS0332). She was unfortunately found to have a new enhancing lesion on surveillance imaging 6 years later, and a biopsy confirmed recurrent tumor. Due to morbidity from initial surgery, the family did not wish to pursue further open resection but agreed to proceed with laser ablation as an alternative. She continues on Avastin/irinotecan/TMZ. Surveillance MRI nearly a year later shows a significant reduction in tumor size and enhancement.

Conclusion
Recurrent medulloblastoma is a highly aggressive tumor that conveys a poor prognosis. LITT offers a less invasive procedure that may serve as an adjunct in treating recurrent tumor or as palliation. Longer term follow-up and additional cases will help understand the efficacy of LITT in recurrent medulloblastoma.
EMBR-22. RATIONAL DEVELOPMENT OF SYNERGISTIC THERAPIES ALONGSIDE BMI1 INHIBITION FOR GROUP 3 MEDULLOBLASTOMA
Authors: Bakhshinyan David , Adile Ashley A , Venugopal Chitra , Brown Kevin , Chan Katherine , Qazi Maleeha A , Chokshi Chirayu , Gwynne William D , Tieu David , Moffat Jason , Singh Sheila 
Published: June 2021

Abstract
Medulloblastoma (MB) is the most common pediatric brain tumor. Of its four distinct molecular subgroups, Group 3 MBs are associated with increased risk of recurrence, metastasis and overall poor patient outcome. In recent years, small molecule inhibitors targeting BMI1 have shown to be efficacious against several types of malignant tumors including pediatric MB. Although in vivo studies provide a promising proof-of-concept for the therapeutic targeting of BMI1 in Group 3 MB, mice that receive treatment eventually succumb to their disease. These results suggest that additional mechanisms may underlie the maintenance of MB and underscores the main obstacle in treating a constantly evolving tumor. After initial preclinical validation of BMI1 inhibitor PTC-596, DNA barcoding clonal tracking technology was leveraged to profile in vivo clonal dynamics of Group 3 MB in response to the established chemoradiotherapy regimen alone and in combination with PTC-596. Comparison of clonal composition of the tumors extracted from the brains and spines post-treatment revealed the persistence of a small number of clones with the ability to escape therapy and drive subsequent tumor expansion. In order to better understand molecular susceptibilities of MB cells post BMI1 inhibition, we undertook an in vitro genome-wide CRISPR/Cas9 screening to identify context-specific MB regulatory pathways to be synergistically targeted along with BMI1. By comparing the results of the in vitro genome wide CRISPR/Cas9 screen to the essential genes in human neural stem cells (hNSCs), we identified several context specific regulators of mTOR, AKT and PLK1 pathways. The combined treatment alongside PTC-596 has demonstrated synergistic efficacy against MB cells with minimal toxicity to hNSCs in vitro and is currently being evaluated in preclinical studies. This study provides the foundation for clinical validation of small-molecule inhibitors synergistic with PTC-596 to improve the durability of remissions and extend survival of patients with treatment-refractory Group 3 MB.
EMBR-24. YB1 IS CRITICAL FOR MEDULLOBLASTOMA TUMOR MAINTENANCE AND DNA REPAIR FOLLOWING THERAPEUTIC INTERVENTION
Authors: McSwain Leon , Kenney Anna , Chen Victor , Huang Tiffany 
Published: June 2021

Abstract
Medulloblastoma (MB) is the most common pediatric central nervous system malignancy. Although the current standard of care leads to ~70% patient survival, the therapies are highly toxic, leading to life-long side effects, and recurrence due to therapeutic resistance is fatal. We sought to investigate mediators of radiation response in mouse models for the Sonic hedgehog (SHH) subgroup MB as well as human cell lines. We previously identified Y-box binding protein 1 (YB1) as a downstream effector of YAP-mediated MB radiation resistance. YB1 is a crucial, yet understudied, protein highly expressed across all 4 subgroups of MB. Through its DNA- and RNA-binding cold shock domain, YB1 mediates both transcriptional and translational changes important for tumor maintenance and therapeutic response. We show that following ionizing radiation, YB1 mediates DNA repair through PARP and that PARP inhibition abrogates YB1-mediated DNA repair in cells overexpressing YB1. Additionally, through its inhibitory effects on p53, YB1 is capable of mediating anti-apoptotic effects in response to genotoxic insult. By targeting YB1 with short hairpin RNA, we show that cells are more amenable to ionizing radiation induced double strand breaks. Additionally, we utilize RNA binding protein immunoprecipitation sequencing to investigate post transcriptional regulation of RNAs bound by YB1. We show that YB1 binds numerous transcripts critical for the identity of early cerebellar progenitor cells, the putative cell of origin for SHH subgroup tumors, in addition to transcripts important for cell cycling and migration.
EMBR-30. A NOVEL PLK1 INHIBITOR ONVANSERTIB EFFECTIVELY SENSITIZES GROUP 3 MEDULLOBLASTOMA TO RADIOTHERAPY
Authors: Wang Dong , Veo Bethany , Pierce Angela , Foamier Susan , Balakrishnan Ilango , Donson Andrew , Alimova Irina , Erlander Mark , Ridinger Maya , Venkataraman Sujatha , Vibhakar Rajeev 
Published: June 2021

