Publications by authors named "Nicola R Sibson"

90 Publications

Radioimmunotherapy for Brain Metastases: The Potential for Inflammation as a Target of Choice.

Front Oncol 2021 24;11:714514. Epub 2021 Aug 24.

Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, GIP CYCERON, Caen, France.

Brain metastases (BM) are frequently detected during the follow-up of patients with malignant tumors, particularly in those with advanced disease. Despite a major progress in systemic anti-cancer treatments, the average overall survival of these patients remains limited (6 months from diagnosis). Also, cognitive decline is regularly reported especially in patients treated with whole brain external beam radiotherapy (WBRT), due to the absorbed radiation dose in healthy brain tissue. New targeted therapies, for an earlier and/or more specific treatment of the tumor and its microenvironment, are needed. Radioimmunotherapy (RIT), a combination of a radionuclide to a specific antibody, appears to be a promising tool. Inflammation, which is involved in multiple steps, including the early phase, of BM development is attractive as a relevant target for RIT. This review will focus on the (1) early biomarkers of inflammation in BM pertinent for RIT, (2) state of the art studies on RIT for BM, and (3) the importance of dosimetry to RIT in BM. These two last points will be addressed in comparison to the conventional EBRT treatment, particularly with respect to the balance between tumor control and healthy tissue complications. Finally, because new diagnostic imaging techniques show a potential for the detection of BM at an early stage of the disease, we focus particularly on this therapeutic window.
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http://dx.doi.org/10.3389/fonc.2021.714514DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8423367PMC
August 2021

Selective blood-brain barrier permeabilisation of brain metastases by a type-1 receptor selective tumour necrosis factor mutein.

Neuro Oncol 2021 Jul 23. Epub 2021 Jul 23.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.

Background: Metastasis to the brain is a major challenge with poor prognosis. The blood-brain barrier (BBB) is a significant impediment to effective treatment, being intact during the early stages of tumour development and heterogeneously permeable at later stages. Intravenous injection of tumour necrosis factor (TNF) selectively induces BBB permeabilisation at sites of brain micrometastasis, in a TNF type-1 receptor (TNFR1) dependent manner. Here, to enable clinical translation, we have developed a TNFR1-selective agonist variant of human TNF that induces BBB permeabilisation, whilst minimising potential toxicity.

Methods: A library of human TNF muteins (mutTNF) were generated and assessed for binding specificity to mouse and human TNFR1/2, endothelial permeabilising activity in vitro, potential immunogenicity and circulatory half-life. The permeabilising ability of the most promising variant was assessed in vivo in a model of brain metastasis.

Results: The primary mutTNF variant showed similar affinity for human TNFR1 than wild-type human TNF, similar affinity for mouse TNFR1 as wild-type mouse TNF, undetectable binding to human/mouse TNFR2, low potential immunogenicity and permeabilisation of an endothelial monolayer. Circulatory half-life was similar to mouse/human TNF and BBB permeabilisation was induced selectively at sites of micrometastases in vivo, with a time window of ≥24h and enabling delivery of agents within a therapeutically-relevant range (0.5-150kDa), including the clinically approved therapy, trastuzumab.

Conclusions: We have developed a clinically-translatable mutTNF that selectively opens the BBB at micrometastatic sites, whilst leaving the rest of the cerebrovasculature intact. This approach will open a window for brain metastasis treatment that currently does not exist.
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http://dx.doi.org/10.1093/neuonc/noab177DOI Listing
July 2021

Multimodal evaluation of hypoxia in brain metastases of lung cancer and interest of hypoxia image-guided radiotherapy.

Sci Rep 2021 May 27;11(1):11239. Epub 2021 May 27.

Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, GIP CYCERON, 14000, Caen, France.

Lung cancer patients frequently develop brain metastases (BM). Despite aggressive treatment including neurosurgery and external-radiotherapy, overall survival remains poor. There is a pressing need to further characterize factors in the microenvironment of BM that may confer resistance to radiotherapy (RT), such as hypoxia. Here, hypoxia was first evaluated in 28 biopsies from patients with non‑small cell lung cancer (NSCLC) BM, using CA-IX immunostaining. Hypoxia characterization (pimonidazole, CA-IX and HIF-1α) was also performed in different preclinical NSCLC BM models induced either by intracerebral injection of tumor cells (H2030-Br3M, H1915) into the cortex and striatum, or intracardial injection of tumor cells (H2030-Br3M). Additionally, [F]-FMISO-PET and oxygen-saturation-mapping-MRI (SatO2-MRI) were carried out in the intracerebral BM models to further characterize tumor hypoxia and evaluate the potential of Hypoxia-image-guided-RT (HIGRT). The effect of RT on proliferation of BM ([F]-FLT-PET), tumor volume and overall survival was determined. We showed that hypoxia is a major yet heterogeneous feature of BM from lung cancer both preclinically and clinically. HIGRT, based on hypoxia heterogeneity observed between cortical and striatal metastases in the intracerebrally induced models, showed significant potential for tumor control and animal survival. These results collectively highlight hypoxia as a hallmark of BM from lung cancer and the value of HIGRT in better controlling tumor growth.
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http://dx.doi.org/10.1038/s41598-021-90662-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159969PMC
May 2021

Microbubbles Containing Lysolipid Enhance Ultrasound-Mediated Blood-Brain Barrier Breakdown In Vivo.

Adv Healthc Mater 2021 02 16;10(3):e2001343. Epub 2020 Nov 16.

Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, OX3 7DQ, UK.

Ultrasound and microbubbles (MBs) offer a noninvasive method of temporarily enhancing blood-brain barrier (BBB) permeability to therapeutics. To reduce off-target effects, it is desirable to minimize the ultrasound pressures required. It has been shown that a new formulation of MBs containing lysolipids (Lyso-MBs) can increase the cellular uptake of a model drug in vitro. The aim of this study is to investigate whether Lyso-MBs can also enhance BBB permeability in vivo. Female BALB/c mice are injected with either Lyso-MBs or control MBs and gadolinium-DTPA (Gd-DTPA) and exposed to ultrasound (500 kHz, 1 Hz pulse repetition frequency, 1 ms pulse length, peak-negative pressures 160-480 kPa) for 2 min. BBB permeabilization is measured via magnetic resonance imaging (7.0 T) of Gd-DTPA extravasation and subsequent histological examination of brain tissue to assess serum immunoglobulin G (IgG) extravasation (n = 8 per group). An approximately twofold enhancement in BBB permeability is produced by the Lyso-MBs at the highest ultrasound pressure compared with the control. These findings indicate that modifying the composition of phospholipid-shelled MBs has the potential to improve the efficiency of BBB opening, without increasing the ultrasound pressure amplitude required. This is particularly relevant for delivery of therapeutics deep within the brain.
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http://dx.doi.org/10.1002/adhm.202001343DOI Listing
February 2021

A novel molecular magnetic resonance imaging agent targeting activated leukocyte cell adhesion molecule as demonstrated in mouse brain metastasis models.

