bluuebunny/crossref_metadata_2025_split huggingface dataset:
CSIG-16. EXPLOITING A NEGATIVE FEEDBACK LOOP LINKING S6 KINASES AND AXL TO REDUCE PYRIMIDINE BIOSYNTHESIS IN PTEN-DEFICIENT GLIOBLASTOMA
Authors: Behrmann Catherine , Sarma Pranjal , Ennis Kelli , Wetzel Collin , Clark Nicholas , Vallabhapurapu Subrahmanya , Reigle James , Meller Jarek , Qi Xiaoyang , Medvedovic Mario , Sengupta Soma , Dasgupta Biplab , Plas David 
Published: November 2022

Abstract
PTEN inactivation triggers oncodependent signal transduction through the PI3K/Akt signal transduction pathway in glioblastoma (GBM). Targeting the PI3K/Akt pathway to counteract PTEN loss in GBM has been impeded by negative feedback signal transduction networks mediated by the downstream protein kinases S6K1 and S6K2. Here, we show that the receptor tyrosine kinase AXL is a major target of that S6K feedback signaling and that combined inactivation of just S6K1 and AXL is an effective therapeutic strategy for treatment of PTEN-deficient GBM. Chemical-genetic interaction studies in gliomasphere and GBM cell lines revealed critical and independent roles for S6K1 and S6K2 in mediating GBM growth in PTEN-deficient cells. Interestingly, S6K2 exerted a dual role in signal transduction: it sustained GBM growth while also exerting negative feedback control on the upstream receptor tyrosine kinase AXL. Genetic inactivation of S6K2 sensitized PTEN-deficient GBMs to AXL inhibition, indicating that derepressed AXL is required for compensatory signaling upon targeting of the PI3K/Akt pathway. Combining the AXL inhibitor BMS-777607 with S6K1 inhibitor LY-2584702 also prevented compensatory AXL signaling and triggered cytotoxic responses selectively in the PTEN-deficient condition. Importantly, combination inhibition of AXL and S6K1 reduced pyrimidine biosynthesis, a known vulnerability of PTEN-deficient GBMs. The oral inhibitors of S6K1 and AXL were found to be brain-penetrant and effective in reducing GBM growth in several mouse models. These results establish that targeting of AXL can circumvent S6 Kinase dependent feedback to reduce pyrimidine biosynthesis and trigger cytotoxic responses in PTEN-deficient GBMs.
CSIG-20. PROTEOGENOMICS PROFILING REVEALS ENRICHED PROTEIN TRANSLATION REGULATORS AS NEW THERAPEUTIC TARGETS IN DIPG
Authors: Vadivel Arun Anguraj , Pajovic Sanja , Phillips Lauren , Simpson Craig , Zhang Cunjie , Bu Ying , Nitz Mark , Moran Michael , Hawkins Cynthia 
Published: November 2022

Abstract
Diffuse intrinsic pontine glioma (DIPG) is a devastating brain tumor arising in the brainstems of children. Current therapies are ineffective resulting in a median survival rate of less than one year and it is the leading cause of brain tumor-related death in children. A novel mutation in histone H3 protein (H3K27M) was recently identified as a genetic initiation event and affects global K27 trimethylation on histone H3 proteins and DNA methylation. The epigenetic changes caused by H3K27M mutation suggest the existence of an H3K27M-specific transcriptome and proteome. We investigated DIPG tissues at the multi-omics level including total proteome, phosphoproteome, methylproteome and metabolome by mass spectrometry. A total of 30 patient tumours were profiled to identify differentially expressed proteins, differentially phosphorylated proteins, and differentially methylated proteins in tumour tissues compared to normal brains. We identified 2995 proteins that are differentially regulated, suggesting changes in key oncogenic pathways including negative regulation of apoptosis, translation, and metabolic pathways such as methionine salvage and TCA cycle in DIPG. The deregulation of these metabolic pathways due to the differentially expressed proteins in DIPG cells was confirmed by metabolomics studies. Protein phosphorylation and protein methylation profiling of DIPG implicated that translation-related proteins were the most highly modified (post-translationally) proteins in DIPG tissues. Furthermore, protein translation measured by CyTOF showed higher translation rates in DIPG and immortalized astrocytes carrying H3K27M than their WT counterparts. We investigated the functional consequence of knockdown of the highest methylated translation regulator EEF1A1 and its methyltransferase METTL13. ShRNA knockdown of both, EEF1A and METTL13 in DIPG cells significantly reduced the cell growth. Multi-omics analysis of DIPG highlighted regulation of protein translation as a potential therapeutic target.
CSIG-21. EXPLORING THE PHENOTYPIC EFFECTS OF TOLL SIGNALING PATHWAYS IN TUMOR PROGRESSION IN EGFR-DRIVEN GLIOBLASTOMA MODELS
Authors: Saborio Julia G , Gulbronson Riley , Young Elizabeth E , Hsu Irene , Read Renee D 
Published: November 2022

