Closed: Metabolic MRI of paediatric-type diffuse high grade glioma and its response to therapy in vivo
Project background
Paediatric-type diffuse high grade glioma (PDHGG), a malignant brain tumour, is a leading cause of tumour-related death in children and young adults. In the majority of cases median survival is only 9-18 months, with 2-year survival rates of less than 5% in patients with certain subtypes (1). Extensive genomic and epigenetic profiling has revealed distinct underlying biology in paediatric disease compared with histologically similar lesions in older adults, which differs by anatomical location. Amongst these, recurrent mutations in genes encoding histones H3.3 and H3.1 have been identified in around half of all PDHGGs, with H3 K27 alterations occurring in diffuse midline gliomas (DMG H3 K27-altered), and H3.3 G34R/V mutations arising in diffuse hemispheric gliomas (DHG H3 G34-mutant). PDHGGs lacking H3 and IDH1 mutations (PDHGG H3-wildtype, IDH-wildtype (wt)), are heterogeneous, with subgroups enriched for MYCN amplification and alterations in receptor tyrosine kinases (RTK) such as EGFR or PDGFRA (2,3). These alterations promote numerous oncogenic signalling pathways, including metabolic adaptations, that are revealing new therapeutic vulnerabilities for improved targeted treatments. Such metabolic reprogramming can also be leveraged by magnetic resonance imaging (MRI) approaches sensitive to tissue biochemistry, potentially providing much-needed early imaging biomarkers of PDHGG detection, delineation and therapeutic response.
MRI is routinely used for diagnosis and monitoring of paediatric brain tumours, however the infiltrative growth patterns of PDHGG can limit the efficiency of conventional MRI to fully delineate active disease in situ, and for early assessment of effective treatment response.
We have established metabolic MRI methods to characterise DMG H3 K27-altered, DHG H3 G34-mutant and H3 wt PDHGG xenografts derived from site-specific orthotopic implantation of patient-derived cells that retain the key genetic/epigenetic features. These models will underpin the pre-clinical work in this project.
Project aims
- Exploit metabolic MRI protocols to interrogate the detection and evolution of intracranial models of PDHGG and to correlate with histopathology.
- Utilise metabolic MRI methods to assess tumour response to treatments that modulate dysregulated tumour metabolism.
- Optimise targeted irradiation protocols for brain tumour treatment using the small animal radiation research platform (SARRP) and assess response to radiotherapy ± targeted therapies using multi-parametric and metabolic MRI.
Further details & requirements
It will be hosted within the Centre for Cancer Imaging (CCI) in Sutton, which provides a state of art, collaborative, multi-disciplinary pre-clinical research environment, with imaging and therapy equipment located adjacent to each other. The project will build upon a longstanding, productive collaboration between Prof. Simon Robinson’s pre-clinical MRI team and the paediatric glioma team lead by Prof. Chris Jones.
Both established and novel orthotopically implanted models of PDHGG, grown in the specific location of the original tumour, will be propagated following protocols routinely used at the ICR. These may come from patient-derived stem cell cultures or from tissue harvested directly from patients. There will also be opportunities to exploit syngeneic models of PDHGG using cells isolated from tumours induced with mutations to model diffuse midline or hemispheric glioma in immunocompetent mice, propagated in the relevant region of the brain in strain-matched mice (4). Whilst these models are not derived from human tumours, they do allow for the study of the influence of the immune system in treatment response, particularly relevant in the context of radiation response.
Metabolic MR techniques which have been established on our dedicated pre-clinical horizontal bore MRI scanner will be exploited alongside conventional MRI imaging. These methods include:
i) Chemical exchange saturation transfer (CEST) MRI
CEST MRI can provide multiple and discrete contrasts relating to immobile (ssMT) and mobile (rNOE) macromolecules, as well as proteins (amides and amines), at high resolution, and is being used clinically to investigate metabolism in adult brain tumours (5). Our preliminary data demonstrate that CEST MRI provides clear delineation of well-defined orthotopic PDHGG xenografts, and has great potential to provide more sensitive imaging biomarkers for the early detection and delineation of diffuse PDHGG tumours than conventional anatomical imaging.
