bluuebunny/crossref_metadata_2025 huggingface dataset:
ATRT-02. MEK/ERK SIGNALLING DEPENDENCY IN ATYPICAL TERATOID RHABDOID TUMOURS
Authors: Shi Hui (Claire) , Sooraj Dhanya , Sun Claire , Daniel Paul , Bradshaw Gabrielle , Cain Jason , Firestein Ron
Published: December 2020

Atypical teratoid rhabdoid tumours (ATRTs) are high-grade malignant paediatric brain tumours with a less than one-year survival rate after diagnosis. Current treatment for ATRT, which includes high-intensive radiotherapy and chemotherapy, results in long-term side effects on ATRT patients. Hence, there is an urgent need to discover targeted therapies that could be used to treat patients with ATRT. As part of the Hudson Monash Paediatric Precision Medicine Program, we have collected 23 ATRT cell lines which we used to performed high-throughput small molecule and genetic (CRISPR) screening to identify new therapies and therapeutic targets. In parallel, we characterised the ATRT cell lines based on transcriptomic (RNA-seq) and epigenetic (methylation) signatures. An integrative multi-omic approach was then used to uncover discrete vulnerabilities in specific subsets of ATRT patients. Strikingly, these include a number of druggable dependencies, such as MEK, CDK, HDAC, and Topoisomerase, that offer a promise of rapid clinical translation. In our study, we focus on MEK dependency in a subtype of ATRT lines to further define the underlying mechanisms and biomarkers. While future studies validating the MEK/ERK signalling dependency in a wider cohort of patient models and in in vivo models are required, these data provide a framework for applying an integrative multi-omic approach in paediatric cancer precision medicine.
ATRT-03. IDENTIFICATION OF microRNA-BASED PROGNOSTIC BIOMARKERS AND CANDIDATE THERAPEUTIC AGENTS FOR ATYPICAL TERATOID/RHABDOID TUMOR
Authors: Zhang Yang , Xu Jianguo
Published: December 2020

BACKGROUND

MicroRNA (miRNA) has been found to be involved in development of many malignant pediatric brain tumors, including atypical teratoid/rhabdoid tumor (AT/RT) that is highly aggressive and carries a dismal prognosis. The current study investigated the potential value of miRNAs and pivotal genes associated with AT/RT using bioinformatics analysis, aiming to identify new prognostic biomarkers and candidate drugs for AT/RT patients.

METHODS

Differentially expressed miRNAs (DEMs) and genes (DEGs) between AT/RT and normal control samples were obtained from GEO database. The target genes of DEMs were predicted via TargetScanHuman7.2 and miRDB, and then intersected with DEGs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of overlapping genes were conducted, followed by construction of protein-protein interaction network. Hub genes were determined by Cytoscape software, and their prognostic values were evaluated using Kaplan-Meier analysis. Connectivity Map database was used to identify latent therapeutic agents.

RESULTS

A total of 11 DEMs (hsa-miR-1224-5p, hsa-miR-128-3p, hsa-miR-17-5p, hsa-miR-18b-5p, hsa-miR-29c-5p, hsa-miR-329-3p, hsa-miR-379-5p, hsa-miR-433-3p, hsa-miR-488-5p, hsa-miR-656-3p and hsa-miR-885-5p) were screened. By intersecting 3275 predicted target genes and 925 DEGs, we finally identified 226 overlapping genes that were enriched in pathways in cancer and MAPK signaling pathway. Four hub genes (GRIA2, NRXN1, SLC6A1 and SYT1) were significantly associated with the overall survival of AT/RT patients. Candidate drugs included histone deacetylase inhibitor (givinostat), DNA synthesis inhibitor (floxuridine), cyclin-dependent kinase inhibitor (purvalanol) and janus kinase inhibitor (lestaurtinib).

CONCLUSION

In summary, this study systematically analyzed AT/RT-related miRNAs and pivotal genes to provide novel prognostic biomarkers and potential therapeutic agents.
ATRT-14. MACROPHAGE-TUMOR CELL INTERACTION PROMOTES ATRT PROGRESSION AND CHEMORESISTANCE
Authors: Melcher Viktoria , Graf Monika , Interlandi Marta , Moreno Natalia , de Faria Flavia W , Kim Su Na , Kastrati Dennis , Korbanka Sonja , Alfert Amelie , Gerß Joachim , zu Hörste Gerd Meyer , Hartmann Wolfgang , Frühwald Michael C , Dugas Martin , Schüller Ulrich , Hasselblatt Martin , Albert Thomas K , Kerl Kornelius
Published: December 2020

Atypical teratoid/rhabdoid tumors (ATRT) are pediatric brain neoplasms that are known for their heterogeneity concerning pathophysiology and outcome. The three genetically rather uniform but epigenetically distinct molecular subgroups of ATRT alone do not sufficiently explain the clinical heterogeneity. Therefore, we examined the tumor microenvironment (TME) in the context of tumor diversity. By using multiplex-immunofluorescent staining and single-cell RNA sequencing (scRNA-seq) we unveiled the pan-macrophage marker CD68 as a subgroup-independent negative prognostic marker for survival of ATRT patients. ScRNA-seq analysis of murine ATRT-SHH, ATRT-MYC and extracranial RT (eRT) provide a delineation of the TME, which is predominantly infiltrated by myeloid cells: more specifically a microglia-enriched niche in ATRT-SHH and a bone marrow-derived macrophage infiltration in ATRT-MYC and eRT. Exploring the cell-cell communication of tumor cells with tumor-associated immune cells, we found that Cd68+ tumor-associated macrophages (TAMs) are central to intercellular communication with tumor cells. Moreover, we uncovered distinct tumor phenotypes in murine ATRT-MYC that share genetic traits with TAMs. These intermediary cells considerably increase the intratumoral heterogeneity of ATRT-MYC tumors. In vitro co-culture experiments recapitulated the capability of ATRT-MYC cells to interchange cell material with macrophages extensively, in contrast to ATRT-SHH cells. We found that microglia are less involved in the exchange of information with ATRT cells and that direct contact is a prerequisite for incorporation. A relapse xenograft model implied that intermediary cells are involved in the acquisition of chemotherapy resistance. We show evidence that TAM-tumor cell interaction is one mechanism of chemotherapy resistance and relapse in ATRT.
ATRT-18. SHH-SUBTYPE ATYPICAL TERATOID/RHABDOID TUMORS ARE SELECTIVELY SENSITIVE TO GEMCITABINE TREATMENT
Authors: Metselaar Dennis , Meel Michaël Hananja , Goulding Joshua , Waranecki Piotr , de Gooijer Mark , Breur Marjolein , van Zanten Sophie Veldhuizen , Bugiani Marianna , Wesseling Pieter , Kaspers Gertjan , Hulleman Esther
Published: December 2020