Abstract
Medulloblastoma (MB) is often accompanied by MYC amplification. PLK1 is an oncogenic kinase that controls cell cycle and proliferation, and it has been preclinically validated as a cancer therapeutic target. Onvansertib (PCM-075) is a novel, orally available PLK1 inhibitor, which shows tumor growth inhibition in many types of cancer. We examined the effect of Onvansertib on MYC-driven medulloblastoma as a monotherapy or in combination with radiation. A Crisper-Cas9 screen was used to discover essential genes for MB tumor growth. Microarray and immunohistochemistry on pediatric patient samples were performed to examine the expression of PLK1. The effect of Onvansertib in vitro was measure by cell viability, colony-forming assays, extreme limiting dilution assay, and RNA-Seq. ALDH activity, cell-cycle distribution, and apoptosis were analyzed by flow cytometry. DNA damage was assessed by immunofluorescence staining. Medulloblastoma xenografts were generated to explore the monotherapy or radio-sensitizing effect. PLK1 is overexpressed in Group 3 MB. The IC50 concentrations of Onvansertib in Group 3 MB cell lines were between 4.9 and 6 nM. Onvansertib reduced colony formation, cell proliferation, stem cell renewal, and induced G2/M arrest in vitro. Moreover, Onvansertib in combination with radiation increased DNA damage and apoptosis compared with radiation alone. The combination of Onvansertib with radiotherapy resulted in marked tumor regression in orthotopic xenografts. These findings suggest that Onvansertib is an effective strategy in combination with radiotherapy in MB.
EMBR-32. INTEGRATED STRESS RESPONSE PLAYS A PRO-SURVIVAL ROLE IN MYC-DRIVEN MEDULLOBLASTOMA
Authors: Langman Sofya , Delaidelli Alberto , Huang Yue Zhou , Sorensen Poul 
Published: June 2021

Abstract
Medulloblastoma (MB) accounts for 20% of diagnosed brain tumors in children. Group 3 (G3) MB subtype is the most aggressive. Molecularly, G3 MB is characterized by MYC overexpression, which drives elevated mRNA translation in tumor cells. PERK is an eukaryotic translation initiation factor 2 (eIF2α) kinase that inhibits mRNA translation under endoplasmic reticulum (ER) stress conditions, such as in response to accumulation of unfolded proteins. When unfolded proteins accumulate in the ER, activated PERK phosphorylates eIF2α. This shuts down global translation and triggers integrated stress response (ISR) to help cells adapt through selective translation of mRNA encoding pro-survival proteins. High mRNA expression of PERK correlates with poor survival in G3 MB patients. In vitro, combination of ER or hypoxic stress with PERK knockdown induces apoptosis in MB cells. ISRIB is an ISR inhibitor that maintains translation rates despite eIF2α phosphorylation. Combining ISRIB with stress such as hypoxia induces apoptosis in MB cells and prevents accumulation of key ISR mediators such as ATF4. In addition, combination of ISRIB and hypoxia induces oxidative stress. Current G3 MB treatment regimens include vincristine, a known ISR inducer. Combination of ISRIB with vincristine amplifies vincristine-induced apoptosis, potentially suggesting novel therapeutic approach for MB. Our findings show that inhibition of ISR in G3 MB represents a powerful inducer of cancer cell death.
EPEN-02. FUNCTION AND DEPENDENCY OF NF-KB ACTIVITY IN C11ORF95-RELA FUSION EPENDYMOMA
Authors: Stuckert Austin , Arabzade Amir , Zhao Yanhua , Chen Hsiao-Chi , Mack Stephen 
Published: June 2021

Abstract

Introduction
Ependymoma is an aggressive type of pediatric brain tumor resistant to chemotherapy, with treatment to date limited to surgical resection and radiation. Thus, identification and validation of molecular targets that can translate into clinical trials in ependymoma is desperately needed to improve patient outcomes. Over 70% of supratentorial ependymoma are driven by an oncogenic fusion between C11orf95 and Rela (denoted CRFUS). CRFUS expression initiates ependymoma development in mice by potentially acting as an oncogenic transcription factor and disrupting gene expression programs. We hypothesized that specific CRFUS interacting proteins are required for tumor formation and could represent lead therapeutic targets.