In this project, longitudinal CEST MRI data will be acquired to map and quantify the evolving metabolic phenotype across orthotopic PDHGG models that encompass a range of molecular subtypes and tumour growth patterns, from expansive to diffusely infiltrative. CEST MRI will also be used to monitor PDHGG response to therapeutic strategies predicted to alter the macromolecular signature of tumours, e.g. radiotherapy, and to evaluate new metabolic interventions. For example, targeting of cholesterol synthesis, which has been identified as a metabolic vulnerability in H3 K27-altered DMG, with statins as part of combinatorial treatment being investigated in the Jones laboratory (6). Conventional histological correlates (e.g. human nuclear antigen (HNA) immunohistochemistry, H&E staining) to CEST contrast signal heterogeneity will be sought.
ii) Deuterium metabolic imaging (DMI)
Deuterium (2H) is a MR visible isotope of hydrogen with low natural abundance. DMI is a MR spectroscopic imaging technique which, coupled with judicious choice of 2H-labelled substrates, can inform on specific metabolic pathways in vivo. The metabolism of both adult brain tumour models in vivo and glioma patients has been investigated by DMI using [6,6- 2H2]-glucose whose metabolism via glycolysis results in detectable labelling of lactate, and following entry of labelled pyruvate into the TCA cycle, detectable glutamine/glutamate (7,8).
We have established a novel in vitro 2H MR spectroscopy assay to dynamically monitor the metabolism of deuterated substrates in live cells. Using this approach, and [6,6- 2H2]-glucose, we have shown a significant reduction in glycolysis in PIK3R1-mutant PDHGG cells treated with the PI3K/mTOR inhibitor paxalisib, which was detected prior to any change in cell viability. This project will utilise this method, and subsequently our established in vivo DMI methodology , to further assess differential glycolytic responses to pax alisib across PDHGG models, and to evaluate response and resistance to other therapeutic agents whose mechanism of action elicits changes in tumour metabolism, for example MEK inhibitor trametinib. In addition, dordaviprone (ONC-201), which drives proteolysis of electron transport chain and TCA cycle proteins, thereby impairing tumour cell metabolism, inducing mitochondrial damage and rendering the tumour in a state of energy depletion, has shown clinical efficacy in DMG alone and in combination with paxalisib (9,10).
Opportunities to explore alternative deuterated metabolic tracers to investigate other potentially targetable metabolic vulnerabilities in PDHGG will also be expoited. DMI has revealed d istinct contrast between orthotopic rat gliomas and normal-appearing brain after [2H3]-acetate infusion, showing higher acetate levels and lower acetate oxidation in the tumour (7). Our 2H MRS in vitro assay and in vivo DMI will be used to investigate whether [ 2H3]-acetate uptake can i) reveal differential metabolism between PDHGG models, and ii) assess tumour response to paxalisib and/or dordaviprone.
Frontline therapy for patients over 3 years old with PDHGG includes radiotherapy, in combination with surgery and chemotherapy where possible, or alone for DMGs arising in the brainstem. Tumour irradiation in this project will be performed using the small animal radiation research platform (SARRP) within the CCI, which replicates modern clinical radiotherapy for conformal treatment of rodent tumour models. The SARRP has an integrated CT scanner for treatment planning, with the potential to import and fuse MRI images, enabling accurate irradiation of individual tumours with 0.5mm precision.
Through a new collaboration with Prof. Josephine Bunch at National Physical Laboratory, we will use correlative mass spectrometry imaging (MSI) of MRI-aligned tissue sections to provide more definitive identification and spatial distribution of the endogenous metabolites contributing to the CEST contrast and DMI data.
Clinical translation of these methods will be explored via the London Collaborative Ultra-high field System (LoCUS) facility, a clinical 7T MRI system located within St. Thomas Hospital, for which the ICR is the lead oncology partner. LoCUS provides a unique opportunity to exploit the greatly increased sensitivity to physiological and metabolic processes afforded by ultra-high field MRI in adult and paediatric patient studies, and we will work with clinical colleagues to develop and apply CEST MRI and DMI on this system, towards investigating tumour metabolism and treatment response in PDHGG patients.
