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  • 1
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    LGG-11. BH3-MIMETICS TARGETING BCL-XL SELECTIVELY IMPACT THE SENESCENT COMPARTMENT OF PILOCYTIC ASTROCYTOMA
    Oxford University Press (OUP) ; 2021
    In:  Neuro-Oncology Vol. 23, No. Supplement_1 ( 2021-06-01), p. i33-i34
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    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 23, No. Supplement_1 ( 2021-06-01), p. i33-i34
    Abstract: Pilocytic astrocytoma (PA) is the most common brain tumor in children. Activation of the mitogen-activated protein kinase (MAPK) pathway is a hallmark of PA. Complete remission in non-resectable tumors is infrequently observed with current therapeutic approaches. Most PA tumors cells are in oncogene-induced senescence (OIS), which may explain the benign growth behavior of PAs but also account for resistance to therapy. Therefore, treatment of PA with senolytic agents such as BH3-mimetics is a promising new approach. Methods Three patient-derived PA cell lines, DKFZ-BT66, DKFZ-BT308 (both KIAA1549:BRAF-fusion positive) and DKFZ-BT314 (BRAF V600E-mutation positive) were used. Depending on inducible expression or repression of SV40 large T antigen all models can reflect both states of PA, proliferation and OIS. Cells in both states were treated with different BH3-mimetics. Inhibition of metabolic activity was measured after 72 hours. Target expression was assessed by RT-qPCR and Western blot. On-target activity of BH3-mimetics was determined by immunoprecipitation (IP) of Bcl-xL/BAK. Results BH3-mimetics with strong binding affinity for Bcl-xL (Navitoclax, A-1131852, A-1155463) showed selectivity for senescent cells in 2/3 models (DKFZ-BT66 and DKFZ-BT314) and acted in nanomolar ranges. IC50s for Navitoclax (Cmax 6600nM in patients) were 40nM (OIS) vs. 200nM (proliferation) and 170nM (OIS) vs. 3700nM (proliferation) in DKFZ-BT66 and DKFZ-BT314, respectively. Target engagement was evident in the Bcl-xL/BAK-IP, and target expression of Bcl-xL was similar in all models studied. The relative resistance of senescent DKFZ-BT308 despite on-target activity is currently being investigated. Conclusion Senolytic treatment of PA with BH3-mimetics targeting Bcl-xL is a promising new strategy directly targeting the major senescent part of the tumor in clinically archivable concentrations. However, our data suggests that not all PAs may respond to treatment. The analysis of comparative gene expression analysis and BH3-profiling is ongoing to define predictive biomarkers.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noab090.135
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
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  • 2
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    LGG-03. EXPLORING THE SIGNALING NETWORK INVOLVED IN MAPK PATHWAY INHIBITION BY THE MEK INHIBITOR TRAMETINIB IN BRAF-FUSION-DRIVEN PEDIATRIC PILOCYTIC ASTROCYTOMA
    Oxford University Press (OUP) ; 2023
    In:  Neuro-Oncology Vol. 25, No. Supplement_1 ( 2023-06-12), p. i55-i55
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    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 25, No. Supplement_1 ( 2023-06-12), p. i55-i55
    Abstract: Pilocytic astrocytomas (PA) are the most common pediatric brain tumors. They are characterized by MAPK pathway alterations, leading to its constitutive activation and modulating the balance between proliferation and oncogene-induced senescence (OIS) sustained by senescence-associated secretory phenotype (SASP). Little is known about the molecular implications of MAPK pathway inhibition in the proliferating and senescent tumor compartments. METHODS DKFZ-BT66 cells derived from a primary KIAA:BRAF-fusion positive PA cell line and BT40 cells derived from pleomorphic xanthoastrocytoma with a BRAFV600E mutation and CDKN2A/B deletion, were used as model systems. RNA-sequencing and phospho-/proteomic datasets were generated in both the proliferative and senescent cells, and treated with the MEKi trametinib for different time-spans. A multi-omics factor analysis tool (MEFISTO) was used to identify key OIS/proliferation effectors. RESULTS Differential gene expression analysis revealed that MEK inhibition leads to the inhibition of the OIS/SASP gene program in senescent DKFZ-BT66. In addition, the protein level of several SASP factors was decreased. This translated in reduced sensitivity towards senolytics drugs, indicating inhibition of senescence features upon MEKi. MEFISTO analysis allowed to identify key transcription factors, genes and proteins involved in MAPK-induced OIS in the senescent PA cells, that were mapped using a prior knowledge network approach. Finally, single sample geneset enrichment analysis showed that most MAPK-related signatures were downregulated upon MEKi treatment, while pathways related to upstream MAPK activators (including several RTK pathways) were predicted to be upregulated, in both proliferating and senescent cells. CONCLUSION This data suggests that MAPKi reverses OIS in senescent PA cells, while inducing the activation of MAPK upstream regulators, identifying putative co-targets for the treatment of PA. Further validation of the targetability of these pathways is pending. Furthermore, the identification of the MAPK-related OIS/SASP genes provide insight about the regulation of OIS/SASP by the MAPK pathway.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noad073.213