Abstract
The treatment options for Glioblastoma (GBM) are currently limited to resection and chemotherapy approaches, but resistance to chemotherapy is common in patients. There is an urgent need for further understanding of the underlying biology of tumorigenesis in order to develop new treatment options. Previous genomic work on GBMs has shown that the epidermal growth factor receptor (EGFR) is frequently amplified and constitutively active in GBM tumors. To discover new factors that contribute to progression of EGFR-driven GBMs, we used our Drosophila GBM model in which GBM-like glial neoplasia can be induced by glial-specific overexpression of constitutively active forms of EGFR and dp110, a subunit of Phosphoinositide 3-kinase (PI3K), using the UAS-GAL4 gene expression system. Using our Drosophila GBM model system, we performed a modifier screen in which we searched for genes and pathways that worsened or ‘enhanced’ glial neoplasia when specifically overexpressed or activated in neoplastic glia. From our screen, we identified the Toll pathway, which in Drosophila activates an NF-κB signaling pathway. Furthermore, the Toll pathway normally functions in innate immune and injury responses as well as in development and cell proliferation. Using our Drosophila GBM model, we are studying how the Toll signaling pathway and its effectors, including NF-κB, contribute to enhanced growth of neoplastic glial cells. Furthermore, using well-defined mouse genetic models and human patient-derived GBM models, we are examining whether Toll pathway regulatory and signaling mechanisms that we have uncovered in Drosophila function in EGFR-mutant GBM tumor stem cells to promote GBM progression and chemotherapy resistance.
CSIG-26. PROTEIN KINASE B (PKB/AKT) PROTECTS IDH-MUTATED GLIOMA FROM FERROPTOSIS VIA NRF2
Authors: Liu Yang , Lang Fengchao , Yang Chunzhang 
Published: November 2022

Abstract

BACKGROUND
Mutations of the isocitrate dehydrogenase (IDH) gene are highly prevalent in WHO II/III glioma. IDH-mutated glioma frequently exhibits strong molecular signatures of PI3K/AKT/mTOR signaling, whereas the precise roles of this oncogenic pathway in IDH-mutated glioma remain elusive.

METHODS
In this study, we performed unbiased RNA sequencing and gene set enrichment analysis (GSEA) to investigate the relevant molecular pathways governed by the Phosphoinositide 3-kinase (PI3K)/AKT in IDH-mutated cancer cells. The role of nuclear factor erythroid 2-related factor 2 (Nrf2) and glutathione de novo synthesis were further analyzed through biochemistry assays. Moreover, the role of AKT in glioma disease outcomes was evaluated in a preclinical animal model bearing IDH-mutated orthoptic intracranial xenograft.

RESULTS
RNA sequencing and GSEA analysis indicated that the AKT pathway significantly correlated with Nrf2-guided gene expression and ferroptosis-related pathways. Mechanistically, AKT activation compromised the phosphorylation of Nrf2 at its SDS domain, which is a critical post-translational modification that determines Nrf2 degradation through an E3 ligase β-transducin repeat-containing protein (β-TrCP). Thus, the activation of the AKT pathway limited the proteolysis of Nrf2 and a remarkably enhanced Nrf2 transcriptional activity, which enables cytoprotective pathways such as antioxidant, tumor microenvironment remodeling, and ferroptosis protection. Moreover, a combination of AKT inhibitor ipatasertib with genotoxic agent temozolomide resulted in potent synthetic lethality in IDH-mutated cancer cells, highlighted with enhanced ferroptotic cell death. Further, the AKT inhibitor and TMZ combination regimen improved disease outcomes in a preclinical animal model with IDH-mutated orthotopic intracranial xenograft, with significantly prolonged overall survival.

