Deuterium metabolic imaging differentiates glioblastoma metabolic subtypes and detects early response to chemoradiotherapy

Metabolic subtypes of glioblastoma have different prognoses and responses to treatment. Deuterium metabolic imaging with 2H-labeled substrates is a potential approach to stratify patients into metabolic subtypes for targeted treatment. Here, we used 2H magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) measurements of [6,6'-2H2]glucose metabolism to identify metabolic subtypes and their responses to chemoradiotherapy in patient-derived glioblastoma xenografts in vivo. The metabolism of patient-derived cells was first characterized in vitro by measuring the oxygen consumption rate, a marker of mitochondrial TCA cycle activity, as well as the extracellular acidification rate and 2H-labeled lactate production from [6,6'-2H2]glucose, which are markers of glycolytic activity. Two cell lines representative of a glycolytic subtype and two representative of a mitochondrial subtype were identified. 2H MRS and MRSI measurements showed similar concentrations of 2H-labeled glucose from [6,6'-2H2]glucose in all four tumor models when implanted orthotopically in mice. The glycolytic subtypes showed higher concentrations of 2H-labeled lactate than the mitochondrial subtypes and normal-appearing brain tissue, whereas the mitochondrial subtypes showed more glutamate/glutamine labeling, a surrogate for TCA cycle activity, than the glycolytic subtypes and normal-appearing brain tissue. The response of the tumors to chemoradiation could be detected within 24 hours of treatment completion, with the mitochondrial subtypes showing a decrease in both 2H-labeled glutamate/glutamine and lactate concentrations and glycolytic tumors showing a decrease in 2H-labeled lactate concentration. This technique has the potential to be used clinically for treatment selection and early detection of treatment response.

The role of branched-chain aminotransferase 1 in driving glioblastoma cell proliferation and invasion varies with tumor subtype

Background

Branched-chain aminotransferase 1 (BCAT1) has been proposed to drive proliferation and invasion of isocitrate dehydrogenase (IDH) wild-type glioblastoma cells. However, the Cancer Genome Atlas (TCGA) dataset shows considerable variation in the expression of this enzyme in glioblastoma. The aim of this study was to determine the role of BCAT1 in driving the proliferation and invasion of glioblastoma cells and xenografts that have widely differing levels of BCAT1 expression and the mechanism responsible.

Methods

The activity of BCAT1 was modulated in IDH wild-type patient-derived glioblastoma cell lines, and in orthotopically implanted tumors derived from these cells, to examine the effects of BCAT1 expression on tumor phenotype.

Results

In cells with constitutively high BCAT1 expression and a glycolytic metabolic phenotype, inducible shRNA knockdown of the enzyme resulted in reduced proliferation and invasion by increasing the concentration of α-ketoglutarate, leading to reduced DNA methylation, HIF-1α destabilization, and reduced expression of the transcription factor Forkhead box protein M1 (FOXM1). Conversely, overexpression of the enzyme increased HIF-1α expression and promoted proliferation and invasion. However, in cells with an oxidative phenotype and very low constitutive expression of BCAT1 increased expression of the enzyme had no effect on invasion and reduced cell proliferation. This occurred despite an increase in HIF-1α levels and could be explained by decreased TCA cycle flux.

Conclusions

There is a wide variation in BCAT1 expression in glioblastoma and its role in proliferation and invasion is dependent on tumor subtype.

Comparison of health-related quality of life in patients with traumatic brain injury, subarachnoid haemorrhage and cervical spine disease

PURPOSE

The degree of disability that is acceptable to patients following traumatic brain injury (TBI) continues to be debated. While the dichotomization of outcome on the Glasgow Outcome Score (GOSE) into 'favourable' and 'unfavourable' continues to guide clinical decisions, this may not reflect an individual's subjective experience. The aim of this study is to assess how patients' self-reported quality of life (QoL) relates to objective outcome assessments and how it compares to other debilitating neurosurgical pathologies, including subarachnoid haemorrhage (SAH) and cervical myelopathy.

