In diffuse intrinsic pontine gliomas, non-coding RNA expression is significantly varied dependent on overall survival

Diffuse intrinsic pontine glioma is a kind of pediatric brain cancer that kills 99 percent of patients within five years and for which there are no conventional chemotherapies. It is crucial for new treatments to comprehend the cancer's transcriptional activity. Using a published dataset, we compared the transcriptomes of tumors from patients who lived longer or less than six months. Among the genes whose expression changed most, we observed that numerous microRNAs and snoRNAs were present. The publication's findings are the first evidence of variable levels of non-coding RNA expression in diffuse intrinsic pontine glioma.

Very long-term of survival, 5 years and more in diffuse intrinsic pontine brainstem gliomas in children and adolescents treated with Radiotherapy and Nimotuzumab

Diffuse intrinsic brainstem gliomas have a bad prognosis, and short-term survival time. Radiotherapy has been the principal treatment, and chemotherapy has not improved outcome. The anti –EGFR monoclonal antibody Nimotuzumab combined with Radiotherapy was tested in a series of 41 children and adolescents with diffuse intrinsic pontine gliomas (DIPG) included between January 2008 and December 2015 and a follow-up till January 2021.They were irradiated in the Instituto Nacional de Oncologia y Radiobiologia, Havana, Cuba with a median dose of 54 Gy. Nimotuzumab was applied at a dose of 150 mg/m2, weekly during the period of irradiation, then every 2 weeks by 8 doses, and them monthly for 1,2 or more years. A response was observed in 87.8% of patients. Prolonged use of Nimotuzumab was feasible and well tolerated. Median age at diagnosis was 7 years old, median survival was 18.8 months. There were minor toxicities, only Grade I or II. Survival rate at 5 years was 34.1%, stablished till years or more. Two relapsing patients were re-irradiated. The combination of irradiation and Nimotuzumab is an option to increase survival in DIPG.

In diffuse intrinsic pontine gliomas, non-coding RNA expression is significantly varied dependent on overall survival

Diffuse intrinsic pontine glioma is a kind of pediatric brain cancer that kills 99 percent of patients within five years and for which there are no conventional chemotherapies. It is crucial for new treatments to comprehend the cancer's transcriptional activity. Using a published dataset, we compared the transcriptomes of tumors from patients who lived longer or less than six months. Among the genes whose expression changed most, we observed that numerous microRNAs and snoRNAs were present. The publication's findings are the first evidence of variable levels of non-coding RNA expression in diffuse intrinsic pontine glioma.

RARE-08. POTENTIAL NEW THERAPIES FOR DIFFUSE INTRINSIC PONTINE GLIOMAS IDENTIFIED THROUGH HIGH THROUGHPUT DRUG SCREENING

Diffuse Intrinsic Pontine Gliomas (DIPGs) are the most devastating of all brain tumors. There are no effective treatments, hence almost all children will die of their tumor within 12-months. There is an urgent need for novel effective therapies for this aggressive tumor. We performed a high-throughput drug screen with over 3,570 biologically active, clinically approved compounds against a panel of neurosphere-forming DIPG cells. We identified 7 compounds - auranofin, fenretinide, ivermectin, lanatoside, parthenolide, SAHA and mefloquine - that were confirmed to have potent anti-tumor activity against a panel of DIPG-neurospheres, with minimal effect on normal cells. Using cytotoxicity and clonogenic assays, we found that these drugs were able to inhibit DIPG-neurosphere proliferation and colony formation in vitro. To determine whether the in vitro efficacy could be replicated in vivo, we tested the activity of each of these compounds in an orthotopic DIPG model. Of the agents tested, fenretinide, auranofin and SAHA were the most active anti-tumor agents, significantly enhancing the survival of tumor bearing animals. Mechanistic studies showed fenretinide enhancing apoptotic cell death of DIPG cells via inhibition of PDGFRa transcription and downregulation of the PI3K/AKT/MTOR pathway. We therefore examined the therapeutic efficacy of fenretinide using a second orthotopic model with PDGFRa amplification. We used two different fenretinide formulations which were found to enhance survival. Fenretinide is clinically available with safety data in children. Validation of the activity of Fenretinide in PDGFRa-amplified or overexpressed DIPGs will lead to the development of a clinical trial, allowing the advancement of fenretinide as potentially the first active therapy for DIPG.