Note: the ICR’s standard minimum entry requirement is a relevant undergraduate Honours degree (First or 2:1).
Pre-requisite qualifications of applicants:
BSc or equivalent in either Biological Sciences or Physics/Engineering
Intended learning outcomes:
- Competency in the maintenance of cultures of primary cells taken from surgical specimens, grown either as monolayers or three-dimensional neurospheres.
- Secure a Home Office licence, become a responsible licensee and become proficient in the propagation of orthotopic brain tumour models in vivo.
- Development and application of non-invasive, clinically translatable MRI modalities for the preclinical assessment of brain tumour metabolism and changes in response to therapeutic intervention in vivo.
- Gain an appreciation of clinical imaging approaches for the assessment of paediatric brain tumours.
- Develop strong and confident communication skills through regular presentations of their work at lab meetings, departmental seminars and report writing.
- Training will be provided within a stimulating research environment in which many projects are of a multidisciplinary or collaborative nature, providing an insight into a wide range of imaging techniques and expertise.
1. Jones C, Karajannis MA, Jones DTW, Kieran MW, Monje M, Baker SJ, et al. Pediatric high-grade glioma: biologically and clinically in need of new thinking. Neuro Oncol 2017;19:153-61.
2. Mackay A, Burford A, Carvalho D, Izquierdo E, Fazal-Salom J, Taylor KR, et al. Integrated Molecular Meta-Analysis of 1,000 Pediatric High-Grade and Diffuse Intrinsic Pontine Glioma. Cancer Cell 2017;32:520-37 e5.
3. Louis DN, Perry A, Wesseling P, Brat DJ, Cree IA, Figarella-Branger D, et al. The 2021 WHO Classification of Tumors of the Central Nervous System: a summary. Neuro Oncol 2021;23:1231-51.
4. McNicholas M, De Cola A, Bashardanesh Z, Foss A, Lloyd CB, Hebert S, et al. A Compendium of Syngeneic, Transplantable Pediatric High-Grade Glioma Models Reveals Subtype-Specific Therapeutic Vulnerabilities. Cancer Discov 2023;13:1592-615.
5. Huang J, Chen Z, Park SW, Lai JHC, Chan KWY. Molecular Imaging of Brain Tumors and Drug Delivery Using CEST MRI: Promises and Challenges. Pharmaceutics 2022;14:
6. Rogers R, Grabovaska Y, Mackay A, Carvalho DM, Dobinson C, Pereira R, et al. A Novel Role For ACVR1/ALK2 in Regulating Cholesterol Biosynthesis Provides a New Combinatiorial Therapeutic Approach for Patients With DMG. Neuro Oncol 2024;26:iv21-iv22.
7. De Feyter HM, Behar KL, Corbin ZA, Fulbright RK, Brown PB, McIntyre S, et al. Deuterium metabolic imaging (DMI) for MRI-based 3D mapping of metabolism in vivo. Sci Adv 2018;4:eaat7314.
8. Simoes RV, Henriques RN, Cardoso BM, Fernandes FF, Carvalho T, Shemesh N. Glucose fluxes in glycolytic and oxidative pathways detected in vivo by deuterium magnetic resonance spectroscopy reflect proliferation in mouse glioblastoma. Neuroimage Clin 2022;33:102932.
9. Venneti S, Kawakibi AR, Ji S, Waszak SM, Sweha SR, Mota M, et al. Clinical Efficacy of ONC201 in H3K27M - Mutant Diffuse Midline Gliomas Is Driven by Disruption of Integrated Metabolic and Epigenetic Pathways. Cancer Discov 2023;13:2370-93.
10. Jackson ER, Duchatel RJ, Staudt DE, Persson ML, Mannan A, Yadavilli S, et al. ONC201 in combination with paxalisib for the treatment of H3K27-altered diffuse midline glioma. Cancer Res 2023;83:2421-37.