METHOD

A retrospective analysis of over 1300 patients seen in Addenbrooke's Hospital, Cambridge, UK with TBI, SAH and patients pre- and post- cervical surgery was performed. QoL was assessed using the SF-36 questionnaire. Kruskal-Wallis test was used to analyse the difference in SF-36 domain scores between the four unpaired patient groups. To determine how the point of dichotomization of GOSE into 'favourable' and 'unfavourable' outcome affected QOL, SF-36 scores were compared between GOSE and mRS.

RESULTS

There was a statistically significant difference in the median Physical Component Score (PCS) and Mental Component Score (MCS) of SF-36 between the three neurosurgical pathologies. Patients with TBI and SAH scored higher on most SF-36 domains when compared with cervical myelopathy patients in the severe category. While patients with Upper Severe Disability on GOSE showed significantly higher PC and MC scores compared to GOSE 3, there was a significant degree of variability in individual responses across the groups.

CONCLUSION

A significant number of patients following TBI and SAH have better self-reported QOL than cervical spine patients and patients' subjective perception and expectations following injury do not always correspond to objective disability. These results can guide discussion of treatment and outcomes with patients and families.

Genetic algorithm-based optimization of pulse sequences

PURPOSE

The performance of pulse sequences in vivo can be limited by fast relaxation rates, magnetic field inhomogeneity, and nonuniform spin excitation. We describe here a method for pulse sequence optimization that uses a stochastic numerical solver that in principle is capable of finding a global optimum. The method provides a simple framework for incorporating any constraint and implementing arbitrarily complex cost functions. Efficient methods for simulating spin dynamics and incorporating frequency selectivity are also described.

METHODS

Optimized pulse sequences for polarization transfer between protons and X-nuclei and excitation pulses that eliminate J-coupling modulation were evaluated experimentally using a surface coil on phantoms, and also the detection of hyperpolarized [2-13 C]lactate in vivo in the case of J-coupling modulation-free excitation.

RESULTS

The optimized polarization transfer pulses improved the SNR by ~50% with a more than twofold reduction in the B1 field, and J-coupling modulation-free excitation was achieved with a more than threefold reduction in pulse length.

CONCLUSION

This process could be used to optimize any pulse when there is a need to improve the uniformity and frequency selectivity of excitation as well as to design new pulses to steer the spin system to any desired achievable state.

ILC2-driven innate immune checkpoint mechanism antagonizes NK cell anti-metastatic function in the lung

Metastasis constitutes the primary cause of cancer-related deaths, with the lung being a commonly affected organ. We found that activation of lung-resident group 2 innate lymphoid cells (ILC2s) orchestrated suppression of natural killer (NK) cell-mediated innate antitumor immunity, leading to increased lung metastases and mortality. Using multiple models of lung metastasis, we show that interleukin (IL)-33-dependent ILC2 activation in the lung is involved centrally in promoting tumor burden. ILC2-driven innate type 2 inflammation is accompanied by profound local suppression of interferon-γ production and cytotoxic function of lung NK cells. ILC2-dependent suppression of NK cells is elaborated via an innate regulatory mechanism, which is reliant on IL-5-induced lung eosinophilia, ultimately limiting the metabolic fitness of NK cells. Single-cell and bulk transcriptomic analysis of lung NK cells reveals that post-transcriptional regulation likely accounts for IL-33-ILC2 dependent suppression of NK cell function. Using mass-spectrometry imaging (MSI) of the lungs of 13 C-Glucose infused mice, and metabolite profiling of ex vivo lung cultures, we find that IL-33 drives localized depletion of glucose via ILC2-dependent recruitment of highly glycolytic eosinophils, which can directly suppress lung NK cell function. Therapeutic targeting of IL-33 or IL-5 reversed NK cell suppression and alleviated cancer burden. Thus, we reveal an important function of IL-33 and ILC2s in promoting tumor metastasis via their capacity to suppress innate type 1 immunity.

