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  • 1
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 24, No. Supplement_1 ( 2022-06-03), p. i171-i171
    Abstract: Medulloblastoma (MB) is the most common embryonal brain tumor in children, characterized by a high level of heterogeneity within this entity. Four major molecular groups have been defined - WNT, Sonic hedgehog (SHH), Group 3 (G3), and Group 4 (G4) - differing widely in genetic alterations and patient outcomes. Targeted treatment approaches are limited for high-risk MB including MYC-amplified G3, G4, or MYCN/GLI2-amplified SHH. Based on earlier studies describing the inhibition of cell cycle regulation as a therapeutic vulnerability in high-risk MB, we aimed to explore the efficacy and mode of action of approved CDK4/6 inhibitors in aggressive MB. First the in vitro sensitivity of pediatric G3 (n=5) MB cell models against palbociclib, ribociclib and abemaciclib was evaluated and compared to adult SHH (n=2) cells serving as MYC-negative controls. Abemaciclib most effectively reduced cell viability, exhibiting a mean IC50 value of 0.9 M in G3 compared to 2.1 M in SHH cells (p=0.007). Upon long-term exposure (7-10 days), again abemaciclib most potently decreased clonogenic survival already at 250nM in G3 MB cells. We observed a G1/S phase cell cycle arrest upon abemaciclib treatment and confirmed this by Western blot analyses, showing decreased Rb phosphorylation accompanied by reduced MAPK signaling. Interestingly, abemaciclib treatment distinctly reduced MYC protein and gene expression levels in MYC-amplified G3 cell models. In addition, exposure to abemaciclib decreased GLI2 and TERT mRNA levels, which was accompanied by induction of cellular senescence. Within the ITCC-P4 project, single mouse trials are currently being performed including abemaciclib treatment in orthotopic MB models. The detailed investigation of the precise mode of action in vitro and in vivo is ongoing. Summarizing, the CDK4/6 clinically approved inhibitor abemaciclib shows promising efficacy against high-risk MB in vitro.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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  • 2
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 24, No. Supplement_1 ( 2022-06-03), p. i51-i52
    Abstract: BCL-6 transcriptional corepressor (BCOR) is an epigenetic regulator that silences gene expression mainly via the polycomb repressive complex 1.1 (PRC1.1). BCOR genomic alterations are found in a variety of different tumors and recently central nervous system (CNS) tumors with BCOR internal tandem duplication (ITD) were classified as a distinct molecular subgroup. We established and characterized two cell models derived from BCOR altered CNS tumor patients. One model is characterized by a frameshift mutation in the BCOR gene resulting in the expression of a truncated protein lacking the C-terminal PUFD domain required for correct assembly of the PRC1.1. Additionally, this model harbors a translocation of the BCOR homologue BCORL1. The second model has a characteristic internal tandem duplication (ITD) within the BCOR gene. To study the effects of mutated BCOR/BCORL1 on gene expression, we performed siRNA mediated knockdown of altered BCOR/BCORL1 transcripts in both models and analyzed transcriptional changes by mRNA expression array. Differentially expressed genes in BCOR/BCORL1 knockdown versus wild type conditions were enriched for signaling pathways involved in cell cycle progression, cell growth, DNA replication and cancer. This suggests that the alterations in BCOR/BCORL1 might have pro-oncogenic effects and thereby contribute to the aggressive phenotype of this disease. Especially in the BCOR ITD model knockdown of BCOR led to transcriptional downregulation of genes associated with the development of brain tumors such as FGF18, PDGFA and PDGFRA. Our results indicate that specific BCOR/BCORL1 alterations might impair its endogenous function as transcriptional repressor and deregulate the expression of multiple PRC1.1 target genes. An in depth characterization of epigenetic and transcriptional changes in BCOR/BCORL1 altered CNS tumors could lead to the identification of critical downstream effectors and ultimately reveal new therapeutic vulnerabilities.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2094060-9
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  • 3
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 24, No. Supplement_7 ( 2022-11-14), p. vii103-vii103