Atypical Teratoid Rhabdoid Tumors (ATRT) are highly malignant embryonal tumors of the central nervous system with a dismal prognosis. ATRT can be divided into three molecular subgroups of which the Sonic Hedgehog (SHH) subgroup is most prevalent. In this study, we developed and validated a novel patient-derived ATRT model, which we used along a panel of other primary ATRT models for large scale drug discovery assays. We found that ATRTs are selectively sensitive to the nucleoside analogue gemcitabine, with SHH-subtype ATRTs being the most sensitive subgroup. Gene expression profiles and protein analysis indicated that gemcitabine treatment causes degradation of Sirtuin 1 (SIRT1), which causes ATRT specific cell-death through NF-kB and p53 activation. Furthermore, we found that this gemcitabine induced loss of SIRT1 results in a nucleus-to-cytoplasm shift of the SHH signaling activator Gli, explaining the additional gemcitabine sensitivity in SHH-subtype ATRT. Treatment of SHH-subgroup ATRT xenograft-bearing mice resulted in a >40% increase in median survival (p<0.01, log-rank test) and long-term survivors in two independent models. To prepare translation of our findings to the clinic, we investigated potential gemcitabine induced resistance mechanisms by conducting kinome-wide CRISPR/Cas9 knockout screens in primary ATRT cells. Through these experiments we found that low-dose gemcitabine treatment combined with inhibition of protein kinase C zeta (PKCζ) prevents regrowth of resistant ATRT subclones. Together, these findings show that ATRT are highly sensitive to gemcitabine treatment; and as such we suggest that gemcitabine may be rapidly incorporated into future treatment regimens for SHH-ATRT.
ATRT-24. CELL SURFACE PROTEOME ANALYSIS OF ATRT IDENTIFIES TARGETS FOR IMMUNOTHERAPY
Authors: Cole Allison , Hoffmeyer Eric , Zanini Marco , Vibhakar Rajeev , Nellan Anandani , Ayrault Olivier , Mitra Siddhartha
Published: December 2020

Atypical teratoid rhabdoid tumor (ATRT) is a rare and fast-growing childhood tumor of the brain and spinal cord. While the recent advances in DNA and RNA sequencing have given deep insights into the biology of cancer, about 90% of ATRTs harbor a single deletion which leads to uncontrolled tumor growth. The lack of targetable genetic abnormalities in ATRT makes it a tough target for therapy and hence radical new approaches are required to develop a treatment. In many cases, the gene expression profile alone DOES NOT represent the presence of the gene product on the surface and cannot detect post-translational modifications such as the addition of sugars which are essential for the interaction of surface proteins with the tumor microenvironment. The ability to escape from surveillance by the immune system is regarded as one of the essential hallmarks of cancer cells. Here we carried out a comprehensive unbiased large-scale surface receptor profiling using high throughput multicolor flow cytometry on surgically resected ATRT patient samples, primary ATRT cell lines, and patient-derived xenograft models. By multiplexing primary samples with antibodies for CD31, CD45, CD11b, CCR2, Cx3cr1, and CD4, and CD8 we eliminated endothelial and immune cells from analysis while also identifying immune populations within the tumor. We identified increased surface expression of CD44, CD146, CD59, CD151, and CD276. These were validated in our screening of primary tumor samples. A combination of CAR-T cell and function-blocking monoclonal antibody approaches have been tested to verify the proof of principle of this approach.
ATRT-27. COST-EFFECTIVE ASSAYS TO SUBGROUP ATRT IN THE DAILY ROUTINE
Authors: Lobon-Iglesias María-Jesús , Tauziede-Espariat Arnault , Andrianteranagna Mamy , Han Zhiyan , Masliah-Planchon Julien , Bourdeaut Franck
Published: December 2020

Three atypical teratoid rhabdoid tumors (ATRT) molecular subgroups with different bio-clinical characteristics have been reported (TYR, SHH and MYC). Molecular subgrouping relies on either methylation profiling (reference methods), or expression profiling. However, the cost-effectiveness of such pangenomic screening is questionable. This work aims to study the reliability of alternative techniques for subgroup classification in the daily routine. Illumina EPIC-arrays were performed on 46 samples. Among those cases, expression profiling were analysed by RNAseq (n=30). We designed a 26-gene panel to assess expression profiling using the Nanostring technology; this was applied to 35 tumors. Immunohistochemistry (IHC) was used for 20 samples; it relied on the expression of MITF, TYR, OTX2 and MYC. We first assessed the concordance between DNA methylation and RNAseq based profilings; then, between RNAseq and Nanostring and, finally, between methylation profiling and Nanostring or IHC, the two rapidest and cheapest tools. The concordance between the two expression-based profiling was 19/21. EPIC-arrays and RNAseq or Nanostring were concordant in 26/30 and 30/35 samples, respectively. The concordance was perfect for methylation-defined MYC subtype. Finally, 17/20 tumor samples were classified in the same subgroup by EPIC-arrays and IHC; the 3/20 misclassified tumors were SHH by methylation but consistently MYC by IHC, Nanostring and RNAseq. There was 90–100% of concordance for TYR subgroup (all techniques). We have designed a gene panel-based expression signature that shows promising concordance with RNAseq and methylation profiling. Nanostring assay and IHC well predict ATRT subgroup classification for MYC and TYR subclass, but less so for methylation-defined SHH ones.
ATRT-28. SINGLE NUCLEI SEQUENCING REVEALS THE DIFFERENT PHENOTYPIC COMPOSITION OF THE ATRT SUBGROUPS
Authors: Johann Pascal , Büllesbach Annette , Ernst Kati , Okonechnikov Konstantin , Jones David T W , Pfister Stefan M , Hasselblatt Martin , Kool Marcel
Published: December 2020