CONCLUSION
Overall, our findings revealed an uncharted oncogenic mechanism in IDH-mutated glioma, highlighted with AKT/Nrf2-guided cytoprotective pathway. Our study also provides critical preclinical evidence for a synthetic lethality approach for IDH mutated cancers.
CSIG-28. THE HEDGEHOG GENE EXPRESSION PROGRAM REGULATES LIPID FEEDBACK MECHANISMS UNDERLYING HEDGEHOG-ASSOCIATED MEDULLOBLASTOMA
Authors: Daggubati Vikas , Choudhury Abrar , Vykunta Akshara , Saulnier Olivier , Gardell Zachary , Reiter Jeremy , Taylor Michael , Raleigh David 
Published: November 2022

Abstract
Misactivation of the Hedgehog pathway can cause cancers such as medulloblastomas, the most common malignant brain tumors in children. Hedgehog signals are transmitted through primary cilia, where Hedgehog ligands bind to Patched1 and activate Smoothened through interactions with cilia-associated sterol lipids. The gene expression programs driving cellular responses to ciliary Hedgehog signals are incompletely understood. Thus, to define Hedgehog target genes and elucidate mechanisms underlying Hedgehog-associated medulloblastomas, we performed RNA sequencing of cells after treatment with Hedgehog ligands (Shh, Dhh, Ihh), cilia-associated lipids (7b,27-dihydroxycholesterol, 24(S),25-epoxycholesterol), or synthetic lipids or small molecules that activate Smoothened (20(S)-hydroxycholesterol, SAG). Nonspecific gene expression changes were identified by performing RNA sequencing (1) after treatment of CRISPR mediated Smo-/- cells with the same Hedgehog pathway agonists, (2) after treatment with vehicle controls, or (3) after treatment with sterol lipids that are unable to activate Smoothened (7a,27-dihydroxycholesterol). Differentially expressed genes were integrated across RNA sequencing of human medulloblastomas (n=458) or the Math1-Cre SmoM2 mouse genetic model of Hedgehog-associated medulloblastoma. Mechanistic studies validating Hedgehog target genes were performed using CRISPR interference, genetic gain-of-function, molecular biology, quantitative immunofluorescence, or cell biology approaches. RNA sequencing after treatment with Hedgehog pathway agonists identified a core gene expression program comprised of 155 genes driving lipid synthesis, metabolism, signaling, adhesion, or angiogenesis. Integration of transcriptomic datasets revealed a conserved gene expression program driving cellular responses to ciliary Hedgehog signals in human or mouse medulloblastomas, including known target genes such as Gli1 or Ptch1, and novel target genes such as Hsd11b1 or Retnla. Retnla is a regulator of sterol synthase expression, and Hsd11b1 is a sterol synthase that opposes the action of Hsd11b2, a driver and druggable dependency underlying Hedgehog-associated medulloblastoma. In support of these findings, mechanistic studies demonstrated Retnla drives expression of Hsd11b2, and showed Hsd11b1 negatively regulates the Hedgehog pathway.
CSIG-30. EPIGENETIC REACTIVATION OF BAI1 BLOCKS ONCOGENIC IGF1R SIGNALLING IN MEDULLOBLASTOMA
Authors: Yamamoto Takahiro , Osuka Satoru , Van Meir Erwin 
Published: November 2022

Abstract
Medulloblastoma (MB) is the most aggressive pediatric brain tumor and a better understanding of this disease is warranted to develop new therapeutic approaches. Brain-specific Angiogenesis Inhibitor 1 (BAI1/ADGRB1) is an orphan seven-transmembrane G protein-coupled receptor predominantly expressed in the brain and epigenetically silenced in MB formation. MDM2 is an E3 ubiquitin ligase that leads to the proteosomal degradation of multiple proteins. We previously found that BAI1 can prevent MDM2 nuclear activity by trapping it at the cell surface, and in the process suppress tumor formation by stabilizing p53. Since MDM2 also ubiquitinates cell surface proteins, we hypothesized that its membrane trapping might increase the degradation of oncogenic tyrosine kinase receptors. To explore this idea, we examined IGF1R, a known cell surface MDM2 target and found that BAI1 negatively regulates IGF1R at the protein level. In contrast, BAI1 expression did not change the protein expression levels of other RTKs (INSR, EGFR). Using co-immunoprecipitation assays we confirmed that MDM2 interacts with both BAI1 and IGF1R in MB cells. In addition, the interaction between IGF1R and β-Arrestin, which is crucial for ubiquitination and down-regulation of IGF1R by acting as an adaptor for MDM2, was increased with BAI1 expression. To examine the impact of BAI1 overexpression on IGF1 receptor signaling, we examined its downstream signaling mediators (Stat3, Akt, Erk). Stat3 and Akt phosphorylation were suppressed upon BAI1 expression, while Erk signaling was activated but through a mechanism independent from IGF1R expression. As IGF1R is known to drive radiation resistance, we examined whether BAI1 could radiosensitize the cells and found that this was indeed the case. Altogether, our data indicate that reactivating BAI1 in MB has dual anti-tumor effects by stabilizing p53 and blocking IGF1R signalling.
CSIG-32. ABL1 AND 2 DRIVE MEDULLOBLASTOMA PROLIFERATION AND ADHESION IN LEPTOMENINGEAL DISSEMINATION
Authors: Thompson Eric , Jones Jill , Kornaherns Reb , Zhang Steven 
Published: November 2022