    Abstract: Pediatric high-grade glioma (pHGG) is an incurable disease with a median survival of less than 6 months post-progression and no effective targeted therapy. PDGFRA is commonly altered in pHGG, but targeting PDGFRA in this disease has been unsuccessful, likely due to poor central nervous system (CNS) penetrance. Avapritinib is a novel and CNS-penetrant PDGFRA/KIT inhibitor that is FDA-approved for adults with unresectable or metastatic PDGFRA exon 18-mutant gastrointestinal stromal tumor (GIST) and is being studied in CNS tumors. We performed a pre-clinical and clinical assessment to determine the potential suitability of avapritinib therapy in PDGFRA-driven glioma. A multi-institutional cohort genetic analysis revealed PDGFRA amplification and mutation in 10.2% and 6.1% of pHGG, respectively. Additionally, PDGFRA expression in the absence of genetic events was significantly increased in H3K27-altered diffuse midline glioma (DMG) compared to H3-wildtype pHGG. Avapritinib performed well in: (i) mutant PDGFRA enzyme inhibition and wildtype inhibition at high dose, (ii) minimal off-target kinase inhibition, (iii) brain penetration (peak 10 µM), and (iv) proliferation/pPDGFRA reduction in PDGFRA-amplified and mutant pHGG cell lines. Avapritinib treatment in an aggressive PDX model of pHGG resulted in significant survival benefit. We pursued treatment of eight pediatric and young adult HGG patients with avapritinib across seven institutions. Patients were a mixture of local (N = 4) and metastatic disease (N = 4); all patients were post-initial radiation, with 7/8 having progressed on prior treatment. 7/8 patients had PDGFRA amplifications or mutations, and 7/8 had H3K27M mutations. Therapy was generally well-tolerated. 4/8 patients showed radiographic response to avapritinib, with one patient demonstrating complete response of target lesion and remains on therapy. Avapritinib levels in patients’ CSF and brain tumor tissue reached micromolar levels. These results demonstrate that avapritinib is a potent, selective, and CNS-penetrant PDGFRA/KIT inhibitor that is promising for further study in pHGG with relevant alterations.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2094060-9
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  • 4
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 25, No. Supplement_1 ( 2023-06-12), p. i29-i29
    Abstract: By single-cell analyses, we previously uncovered distinct intratumoral transcriptomic ependymoma (EPN) cell states and developmental trajectories correlating with molecular subtype and biological behavior. However, the relation of these cell states to characteristic EPN tissue architecture and tumor microenvironment remains widely unknown. We aimed to characterize the spatial architecture and elucidate regulatory circuits in EPN via spatial transcriptomics (10X Visium) of tumor specimens matching our previously generated single-cell transcriptome data spanning all EPN subtypes (ZFTA, YAP1, PFA, PFB). We investigated whether spatially restricted cell-cell interactions correlate with our previously identified cell states. Analyses revealed distinct spatially resolved cell populations in supratentorial and posterior fossa EPN. All subgroups showed several (5-9) spatially discrete cell clusters. Via non-negative matrix factorization (NMF), cell-specific spatial clusters emerged correlating with previous single-cell programs. ZFTA EPN highly correlates with ZFTA-specific metaprograms whereas all other subgroups did not show ZFTA-specific gene expression. Explicit genes such as DLK1 are exclusively upregulated in ZFTA EPN indicating spatially distinct aberrant Notch pathway signaling. Interestingly, this subgroup revealed spatial zones with upregulation of metabolic genes and endothelial markers anti-correlating with a ZFTA-specific program. Ependymal and neuronal-precursor-like signatures were enriched in our unique YAP1 EPN sample in a spatially restricted pattern, whereas GFAP was ubiquitously expressed. PFA was characterized by a neural stem cell (NSC)-like niche accompanied by metabolic and immune-reactive gene signatures. PFB showed a similar cell niche associated with NSC-like and glial-progenitor-like genes enriched simultaneously, further highlighting the NSC characteristic of posterior fossa tumors. Ependymal signatures were absent in PFA and present in PFB indicating more differentiated cell populations in PFB. Summarizing, we confirm presence of distinct intratumoral cell states within ependymoma tissue and reveal their spatial organization. In depth analysis and functional validation in matched ependymoma models will enable interrogation of underlying tumor promoting signaling events driving intratumoral developmental trajectories.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2094060-9