Atypical teratoid/rhabdoid tumors (ATRT) represents a genomically homogeneous disease characterized by loss of SMARCB1 protein in the vast majority of cases. In recent years, it has become clear that these tumors display a high degree of intertumoral heterogeneity with three molecularly distinct subgroups. However, the degree of intratumoral heterogeneity and the information on cellular subpopulations currently remains largely an unchartered territory. To explore the transcriptomic composition of ATRTs, we performed single nuclei RNA sequencing for 16 ATRTs representing all three molecular subgroups (5 ATRT-TYR, 7 ATRT-SHH, 4 ATRT-MYC). By performing tSNE cluster analyses of all the single cell data (~50.000 cells have been sequenced), we were able to gain unprecedented insights into the phenotypic composition of ATRTs and unravelled substantial differences between the three subgroups. Integrating transcriptomic information from non-neoplastic brain cells and the data derived from single nuclei sequencing, we found an OPC like gene signature in ATRT-SHH. In contrast, ATRT-TYR subpopulations overexpressed more markers of neuronal stem cells suggesting a larger fraction of undifferentiated cells in this subgroup. We also identified a subpopulation of cells with a clear overexpression of cell cycle associated genes (CDK4, CDKN3), predominantly present in ATRT-MYC samples, a finding which may harbour important consequences for a targeted therapy with e.g. CDK inhibitors. In summary, our analyses reveal different cellular compartments in ATRT and provide important insights into the cellular differentiation of the three ATRT-subgroups. Further analyses to achieve a specific mapping of ATRT to its physiological cell of origin are currently being pursued.
ATRT-33. ENABLING RAPID CLASSIFICATION OF ATRT WITH NANOSTRING NCOUNTER PLATFORM
Authors: Ho Ben , Arnoldo Anthony , Zhong Yvonne , Lu Mei , Torchia Jonathon , Yao Fupan , Hawkins Cynthia , Huang Annie
Published: December 2020

In recent years, using gene expression and methylation array platform, multiple research groups have reported the presence of at least three major Atypical Teratoid Rhabdoid Tumor (ATRT) subtypes that exhibit distinct epigenetic, transcriptomic and clinical features. Yet, utilizing ATRT subtypes in a clinical setting remains challenging due to a lack of suitable biological markers, limited sample quantities and relatively high cost of current assays. To address this gap between research and clinical practice, we have designed an assay that utilizes a custom 35 signature genes panel for the NanoString nCounter System and have created a flexible machine learning classifier package for ATRT tumour subtyping. We have analyzed 71 ATRT primary tumours with matching gene expression data using the 35 genes panel. 60% of the data was used for models training (10 repeats of 10-fold cross validation with subgroup balanced sample splitting) resulting in overall 94.6% training accuracy. The remaining 40% of the samples were used for model validation and the assay was able to achieve 92–100% accuracy with no subgroup bias. To demonstrate the flexibility of the workflow, we have tested it against other transcriptome-based methods such as gene expression array and RNASeq. We have also demonstrated its use in samples that were not classifiable by methylation-based method. We are presenting here a rapid and accurate ATRT subtyping assay for clinical usage that is compatible with archived ATRT tissues.
COVD-04. CHARACTERISTICS OF SARS-COV-2 IN 64 CHILDREN WITH CNS TUMORS: A REPORT FROM THE SIOP/ST. JUDE CHILDREN’S RESEARCH HOSPITAL (SJCRH) GLOBAL COVID-19 CHILDHOOD CANCER REGISTRY
Authors: Moreira Daniel , Bouffet Eric , Bhakta Nickhill , Chantada Guillermo , Chen Yichen , Faughnan Lane , Vedaraju Yuvanesh , Avula Maghana , Homsi Maysam , Naidu Paula , Pappas Andrew , Ranadive Radhikesh , Santana Victor , Sullivan Michael , Baroni Lorena , Caniza Miguela , Devidas Meenakshi , Pritchard-Jones Kathy , Rodriguez-Galindo Carlos , Mukkada Sheena
Published: December 2020

BACKGROUND

The GCCCR is a collaboration between SIOP and SJCRH to describe the natural history of SARS-CoV-2 in children with cancer across the world.

METHODS

The GCCCR is a deidentified registry of patients <19 years of age with cancer or recipients of a hematopoietic stem cell transplant and laboratory-confirmed SARS-CoV-2 infection. Demographic data, cancer diagnosis, cancer-directed therapy, and clinical characteristics of SARS-CoV-2 infection were collected. Outcomes were collected at 30-days and 60-days post infection.

RESULTS

As of August 10th 2020, the GCCCR included 730 cases from 35 countries, including 64 children with CNS tumors (8.8%) from 17 countries. The most frequent diagnoses were embryonal tumors (31.2%) and low-grade glioma (17.2%). Thirty-nine (60.9%) children were asymptomatic from infection, while 19 (29.7%) patients required hospital admission and 2 (6.3%) transferred to the intensive care unit. There was a significant association between infection severity and ANC <500 (p=0.04). At the time of infection, 44 (68.8%) patients were undergoing cancer-directed therapy. Thirty-two cases have follow-up data. No modification in cancer-directed therapy occurred in 11 (34.4%) patients, while chemotherapy was modified in 6 (18.8%), radiotherapy delayed in 2 (6.3%), and surgery postponed in 1 (3.1%). No patients died from SARS-CoV-2 infection, although 2 died from non-COVID-19 related causes.