J Cereb Blood Flow Metab 2021 07 5;41(7):1592-1607. Epub 2020 Nov 5.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.

Molecular magnetic resonance imaging (MRI) allows visualization of biological processes at the molecular level. Upregulation of endothelial ALCAM (activated leukocyte cell adhesion molecule) is a key element for leukocyte recruitment in neurological disease. The aim of this study, therefore, was to develop a novel molecular MRI contrast agent, by conjugating anti-ALCAM antibodies to microparticles of iron oxide (MPIO), for detection of endothelial ALCAM expression . Binding specificity of ALCAM-MPIO was demonstrated under static and flow conditions. Subsequently, in a proof-of-concept study, mouse models of brain metastasis were induced by intracardial injection of brain-tropic human breast carcinoma, lung adenocarcinoma or melanoma cells to upregulate endothelial ALCAM. At selected time-points, mice were injected intravenously with ALCAM-MPIO, and ALCAM-MPIO induced hypointensities were observed on T*-weighted images in all three models. Post-gadolinium MRI confirmed an intact blood-brain barrier, indicating endoluminal binding. Correlation between endothelial ALCAM expression and ALCAM-MPIO binding was confirmed histologically. Statistical analysis indicated high sensitivity (80-90%) and specificity (79-83%) for detection of endothelial ALCAM with ALCAM-MPIO. Given reports of endothelial ALCAM upregulation in numerous neurological diseases, this advance in our ability to image ALCAM may yield substantial improvements for both diagnosis and targeted therapy.
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http://dx.doi.org/10.1177/0271678X20968943DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8217895PMC
July 2021

Study of common quantification methods of amide proton transfer magnetic resonance imaging for ischemic stroke detection.

Magn Reson Med 2021 04 26;85(4):2188-2200. Epub 2020 Oct 26.

Department of Mechatronics and Biomedical Engineering, Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kajang, Selangor, Malaysia.

Purpose: To assess the correlation and differences between common amide proton transfer (APT) quantification methods in the diagnosis of ischemic stroke.

Methods: Five APT quantification methods, including asymmetry analysis and its variants as well as two Lorentzian model-based methods, were applied to data acquired from six rats that underwent middle cerebral artery occlusion scanned at 9.4T. Diffusion and perfusion-weighted images, and water relaxation time maps were also acquired to study the relationship of these conventional imaging modalities with the different APT quantification methods.

Results: The APT ischemic area estimates had varying sizes (Jaccard index: 0.544 ≤ J ≤ 0.971) and had varying correlations in their distributions (Pearson correlation coefficient: 0.104 ≤ r ≤ 0.995), revealing discrepancies in the quantified ischemic areas. The Lorentzian methods produced the highest contrast-to-noise ratios (CNRs; 1.427 ≤ CNR ≤ 2.002), but generated APT ischemic areas that were comparable in size to the cerebral blood flow (CBF) deficit areas; asymmetry analysis and its variants produced APT ischemic areas that were smaller than the CBF deficit areas but larger than the apparent diffusion coefficient deficit areas, though having lower CNRs (0.561 ≤ CNR ≤ 1.083).

Conclusion: There is a need to further investigate the accuracy and correlation of each quantification method with the pathophysiology using a larger scale multi-imaging modality and multi-time-point clinical study. Future studies should include the magnetization transfer ratio asymmetry results alongside the findings of the study to facilitate the comparison of results between different centers and also the published literature.
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http://dx.doi.org/10.1002/mrm.28565DOI Listing
April 2021

STAT3-Mediated Astrocyte Reactivity Associated with Brain Metastasis Contributes to Neurovascular Dysfunction.

Cancer Res 2020 12 26;80(24):5642-5655. Epub 2020 Oct 26.

Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Churchill Hospital, Oxford, United Kingdom.

Astrocytes are thought to play a pivotal role in coupling neural activity and cerebral blood flow. However, it has been shown that astrocytes undergo morphologic changes in response to brain metastasis, switching to a reactive phenotype, which has the potential to significantly compromise cerebrovascular function and contribute to the neurological sequelae associated with brain metastasis. Given that STAT3 is a key regulator of astrocyte reactivity, we aimed here to determine the impact of STAT3-mediated astrocyte reactivity on neurovascular function in brain metastasis. Rat models of brain metastasis and ciliary neurotrophic factor were used to induce astrocyte reactivity. Multimodal imaging, electrophysiology, and IHC were performed to determine the relationship between reactive astrocytes and changes in the cerebrovascular response to electrical and physiological stimuli. Subsequently, the STAT3 pathway in astrocytes was inhibited with WP1066 to determine the role of STAT3-mediated astrocyte reactivity, specifically, in brain metastasis. Astrocyte reactivity associated with brain metastases impaired cerebrovascular responses to stimuli at both the cellular and functional level and disrupted astrocyte-endothelial interactions in both animal models and human brain metastasis samples. Inhibition of STAT3-mediated astrocyte reactivity in rats with brain metastases restored cerebrovascular function, as shown by imaging, and limited cerebrovascular changes associated with tumor growth. Together these findings suggest that inhibiting STAT3-mediated astrocyte reactivity may confer significant improvements in neurological outcome for patients with brain metastases and could potentially be tested in other brain tumors. SIGNIFICANCE: These findings demonstrate that selectively targeting STAT3-mediated astrocyte reactivity ameliorates the cerebrovascular dysfunction associated with brain metastasis, providing a potential therapeutic avenue for improved patient outcome.
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http://dx.doi.org/10.1158/0008-5472.CAN-20-2251DOI Listing
December 2020

Brain Metastasis Cell Lines Panel: A Public Resource of Organotropic Cell Lines.

Cancer Res 2020 10 8;80(20):4314-4323. Epub 2020 Jul 8.

Neurology Clinic and National Center for Tumor Diseases, University Hospital Heidelberg, and Clinical Cooperation Unit Neurooncology, German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.