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  • 5
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 25, No. Supplement_1 ( 2023-06-12), p. i43-i44
    Abstract: PDGFRA is commonly altered in pediatric and young adult high-grade gliomas (pHGGs) including histone 3 lysine 27-mutated diffuse midline gliomas (H3K27M DMG), a fatal disease with no current options for cure. We performed comprehensive genomic and transcriptomic analyses of n=259 pediatric high-grade glioma cases which revealed PDGFRA genomic alterations in ~15% of patients. H3K27M DMGs had significantly higher PDGFRA expression compared to H3 wild-type tumors regardless of genomic alteration. Tumors with PDGFRA gene amplification demonstrated significantly elevated PDGFRA expression in both H3K27M DMGs and H3 wild-type pHGGs relative to tumors with wild-type or point mutated PDGFRA. We tested a range of PDGFRA inhibitors against a panel of patient derived pediatric H3K27M DMG, pHGG, and adult HGG. Amongst the inhibitors tested, avapritinib, a potent small molecule inhibitor with relatively selective activity against both wild-type and mutant PDGFRA showed potent toxicity against a wide array of pediatric and adult cell lines. This molecule also demonstrated supra-micromolar blood brain barrier penetration in pre-clinical in vivo models, and demonstrated significant decrease in tumor growth and improved survival in orthotopic mouse xenograft models. Finally, building on this preclinical activity, we report the first clinical experience using avapritinib in eight pediatric and young adult patients with high-grade glioma (H3K27M DMG and/or PDGFRA altered). Avapritinib usage showed no significant acute toxicities within this patient cohort. Most importantly, our preliminary data reveal radiographic response evaluated by RAPNO criteria in 50% of patients, a striking outcome rarely seen in this patient population. In summary, we report that avapritinib, a selective, CNS penetrant small molecule inhibitor of PDGFRA has potent activity in preclinical models and produced promising clinical responses with good tolerability in pediatric and young adult patients with high-grade glioma, suggesting a promising role for avapritinib therapy in pediatric high grade glioma.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2094060-9
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  • 6
    In: Acta Neuropathologica, Springer Science and Business Media LLC, Vol. 145, No. 6 ( 2023-06), p. 843-846
    Type of Medium: Online Resource
    ISSN: 0001-6322 , 1432-0533
    RVK:
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 1458410-4
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  • 7
    In: Journal of Personalized Medicine, MDPI AG, Vol. 10, No. 4 ( 2020-12-18), p. 290-
    Abstract: Targeting oncogenic fusion-genes in pediatric high-grade gliomas (pHGG) with entrectinib has emerged as a highly promising therapeutic approach. Despite ongoing clinical studies, to date, no reports on the treatment of cerebrospinal fluid (CSF) disseminated fusion-positive pHGG exist. Moreover, clinically important information of combination with other treatment modalities such as intrathecal therapy, radiotherapy and other targeted agents is missing. We report on our clinical experience of entrectinib therapy in two CSF disseminated ROS1/NTRK-fusion-positive pHGG cases. Combination of entrectinib with radiotherapy or intrathecal chemotherapy appears to be safe and has the potential to act synergistically with entrectinib treatment. In addition, we demonstrate CSF penetrance of entrectinib for the first time in patient samples suggesting target engagement even upon CSF dissemination. Moreover, in vitro analyses of two novel cell models derived from one case with NTRK-fusion revealed that combination therapy with either a MEK (trametinib) or a CDK4/6 (abemaciclib) inhibitor synergistically enhances entrectinib anticancer effects. In summary, our comprehensive study, including clinical experience, CSF penetrance and in vitro data on entrectinib therapy of NTRK/ROS1-fusion-positive pHGG, provides essential clinical and preclinical insights into the multimodal treatment of these highly aggressive tumors. Our data suggest that combined inhibition of NTRK/ROS1 and other therapeutic vulnerabilities enhances the antitumor effect, which should be followed-up in further preclinical and clinical studies.