Abstract

INTRODUCTION
The molecular mechanisms that drive leptomeningeal dissemination (LD) of medulloblastoma (MB) are largely unknown. The Abelson (ABL) family kinases, originally identified as oncogenes in leukemia, play an important role in lung cancer cell migration, invasion, cell adhesion, and chemotherapy resistance. The objective of this work was to elucidate the role of ABL kinases in MB LD.

METHODS
ABL1 and ABL2 mRNA expression of patient specimens was analyzed. shRNA knockdowns of ABL1/2 and pharmacologic inhibition of ABL1/2 were used for in vitro and in vivo analyses of MB LD.

RESULTS
ABL1 and ABL2 levels were significantly higher in MB patients with LD than without (p=2.6x10-10 and 7.2x10-7, respectively) and overall survival was significantly reduced in patients with high ABL1 and 2 expression (p=0.019 and 0.00027, respectively). In vitro pharmacologic inhibition and genetic knockdown of ABL1 and ABL2 in Group 3/4 MB resulted in statistically significant cell death, decreased adhesion to vitronectin (a key leptomeningeal extracellular matrix [ECM] protein), decreased migration through ECM extract, and decreased c-myc expression in multiple MB cell types. In mouse models of MB LD, ABL1/2 knockdown significantly decreased LD as determined by bioluminescence and improved overall survival (p=0.0044). Pharmacologic inhibition of ABL1/2 using nilotinib resulted in improved median overall survival (64 vs. 76.5 days).

CONCLUSIONS
ABL1 and ABL2 are preferentially expressed in patients with MB LD at diagnosis and are associated with poor survival. Both genetic inactivation and pharmacologic inhibition of ABL1 and 2 decreased MB LD in vitro and in vivo, likely via reduction of c-myc signaling. This preliminary work suggests a key role for ABL1/2 in driving MB LD.
CSIG-33. BCOR LOSS PROMOTES RETINOBLASTOMA GROWTH AND DISSEMINATION BY MODULATING INSULIN-LIKE GROWTH FACTOR 2
Authors: Eberhart Charles , Alaali Lujain , Lee Su Chan 
Published: November 2022

Abstract
While loss of RB function is the most common genetic alteration in the pediatric embryonal eye tumor retinoblastoma, mutations leading to BCL-6 corepressor (BCOR) loss of function are the second most common alteration. BCOR mutations are found in more aggressive tumors, and are associated with metastasis and poor prognosis. We investigated the effects of BCOR loss or overexpression in retinoblastoma cells in order to better understand its functional role, and to determine if it represents a new therapeutic target in these tumors. Six established retinoblastoma cell lines were examined, and BCOR protein was most highly expressed in WERI-RB1, but absent in Y79 and two other lines. BCOR knock down in WERI-RB1 cells using shRNA caused markedly increased migration and proliferation. BCOR was also knocked out in these cells using CRSPR, resulting in more than three-fold increased size of intraocular murine xenografts and extensive extraocular extension of tumors. In terms of mechanism, BCOR loss of function induces IGF2 transcription, resulting in an activation of IGF1R and the ERK signaling pathway. In contrast, overexpressing BCOR in Y79 retinoblastoma cells with no baseline protein had opposite effects on IGF2. Targeting IGF2/IGF1R signaling pharmacologically using Lincitinib inhibited proliferation and migration in BCOR-negative retinoblastoma cells. Increased IGF2 transcription was regulated at least in part by hyper methylation of CCCTC-binding factor (CTCF)-binding regions in the IGF2/H19 imprinting control region (ICR), suggesting that BCOR knock down promotes increased methylation at this site. In summary, our studies revealed that BCOR loss promotes the growth and invasion of retinoblastoma cells in vitro and in vivo, at least in part via modulating IGF2 transcription, suggesting new potential therapeutic targets for these aggressive childhood tumors of the eye.
RADT-01. GAMMA KNIFE STEREOTACTIC RADIOSURGERY FOR PATIENTS WITH 10 OR MORE BRAIN METASTASES AT INITIAL CNS PRESENTATION
Authors: DePaoli Bradley , Khaleghi Serena , Duffy Edward , Hall Michael , Rivers Charlotte 
Published: November 2022