ILC2-driven innate immune checkpoint mechanism antagonizes NK cell antimetastatic function in the lung

Metastasis constitutes the primary cause of cancer-related deaths, with the lung being a commonly affected organ. We found that activation of lung-resident group 2 innate lymphoid cells (ILC2s) orchestrated suppression of natural killer (NK) cell-mediated innate antitumor immunity, leading to increased lung metastases and mortality. Using multiple models of lung metastasis, we show that interleukin (IL)-33-dependent ILC2 activation in the lung is involved centrally in promoting tumor burden. ILC2-driven innate type 2 inflammation is accompanied by profound local suppression of interferon-γ production and cytotoxic function of lung NK cells. ILC2-dependent suppression of NK cells is elaborated via an innate regulatory mechanism, which is reliant on IL-5-induced lung eosinophilia, ultimately limiting the metabolic fitness of NK cells. Therapeutic targeting of IL-33 or IL-5 reversed NK cell suppression and alleviated cancer burden. Thus, we reveal an important function of IL-33 and ILC2s in promoting tumor metastasis via their capacity to suppress innate type 1 immunity.

CBMT-33. VISUALIZING THE METABOLISM OF GLIOBLASTOMA PATIENT-DERIVED ORTHOTOPIC XENOGRAFTS BY MASS SPECTROMETRY IMAGING

INTRODUCTION. Glioblastoma multiforme (GBM) has a dismal prognosis, which has been attributed to extensive inter- and intra-tumoural heterogeneity. To investigate the metabolic heterogeneity of GBM, we employed desorption electrospray ionization (DESI) imaging on snap frozen samples of GBM patient-derived orthotopic xenografts (PDOX) in rat brains, following infusion of [U-13C]glucose. METHODS. Athymic nude rats (n=3) were infused with [U-13C]glucose (0.4 mg/g body weight bolus, 0.012 mg/g/min at 300 µL/h infusion [1]) for 40, 80 and 120 min, followed by cardiac puncture to measure blood [U-13C]glucose levels using 13C NMR spectroscopy. A second set of rats (n=2) were implanted intracranially with patient-derived GBM cells. The presence of tumour was confirmed by T2-weighted MRI. One animal was infused with [U-13C]glucose for 2 h, while another with [12C]glucose. The brains were snap frozen in liquid nitrogen followed by analysis with DESI imaging in negative ion mode (35 µm resolution). RESULTS. After a 2 h infusion, 43% of the circulating glucose was 13C labelled. Unsupervised spatial clustering of the MSI data resulted in segmentation of normal brain from tumour. Levels of [12C and 13C]glucose were high in the peri-tumoural region and low within the tumour. [12C and 13C]lactate showed the opposite distribution, indicating that the rate of glucose utilization within the tumour exceeded the rate of delivery. The peri-necrotic and peri-tumoural areas had higher levels of glutamate compared to the rest of the tumour. CONCLUSIONS. The results demonstrate that the PDOX is metabolically heterogeneous and differs from surrounding brain. While the tumour was predominately glycolytic, the presence of glutamate in peri-necrotic and peri-tumoral regions indicates the presence of increased TCA cycle activity. Comparison of MSI data with histological staining of brain sections should yield additional information about the relationship between the tumour and its microenvironment.

P42 Predicting bleeding risk during meningioma surgery

Objectives

Surgical treatment of meningioma is frequently accompanied by significant intraoperative blood loss and the associated risks of blood transfusion. Surgical adjuncts such as pre-operative embolisation and the use of tranexamic acid have attendant risks. An ability to estimate blood loss can appropriately target these interventions.

Design

Retrospective study

Subjects

Patients following surgery for meningioma between 2015–2018

Methods

Intraoperative blood loss, pre- to post-operative haemoglobin difference and blood transfusion were evaluated. Pre-operative imaging included size, shape and location of meningioma, involvement of sinuses and blood vessels, T1 and T2 weighted characteristics, restricted diffusion, peritumoral oedema, dural tail and hyperostosis. Multivariate analysis was used to determine the relationship between meningioma characteristics and blood loss.

Results

Tumour diameter and venous sinus opening were significantly related to blood loss on multivariate analysis (p=0.004 and p=0.001 respectively). Furthermore, on univariate analysis additional factors included procedure duration (p<0.0001), pre-operative radiotherapy (p=0.042) and pre-operative platelet count (p=0.03).

Conclusions

Only size of tumour and opening venous sinuses was related to intraoperative bloods loss in this cohort of patients. Further research is required to define tumour characteristics that can be used to identify patients suitable for pre- and intra-operative adjunct therapies.