    Type of Medium: Online Resource
    ISSN: 2075-4426
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
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  • 8
    In: Journal of Personalized Medicine, MDPI AG, Vol. 11, No. 4 ( 2021-04-12), p. 292-
    Abstract: Primary diffuse leptomeningeal melanomatosis (PDLMM) is an extremely rare and aggressive cancer type for which best treatment strategies remain to be elucidated. Herein, we present current and prospective diagnostic strategies and treatment management of PDLMM. Against the background of an extensive literature review of published PDLMM cases and currently employed therapeutic strategies, we present an illustrative case of a pediatric patient suffering from PDLMM. We report the first case of a pediatric patient with PDLMM who received combination treatment including trametinib and everolimus, followed by intravenous nivolumab and ipilimumab with concomitant intensive intraventricular chemotherapy, resulting in temporary significant clinical improvement and overall survival of 7 months. Following this clinical experience, we performed a comprehensive literature review, identifying 26 additional cases. By these means, we provide insight into current knowledge on clinical and molecular characteristics of PDLMM. Analysis of these cases revealed that the unspecific clinical presentation, such as unrecognized increased intracranial pressure (present in 67%), is a frequent reason for the delay in diagnosis. Mortality remains substantial despite diverse therapeutic approaches with a median overall survival of 4 months from diagnosis. On the molecular level, to date, the only oncogenic driver reported so far is mutation of NRAS (n = 3), underlining a close biological relation to malignant melanoma and neurocutaneous melanosis. We further show, for the first time, that this somatic mutation can be exploited for cerebrospinal fluid liquid biopsy detection, revealing a novel potential biomarker for diagnosis and monitoring of PDLMM. Last, we use a unique patient derived PDLMM cell model to provide first insights into in vitro drug sensitivities. In summary, we provide future diagnostic and therapeutic guidance for PDLMM and first insights into the use of liquid biopsy and in vitro models for this orphan cancer type.
    Type of Medium: Online Resource
    ISSN: 2075-4426
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 9
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 83, No. 7_Supplement ( 2023-04-04), p. 5719-5719
    Abstract: PDGFRA has been shown to be commonly altered in high-grade gliomas (HGGs), including histone 3 lysine 27-mutated diffuse midline gliomas (H3K27M DMG), a disease with almost no long-term survivors. Here, we performed comprehensive genomic and transcriptomic analysis of 260 high-grade glioma cases, which revealed PDGFRA genomic alterations (mutations and/or amplifications) in 13% of patients. H3K27M DMGs had significantly higher PDGFRA expression compared to H3 wild-type tumors, and PDGFRA gene amplification resulted in even higher expression levels in H3K27M DMGs as well as H3 wild-type HGGs. We tested a panel of patient- derived pHGG/H3K27M DMG models against a range of PDGFRA inhibitors, including avapritinib, a potent small molecule inhibitor with relatively selective activity against both wild-type and mutant PDGFRA. Avapritinib showed supra-micromolar blood-brain barrier penetration in our pre-clinical models and demonstrated significant survival impact in an aggressive patient-derived H3K27M DMG mouse xenograft model. Finally, building on this preclinical activity, we report here the first clinical experience using avapritinib in eight pediatric and young adult patients with high-grade glioma (H3K27M DMG and/or PDGFRA altered). Avapritinib has thus far been well tolerated with no significant acute toxicities. Most importantly, our preliminary data reveal radiographic response evaluated by RAPNO criteria in 50% of patients, a striking outcome rarely seen in this patient population. In summary, we report that