Spread of cancer to the brain remains an unmet clinical need in spite of the increasing number of cases among patients with lung, breast cancer, and melanoma most notably. Although research on brain metastasis was considered a minor aspect in the past due to its untreatable nature and invariable lethality, nowadays, limited but encouraging examples have questioned this statement, making it more attractive for basic and clinical researchers. Evidences of its own biological identity (i.e., specific microenvironment) and particular therapeutic requirements (i.e., presence of blood-brain barrier, blood-tumor barrier, molecular differences with the primary tumor) are thought to be critical aspects that must be functionally exploited using preclinical models. We present the coordinated effort of 19 laboratories to compile comprehensive information related to brain metastasis experimental models. Each laboratory has provided details on the cancer cell lines they have generated or characterized as being capable of forming metastatic colonies in the brain, as well as principle methodologies of brain metastasis research. The Brain Metastasis Cell Lines Panel (BrMPanel) represents the first of its class and includes information about the cell line, how tropism to the brain was established, and the behavior of each model . These and other aspects described are intended to assist investigators in choosing the most suitable cell line for research on brain metastasis. The main goal of this effort is to facilitate research on this unmet clinical need, to improve models through a collaborative environment, and to promote the exchange of information on these valuable resources.
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http://dx.doi.org/10.1158/0008-5472.CAN-20-0291DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7572582PMC
October 2020

White matter structure and myelin-related gene expression alterations with experience in adult rats.

Prog Neurobiol 2020 04 27;187:101770. Epub 2020 Jan 27.

Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.

White matter (WM) plasticity during adulthood is a recently described phenomenon by which experience can shape brain structure. It has been observed in humans using diffusion tensor imaging (DTI) and myelination has been suggested as a possible mechanism. Here, we set out to identify molecular and cellular changes associated with WM plasticity measured by DTI. We combined DTI, immunohistochemistry and mRNA expression analysis and examined the effects of somatosensory experience in adult rats. First, we observed experience-induced DTI differences in WM and in grey matter structure. C-Fos mRNA expression, a marker of cortical activity, in the barrel cortex correlated with the MRI WM metrics, indicating that molecular correlates of cortical activity relate to macroscale measures of WM structure. Analysis of myelin-related genes revealed higher myelin basic protein (MBP) mRNA expression. Higher MBP protein expression was also found via immunohistochemistry in WM. Finally, unbiased RNA sequencing analysis identified 134 differentially expressed genes encoding proteins involved in functions related to cell proliferation and differentiation, regulation of myelination and neuronal activity modulation. In conclusion, macroscale measures of WM plasticity are supported by both molecular and cellular evidence and confirm that myelination is one of the underlying mechanisms.
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http://dx.doi.org/10.1016/j.pneurobio.2020.101770DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7086231PMC
April 2020

Improving Delineation of True Tumor Volume With Multimodal MRI in a Rat Model of Brain Metastasis.

Int J Radiat Oncol Biol Phys 2020 04 17;106(5):1028-1038. Epub 2020 Jan 17.

Department of Oncology, Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford. Electronic address:

Purpose: Brain metastases are almost universally lethal with short median survival times. Despite this, they are often potentially curable, with therapy failing only because of local relapse. One key reason relapse occurs is because treatment planning did not delineate metastasis margins sufficiently or accurately, allowing residual tumor to regrow. The aim of this study was to determine the extent to which multimodal magnetic resonance imaging (MRI), with a simple and automated analysis pipeline, could improve upon current clinical practice of single-modality, independent-observer tumor delineation.

Methods And Materials: We used a single rat model of brain metastasis (ENU1564 breast carcinoma cells in BD-IX rats), with and without radiation therapy. Multimodal MRI data were acquired using sequences either in current clinical use or in clinical trial and included postgadolinium T-weighted images and maps of blood flow, blood volume, T and T relaxation times, and apparent diffusion coefficient.

Results: In all cases, independent observers underestimated the true size of metastases from single-modality gadolinium-enhanced MRI (85 ± 36 μL vs 131 ± 40 μL histologic measurement), although multimodal MRI more accurately delineated tumor volume (132 ± 41 μL). Multimodal MRI offered increased sensitivity compared with independent observer for detecting metastasis (0.82 vs 0.61, respectively), with only a slight decrease in specificity (0.86 vs 0.98). Blood flow maps conferred the greatest improvements in margin detection for late-stage metastases after radiation therapy. Gadolinium-enhanced T-weighted images conferred the greatest increase in accuracy of detection for smaller metastases.

Conclusions: These findings suggest that multimodal MRI of brain metastases could significantly improve the visualization of brain metastasis margins, beyond current clinical practice, with the potential to decrease relapse rates and increase patient survival. This finding now needs validation in additional tumor models or clinical cohorts.
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http://dx.doi.org/10.1016/j.ijrobp.2019.12.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7082766PMC
April 2020

Improved detection of molecularly targeted iron oxide particles in mouse brain using B field stabilised high resolution MRI.

Magn Reson Imaging 2020 04 11;67:101-108. Epub 2020 Jan 11.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, United Kingdom.

Purpose: High resolution multi-gradient echo (MGE) scanning is typically used for detection of molecularly targeted iron oxide particles. The images of individual echoes are often combined to generate a composite image with improved SNR from the early echoes and boosted contrast from later echoes. In 3D implementations prolonged scanning at high gradient duty cycles induces a B shift that predominantly affects image alignment in the slow phase encoding dimension of 3D MGE images. The effect corrupts the composite echo image and limits the image resolution that is realised. A real-time adaptive B stabilisation during respiration gated 3D MGE scanning is shown to reduce image misalignment and improve detection of molecularly targeted iron oxide particles in composite images of the mouse brain.

Methods: An optional B measurement block consisting of a 16 μs hard pulse with FA 1°, an acquisition delay of 3.2 ms, followed by gradient spoiling in all three axes was added to a respiration gated 3D MGE scan. During the acquisition delay of each B measurement block the NMR signal was routed to a custom built B stabilisation unit which mixed the signal to an audio frequency nominally centred around 1000 Hz to enable an Arduino based single channel receiver to measure frequency shifts. The frequency shift was used to effect correction to the main magnetic field via the B coil. The efficacy of B stabilisation and respiration gating was validated in vivo and used to improve detection of molecularly targeted microparticles of iron oxide (MPIO) in a mouse model of acute neuroinflammation.

Results: Without B stabilisation 3D MGE image data exhibit varying mixtures of translation, scaling and blurring, which compromise the fidelity of the composite image. The real-time adaptive B stabilisation minimises corruption of the composite image as the images from the different echoes are properly aligned. The improved detection of molecularly targeted MPIO easily compensates for the scan time penalty of 14% incurred by the B stabilisation method employed. Respiration gating of the B measurement and the MRI scan was required to preserve high resolution detail, especially towards the back of the brain.

Conclusions: High resolution imaging for the detection of molecularly targeted iron oxide particles in the mouse brain requires good stabilisation of the main B field, and can benefit from a respiration gated image acquisition strategy.
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http://dx.doi.org/10.1016/j.mri.2020.01.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7049896PMC
April 2020

Radionuclide spatial distribution and dose deposition for in vitro assessments of Pb-αVCAM-1 targeted alpha therapy.

Med Phys 2020 Mar 30;47(3):1317-1326. Epub 2020 Jan 30.