CONCLUSION

The frequency and severity of COVID infection among children with CNS tumors appears to be proportionally lower compared to other children with cancer. Although this is the largest cohort of patients reported to date, additional insight is needed, including the effects of treatment modifications on outcomes.
DDEL-01. ENHANCING DRUG DELIVERY WITH MRgFUS FOR DIFFUSE INTRINSIC PONTINE GLIOMA MODEL
Authors: Ishida Joji , Alli Saira , Bondoc Andrew , Golbourn Brian , Sabha Nesrin , Mikloska Kristina , Srikanthan Dilakshan , Luck Amanda , Smith Christian , Hynynen Kullervo , Rutka James
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) is a surgically unresectable and devasting tumor in children. To date, there have been no effective chemotherapeutics despite a myriad of clinical trials. The intact blood-brain barrier (BBB) in part is responsible for the limited clinical response to chemotherapy. MRI guided focused ultrasound (MRgFUS) is a promising non-invasive tissue ablative method for CNS tumors. Moreover, MRgFUS allows for the temporary disruption of BBB. Our first objective was to determine the feasibility and safety of temporary BBB disruption within the brainstem using MRgFUS following intravenous (IV) administration of microbubbles in vivo. Our second objective was to select effective chemotherapeutics against DIPG cell lines, and to examine their therapeutic effects with MRgFUS in a mouse model of DIPG which exhibits an intact BBB. The non-invasive opening of the BBB was determined in the brainstem of normal rodents using physiological monitoring and histological analysis. Doxorubicin was selected from a drug screen consisting of conventional chemotherapeutics using SU-DIPG4 and SU-DIPG17 cell lines. We established SU-DIPG17 xenografts which demonstrated diffusely infiltrative tumor growth similar to human DIPG. By LC-MS/MS analysis, MRgFUS led to a 4-fold increase in doxorubicin concentrations within the brainstem tumors following IV administration when compared to IV administration alone, We demonstrated feasibility and safety of MRgFUS in the rodent brainstem and have shown that MRgFUS increases doxorubicin uptake in the brainstem of a rodent model of DIPG. These preclinical data will be helpful in designing clinical trials of BBB disruption using MRgFUS for DIPG in children.
DDEL-02. DECREASED TOXICITY OF CONVENTIONAL DOSE CHEMOTHERAPY UTILIZING BODY WEIGHT INSTEAD OF BODY SURFACE AREA FOR DOSING IN YOUNG CHILDREN <6 YEARS OLD ENROLLED ON THE “HEAD START” 4 CLINICAL TRIAL
Authors: Dhall Girish , Khatib Ziad , Maher Ossama , Blue Megan , Harmon Myeshia , Patel Parth , Finlay Jonathan
Published: December 2020

Metabolism of drugs in infants and young children is significantly different from older individuals due to differences in distribution, protein-binding capacity, hepatic metabolism and renal excretion. To be consistent with Children’s Oncology Group (COG) guidelines, body surface area (BSA) was used to dose chemotherapeutics in children >3 years old enrolled on “Head Start” 4 clinical trial (HS 4). Four of 30 patients enrolled on HS 4 developed sinusoidal obstruction syndrome (SOS) while receiving induction chemotherapy with cisplatin, etoposide, vincristine, cyclophosphamide and high-dose methotrexate using BSA for dosing (mg/m2). Patients #1 and #2 were both 2-years old at diagnosis, received and tolerated the first two cycles with mg/kg dosing uneventfully, then turned 3-years old and received cycle #3 with mg/m2 dosing as per protocol guidelines, and developed SOS. Patient #3 was 3-years old at diagnosis, received induction chemotherapy with mg/m2 dosing, and developed SOS during the very first cycle. Patient #4 was 4-years old at diagnosis and received all 3 induction cycles with mg/m2 dosing, developed serious nephrotoxicity during cycle #1 followed by SOS during cycle #3. The HS 4 trial was amended and reopened after external, independent Data Safety Monitoring Board review to dose all chemotherapy drugs in children <6 years old with mg/kg dosing instead of BSA. None of 75 patients enrolled since the amendment developed SOS during induction. These data suggest using caution while dosing young children <6 years of age with intensive induction chemotherapy by BSA.
DDEL-03. LONG-TERM INTRAVENTRICULAR THERAPY ALTERNATING ETOPOSIDE AND LIPOSOMAL CYTARABINE: EXPERIENCE IN 75 CHILDREN AND ADOLESCENTS WITH MALIGNANT BRAIN TUMORS
Authors: Stepien Natalia , Peyrl Andreas , Azizi Amedeo , Gojo Johannes , Mayr Lisa , Reisinger Dominik , Haberler Christine , Czech Thomas , Slavc Irene
Published: December 2020

BACKGROUND

Malignant brain tumors of childhood carry a high risk for leptomeningeal dissemination and tumor cells floating in the CSF are often not amenable to systemic and/or antiangiogenic chemotherapy. We report on our experience with an intraventricular therapy consisting of alternating cycles of liposomal cytarabine and etoposide.

PATIENTS AND METHODS

Between 2004 and 2017, 75 patients aged 0.6 to 22 years (median 11) with various malignant brain tumors received intraventricular etoposide 0.25mg (<1year) - 0.5mg on five consecutive days alternating with liposomal cytarabine at a dose of 25mg (<3 years) - 50mg via an Ommaya reservoir.

RESULTS

5533 doses of etoposide (5–277/patient, median 141) corresponding to 1–56 five-day-cycles/patient alternating with 534 doses of liposomal cytarabine (1–21/patient, median 11) were administered. Treatment was given over a period of 1 – 146 months (median 73.5). Toxicities did occur but were infrequent and mostly mild. Since all patients received some sort of concurrent anti-cancer therapy, the efficacy of intrathecal therapy cannot be assessed independently. However, 29/75 patients are still alive, and none of the patients had tumor cells in the CSF at their last evaluation.