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
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  • 3
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    LGG-14. MULTI-OMIC ANALYSIS OF MAPK ACTIVATION IN PEDIATRIC PILOCYTIC ASTROCYTOMA
    Oxford University Press (OUP) ; 2020
    In:  Neuro-Oncology Vol. 22, No. Supplement_3 ( 2020-12-04), p. iii368-iii368
    Details
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 22, No. Supplement_3 ( 2020-12-04), p. iii368-iii368
    Abstract: Pilocytic astrocytomas (PA) are low-grade gliomas (pLGG) and are the most frequent childhood brain tumors. They are characterized by oncogene-induced senescence (OIS) initiated and sustained by senescence-associated secretory phenotype (SASP) factors. OIS and SASP in PA are thought to be driven by aberrations of the mitogen-activated protein kinase (MAPK) pathway (e.g. KIAA1549:BRAF fusion, BRAFV600E mutation, for the most common MAPK alterations occuring in PA), leading to its sustained activation. The MAPK pathway cascade is activated in a sequential manner: 1) ERK activation, which phosphorylates downstream partners in both cytoplasm and nucleus. 2) ERK-mediated induction of immediate early genes encoding transcription factors. 3) Induction of MAPK target genes expression. 4) Activation of downstream pathways. Our aim is to unravel the molecular partners involved at each level of the sustained MAPK pathway activation in pLGG with different genetic backgrounds (KIAA1549:BRAF fusion and BRAFV600E mutation), and leading to the induction of OIS and SASP factors expression. pLGG cell lines DKFZ-BT66 (KIAA1549:BRAF) and BT-40 (BRAFV600E) were treated with the MEK inhibitor trametinib at key time points, and gene expression profile analysis was performed, allowing transcriptome analysis at each step of the MAPK cascade. This will be combined with a whole proteomic and phospho-proteomic analysis. Combination of the transcriptome and proteome data layers will allow the identification of a) downstream targetable partners activated by the MAPK pathway involved in PA senescence, b) new putative targets that might bring benefit in combination with MAPK inhibitors.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noaa222.396
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
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  • 4
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    LGG-04. MULTIOMIC ANALYSIS OF MAPK PATHWAY ACTIVITY IN PEDIATRIC PILOCYTIC ASTROCYTOMA
    Oxford University Press (OUP) ; 2021
    In:  Neuro-Oncology Vol. 23, No. Supplement_1 ( 2021-06-01), p. i31-i32
    Details
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 23, No. Supplement_1 ( 2021-06-01), p. i31-i32
    Abstract: Pilocytic astrocytomas (PA) are the most common pediatric brain tumors. They are characterized by MAPK pathway alterations, leading to its constitutive activation and modulating the balance between cell proliferation and the oncogene-induced senescence (OIS) sustained by senescence-associated secretory phenotype (SASP) factors. This makes PA suitable for MAPK inhibitor (MAPKi) therapies, showing encouraging results in phase 1/2 clinical trials. Little is known about the molecular implications of MAPK downregulation in the proliferating and senescent compartments. Methods DKFZ-BT66 PA cells derived from a primary KIAA:BRAF-fusion positive PA cell line, were used as model system. Gene expression and phospho-proteomic datasets were generated from DKFZ-BT66 cells, in both the proliferative and senescent states, and treated with the MEKi trametinib for different time-spans. A time course analysis based on differentially expressed genes was performed, followed by a single-sample gene set enrichment analysis (ssGSEA). Analysis of the phospho-proteomic data is ongoing. Results Differential gene expression analysis revealed that MEK inhibition leads to the inhibition of the OIS-SASP gene program in senescent DKFZ-BT66. ssGSEA showed that most MAPK-related signatures were downregulated upon MEKi treatment, while pathways related to upstream MAPK activators (including FGFR, NTRK and TGFB pathways) were upregulated, in both proliferating and senescent DKFZ-BT66. Genes regulated by the MAPK pathway and involved in OIS-SASP were identified by analyzing genes differentially regulated between proliferating and senescent DKFZ-BT66, and modulated upon MEKi treatment. Conclusion This data suggests that MAPKi reverses OIS in senescent PA cells, while inducing the activation of MAPK upstream regulators in proliferating and senescent PA cells, identifying putative co-targets that could help prevent growth rebound upon MAPKi withdrawal. Furthermore, the identification of the MAPK-related OIS-SASP genes provide insight about the regulation of OIS-SASP by the MAPK pathway. Validation of this data with the ongoing phospho-proteomic analysis and in primary samples is needed.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noab090.128