CR-UK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.

Purpose: Targeted alpha therapy (TAT) takes advantage of the short-range and high-linear energy transfer of α-particles and is increasingly used, especially for the treatment of metastatic lesions. Nevertheless, dosimetry of α-emitters is challenging for the very same reasons, even for in vitro experiments. Assumptions, such as the uniformity of the distribution of radionuclides in the culture medium, are commonly made, which could have a profound impact on dose calculations. In this study we measured the spatial distribution of α-emitting Pb coupled to an anti-VCAM-1 antibody ( Pb-αVCAM-1) and its evolution over time in the context of in vitro irradiations.

Methods: Two experimental setups were implemented without cells to measure α-particle count rates and energy spectra in culture medium containing 15 kBq of Pb-α-VCAM-1. Silicon detectors were placed above and below cell culture dishes for 20 h. One of the dishes had a 2.5-µm-thick mylar-base allowing easy detection of the α-particles. Monte Carlo simulations were performed to analyze experimental spectra. Experimental setups were modeled and α-energy spectra were simulated in the silicon detectors for different decay positions in the culture medium. Simulated spectra were then used to deconvolute experimental spectra to determine the spatial distribution of Pb-αVCAM-1 in the medium. This distribution was finally used to calculate the dose deposition in cell culture experiments.

Results: Experimental count rates and energy spectra showed differences in measurements taken at the top and the bottom of dishes and temporal variations that did not follow Pb decay. The radionuclide spatial distribution was shown to be composed of a uniform distribution and concentration gradients at the top and the bottom, which were subjected to temporal variations that may be explained by gravity and electrostatic attraction. The absorbed dose in cells calculated from this distribution was compared with the dose expected for a uniform and static distribution and found to be 1.75 times higher, which is highly significant to interpret biological observations.

Conclusions: This study demonstrated that accurate dosimetry of α-emitters requires the experimental determination of radionuclide spatial and temporal distribution and highlighted that in vitro assessment of dose for TAT cannot only rely on a uniform distribution of activity in the culture medium. The reliability and reproducibility of future experiments should benefit from specifically developed dosimetry tools and methods.
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http://dx.doi.org/10.1002/mp.13969DOI Listing
March 2020

Extracellular vesicle integrins act as a nexus for platelet adhesion in cerebral microvessels.

Sci Rep 2019 11 1;9(1):15847. Epub 2019 Nov 1.

Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, United Kingdom.

Circulating extracellular vesicles (EVs) regulate signaling pathways via receptor-ligand interactions and content delivery, after attachment or internalization by endothelial cells. However, they originate from diverse cell populations and are heterogeneous in composition. To determine the effects of specific surface molecules, the use of synthetic EV mimetics permits the study of specific EV receptor-ligand interactions. Here, we used endogenous EVs derived from the circulation of rats, as well as ligand-decorated synthetic microparticles (MPs) to examine the role of integrin αvβ3 in platelet adhesion under flow in structurally intact cerebral arteries. At an intraluminal pressure of 50 mmHg and flow rate of 10 µl/min, platelets were delivered to the artery lumen and imaged with whole-field fluorescent microscopy. Under basal conditions very few platelets bound to the endothelium. However, adhesion events were markedly increased following the introduction of arginine-glycine-aspartate (RGD)-labelled synthetic MPs or endogenously-derived EVs from experimental stroke animals carrying excess RGD proteins, including vitronectin, CD40-ligand and thrombospondin-1. These data, which were generated in a dynamic and physiologically relevant system, demonstrate the importance of vesicle-carried RGD ligands in platelet adherence to the cerebrovascular endothelium and highlight the ability of synthetic EVs to isolate and identify key components of the molecular handshake between EVs and their targets.
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http://dx.doi.org/10.1038/s41598-019-52127-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6825169PMC
November 2019

VCAM-1 targeted alpha-particle therapy for early brain metastases.

Neuro Oncol 2020 03;22(3):357-368

Normandie University, UNICAEN, CEA, CNRS, ISTCT/CERVOxy group, GIP CYCERON, Caen, France.

Background: Brain metastases (BM) develop frequently in patients with breast cancer. Despite the use of external beam radiotherapy (EBRT), the average overall survival is short (6 months from diagnosis). The therapeutic challenge is to deliver molecularly targeted therapy at an early stage when relatively few metastatic tumor cells have invaded the brain. Vascular cell adhesion molecule 1 (VCAM-1), overexpressed by nearby endothelial cells during the early stages of BM development, is a promising target. The aim of this study was to investigate the therapeutic value of targeted alpha-particle radiotherapy, combining lead-212 (212Pb) with an anti-VCAM-1 antibody (212Pb-αVCAM-1).

Methods: Human breast carcinoma cells that metastasize to the brain, MDA-231-Br-GFP, were injected into the left cardiac ventricle of nude mice. Twenty-one days after injection, 212Pb-αVCAM-1 uptake in early BM was determined in a biodistribution study and systemic/brain toxicity was evaluated. Therapeutic efficacy was assessed using MR imaging and histology. Overall survival after 212Pb-αVCAM-1 treatment was compared with that observed after standard EBRT.

Results: 212Pb-αVCAM-1 was taken up into early BM with a tumor/healthy brain dose deposition ratio of 6 (5.52e108 and 0.92e108) disintegrations per gram of BM and healthy tissue, respectively. MRI analyses showed a statistically significant reduction in metastatic burden after 212Pb-αVCAM-1 treatment compared with EBRT (P < 0.001), translating to an increase in overall survival of 29% at 40 days post prescription (P < 0.01). No major toxicity was observed.

Conclusions: The present investigation demonstrates that 212Pb-αVCAM-1 specifically accumulates at sites of early BM causing tumor growth inhibition.
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http://dx.doi.org/10.1093/neuonc/noz169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7162423PMC
March 2020

Imaging of translocator protein upregulation is selective for pro-inflammatory polarized astrocytes and microglia.

Glia 2020 02 3;68(2):280-297. Epub 2019 Sep 3.

Department of Oncology, Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK.