CONCLUSION

In conclusion, alternating intraventricular liposomal cytarabine and etoposide produced responses and proved to be an important adjunct for patients receiving drugs with a low penetrance into the CSF. Since production of liposomal cytarabine was discontinued in 2017 it remains to be determined whether substitution of the slow release formulation by aqueous cytarabine on days 1, 4, 8, and 11 may produce similar results.
DDEL-09. HIGH DOSE MTX110 (SOLUBLE PANOBINOSTAT) SAFELY ADMINISTERED INTO THE FOURTH VENTRICLE IN A NON-HUMAN PRIMATE MODEL
Authors: Sirianni Rachael W , Kharas Natasha , Yu Bangning , Janssen Christopher F , Trimble Amanda , Ballester Leomar Y , Patel Rajan , Mohammad Afroz S , Elmquist William F , Sandberg David I
Published: December 2020

OBJECTIVE

This study tested the safety and pharmacokinetics of short-term and long-term administration of MTX110 (soluble panobinostat; Midatech Pharma, UK) into the fourth ventricle of non-human primates.

METHODS

Four rhesus macaque monkeys underwent posterior fossa craniectomy and catheter insertion into the fourth ventricle. In Group I (n=2), catheters were externalized and lumbar drain catheters were placed simultaneously to assess cerebrospinal fluid (CSF) distribution after short-term infusions. MTX110 (0.5 ml of 300 μM panobinostat solution) was infused into the fourth ventricle daily for five consecutive days. Serial CSF and serum panobinostat levels were measured. In Group II (n=2), fourth ventricle catheters were connected to a subcutaneously-placed port for subsequent long-term infusions. Four cycles of MTX110, each consisting of 5 daily infusions (0.5 ml of 300 μM panobinostat solution), were administered over 8 weeks. Animals underwent detailed neurological evaluations, MRI scans, and post-mortem histological analysis.

RESULTS

Neurological assessments, MRI, and histology confirmed catheter placement and an absence of neurotoxicity. Panobinostat was undetectable in serum collected two and four hours after infusions in all samples in both groups. In Group I, mean peak panobinostat level in fourth ventricle CSF (6242 ng/ml) was significantly higher than in lumbar CSF (9 ng/ml; p < 0.0001). In Group II, mean peak CSF panobinostat level (11,042 ng/ml) was significantly higher than mean trough CSF level (33 ng/ml; p<0.0001).

CONCLUSION

MTX110 can be safely delivered via 4th ventricle at supra-therapeutic doses. These results provide data for a pilot clinical trial in patients with recurrent medulloblastoma.
DDEL-12. NANOPARTICLE DELIVERY OF DOXORUBICIN FOR THE TREATMENT OF DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Ung Caitlin , Tsoli Maria , Liu Jie , Cassano Domenico , Upton Dannielle , Ehteda Anahid , Mansfield Friederike , Failes Tim , Kavallaris Maria , Arndt Greg , Vittorio Orazio , Voliani Valerio , Cirilo Giuseppe , Ziegler David S
Published: December 2020

DIPGs are the most aggressive pediatric brain tumors. Currently, the only treatment is irradiation but due to its palliative nature patients die within 12 months. Effective delivery of chemotherapy across the blood-brain barrier (BBB) has been a key challenge for the eradication of this disease. We have developed a novel gold nanoparticle functionalised with human serum albumin (Au-NP, 98.8 ±19 nm) for the delivery of doxorubicin. In this study, we evaluated the cytotoxic efficacy of doxorubicin delivered through gold nanoparticles (Au-NP-Dox). We found that DIPG neurospheres were equally sensitive to doxorubicin and Au-NP-Dox (at equimolar concentration) by alamar blue assay. Colony formation assays demonstrated a significantly more potent effect of Au-NP-Dox compared to doxorubicin alone, while the Au-NP had no effect. Furthermore, western blot analysis indicated increased apoptotic markers cleaved Parp, caspase 3/7 and phosphorylated H2AX in Au-NP-Dox treated DIPG neurospheres. Live cell content and confocal imaging demonstrated significantly higher uptake of Au-NP-Dox compared to doxorubicin alone. Treatment of a DIPG orthotopic mouse model with Au-NP-Dox showed no signs of toxicity with stable weights being maintained during treatment. However, in contrast to the above in vitro findings the in vivo study showed no anti-tumor effect possibly due to poor penetration of Au-NP-Dox into the brain. We are currently evaluating whether efficacy can be improved using measures to open the BBB transiently. This study highlights the need for rigorous in vivo testing of new treatment strategies before clinical translation to reduce the risk of administration of ineffective treatments.
DDEL-13. FOCUSED ULTRASOUND MEDIATED BLOOD BRAIN BARRIER DISRUPTION IN A MURINE MODEL OF PONTINE GLIOMA: A SAFETY AND FEASIBILITY STUDY
Authors: Englander Zachary , Wei Hong-Jian , Pouliopoulos Antonios , Upadhyayula Pavan , Jan Chia-Ing , Spinazzi Eleonora , Canoll Peter , Bruce Jeffrey , Feldstein Neil , Zacharoulis Stergios , Konofagou Elisa , Wu Cheng-Chia
Published: December 2020

BACKGROUND

Drug delivery remains a major obstacle in DIPG, as the blood brain barrier (BBB) limits the penetration of systemic therapies to the brainstem. Focused ultrasound (FUS) is an exciting new technology that, when combined with microbubbles, can open the BBB permitting the entry of drugs across the cerebrovasculature. Given that the utility of FUS in brainstem tumors remains unknown, the purpose of our study was to determine the safety and feasibility of this technique in a murine pontine glioma model.