Methods
To study CRFUS ependymoma, a natively-forming tumor model of CRFUS generated by in utero electroporation of the developing mouse brain was utilized. Tumor cells were isolated and then subjected to nuclear Rapid Immunoprecipitation and Mass Spectrometry Analysis of Endogenous Proteins (RIME) of HA-tagged CRFUS protein. Immunoprecipitation and Western Blot (IP-WB) were utilized to probe for leading protein interactions.

Results
We identified NF-kB proteins consistent with canonical Rela mediated transcription (NFKB1 and NFKB2) as well as novel protein interactomes that converged on RNA splicing and translational regulation. In addition, we identified a large series of novel chromatin-binding proteins as candidates potentially required for CRFUS mediated tumorigenesis.

Conclusions
Further study is ongoing to validate key CRFUS protein interaction dependency on tumor development. ChIP-Seq (chromatin immunoprecipitation with massively parallel DNA sequencing) and CUT&RUN (cleavage under target and release using nuclease) assays have been employed to further analyze the functional role of canonical Rela pathway members. By interrogating these mechanisms, novel therapeutic targets and pathways may be identified in parallel with dissecting the molecular basis of CRFUS driven ependymoma.
GERM-01. RECURRENCE PATTERN AND SURVIVAL FOR RELAPSED INTRACRANIAL NON-GERMINOMATOUS GERM CELL TUMORS: A SINGLE-INSTITUTION EXPERIENCE
Authors: Wen Lei 
Published: June 2021

Abstract

Purpose
Intracranial non-germinomatous germ cell tumors (NGGCTs) have lower overall survival than germinoma because relatively higher recurrence usually occurs after first line therapy.

Methods
Between January 2003 and December 2018, 111 consecutive patients diagnosed with NGGCTs reviewed. Those who progressed after first line therapy were included in this study. Data of first line treatment, salvage treatment, clinicopathological features and survival were collected and analyzed.

Results
Totally, thirty patients (30/111, 27.0%) relapsed in our cohort, including 19 patients with accurate relapse information detail, and 11 patients who died of disease progression during follow up but without exact time and site of relapse. The median OS from diagnosis of the disease was 49.2 months (95% CI: 14.1 to 84.3 months) and 3-year OS was 54.3%. Patients who received both CSI and chemotherapy relapsed less than those who received reduced volume of radiotherapy or only CSI or only chemotherapy (22.5% vs. 45.5%, p=0.034). Of 19 patients who had detail information of recurrence time and site, the median time from diagnosis of disease to relapse was 9.5 months (2.2 to 72.1 months). Regarding to recurrence site, most patients relapsed in primary site (10/19, 52.6%) or distant intracranial (6/19, 31.6%). The recurrence site of other 3 patients were spinal (n=1), ventricular (n=1) and peritoneal (n=1).

Conclusion
Protracted follow-up is recommended because late recurrence is not uncommon. Primary tumor site and distant intracranial are the most prevalent relapsed location. Patients who relapsed could benefited from both CSI and salvage chemotherapy.
GERM-02. MANAGEMENT STRATEGY FOR CHEMO-REFRACTORY, PROGRESSIVE PEDIATRIC IMMATURE TERATOMA
Authors: McNutt Sarah , Shah Nidhi , Rizk Elias 
Published: June 2021

Abstract

Background
Localized NGGCT, a heterogeneous entity, treated with chemo-radiotherapy harbors an overall survival of around 93% based. Here, we present a case of a child whose immature teratoma progressed on chemotherapy, while tumor markers remain within normal range. Salvage therapy for progressive immature teratoma is variable, and can include surgery, chemotherapy and/or craniospinal radiation. Case: 10 year old boy with precocious puberty presented to the local Emergency room with tonic-clonic seizures. Imaging showed a localized pineal mass, with mixed cystic and solid components. Biopsy results were diagnostic for mixed germ cell tumor with components of immature teratoma. Prior to the start of chemotherapy, serum and cerebrospinal fluid (CSF) tumor markers showed slight elevation of both alpha feto- protein (AFP) and beta-human chorionic gonadotropin hormone (β-HCG). The patient underwent two cycles of chemotherapy per ACNS1123, stratum 1, with normalization of tumor markers. Unfortunately, near the end of Cycle 2 of chemotherapy, patient presented with clinical signs of herniation, and was noted to have significant progression of pineal mass on imaging. Tumor was gross totally resected, with pathology conclusive for only immature teratoma. Pre- and post-operative tumor markers remained normal. Proton-beam craniospinal radiation was then administered. Patient is now almost 6 months off therapy, with unremarkable serum and CSF tumor markers, as well as serial imaging that remains negative for disease, with neurological development appropriate for age.