Translocator protein (TSPO) expression is increased in activated glia, and has been used as a marker of neuroinflammation in PET imaging. However, the extent to which TSPO upregulation reflects a pro- or anti-inflammatory phenotype remains unclear. Our aim was to determine whether TSPO upregulation in astrocytes and microglia/macrophages is limited to a specific inflammatory phenotype. TSPO upregulation was assessed by flow cytometry in cultured astrocytes, microglia, and macrophages stimulated with lipopolysaccharide (LPS), tumor necrosis factor (TNF), or interleukin-4 (Il-4). Subsequently, mice were injected intracerebrally with either a TNF-inducing adenovirus (AdTNF) or IL-4. Glial expression of TSPO and pro-/anti-inflammatory markers was assessed by immunohistochemistry/fluorescence and flow cytometry. Finally, AdTNF or IL-4 injected mice underwent PET imaging with injection of the TSPO radioligand F-DPA-713, followed by ex vivo autoradiography. TSPO expression was significantly increased in pro-inflammatory microglia/macrophages and astrocytes both in vitro, and in vivo after AdTNF injection (p < .001 vs. control hemisphere), determined both histologically and by FACS. Both PET imaging and autoradiography revealed a significant (p < .001) increase in F-DPA-713 binding in the ipsilateral hemisphere of AdTNF-injected mice. In contrast, no increase in either TSPO expression assessed histologically and by FACS, or ligand binding by PET/autoradiography was observed after IL-4 injection. Taken together, these results suggest that TSPO imaging specifically reveals the pro-inflammatory population of activated glial cells in the brain in response to inflammatory stimuli. Since the inflammatory phenotype of glial cells is critical to their role in neurological disease, these findings may enhance the utility and application of TSPO imaging.
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http://dx.doi.org/10.1002/glia.23716DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6916298PMC
February 2020

Development of Therapeutic Anti-JAGGED1 Antibodies for Cancer Therapy.

Mol Cancer Ther 2019 11 8;18(11):2030-2042. Epub 2019 Aug 8.

NDCLS, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom.

The role of Notch signaling and its ligand JAGGED1 (JAG1) in tumor biology has been firmly established, making them appealing therapeutic targets for cancer treatment. Here, we report the development and characterization of human/rat-specific JAG1-neutralizing mAbs. Epitope mapping identified their binding to the Notch receptor interaction site within the JAG1 Delta/Serrate/Lag2 domain, where E228D substitution prevented effective binding to the murine Jag1 ortholog. These antibodies were able to specifically inhibit JAG1-Notch binding , downregulate Notch signaling in cancer cells, and block the heterotypic JAG1-mediated Notch signaling between endothelial and vascular smooth muscle cells. Functionally, treatment impaired three-dimensional growth of breast cancer cell spheroids, in association with a reduction in cancer stem cell number. testing showed variable effects on human xenograft growth when only tumor-expressed JAG1 was targeted (mouse models) but a more robust effect when stromal-expressed Jag1 was also targeted (rat MDA-MB-231 xenograft model). Importantly, treatment of established triple receptor-negative breast cancer brain metastasis in rats showed a significant reduction in neoplastic growth. MRI imaging demonstrated that this was associated with a substantial improvement in blood-brain barrier function and tumor perfusion. Lastly, JAG1-targeting antibody treatment did not cause any detectable toxicity, further supporting its clinical potential for cancer therapy.
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http://dx.doi.org/10.1158/1535-7163.MCT-18-1176DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7611158PMC
November 2019

Tumor pH and Protein Concentration Contribute to the Signal of Amide Proton Transfer Magnetic Resonance Imaging.

Cancer Res 2019 04 24;79(7):1343-1352. Epub 2019 Jan 24.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, United Kingdom.

Abnormal pH is a common feature of malignant tumors and has been associated clinically with suboptimal outcomes. Amide proton transfer magnetic resonance imaging (APT MRI) holds promise as a means to noninvasively measure tumor pH, yet multiple factors collectively make quantification of tumor pH from APT MRI data challenging. The purpose of this study was to improve our understanding of the biophysical sources of altered APT MRI signals in tumors. Combining APT MRI measurements with histological measurements of protein concentration in a rat model of brain metastasis, we determined that the proportion of APT MRI signal originating from changes in protein concentration was approximately 66%, with the remaining 34% originating from changes in tumor pH. In a mouse model of hypopharyngeal squamous cell carcinoma (FaDu), APT MRI showed that a reduction in tumor hypoxia was associated with a shift in tumor pH. The results of this study extend our understanding of APT MRI data and may enable the use of APT MRI to infer the pH of individual patients' tumors as either a biomarker for therapy stratification or as a measure of therapeutic response in clinical settings. SIGNIFICANCE: These findings advance our understanding of amide proton transfer magnetic resonance imaging (APT MRI) of tumors and may improve the interpretation of APT MRI in clinical settings.
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http://dx.doi.org/10.1158/0008-5472.CAN-18-2168DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6462213PMC
April 2019

Sensitivity of Multiphase Pseudocontinuous Arterial Spin Labelling (MP pCASL) Magnetic Resonance Imaging for Measuring Brain and Tumour Blood Flow in Mice.

Contrast Media Mol Imaging 2018 7;2018:4580919. Epub 2018 Nov 7.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, OX3 7LE, Oxford, UK.

Brain and tumour blood flow can be measured noninvasively using arterial spin labelling (ASL) magnetic resonance imaging (MRI), but reliable quantification in mouse models remains difficult. Pseudocontinuous ASL (pCASL) is recommended as the clinical standard for ASL and can be improved using multiphase labelling (MP pCASL). The aim of this study was to optimise and validate MP pCASL MRI for cerebral blood flow (CBF) measurement in mice and to assess its sensitivity to tumour perfusion. Following optimization of the MP pCASL sequence, CBF data were compared with gold-standard autoradiography, showing close agreement. Subsequently, MP pCASL data were acquired at weekly intervals in models of primary and secondary brain tumours, and tumour microvessel density was determined histologically. MP pCASL measurements in a secondary brain tumour model revealed a significant reduction in blood flow at day 35 after induction, despite a higher density of blood vessels. Tumour core regions also showed reduced blood flow compared with the tumour rim. Similarly, significant reductions in CBF were found in a model of glioma 28 days after tumour induction, together with an increased density of blood vessels. These findings indicate that MP pCASL MRI provides accurate and robust measurements of cerebral blood flow in naïve mice and is sensitive to changes in tumour perfusion.
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http://dx.doi.org/10.1155/2018/4580919DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6247770PMC
May 2019

The Multifarious Role of Microglia in Brain Metastasis.

Front Cell Neurosci 2018 12;12:414. Epub 2018 Nov 12.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, United Kingdom.