METHODS

A syngeneic orthotopic model was established by stereotactic injection of PDGF-B+PTEN-/-p53-/- murine glioma cells (10,000/1ul) into the pons of B6 albino mice. A single-element, spherical-segment FUS transducer (center frequency=1.5MHz) driven by a function generator through a power amplifier (acoustic pressure=0.7MPa) was used with concurrent intravenous microbubble injection (FUS+MB) to sonicate the tumor on post-injection day 14. BBB opening was confirmed with gadolinium-enhanced MRI and Evans blue. Kondziela inverted screen (KIS) testing was completed to measure motor function. Mice were either immediately sacrificed for histopathological assessment or serially monitored for survival.

RESULTS

In mice treated with FUS (n=11), there was no measured deficit in KIS testing. Additionally, the degree of intra-tumoral hemorrhage and inflammation on H&E in control (n=5) and treated mice (n=5) was similar. Lastly, there was no difference in survival between the groups (control, n=6, median=26 days; FUS, n=6, median=25 days, p>0.05).

CONCLUSION

FUS+MB is a safe and feasible technique to open the BBB in a preclinical pontine glioma model.
DDEL-15. NANOTHERAPEUTIC TARGETING OF TUMOR ENDOTHELIUM FOR ENHANCING DRUG DELIVERY PAST THE BLOOD-BRAIN BARRIER
Authors: Kiguchi Hiro , Tylawsky Daniel , Vaynshteyn Jake , Gerwin Jeffrey , Manzari Mandana , Shah Janki , Li Na , Shamay Yosi , Greenblatt Matthew , Heller Daniel , Raju Praveen
Published: December 2020

OBJECTIVE

The Sonic Hedgehog (SHH) medulloblastoma subgroup accounts for ~25% of all cases and has an intermediate prognosis. Current therapies result in devastating morbidities including intellectual disability and secondary malignancies. Although molecularly targeted agents against the SHH pathway have demonstrated efficacy, on-target bone toxicities suggest new therapeutic approaches are needed.

METHODS

We investigated the SHH pathway inhibitor, vismodegib, packaged in a fucoidan-based nanoparticle (Fi-Vis) that targets P-selectin expressed on endothelial cells and induced by low-dose ionizing radiation (XRT) in a time- and dose-dependent manner. This P-selectin targeting nanoparticle shows selectivity toward tumor and not normal brain vasculature in a GEM SHH medulloblastoma model as assessed by ex vivo infrared imaging and molecular studies.

RESULTS

Quantitative RT-PCR analysis of SHH medulloblastoma following single dose XRT and Fi-Vis treatment (10mg/kg) showed synergistic reduction of Gli1 expression (>90% target inhibition). We demonstrate that low-dose XRT (0.25Gy) can induce P-selectin expression specifically on medulloblastoma tumor endothelium and synergize with low-dose Fi-Vis (10mg/kg) to significantly enhance mouse survival (p<0.01) compared to radiation or Fi-Vis alone. Assessment of bone toxicity using micro-CT and histological analysis following Fi-Vis administration in postnatal (P10) mice shows no bone toxicity when compared to free vismodegib. Finally, in vitro studies using bEnd.3 brain endothelial cells and in vivo studies using Cav1 knockout mice suggest a caveolin-1 mediated transcytosis mechanism for nanoparticle entry across the blood-brain barrier.

CONCLUSIONS

These data suggest applicability of combined XRT and tumor vasculature-targeted nanotherapeutic dose de-escalation strategies for SHH medulloblastoma with implications for other pediatric brain tumors.
DDEL-17. TRIPLE INTRAVENTRICULAR CHEMOTHERAPY FOR TREATMENT OF RELAPSED CHOROID PLEXUS CARCINOMA
Authors: Lau Grace , Janson Lisa , Drummond Julie , Zhukova Nataliya , Wood Paul
Published: December 2020

Limited evidence for the optimal management of relapsed choroid plexus carcinoma (CPC) exists, with a few case reports involving surgery, radiotherapy and intravenous chemotherapy. However, the safety and tolerability of intraventricular chemotherapy in this setting has not been widely studied. We describe a case where triple intraventricular chemotherapy was administered to a child with relapsed metastatic CPC. A 7-year-old male with a history of CPC presented with relapsed metastatic disease. At initial diagnosis at 4 years of age, treatment involved gross total resection of an intraventricular mass in the left temporal region followed by chemotherapy and autologous stem cell transplantation (SCT) according to HEADSTART II-D. One year after SCT, craniospinal radiation was delivered following radiological relapse, achieving a partial response. Given previous treatment-limiting myelosuppression, intraventricular chemotherapy via Ommaya® reservoir with thiotepa 5mg, etoposide 0.5mg and topotecan 0.4mg twice a week (non-weight-based dosing) was commenced taking into consideration pharmaceutical formulation aspects for optimal intraventricular drug delivery. After six cycles of intraventricular chemotherapy, palliative radiotherapy was administered due to radiological progression. Following completion, weekly triple intraventricular chemotherapy continued for 9 months. The patient remained out of hospital with the main side effects being fatigue and occasional nausea amenable to ondansetron. This case study demonstrates the safety and tolerability of a triple intraventricular chemotherapy regimen used to delay disease progression and prolong quality of life in a child with relapsed CPC in the palliative setting. This could provide an alternative treatment regimen for patients with relapsed disease.
DIPG-14. TARGETING POLO-LIKE KINASE 1 IN COMBINATION WITH KEY ONCOGENIC DRIVERS IN DIPG: FROM SINGLE AGENT TO COMBINATION STRATEGIES
Authors: Franshaw Laura , Hayden Elisha , Joshi Swapna , Liu Jie , Ehteda Anahid , Pang Chi Nam Ignatius , Tsoli Maria , Ziegler David S
Published: December 2020