Cerebral vasospasm and delayed ischaemic deficit following elective aneurysm clipping

Although common after subarachnoid haemorrhage, cerebral vasospasm (CVS) and delayed ischaemic neurological deficit (DIND) rarely occur following elective clipping of unruptured aneurysms. The onset of this complication is variable and its pathophysiology is poorly understood. We report two patients with CVS associated with DIND following unruptured aneurysmal clipping. The literature is reviewed and the potential mechanisms in the context of patient presentations are discussed. A woman aged 53 and a man aged 70 were treated with elective clipping of unruptured middle cerebral artery aneurysms, the older patient also having an anterior communicating artery aneurysm clipped. The operations were uncomplicated with no intra-operative bleeding, no retraction, no contusion, no middle cerebral artery (MCA) temporary clipping, and no intra-operative rupture. Routine post-operative CT scan and CT angiogram showed that in both patients the aneurysms were excluded from the circulation and there was no perioperative subarachnoid blood. Both patients had no neurological deficit post-operatively, but on day 2 developed DIND and vasospasm of the MCA. Both patients had angiographic improvement with intra-arterial verapamil treatment. In one patient, this was done promptly and the patient made a complete recovery, but in the other, the diagnosis was delayed for more than 24hours and the patient had residual hemiparesis and dysphasia due to MCA territory infarction. CVS and DIND following treatment of unruptured aneurysms is a very rare event. However, clinicians should be vigilant as prompt diagnosis and management is required to minimise the risk of cerebral infarction and poor outcome.

ASSESSING THE IMPACT OF A NEWLY INTRODUCED ELECTRONIC PRESCRIBING SYSTEM ACROSS A PAEDIATRIC DEPARTMENT - LESSONS LEARNED

AIM

Prescribing audits have shown that the Women's and Children's Directorate reported higher number of prescription errors on the paediatric and neonatal wards compared to other areas in the Trust. Over the last three years a multidisciplinary prescribing team (PT), which included senior clinicians, pharmacists and trainees introduced a number of initiatives to improve the quality of prescribing. Strategies included structured departmental inductions, setting up of designated prescribing areas and reviewing errors with the prescriber. Year on year there were fewer prescribing errors.1 With the introduction of a new electronic prescribing system in October 2014 prescribing error rates were expected to decrease further, eradicating omissions around allergy recording, ward location and drug names. The aim of this abstract is to highlight the impact of the new system and describe lessons learned.

METHOD

In the summer of 2014, all inpatient drug charts across the department were reviewed on three non-consecutive days over a period of three weeks. Prescribing errors were identified by the ward pharmacist. Errors were grouped according to type and further analyzed by the PT. Errors deemed to have no clinical significance were excluded. Error rates were compared to the previous audits performed with identical methodology. Following the introduction of the electronic prescribing system, the ward pharmacists continued to review prescription charts on daily basis and generate regular error reports to notify the staff of new challenges.

RESULTS

There were 174 (14%) errors out of 1225 prescriptions on 181 drug charts. The most commonly made mistakes included drug name errors, strength of preparation, allergies and ward documentation, prescriber's signature omissions, and antibiotic review and end dates. The introduction of an electronic system has eliminated drug name, strength of preparation, allergy recording and ward errors. However, serious challenges have been identified: entering of an incorrect weight resulted in all drug dosages being inaccurate; the timing of drug levels for Vancomycin and Gentamicin and the administration of subsequent doses have been problematic. Communication difficulties between all staff groups has led to dosage omission, duplicate administration and confusion around start and stop dates. The ability to prescribe away from the bedside and indeed the ward has compounded some of these problems.

CONCLUSION

The implementation of a new electronic system has reduced prescribing errors but has also resulted in new challenges, some with significant patient safety implications. The lessons learned and good practice introduced following previous audits of "traditional paper based" prescribing are equally important with electronic prescribing. Communication between staff groups is crucial. It is likely that the full benefits of the system will be realized a year after its introduction. On-going audit is required to assess the impact and safety of the electronic prescribing and lessons learned.