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
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  • 5
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    OTHR-32. The Pediatric Targeted Therapy 2.0 registry: robust molecular diagnostics for precision oncology
    Oxford University Press (OUP) ; 2022
    In:  Neuro-Oncology Vol. 24, No. Supplement_1 ( 2022-06-03), p. i154-i154
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    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 24, No. Supplement_1 ( 2022-06-03), p. i154-i154
    Abstract: BACKGROUND: The Pediatric Targeted Therapy (PTT) 2.0 program was established to enable precision oncology for relapsed pediatric oncology patients by performing a set of molecular analyses on tumor samples to improve diagnostic accuracy and to detect actionable alterations. METHODS: International pediatric oncology patients with relapse or progression after standard of care treatment independent of histological diagnosis were included. Required material was an FFPE sample from any disease episode available to perform a DNA methylation array, customized targeted gene panel sequencing (130 genes), RNA Sanger sequencing in selected cases, and a pathway-specific immunohistochemistry (IHC) panel. For sequencing a blood sample was used as paired constitutional DNA, allowing for detection of potential cancer predisposition syndromes. All molecular results were discussed in an interdisciplinary tumor board and reported back to the submitting centers. The clinical impact of reported findings was assessed by a serial questionnaire-based two year follow-up. RESULTS: n=266 patients were registered, the molecular workup was successfully performed for n=263 (99%) patients. The most frequent diagnostic category was central nervous system tumors (n=172/263, 65%). Integrated molecular diagnostics suggested a refined or changed diagnosis in n=95/172 (55%) brain tumors. Actionable targets were detected in n=106/172 (61%) cases. In n=11/155 (7.1%) of brain tumor patients pathogenic or likely pathogenic constitutional DNA variants with clinical relevance were identified, n=5 (45%) of which were previously unknown. Clinical follow-up of revealed that n=11/131 (12%) of brain tumor patients received mechanism-of-action based treatment matched to the molecular findings in PTT2.0. CONCLUSIONS: Molecular diagnostics adds robust and clinically relevant information on diagnosis, actionable alterations, and cancer predisposition syndromes in CNS and other pediatric tumors even when tissue from the current disease episode is limited.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noac079.570
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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  • 6
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    The first-in-class ERK inhibitor ulixertinib shows promising activity in mitogen-activated protein kinase (MAPK)-driven pediatric low-grade glioma models
    Oxford University Press (OUP) ; 2023
    In:  Neuro-Oncology Vol. 25, No. 3 ( 2023-03-14), p. 566-579
    Details
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 25, No. 3 ( 2023-03-14), p. 566-579
    Abstract: Pediatric low-grade gliomas (pLGG) are the most common pediatric central nervous system tumors, with driving alterations typically occurring in the MAPK pathway. The ERK1/2 inhibitor ulixertinib (BVD-523) has shown promising responses in adult patients with mitogen-activated protein kinase (MAPK)-driven solid tumors. Methods We investigated the antitumoral activity of ulixertinib monotherapy as well as in combination with MEK inhibitors (MEKi), BH3-mimetics, or chemotherapy in pLGG. Patient-derived pLGG models reflecting the two most common alterations in the disease, KIAA1549:BRAF-fusion and BRAFV600E mutation (DKFZ-BT66 and BT40, respectively) were used for in vitro and in vivo (zebrafish embryos and mice) efficacy testing. Results Ulixertinib inhibited MAPK pathway activity in both models, and reduced cell viability in BT40 with clinically achievable concentrations in the low nanomolar range. Combination treatment of ulixertinib with MEKi or BH3-mimetics showed strong evidence of antiproliferative synergy in vitro. Ulixertinib showed on-target activity in all tested combinations. In vivo, sufficient penetrance of the drug into brain tumor tissue in concentrations above the in vitro IC50 and reduction of MAPK pathway activity was achieved. In a preclinical mouse trial, ulixertinib mono- and combined therapies slowed tumor growth and increased survival. Conclusions These data indicate a high clinical potential of ulixertinib for the treatment of pLGG and strongly support its first clinical evaluation in pLGG as single agent and in combination therapy in a currently planned international phase I/II umbrella trial.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noac183
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