avapritinib is a selective, CNS-penetrant small molecule inhibitor of PDGFRA that shows potent activity in preclinical models and produces promising clinical responses with good tolerability in patients with high-grade glioma. This suggests a promising role for avapritinib therapy in this population with previously dismal outcomes. Citation Format: Lisa Mayr, Maria Trissal, Kallen Schwark, Jenna Labelle, Andrew Groves, Julia Furtner-Srajer, Jeffrey Supko, Liesa Weiler-Wichtl, Olivia Hack, Jacob Rozowsky, Joana G. Marques, Eshini Pandatharatna, Ulrike Leiss, Verena Rosenmayr, Frank Dubois, Noah F. Greenwald, Sibylle Madlener, Armin S. Guntner, Hana Pálová, Natalia Stepien, Daniela Lötsch-Gojo, Christian Dorfer, Karin Dieckmann, Andreas Peyrl, Amedeo A. Azizi, Alicia Baumgartner, Ondřej Slabý, Petra Pokorná, Pratiti Bandopadhayay, Rameen Beroukhim, Keith Ligon, Christof Kramm, Annika Bronsema, Simon Bailey, Ana Guerreiro Stücklin, Sabine Mueller, David T. Jones, Natalie Jäger, Jaroslav Štěrba, Leonhard Müllauer, Christine Haberler, Chandan Kumar-Sinha, Arul Chinnaiyan, Rajen Mody, Mary Skrypek, Nina Martinez, Daniel C. Bowers, Carl Koschmann, Johannes Gojo, Mariella Filbin. Clinical response to the PDGFRα inhibitor avapritinib in high-grade glioma patients. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5719.
    Type of Medium: Online Resource
    ISSN: 1538-7445
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2023
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  • 10
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 23, No. Supplement_6 ( 2021-11-12), p. vi33-vi34
    Abstract: High-grade gliomas are among the most aggressive brain tumors across all age groups. BRAF is within the most frequently altered genes in pediatric glioma, sometimes connected with telomerase reverse transcriptase (TERT) promoter mutations, predicting a particularly aggressive course of disease. Precision medicine approaches targeting the MAPK pathway have shown promising results in patients with BRAF-mutated glioma. Although acquired insensitivity to BRAF inhibitors appears as major issue for therapy failure, underlying molecular mechanisms are still poorly understood. METHODS Cell models from an anaplastic pleomorphic xanthoastrocytoma with BRAF V600E and TERT promoter mutations and the recurrent tumor, operated following MAPK pathway-targeting therapy, were established. Furthermore, a dabrafenib-resistant subline of the recurrent tumor was generated. The patient-derived cell models were genetically characterized using array-based genomic hybridization (aCGH). Sensitivity of the cells towards different MAPK pathway inhibitors was tested. Basal expression and activation of MAPK pathway and downstream signals were analyzed by qRT-PCR and Western blots. RESULTS Screening a panel of both primary and immortalized glioma cell models with different BRAF and TERT promoter status revealed significantly induced MAPK pathway activation and enhanced TERT levels in BRAF V600E and TERT promoter double-mutant gliomas. Furthermore, cells with both mutations were hyper-sensitive towards BRAF-targeting agents and BRAF inhibition resulted in reduced TERT levels. ETS1 expression was strongly increased in the recurrent tumor and identified as important player in telomerase re-activation. aCGH revealed gains of chromosomal regions encoding for different ETS-factors in the dabrafenib-resistant subline. Western blot analyses suggested a BRAF/ERK-independent survival mechanism in the dabrafenib-resistant subline. Accordingly, dabrafenib insensitivity triggered cross-resistance towards the MEK inhibitor trametinib. Uncoupled from the MAPK pathway, ETS1 expression was further upregulated in the dabrafenib-resistant subline. CONSLUSION: Taken together, our data demonstrate that MAPK-independent ETS transcription factor upregulation is a central mechanism of BRAF inhibitor therapy failure in BRAF-mutated pediatric glioma patients.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 2094060-9
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