The immune landscape in brain metastasis is a very heterogeneous framework. Amongst a broad plethora of cells within the tumor microenvironment, the presence of activated microglia has been perfectly described. The innate role of microglial cells is to detect and eliminate any insults that may disturb the regular behavior of the brain. As part of its defensive role, it releases pro- and anti-inflammatory cytokines that aim to modulate the inflammatory scenario at the metastatic . However, the long term effects that these cells may exert on the metastatic progression is not clear. One of the biggest challenges in the field is to distinguish between brain resident microglial cells and infiltrated bone-marrow derived macrophages. Part of this issue is the fact that both cell types share similar phenotypes. Current studies are based on the modulation of the immune response against cancer cells (immunotherapy). However, most of current clinical trials and newly developed drugs focus on the adaptive immune response (e.g., immune blockade check-points). Additionally, the unique structure of the central nervous system with the presence of the blood-brain barrier have hindered a significant advance in novel therapies against brain metastasis. In this manuscript, we describe current advances in characterization of tumor-associated microglia and macrophages, the importance of microglia during the anti-cancerous response, and the future direction for the development of new strategies against this complex disease.
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http://dx.doi.org/10.3389/fncel.2018.00414DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6240594PMC
November 2018

Dy-DOTA integrated mesoporous silica nanoparticles as promising ultrahigh field magnetic resonance imaging contrast agents.

Nanoscale 2018 Dec 14;10(45):21041-21045. Epub 2018 Nov 14.

Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.

Integrating Dy-DOTA motifs into mesoporous silica nanoparticle scaffolds generates remarkable ultrahigh field T relaxivities for a well-defined and tailorable contrast agent, attributed to enhanced Curie outer-sphere contributions as supported by simulation.
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http://dx.doi.org/10.1039/c8nr07198eDOI Listing
December 2018

VCAM-1-targeted MRI Enables Detection of Brain Micrometastases from Different Primary Tumors.

Clin Cancer Res 2019 01 2;25(2):533-543. Epub 2018 Nov 2.

Department of Oncology, Cancer Research UK and Medical Research Council, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom.

Purpose: A major issue for the effective treatment of brain metastasis is the late stage of diagnosis with existing clinical tools. The aim of this study was to evaluate the potential of vascular cell adhesion molecule 1 (VCAM-1)-targeted MRI for early detection of brain micrometastases in mouse models across multiple primary tumor types. Xenograft models of brain micrometastasis for human breast carcinoma (MDA231Br-GFP), lung adenocarcinoma (SEBTA-001), and melanoma (H1_DL2) were established via intracardiac injection in mice. Animals ( = 5-6/group) were injected intravenously with VCAM-1-targeted microparticles of iron oxide (VCAM-MPIO) and, subsequently, underwent *-weighted MRI. Control groups of naïve mice injected with VCAM-MPIO and tumor-bearing mice injected with nontargeting IgG-MPIO were included.

Results: All models showed disseminated micrometastases in the brain, together with endothelial VCAM-1 upregulation across the time course. *-weighted MRI of all tumor-bearing mice injected with VCAM-MPIO showed significantly more signal hypointensities ( < 0.001; two-sided) than control cohorts, despite a lack of blood-brain barrier (BBB) impairment. Specific MPIO binding to VCAM-1-positive tumor-associated vessels was confirmed histologically. VCAM-1 expression was demonstrated in human brain metastasis samples, across all three primary tumor types.

Conclusions: VCAM-1-targeted MRI enables the detection of brain micrometastases from the three primary tumor types known to cause the majority of clinical cases. These findings represent an important step forward in the development of a broadly applicable and clinically relevant imaging technique for early diagnosis of brain metastasis, with significant implications for improved patient survival.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-1889DOI Listing
January 2019

Optimization of molecularly targeted MRI in the brain: empirical comparison of sequences and particles.

Int J Nanomedicine 2018 25;13:4345-4359. Epub 2018 Jul 25.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK,

Background: Molecular MRI is an evolving field of research with strong translational potential. Selection of the appropriate MRI sequence, field strength and contrast agent depend largely on the application. The primary aims of the current study were to: 1) assess the sensitivity of different MRI sequences for detection of iron oxide particles in mouse brain; 2) determine the effect of magnetic field strength on detection of iron oxide particles in vivo; and 3) compare the sensitivity of targeted microparticles of iron oxide (MPIO) or ultra-small superparamagnetic iron oxide (USPIO) for detection of vascular cell adhesion molecule-1 (VCAM-1) in vivo.

Methods: Mice were injected intrastriatally with interleukin 1β to induce VCAM-1 expression on the cerebral vasculature. Subsequently, animals were injected intravenously with either VCAM-MPIO or VCAM-USPIO and imaged 1 or 13 hours post-injection, respectively. MRI was performed at 4.7, 7.0, or 9.4 T, using three different *-weighted sequences: single gradient echo 3D (GE3D), multi-gradient echo 3D (MGE3D) and balanced steady-state free precession 3D (bSSFP3D).

Results: MGE3D yielded the highest signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for the detection of iron oxide particles. All sequences showed a significant increase in SNR and CNR from 4.7 to 7.0 T, but no further improvement at 9.4 T. However, whilst targeted MPIO enabled sensitive detection of VCAM-1 expression on the cerebral vasculature, the long half-life (16.5 h vs 1.2 min) and lower relaxivity per particle (1.29×10 vs 1.18×10 Hz L/particle) of USPIO vs. MPIO rendered them impractical for molecular MRI.

Conclusion: These findings demonstrate clear advantages of MPIO compared to USPIO for molecularly-targeted MRI, and indicate that the MGE3D sequence is optimal for MPIO detection. Moreover, higher field strengths (7.0/9.4 T) showed enhanced sensitivity over lower field strengths (4.7 T). With the development of biodegradable MPIO, these agents hold promise for clinical translation.
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http://dx.doi.org/10.2147/IJN.S158071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6064157PMC
September 2018

What is special about the human arcuate fasciculus? Lateralization, projections, and expansion.

Cortex 2019 09 12;118:107-115. Epub 2018 May 12.

Wellcome Centre for Integrative Neuroimaging, Centre for Functional MRI of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom; Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, the Netherlands.

Evolutionary adaptations of the human brain are the basis for our unique abilities such as language. An expansion of the arcuate fasciculus (AF), the dorsal language tract, in the human lineage involving left lateralization is considered canonical, but this hypothesis has not been tested in relation to other architectural adaptations in the human brain. Using diffusion-weighted MRI, we examined AF in the human and macaque and quantified species differences in white matter architecture and surface representations. To compare surface results in the two species, we transformed macaque representations to human space using a landmark-based monkey-to-human cortical expansion model. We found that the human dorsal AF, but not the ventral inferior fronto-occipital fasciculus (IFO), is left-lateralized. In the monkey AF is not lateralized. Moreover, compared to the macaque, human AF is relatively increased with respect to IFO. A comparison of human and transformed macaque surface representations suggests that cortical expansion alone cannot account for the species differences in the surface representation of AF. Our results show that the human AF has undergone critical anatomical modifications in comparison with the macaque AF. More generally, this work demonstrates that studies on the human brain specializations underlying the language connectome can benefit from current methodological advances in comparative neuroanatomy.
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http://dx.doi.org/10.1016/j.cortex.2018.05.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6699597PMC
September 2019

Quantitative blood flow measurement in rat brain with multiphase arterial spin labelling magnetic resonance imaging.