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  • 7
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    LGG-02. DRUG-CLASS SPECIFIC GENE-BASED MAPK SENSITIVITY SCORES (MSS) PREDICT SENSITIVITY TO MAPK INHIBITORS AND IDENTIFY IMMUNE INFILTRATION AS PUTATIVE TARGET IN PEDIATRIC LOW-GRADE GLIOMAS
    Oxford University Press (OUP) ; 2023
    In:  Neuro-Oncology Vol. 25, No. Supplement_1 ( 2023-06-12), p. i55-i55
    Details
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 25, No. Supplement_1 ( 2023-06-12), p. i55-i55
    Abstract: Pediatric low-grade gliomas (pLGG), the most common brain tumors in children, are driven by alterations in the MAPK pathway. Several clinical trials have shown the potential for MAPK inhibitors (MAPKi) treatment in pLGG. However, the range of response is broad, even within entities sharing the same driving genetic MAPK alteration. A predictive stratification tool is needed to identify patients that will be more likely to benefit from MAPKi therapy. METHODS We generated gene-expression-based MAPKi sensitivity scores (MSS) for each MAPKi class (BRAFi, MEKi, ERKi), based on MAPK-related genes differentially regulated between MAPKi sensitive and non-sensitive cell lines from the Genomics of Drug Sensitivity in Cancer (GDSC) dataset. Single sample Gene Set Enrichment Analysis (ssGSEA) was used to measure and validate our MSSs in the GDSC dataset and an independent PDX dataset (XevaDB). The validated signatures were tested in a pLGG-specific background, using gene expression data from PA cell lines and primary pLGG samples. RESULTS Our MSS could differentiate MAPKi sensitive cells in the GDSC dataset, and significantly correlated with MAPKi response in the XevaDB PDX dataset. The MSS were able to differentiate glioma entities with differing MAPK alterations from non-MAPK altered entities, and showed the highest scores in pLGG. The MSSs were heterogeneous within pLGG entities with a common MAPK alteration, as observed in MAPKi clinical studies. Intriguingly, a strong correlation between our MSS and the predicted immune cell infiltration rate, as determined by the Estimate score, was observed and confirmed in a pLGG scRNA sequencing dataset. CONCLUSION These data demonstrate the relevance of gene-expression signatures to predict response to MAPKi treatment in pLGG, and will be further investigated in a prospective manner in upcoming clinical trials. In addition, our data could suggest a role of immune infiltration in the response to MAPKi in pLGG that warrants further validation.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noad073.212
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
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  • 8
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    MAPK inhibitor sensitivity scores predict sensitivity driven by the immune infiltration in pediatric low-grade gliomas
    Springer Science and Business Media LLC ; 2023
    In:  Nature Communications Vol. 14, No. 1 ( 2023-07-27)
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    In: Nature Communications, Springer Science and Business Media LLC, Vol. 14, No. 1 ( 2023-07-27)
    Abstract: Pediatric low-grade gliomas (pLGG) show heterogeneous responses to MAPK inhibitors (MAPKi) in clinical trials. Thus, more complex stratification biomarkers are needed to identify patients likely to benefit from MAPKi therapy. Here, we identify MAPK-related genes enriched in MAPKi-sensitive cell lines using the GDSC dataset and apply them to calculate class-specific MAPKi sensitivity scores (MSSs) via single-sample gene set enrichment analysis. The MSSs discriminate MAPKi-sensitive and non-sensitive cells in the GDSC dataset and significantly correlate with response to MAPKi in an independent PDX dataset. The MSSs discern gliomas with varying MAPK alterations and are higher in pLGG compared to other pediatric CNS tumors. Heterogenous MSSs within pLGGs with the same MAPK alteration identify proportions of potentially sensitive patients. The MEKi MSS predicts treatment response in a small set of pLGG patients treated with trametinib. High MSSs correlate with a higher immune cell infiltration, with high expression in the microglia compartment in single-cell RNA sequencing data, while low MSSs correlate with low immune infiltration and increased neuronal score. The MSSs represent predictive tools for the stratification of pLGG patients and should be prospectively validated in clinical trials. Our data supports a role for microglia in the response to MAPKi.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    URL: Article
    DOI: 10.1038/s41467-023-40235-8
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
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  • 9
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    LGG-27. Molecular implications of mitogen-activated protein kinase pathway inhibition by the MEK inhibitor trametinib in BRAF-fusion-driven pediatric pilocytic astrocytoma
    Oxford University Press (OUP) ; 2022
    In:  Neuro-Oncology Vol. 24, No. Supplement_1 ( 2022-06-03), p. i94-i94
    Details