Diffuse Intrinsic Pontine Glioma (DIPG) are devastating paediatric brainstem tumours. Loss of function mutations in DIPG decrease genetic stability and impair DNA damage response pathways promoting tumourigenesis. Polo-like Kinase 1 (PLK1) is a pivotal controller of cell growth, regulating key intermediaries of DNA replication, homologous repair, the cell cycle and cell division. We have found DIPG cultures consistently overexpress PLK1 with inhibition resulting in decreased tumour cell growth, heightened cell cycle arrest and apoptosis. Single agent treatment using PLK1 inhibitors unprecedentedly doubled the median survival of animals harbouring DIPG tumours. Through gene expression analysis, we’ve showed PLK1 inhibition affected multiple pathways which control the cell cycle, cell death regulation, microtubule organization and regulation of cell migration. We found these pathways of differentially expressed genes were significantly enriched for known targets of both E2F1 and E2F4. Analysis of gene expression and proteomic studies also revealed PLK1 inhibition decreased the activation and expression of key tumour promoting mediators within multiple phases of the cell cycle, decreased expression of tumour promoters including MYC and the PI3K/mTOR pathway and reactivated tumour suppressors p53 and PTEN. Assessing these changes in the treated transcriptome and proteome, we aim to develop multiple potentially translatable combination treatment strategies for DIPG. We have performed mechanistic studies and identified synergism with PLK1 inhibitors and the epigenetic regulator panobinostat, bet/bromodomain inhibitor JQ1, dual PI3K/mTOR inhibitor bimiralisib and PI3K inhibitor BKM120. Finally, we found PLK1 inhibitors act as potent radiosensitizers, enhancing the therapeutic effects of radiotherapy in vitro and in vivo.
DIPG-15. POLYAMINE PATHWAY INHIBITION IS A POTENT NOVEL THERAPEUTIC STRATEGY AGAINST DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Khan Aaminah , Gamble Laura , Upton Dannielle , Yu Denise , Ehteda Anahid , Pandher Ruby , Mayoh Chelsea , Burns Mark , Norris Murray , Haber Michelle , Tsoli Maria , Ziegler David
Published: December 2020

DIPG is an aggressive paediatric brainstem tumour, with a median survival of less than 1 year. Polyamines are intracellular polycations that control important aspects of cell growth and are often upregulated in cancer. Difluoromethylornithine (DFMO) is an FDA-approved inhibitor of the enzyme ornithine decarboxylase (ODC1) which is a key driver of polyamine synthesis. We investigated the efficacy of polyamine pathway inhibitors as a therapeutic strategy against DIPG. We found high expression levels of synthetic enzymes in the polyamine pathway in primary patient samples and cultures. Using cytotoxicity and clonogenic assays, we found that DFMO inhibited the proliferation of DIPG neurospheres. However, DIPG cells compensated for DFMO inhibition by increasing expression of the polyamine transporter SLC3A2. Gene expression analysis showed that the polyamine transporter, SLC3A2, was significantly overexpressed in DIPG compared with all other high-risk childhood cancers. Addition of polyamine transporter inhibitor AMXT 1501 to DFMO led to synergistic inhibition of DIPG proliferation. Consistent with the in vitro results, the combination treatment significantly prolonged the survival of mice bearing 3 different DIPG orthografts with 2/3 of the animals surviving up to 160 days. Addition of irradiation further improved the survival of mice treated with DFMO and AMXT 1501. Our results suggest that DIPG tumours are exquisitely sensitive to polyamine inhibitors and that dual blockade of polyamine synthesis and transport is a promising novel therapeutic strategy. AMXT 1501 is currently in clinical development for adult cancers (NCT03536728). A clinical trial for DIPG patients is planned through the CONNECT consortium.
DIPG-18. IDENTIFICATION OF TARGETABLE PATHWAY DEPENDENCIES IN DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Parackal Sarah , Chong Wai Chin , Bradshaw Gabrielle , Sun Claire , Daniel Paul , Roussel Enola , Jayasekara Samantha , Crombie Duncan , Firestein Ron , Cain Jason
Published: December 2020