HGG-22. EVALUATING THE REGULATION OF BLOOD-BRAIN BARRIER INTEGRITY IN DIPG MOUSE MODELS

Diffuse intrinsic pontine gliomas (DIPGs) are considered to maintain a fairly intact blood-brain barrier (BBB) based on patient imaging tumor histology. In characterizing recently developed DIPG and HGG mouse models, we identified differences in BBB function and increased Angiopoietin1 (Angpt1) in H3 K27M DIPG models. We hypothesize that H3 K27M mutations promote the maintenance of DIPG BBB integrity through upregulation of Angpt1. To determine DIPG and HGG BBB phenotypes we performed an intergrative analysis of vascular histology and endothelial transcriptomes Ongoing studies using electroporation based DIPG mouse models are being performed examine the regulation and function of Angpt1 in DIPG BBB integrity. We have initiated studies comparing H3 K27M DIPG mouse models to H3 WT and G34R cortical HGG mouse models, demonstrating that DIPG models show minimal changes in vascular phenotype, including vessel density, branching, and diameter compared to cortical HGG models. Comparing DIPG and HGG purified endothelial transcriptomes, HGG ECs displayed enrichments of inflammatory signals and proliferation gene sets, and increased expression of tip cell identity genes. We identified Angpt1 as selectively upregulated in H3 K27M mouse models and derived cell lines. Preliminary data suggests Angpt1 supports the maintenance of BBB integrity in DIPG models. BBB phenotype differences are present in DIPG and HGG mouse models. Uncovering mutation specific mechanisms that regulate BBB function in brain tumors will be critical to advance our understanding of brain tumor pathogenesis and treatment response.

EPCT-07. ID1 IS A KEY TRANSCRIPTIONAL REGULATOR OF DIPG INVASION AND IS TARGETABLE WITH CANNABIDIOL

Diffuse intrinsic pontine gliomas (DIPGs) are lethal pediatric brain tumors with no effective therapies beyond radiation. The highly invasive nature of DIPG is key to its aggressive phenotype, but the factors and mechanisms contributing to this aggressive invasion are unknown. Inhibitor of DNA binding (ID) proteins, key regulators of lineage commitment during embryogenesis, are implicated in tumorigenesis in multiple human solid tumors. Prior work showed that recurrent H3F3A and ACVR1 mutations increase ID1 expression in cultured astrocytes. However, the impact and targetability of ID1 have not been explored in human DIPG. Exome and transcriptome sequencing analyses of multi-focal DIPG tumors and normal brain tissue from autopsy (n=52) revealed that ID1 expression is significantly elevated in DIPG samples. Higher ID1 expression correlates with reduced survival in DIPG patients and increased regional invasion in multi-focal autopsy samples. Analyses of developing mouse brain RNA/ChIP-Seq data revealed high ID1 expression and H3K27ac promoter binding in prenatal hindbrain compared to all other prenatal and postnatal brain regions. ChIP-qPCR for H3K27ac and H3K27me3 revealed that ID1 gene regulatory regions are epigenetically poised for upregulation in DIPG tissues compared to normal brain, regardless of H3/ACVR1 mutational status. These data support that the developing pons is regionally poised for ID1 activation. Genetic (shRNA) ID1 knockdown of primary human H3.3K27M-DIPG cells (DIPG007) resulted in significantly reduced invasion/migration and significantly improved survival of K27M-DIPG mice. Knockdown of ID1 in DIPG cells also resulted in down-regulation of the WNK1-NKCC1 pathway, which regulates tumor cell electrolyte homeostasis and migration. Finally, treatment of DIPG007 cells with cannabidiol (CBD) reduced ID1 levels, viability of DIPG cells and significantly improved survival of K27M-DIPG mice. In summary, our findings indicate that multifactorial (genetic and regional) epigenetic upregulation of ID1 drives DIPG invasiveness; and that targeting ID1 with CBD could potentially be an effective therapy for DIPG.

HGG-14. ACT001 – A PROMISING THERAPEUTIC FOR DIFFUSE INTRINSIC PONTINE GLIOMAS

Diffuse Intrinsic Pontine Gliomas (DIPGs) are a subset of Diffuse Midline Gliomas (DMG) and are the most devastating of all brain tumors. There are no effective treatments and all children die of their tumor within 12-months. We performed a high-throughput drug screen with 3,570 biologically active, clinically approved compounds against a panel of DIPG cultures. Parthenolide, a compound derived from the herb T.parthenium, was found to be one of the most effective drugs tested, demonstrating significant anti-tumor activity. However, parthenolide also affected healthy cell viability and showed no in-vivo efficacy. ACT001 is a novel agent in clinical development that is a fumarate salt form of dimethylamino-micheliolide, which is semi-synthesized from parthenolide. ACT001 is blood-brain-barrier permeable and exerts an anti-tumor effect via inhibition of NF-κB and STAT3 pathways. ACT001 demonstrated potent anti-tumor activity against a panel of DIPG-neurospheres, with minimal effect on normal cells and inhibited colony formation in-vitro. To determine whether this activity could be replicated in-vivo, we tested ACT001 in a DIPG-orthotopic model. ACT001 was well tolerated and significantly improved survival of tumor-bearing animals, extending survival by 33% in ACT001 treated mice. We have initiated a Phase 1 paediatric trial of ACT001 for children with relapsed/refractory solid or CNS tumors, with an expansion cohort planned for patients with DIPG/DMG. Eleven patients have been enrolled, and the dose escalated from dose level-1 at 188mg/m2 bd to dose level-4 at 700mg/m2 bd. To date, no dose limiting or Grade 3/4 toxicities have been observed. At the highest dose level, clinical activity has been demonstrated in two patients, one with DIPG with a reduction in tumor burden, and another with DMG with H3K27M mutation with an objective radiographic and clinical response. These combined preclinical and clinical results suggest that ACT001 is an active novel therapy for patients with DIPG/DMG.