J Cereb Blood Flow Metab 2019 08 2;39(8):1557-1569. Epub 2018 Mar 2.

1 Department of Oncology, Cancer Research UK & Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK.

Cerebral blood flow is an important parameter in many diseases and functional studies that can be accurately measured in humans using arterial spin labelling (ASL) MRI. However, although rat models are frequently used for preclinical studies of both human disease and brain function, rat CBF measurements show poor consistency between studies. This lack of reproducibility is due, partly, to the smaller size and differing head geometry of rats compared to humans, as well as the differing analysis methodologies employed and higher field strengths used for preclinical MRI. To address these issues, we have implemented, optimised and validated a multiphase pseudo-continuous ASL technique, which overcomes many of the limitations of rat CBF measurement. Three rat strains (Wistar, Sprague Dawley and Berlin Druckrey IX) were used, and CBF values validated against gold-standard autoradiography measurements. Label positioning was found to be optimal at 45°, while post-label delay was optimised to 0.55 s. Whole brain CBF measures were 109 ± 22, 111 ± 18 and 100 ± 15 mL/100 g/min by multiphase pCASL, and 108 ± 12, 116 ± 14 and 122 ± 16 mL/100 g/min by autoradiography in Wistar, SD and BDIX cohorts, respectively. Tumour model analysis shows that the developed methods also apply in disease states. Thus, optimised multiphase pCASL provides robust, reproducible and non-invasive measurement of CBF in rats.
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http://dx.doi.org/10.1177/0271678X18756218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6681434PMC
August 2019

Dosimetric evaluation of radionuclides for VCAM-1-targeted radionuclide therapy of early brain metastases.

Theranostics 2018 1;8(1):292-303. Epub 2018 Jan 1.

CR-UK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, United Kingdom.

Brain metastases develop frequently in patients with breast cancer, and present a pressing therapeutic challenge. Expression of vascular cell adhesion molecule 1 (VCAM-1) is upregulated on brain endothelial cells during the early stages of metastasis and provides a target for the detection and treatment of early brain metastases. The aim of this study was to use a model of early brain metastasis to evaluate the efficacy of α-emitting radionuclides, Tb, At, Pb, Bi and Ac; β-emitting radionuclides, Y, Tb and Lu; and Auger electron (AE)-emitters Ga, Zr, In and I, for targeted radionuclide therapy (TRT).

Methods: Histologic sections and two photon microscopy of mouse brain parenchyma were used to inform a cylindrical vessel geometry using the Geant4 general purpose Monte Carlo (MC) toolkit with the Geant4-DNA low energy physics models. Energy deposition was evaluated as a radial function and the resulting phase spaces were superimposed on a DNA model to estimate double-strand break (DSB) yields for representative β- and α-emitters, Lu and Pb. Relative biological effectiveness (RBE) values were determined by only evaluating DNA damage due to physical interactions.

Results: Lu produced 2.69 ± 0.08 DSB per GbpGy, without significant variation from the lumen of the vessel to a radius of 100 µm. The DSB yield of Pb included two local maxima produced by the 6.1 MeV and 8.8 MeV α-emissions from decay products, Bi and Po, with yields of 7.64 ± 0.12 and 9.15 ± 0.24 per GbpGy, respectively. Given its higher DSB yield Pb may be more effective for short range targeting of early micrometastatic lesions than Lu.

Conclusion: MC simulation of a model of early brain metastases provides invaluable insight into the potential efficacy of α-, β- and AE-emitting radionuclides for TRT. Pb, which has the attributes of a theranostic radionuclide since it can be used for SPECT imaging, showed a favorable dose profile and RBE.
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http://dx.doi.org/10.7150/thno.22217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5743475PMC
November 2018

Metabolomics reveals distinct, antibody-independent, molecular signatures of MS, AQP4-antibody and MOG-antibody disease.

Acta Neuropathol Commun 2017 Dec 6;5(1):95. Epub 2017 Dec 6.

Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Level 3, West Wing, Headley Way, Oxford, OX3 9DU, UK.

The overlapping clinical features of relapsing remitting multiple sclerosis (RRMS), aquaporin-4 (AQP4)-antibody (Ab) neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein (MOG)-Ab disease mean that detection of disease specific serum antibodies is the gold standard in diagnostics. However, antibody levels are not prognostic and may become undetectable after treatment or during remission. Therefore, there is still a need to discover antibody-independent biomarkers. We sought to discover whether plasma metabolic profiling could provide biomarkers of these three diseases and explore if the metabolic differences are independent of antibody titre. Plasma samples from 108 patients (34 RRMS, 54 AQP4-Ab NMOSD, and 20 MOG-Ab disease) were analysed by nuclear magnetic resonance spectroscopy followed by lipoprotein profiling. Orthogonal partial-least squares discriminatory analysis (OPLS-DA) was used to identify significant differences in the plasma metabolite concentrations and produce models (mathematical algorithms) capable of identifying these diseases. In all instances, the models were highly discriminatory, with a distinct metabolite pattern identified for each disease. In addition, OPLS-DA identified AQP4-Ab NMOSD patient samples with low/undetectable antibody levels with an accuracy of 92%. The AQP4-Ab NMOSD metabolic profile was characterised by decreased levels of scyllo-inositol and small high density lipoprotein particles along with an increase in large low density lipoprotein particles relative to both RRMS and MOG-Ab disease. RRMS plasma exhibited increased histidine and glucose, along with decreased lactate, alanine, and large high density lipoproteins while MOG-Ab disease plasma was defined by increases in formate and leucine coupled with decreased myo-inositol. Despite overlap in clinical measures in these three diseases, the distinct plasma metabolic patterns support their distinct serological profiles and confirm that these conditions are indeed different at a molecular level. The metabolites identified provide a molecular signature of each condition which is independent of antibody titre and EDSS, with potential use for disease monitoring and diagnosis.
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http://dx.doi.org/10.1186/s40478-017-0495-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5718082PMC
December 2017

Anti-inflammatory Microglia/Macrophages As a Potential Therapeutic Target in Brain Metastasis.

Front Oncol 2017 30;7:251. Epub 2017 Oct 30.

Department of Oncology, Cancer Research UK and Medical Research Council, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom.