    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 24, No. Supplement_1 ( 2022-06-03), p. i94-i94
    Abstract: Pilocytic astrocytomas (PA) are the most common pediatric brain tumors. They are characterized by driving alterations in the mitogen-activated protein kinase (MAPK) pathway, leading to its constitutive activation and modulating the balance between cell proliferation and oncogene-induced senescence (OIS) sustained by senescence-associated secretory phenotype (SASP) factors. This makes PA susceptible to MAPK inhibitor (MAPKi) therapies, which show encouraging results in phase 1/2 clinical trials. However, little is known about the molecular implications of MAPK inhibition in PA. The DKFZ-BT66 cell line, derived from a primary KIAA:BRAF-fusion positive PA, was used as a model system. DKFZ-BT66 were treated with the MEKi trametinib for different durations in both proliferative and senescent states. Gene expression was analyzed by gene expression profiling and protein expression/phospho-regulation by data-dependent mass spectrometry followed by label-free quantitative analysis. A time course analysis based on differentially expressed genes and phosphorylated proteins was performed, followed by a single-sample gene set enrichment analysis (ssGSEA) and kinase substrate enrichment analysis, respectively. Differential gene expression analysis revealed that MEK inhibition led to the inhibition of the OIS/SASP gene programs in senescent DKFZ-BT66, with downregulation of key OIS/SASP partners such as IL1B on the protein level. This functionally translated into a de-sensitization of these cells towards the senolytic agent navitoclax. ssGSEA showed that most MAPK-related signatures were downregulated upon MEKi treatment, while pathways related to upstream MAPK activators (including FGFR, NTRK and TGFB pathways) were upregulated, in both proliferating and senescent DKFZ-BT66. This data indicates that MAPKi reverses OIS in senescent PA cells, while inducing the activation of MAPK upstream regulators in proliferating and senescent PA cells, identifying putative co-targets that could help increase treatment’s efficacy. Validation of these targets by post-translational modification enrichment analysis of the phospho-proteomics dataset is ongoing.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noac079.341
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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  • 10
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    EMBR-01. CLASS I HDAC INHIBITORS AND PLK1 INHIBITORS SYNERGIZE IN MYC -AMPLIFIED MEDULLOBLASTOMA
    Oxford University Press (OUP) ; 2021
    In:  Neuro-Oncology Vol. 23, No. Supplement_1 ( 2021-06-01), p. i5-i5
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    In: Neuro-Oncology, Oxford University Press (OUP), Vol. 23, No. Supplement_1 ( 2021-06-01), p. i5-i5
    Abstract: Medulloblastoma (MB) is one of the most common malignant pediatric CNS tumors. Patients with Group 3 MBs harboring MYC amplification exhibit low survival rates. Surviving patients suffer from therapy-induced sequelae, which calls for new targeted therapy strategies. We and others have previously shown the sensitivity of MYC-amplified MB to class I histone deacetylase (HDAC) inhibition. After demonstrating that the MYC target gene PLK1 is significantly downregulated upon class I HDACi treatment, we hypothesized that inhibition of both HDACs and PLK1 could have synergistic effects. Methods Cell metabolic activity changes upon HDAC and PLK1 inhibitor treatment were measured in MYC-amplified and non-amplified MB cell lines, as well as in an additional MYC-inducible cell line. The interaction effect of both inhibitors was determined by computation of the combination index (CI) using the Chou-Talalay method. Results were validated assessing cell viability, cell cycle, and apoptosis induction. Transcription profile changes after combination treatment were evaluated. Results MYC-amplified MB cell lines were more sensitive than non-amplified cell lines to PLK1i treatment, showing IC50 in clinically achievable concentration ranges. Inhibition of class I HDACs and PLK1 synergistically reduced cell metabolic activity in lower concentrations in MYC-amplified compared to non-amplified MB cell lines. We also observed a significant loss of viability and cells in G1 phase, as well as induction of apoptosis after combination treatment in MYC-amplified cells. MYC target gene sets were significantly downregulated in the MYC-amplified cell line HD-MB03 after treatment with combination. We demonstrated reduction of MYC protein levels upon PLK1i treatment. In vivo evaluation of combination treatment using orthotopic Group 3 MYC-amplified MB PDX models is ongoing. Conclusion Our data suggest that MYC-amplification is a predictive marker for PLK1i treatment in MB. The combination of HDACi and PLKi could be a candidate therapy for future clinical trials for MYC-amplified group 3 MB.
    Type of Medium: Online Resource
    ISSN: 1522-8517 , 1523-5866
    URL: Article
    DOI: 10.1093/neuonc/noab090.019
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
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