Conclusion
This case highlights the unusual nature of progression of an immature teratoma with no elevation of tumor markers while on chemotherapy. While salvage chemotherapy, in the form of a metronomic regimen or high-dose consolidative regimen, can be considered, these do present quite a bit of short-term and long-term toxicity to the growing child. Craniospinal irradiation followed by close monitoring is a reasonable alternative, with less short-term toxicity, for an entity that is radio-sensitive.
HGG-08. CREATION OF AN IN VITRO AND IN VIVO MODEL SYSTEM FOR THE STUDY OF H3.1K27M DIPG
Authors: Lagas Joseph , Yang Lihua , Becher Oren , Rubin Joshua 
Published: June 2021

Abstract
Diffuse Intrinsic Pontine Glioma (DIPG) is a devastating pediatric high-grade glioma that occurs in the brainstem with a median survival of less than 1 year. A greater understanding of the early tumorigenic events is essential for the development of effective therapeutics. DIPG is characterized by founder mutations in histone H3, either H3.1K27M or H3.3K27M. These mutations cause global hypomethylation, resulting in aberrant gene expression. Little is known about how this mechanism contributes to tumorigenesis. Interestingly, H3.1K27M DIPG show an increased incidence in females, whereas H3.3K27M DIPG shows no sex difference. This illustrates that the tumorigenic potential of H3.1K27M may be different between the sexes. Few models of DIPG incorporate the study of H3.1K27M despite the fact that it represents a unique opportunity to obtain valuable information on the tumorigenesis of DIPG through the study of the sex difference. Thus, we have created an in vitro and in vivo model system for H3.1K27M DIPG utilizing the RCAS mouse model system. This system utilizes RCAS vectors and a RCAS-ntva transgenic mouse line to deliver specific mutations to nestin expressing cells in the brainstem, including oligodendrocyte progenitor cells (OPCs), the predicted cell of origin. Delivering H3.1K27M, ACVR1 R206H, and PDGFaa at postnatal day 7 produces DIPG-like tumors in vivo, confirmed by H and E staining, between 60–110 days post injection. Additionally, confirmed through immunofluorescence staining, we can isolate a pure population of OPCs via immunopanning and infect them with RCAS vectors in vitro to produce stable expression of H3.1K27M. Introduction of H3.1K27M alone into male and female OPC cultures provides an opportunity to compare the early tumorigenic effects of H3.1K27M between the sexes in vitro. These results demonstrate that we have created an in vitro and in vivo H3.1K27M DIPG model system for the study of sex differences and tumorigenesis in DIPG.
HGG-19. 5-AMINOLEVULINIC ACID (5-ALA)-GUIDED RESECTION OF PEDIATRIC BRAIN TUMORS
Authors: Schwake Michael , Bruns Ann-Katrin , Müther Michael , Schipmann Stephanie , Stummer Walter 
Published: June 2021

Abstract

Between tumor and normal brain, allowing a higher degree of resection, and improved patient outcomes. In recent years, several reports have emerged regarding the use of 5-ALA in other brain tumor entities, including pediatric brains tumors. Since gross total resection (GTR) of many brain tumors in children is crucial, the role of 5-ALA-guided resection requires elucidation.

Methods
A systematic literature review of EMBASE and MEDLINE/PubMed databases revealed 20 eligible publications encompassing 186 5-ALA-guided operations on pediatric brain tumors. To reduce bias, publications were revised independently by two authors.

Results
5-ALA-guided resection enabled the surgeons to identify the tumor more easily and was considered helpful mainly in cases of glioblastoma (GBM, 21/27, 78%), anaplastic ependymoma WHO grade III (10/14, 71%), and anaplastic astrocytoma (4/6, 67%). In contrast, cases of pilocytic astrocytomas (PAs) and medulloblastomas 5-ALA-guided surgery did not show consistent fluorescent signals and 5-ALA was considered helpful only in 12% and 22% of cases, respectively. Accumulation of fluorescent porphyrins seems to depend on WHO tumor grading. In case fluorescence signal was considered helpful, it was associated with a greater degree of resection. One study showed an association between visible fluoresce signal and concentration of protopophyrin IX (PPIX) concentration. A threshold of 4μg/ml was required in order to visualize the fluorescence signal. The rate of adverse events related to 5-ALA was negligible, especially new postoperative sequelae.

Conclusion
5-ALA could play a role in resection of malignant, contrast enhancing, supratentorial pediatric brain tumors. At present, we are conducting a prospective phase I-II multicenter clinical trial to evaluate side effects and feasibility of 5-ALA guided surgery.