Diffuse Intrinsic Pontine Glioma (DIPG) is a highly aggressive paediatric brainstem tumour with a dismal prognosis. Recurrent heterozygous mutations (p.K27M) in Histone H3 variant genes have been identified in the majority of DIPG cases. While the exact mechanism of H3K27M’s function is poorly understood, evidence suggests a role for epigenetic dysregulation in disease pathogenesis. This study aims to use functional genomics to identify novel therapeutic dependencies in H3K27M DIPG. DIPG drug sensitivity screening was carried out in twelve established and validated patient derived cell lines (10 H3.3K27M and 2 Wt) using an FDA approved drug library containing 1480 compounds. Highly prevalent targets identified from this screen include HDAC, microtubule, proteasome and CDK inhibitors. Additionally, a custom pooled CRISPR knockout library of druggable targets (300 genes, 1200 guide RNAs) was used to identify key DIPG cell survival pathways. To date five DIPG cell lines (1 Wt; 1 H3.1; 3 H3.3) have undergone screening. Knockdown of known DIPG driver genes (TP53; PDGFRA; PIK3CA and PIK3CR1) resulted in reduced cell viability, consistent with their proposed function and validating knockout screen utility. Preliminary data demonstrates Wt and H3K27M DIPGs cluster independently based on genes required for survival, suggesting differing tumorigenesis mechanisms and the potential for therapeutically targeting genotype specific pathways. Correlation of parallel drug screen and RNA-seq data will potentially reveal H3-dependent pathways for therapeutic exploitation. Collectively, we show a functional genomics approach is able to identify genotype-specific pathway dependencies in DIPG, paving the way for molecularly informed personalized therapies for patients.
DIPG-27. TARGETING FACILITATES CHROMATIN TRANSCRIPTION (FACT) AS A NOVEL STRATEGY FOR DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG) THAT ENHANCES RESPONSE TO HISTONE DEACETYLASE (HDAC) INHIBITION
Authors: Ehteda Anahid , Franshaw Laura , Liu Jie , Joshi Swapna , Simon Sandy , Pang Chi Nam Ignatius , Giorgi Federico , Pandher Ruby , Ung Caitlin , Tolhurst Ornella , Mayoh Chelsea , Khan Aaminah , Hayden Elisha , Gopalakrishnan Anjana , Trebilcock Peter , Upton Dannielle , Lehmann Rebecca , George Sandra , Vittorio Orazio , Tsoli Maria , Gurova Katerina , Gudkov Andrei Gudkov , Norris Murray D , Haber Michelle , Ziegler David S
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) is an aggressive and incurable childhood brain tumour for which new treatments are needed. A high throughput drug screen of 3500 pharmaceutical compounds identified anti-malarials, including quinacrine as having potent activity against DIPG neurospheres. CBL0137, a compound modelled on quinacrine, is an anti-cancer compound which targets Facilitates Chromatin Transcription (FACT), a chromatin remodelling complex involved in transcription, replication, and DNA repair. CBL0137 effectively crosses the blood-brain barrier and is currently in Phase I trials in adult cancer. CBL0137 induced apoptosis in DIPG neurospheres in vitro and had profound cytotoxic activity against a panel of DIPG cultures. In a DIPG orthotopic model, treatment with CBL0137 significantly improved survival. We found that treatment with CBL0137 up-regulated TP53 and increased histone H3.3 acetylation and tri-methylation in DIPG cells. We therefore examined the interaction between CBL0137 and the HDAC inhibitor, panobinostat. In vitro experiments showed that the two agents had profound synergistic activity against DIPG neurospheres in clonogenic assays and enhanced apoptosis. Transcriptomic analysis and immunoblotting indicated that combination treatment activated signalling pathways controlled by Retinoblastoma (RB)/E2F1 and subsequently increased phosphorylation and enzymatic activity of enhancer of zeste homolog 2 (EZH2). Consistent with the in vitro results, the combination of CBL0137 and panobinostat significantly prolonged the survival of two orthotopic models of DIPG, while histological analysis showed increased H3K27me3 and decreased Ki67 positive cells. Given these promising results, a paediatric trial of CBL0137 is planned to open through the Children’s Oncology Group with an expansion cohort for DIPG patients.
DIPG-28. REPEATED LOW DOSE RT FOR PEDIATRIC DIPG – LESS DISEASE BURDEN WITH COMPARABLE OUTCOMES
Authors: Wu Yao Yu , Tseng Chen Kan
Published: December 2020

PURPOSE

Pediatric diffuse intrinsic pontine glioma (DIPG) is the most dismal prognosis pediatric brain tumor. Six weeks radiation therapy (RT) remains the mainstay of treatment. The aim of the current study was to compare the results of firstly reported repeated low dose RT (rLRT) with conventional RT (CRT). METHODS AND MATERIALS: This retrospective review included 24 children with DIPG, aged 3 -18 years, underwent CRT (52- 60.0 Gy in 1.8- 2.0 Gy, n = 16) or rLRT (18 - 30 Gy in 1.5–2.0 Gy per cycle for 1–3 cycles, n = 8). All children had typical symptoms and MRI features of DIPG, or biopsy-proven DIPG.

RESULTS

The median overall survival (OS) was 12.6 months in rLRT group and 11.4 months in CRT group (p =0.347), progression-free survival (PFS) was 3.6 months in rLRT group and 6.5 months in CRT group (p = 0.821), no significant survival difference was observed between two groups. Temporary discontinuation or tapering of steroids rate was significantly higher in rLRT group (100% vs 60%, p = 0.028). Although not statistically significant, mean non-hospitalized days were longer in the rLRT group, 403 days versus 305 days in the CRT group, as were mean cumulative progression-free days, 276 days versus 163 days and 1-year free from CSF diversion rate was higher, 100% versus 64.9%.

CONCLUSIONS

For patients with newly diagnosed DIPG, repeated low dose RT, given over 3 to 4 weeks per cycle for 1 to 3 cycles, offers comparable survival outcome with less disease burden compared with conventional RT.
DIPG-32. AKT SIGNALING DRIVES RESISTANCE TO ONC201 IN DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Jackson Evangeline R , Duchatel Ryan J , Mannan Abdul , Hulleman Esther , Carcaboso Angel M , Monje Michelle , McCowage Geoff B , Alvaro Frank , Dun Matthew D
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive, childhood brainstem cancer with a median overall survival of 10 months post diagnosis. Remarkably, 80–90% of patients harbor recurring point mutation in histone H3, which induces a lysine for methionine substitution at amino acid 27 (H3K27M) in either H3.1 (HIST1H3B ~25%) or H3.3 (H3F3A ~65%) variants. Using the blood-brain barrier (BBB) permeable DRD2 antagonist, ONC201 (in clinical trials for DIPG and H3K27M-mutant gliomas – NCT03416530), we hypothesized that DRD2 antagonism would induce TRAIL expression via indirect inhibition of AKT and ERK signaling, to drive apoptosis in both H3.1K27M and H3.3K27M patient-derived DIPG cell lines alike. For the first time, we reveal that ONC201 shows efficacy in 100% of WT-H3 and H3.1K27M mutant DIPG cell lines (n=5), compared to 50% of H3.3K27M mutant DIPGs (n=6). Investigations to identify the mechanisms of resistance to ONC201, revealed that cell lines with decreased sensitivity upregulated the PI3K/AKT/MTOR signaling axis to drive phosphorylation of AKT and increase metabolic activity. Combined administration of ONC201 and the BBB-permeable PI3K/AKT inhibitor, paxalisib (previously GDC-0084, in clinical trials for newly diagnosed DIPG – NCT03696355), showed synergistic cytotoxicity, reduced PI3K/AKT signaling and metabolic reprogramming to drive apoptosis in all DIPG cell lines tested. This combination was used to treat a 3-year-old DIPG patient, commencing 14 weeks post disease progression, completing 40 weeks of therapy prior to her passing, December 2019. These studies highlight the potential of combined administration of two safe, BBB penetrant, oral targeted therapies and supports testing under clinical trial conditions.