Abstract
Stereotactic radiosurgery (SRS) is an established treatment modality for patients with up to 10 brain metastases. Previous guidelines have recommended whole brain radiation therapy (WBRT) for patients with &gt; 10 brain metastases, but many providers and patients have opted for SRS in an attempt to minimize neurocognitive toxicity. There is growing literature supporting SRS in patients with ≥ 10 brain metastases in both the up-front and salvage settings. Data remains limited in how to best manage patients with ≥ 10 brain metastases at their first central nervous system (CNS) presentation. A retrospective review was performed on all patients with ≥ 10 brain metastases at their first CNS presentation treated with Gamma Knife SRS since 2010 at our institution. Patients with prior surgery for neurological symptoms were included, but patients who had received prior CNS radiation were excluded. Patients could be treated in a single stage or as many stages necessary to treat all metastases. Demographics and clinical data were collected. Descriptive statistics were used to summarize variables. 91 patients were identified with a median age of 64 years old. The median brain metastases treated was 13 with a range of 10-57. Local failure was 11% and occurred at a median 10.8 months. Distant failure was 51.6% and occurred at a median 2.7 months. 30.8% of patients required repeat SRS and 18.7% of patients required salvage WBRT. Median survival was 7.2 months. 1-year and 2-year overall survival were 34.8% and 16.5%, respectively. Radiation necrosis occurred in 4.4%. Grade 2 toxicity occurred in 36.3% and Grade 3+ toxicity occurred in 7.7%. There were no grade 5 toxicities and only 5.5% of patients died from clear neurological causes. Upfront SRS provides acceptable local control, survival, and toxicity in patients with ≥ 10 metastases at CNS presentation and can be considered for first-line treatment.
RADT-03. GOLDILOCKS AND THE THREE DOSES OF RADIOSURGERY FOR SMALL BRAIN METASTASES
Authors: Kutuk Tugce , Kotecha Rupesh , Tolakanahalli Ranjini , Appel Haley , Hall Matthew , Wieczorek D Jay , Lee Yongsook , McDermott Michael , Ahluwalia Manmeet , Gutierrez Alonso , Mehta Minesh , Tom Martin 
Published: November 2022

Abstract

INTRODUCTION
The optimal dose for single-fraction radiosurgery (SRS) for small brain metastases (BM) (&lt; 2 cm) has not been established considerable variability in dose selection.

METHODS
Consecutive patients diagnosed with intact BM &lt; 2 cm in maximum dimension treated with SRS to prescription doses of 24, 22, or 20 Gy on the Gamma Knife® between 3/2019-1/2021 were reviewed. Institutional dosing prescriptions were: 24 Gy for &lt; 10 lesions, 22 Gy for 10-20, and 20 Gy for &gt;20). Endpoints included freedom-from-local-failure (FFLF) and radionecrosis on a per-lesion basis calculated from date of SRS to event. Univariable and multivariable analyses were performed using the Kaplan-Meier method and Cox proportional hazards regression.

RESULTS
133 patients with 863 BM met inclusion criteria. Prescription dose was 24 Gy for 416 (48.2%) lesions, 22 Gy for 266 (30.8%), and 20 Gy for 181 (21.0%). 20 Gy was associated (all p&lt; 0.001) with younger age, presence of extracranial-disease, progressive extracranial-disease, lung primary, higher number of BM per SRS course (median 17 for 20 Gy, 14 for 22 Gy, 6 for 24 Gy), and smaller per-lesion tumor volume. With a median follow-up of 15 months, 76 (8.8%) LFs occurred. Actuarial 1-year FFLF was 91.2% (95%CI: 88.6-94.8%) for 24 Gy, 92.5% (89.1-95.9%) for 22 Gy, and 77.9% (71.2-84.6%) for 20 Gy (p&lt; 0.001). On multivariable analysis, factors independently associated with adverse FFLF (all p&lt; 0.05) were male sex, presence of extracranial-disease, breast or lung primary, and 20 Gy prescription dose (HR: 2.52, 95%CI: 1.34-4.76). The cumulative 1-year radionecrosis rate was 7.0% for 24 Gy, 4.0% for 22 Gy, and 3.8% for 20 Gy (p=0.035).

CONCLUSION
For BM &lt; 2 cm, we propose a testable hypothesis that 22 Gy prescription dose may represent the “Goldilocks zone”- superior to 20 Gy regarding LF and superior to 24 Gy concerning radionecrosis.