Brain metastasis is a common complication of cancer patients and is associated with poor survival. Histological data from patients with brain metastases suggest that microglia are the major immune population activated around the metastatic foci. Microglia and macrophages have the ability to polarize to different phenotypes and to exert both tumorigenic and cytotoxic effects. However, the role of microglia/macrophages during the early stages of metastatic growth in the brain has not yet been determined. The aim of this study was to profile microglial/macrophage activation in a mouse model of breast cancer brain metastasis during the early stages of tumor growth, and to assess the role of the anti-inflammatory microglial/macrophage population, specifically, during this phase. Following intracerebral injection of 5 × 10 4T1-GFP mammary carcinoma cells into female BALB/c mice, robust microglial/macrophage activation around the 4T1 metastatic foci was evident throughout the time-course studied (28 days) and correlated positively with tumor volume ( = 0.67). Populations of classically (proinflammatory) and alternatively (anti-inflammatory) activated microglia/macrophages were identified immunohistochemically by expression of either induced nitric oxide synthase/cyclooxygenase 2 or mannose receptor 1/arginase 1, respectively. Temporally, levels of both pro- and anti-inflammatory cells were broadly stable across the time-course. Subsequently, selective depletion of the anti-inflammatory microglia/macrophage population by intracerebral injection of mannosylated clodronate liposomes significantly reduced metastatic tumor burden ( < 0.01). Moreover, increased levels of apoptosis were associated with tumors in clodronate liposome treated animals compared to controls ( < 0.05). These findings suggest that microglia/macrophages are important effectors of the inflammatory response in the early stages of brain metastasis, and that targeting the anti-inflammatory microglial/macrophage population may offer an effective new therapeutic avenue for patients with brain metastases.
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http://dx.doi.org/10.3389/fonc.2017.00251DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5670100PMC
October 2017

Covalent assembly of nanoparticles as a peptidase-degradable platform for molecular MRI.

Nat Commun 2017 02 15;8:14254. Epub 2017 Feb 15.

Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK.

Ligand-conjugated microparticles of iron oxide (MPIO) have the potential to provide high sensitivity contrast for molecular magnetic resonance imaging (MRI). However, the accumulation and persistence of non-biodegradable micron-sized particles in liver and spleen precludes their clinical use and limits the translational potential of MPIO-based contrast agents. Here we show that ligand-targeted MPIO derived from multiple iron oxide nanoparticles may be coupled covalently through peptide linkers that are designed to be cleaved by intracellular macrophage proteases. The synthesized particles possess potential characteristics for targeted MRI contrast agents, including high relaxivity, unappreciable sedimentation, clearance from circulation and no overt toxicity. Importantly, we demonstrate that these particles are rapidly degraded both in vitro and in vivo, and that the targeted probes can be used for detection of inflammation in vivo using MRI. This approach provides a platform for molecular MRI contrast agents that is potentially more suitable for translation to humans.
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http://dx.doi.org/10.1038/ncomms14254DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5316865PMC
February 2017

A Critical Role for Astrocytes in Hypercapnic Vasodilation in Brain.

J Neurosci 2017 03 30;37(9):2403-2414. Epub 2017 Jan 30.

Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada,

Cerebral blood flow (CBF) is controlled by arterial blood pressure, arterial CO, arterial O, and brain activity and is largely constant in the awake state. Although small changes in arterial CO are particularly potent to change CBF (1 mmHg variation in arterial CO changes CBF by 3%-4%), the coupling mechanism is incompletely understood. We tested the hypothesis that astrocytic prostaglandin E (PgE) plays a key role for cerebrovascular CO reactivity, and that preserved synthesis of glutathione is essential for the full development of this response. We combined two-photon imaging microscopy in brain slices with work in rats and C57BL/6J mice to examine the hemodynamic responses to CO and somatosensory stimulation before and after inhibition of astrocytic glutathione and PgE synthesis. We demonstrate that hypercapnia (increased CO) evokes an increase in astrocyte [Ca] and stimulates COX-1 activity. The enzyme downstream of COX-1 that synthesizes PgE (microsomal prostaglandin E synthase-1) depends critically for its vasodilator activity on the level of glutathione in the brain. We show that, when glutathione levels are reduced, astrocyte calcium-evoked release of PgE is decreased and vasodilation triggered by increased astrocyte [Ca] and by hypercapnia is inhibited. Astrocyte synthetic pathways, dependent on glutathione, are involved in cerebrovascular reactivity to CO Reductions in glutathione levels in aging, stroke, or schizophrenia could lead to dysfunctional regulation of CBF and subsequent neuronal damage. Neuronal activity leads to the generation of CO, which has previously been shown to evoke cerebral blood flow (CBF) increases via the release of the vasodilator PgE We demonstrate that hypercapnia (increased CO) evokes increases in astrocyte calcium signaling, which in turn stimulates COX-1 activity and generates downstream PgE production. We demonstrate that astrocyte calcium-evoked production of the vasodilator PgE is critically dependent on brain levels of the antioxidant glutathione. These data suggest a novel role for astrocytes in the regulation of CO-evoked CBF responses. Furthermore, these results suggest that depleted glutathione levels, which occur in aging and stroke, will give rise to dysfunctional CBF regulation and may result in subsequent neuronal damage.
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http://dx.doi.org/10.1523/JNEUROSCI.0005-16.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5354350PMC
March 2017

Early Diagnosis of Brain Metastases Using a Biofluids-Metabolomics Approach in Mice.

Theranostics 2016 12;6(12):2161-2169. Epub 2016 Sep 12.

Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.

Over 20% of cancer patients will develop brain metastases. Prognosis is currently extremely poor, largely owing to late-stage diagnosis. We hypothesized that biofluid metabolomics could detect tumours at the micrometastatic stage, prior to the current clinical gold-standard of blood-brain barrier breakdown. Metastatic mammary carcinoma cells (4T1-GFP) were injected into BALB/c mice via intracerebral, intracardiac or intravenous routes to induce differing cerebral and systemic tumour burdens. B16F10 melanoma and MDA231BR-GFP human breast carcinoma cells were used for additional modelling. Urine metabolite composition was analysed by H NMR spectroscopy. Statistical pattern recognition and modelling was applied to identify differences or commonalities indicative of brain metastasis burden. Significant metabolic profile separations were found between control cohorts and animals with tumour burdens at all time-points for the intracerebral 4T1-GFP time-course. Models became stronger, with higher sensitivity and specificity, as the time-course progressed indicating a more severe tumour burden. Sensitivity and specificity for predicting a blinded testing set were 0.89 and 0.82, respectively, at day 5, both rising to 1.00 at day 35. Significant separations were also found between control and all 4T1-GFP injected mice irrespective of route. Likewise, significant separations were observed in B16F10 and MDA231BR-GFP cell line models. Metabolites underpinning each separation were identified These findings demonstrate that brain metastases can be diagnosed in an animal model based on urinary metabolomics from micrometastatic stages. Furthermore, it is possible to separate differing systemic and CNS tumour burdens, suggesting a metabolite fingerprint specific to brain metastasis. This method has strong potential for clinical translation.
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http://dx.doi.org/10.7150/thno.16538DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5135440PMC
October 2017
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