Publications by authors named "Niloufar Zarghami"

8 Publications

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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

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

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

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

Half brain irradiation in a murine model of breast cancer brain metastasis: magnetic resonance imaging and histological assessments of dose-response.

Radiat Oncol 2018 Jun 1;13(1):104. Epub 2018 Jun 1.

Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.

Background: Brain metastasis is becoming increasingly prevalent in breast cancer due to improved extra-cranial disease control. With emerging availability of modern image-guided radiation platforms, mouse models of brain metastases and small animal magnetic resonance imaging (MRI), we examined brain metastases' responses from radiotherapy in the pre-clinical setting. In this study, we employed half brain irradiation to reduce inter-subject variability in metastases dose-response evaluations.

Methods: Half brain irradiation was performed on a micro-CT/RT system in a human breast cancer (MDA-MB-231-BR) brain metastasis mouse model. Radiation induced DNA double stranded breaks in tumors and normal mouse brain tissue were quantified using γ-H2AX immunohistochemistry at 30 min (acute) and 11 days (longitudinal) after half-brain treatment for doses of 8, 16 and 24 Gy. In addition, tumor responses were assessed volumetrically with in-vivo longitudinal MRI and histologically for tumor cell density and nuclear size.

Results: In the acute setting, γ-H2AX staining in tumors saturated at higher doses while normal mouse brain tissue continued to increase linearly in the phosphorylation of H2AX. While γ-H2AX fluorescence intensities returned to the background level in the brain 11 days after treatment, the residual γ-H2AX phosphorylation in the radiated tumors remained elevated compared to un-irradiated contralateral tumors. With radiation, MRI-derived relative tumor growth was significantly reduced compared to the un-irradiated side. While there was no difference in MRI tumor volume growth between 16 and 24 Gy, there was a significant reduction in tumor cell density from histology with increasing dose. In the longitudinal study, nuclear size in the residual tumor cells increased significantly as the radiation dose was increased.

Conclusions: Radiation damages to the DNAs in the normal brain parenchyma are resolved over time, but remain unrepaired in the treated tumors. Furthermore, there is a radiation dose response in nuclear size of surviving tumor cells. Increase in nuclear size together with unrepaired DNA damage indicated that the surviving tumor cells post radiation had continued to progress in the cell cycle with DNA replication, but failed cytokinesis. Half brain irradiation provides efficient evaluation of dose-response for cancer cell lines, a pre-requisite to perform experiments to understand radio-resistance in brain metastases.
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http://dx.doi.org/10.1186/s13014-018-1028-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5984731PMC
June 2018

MRI surveillance of cancer cell fate in a brain metastasis model after early radiotherapy.

Magn Reson Med 2017 10 14;78(4):1506-1512. Epub 2016 Nov 14.

Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada.

Purpose: Incidence of brain metastasis attributed to breast cancer is increasing and prognosis is poor. It is thought that disseminated dormant cancer cells persist in metastatic organs and may evade treatments, thereby facilitating a mechanism for recurrence. Radiotherapy is used to treat brain metastases clinically, but assessment has been limited to macroscopic tumor volumes detectable by clinical imaging. Here, we use cellular MRI to understand the concurrent responses of metastases and nonproliferative or slowly cycling cancer cells to radiotherapy.

Methods: MRI cell tracking was used to investigate the impact of early cranial irradiation on the fate of individual iron-labeled cancer cells and outgrowth of breast cancer brain metastases in the human MDA-MB-231-BR-HER2 cell model.

Results: Early whole-brain radiotherapy significantly reduced the outgrowth of metastases from individual disseminated cancer cells in treated animals compared to controls. However, the numbers of nonproliferative iron-retaining cancer cells in the brain were not significantly different.

Conclusions: Radiotherapy, when given early in cancer progression, is effective in preventing the outgrowth of solitary cancer cells to brain metastases. Future studies of the nonproliferative cancer cells' clonogenic potentials are warranted, given that their persistent presence suggests that they may have evaded treatment. Magn Reson Med 78:1506-1512, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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http://dx.doi.org/10.1002/mrm.26541DOI Listing
October 2017

Evaluating Changes to Blood-Brain Barrier Integrity in Brain Metastasis over Time and after Radiation Treatment.

Transl Oncol 2016 Jun 17;9(3):219-27. Epub 2016 May 17.

Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. Electronic address:

Introduction: The incidence of brain metastasis due to breast cancer is increasing, and prognosis is poor. Treatment is challenging because the blood-brain barrier (BBB) limits efficacy of systemic therapies. In this work, we develop a clinically relevant whole brain radiotherapy (WBRT) plan to investigate the impact of radiation on brain metastasis development and BBB permeability in a murine model. We hypothesize that radiotherapy will decrease tumor burden and increase tumor permeability, which could offer a mechanism to increase drug uptake in brain metastases.

Methods: Contrast-enhanced magnetic resonance imaging (MRI) and high-resolution anatomical MRI were used to evaluate BBB integrity associated with brain metastases due to breast cancer in the MDA-MB-231-BR-HER2 model during their natural development. Novel image-guided microirradiation technology was employed to develop WBRT treatment plans and to investigate if this altered brain metastatic growth or permeability. Histology and immunohistochemistry were performed on whole brain slices corresponding with MRI to validate and further investigate radiological findings.

Results: Herein, we show successful implementation of microirradiation technology that can deliver WBRT to small animals. We further report that WBRT following diagnosis of brain metastasis can mitigate, but not eliminate, tumor growth in the MDA-MB-231-BR-HER2 model. Moreover, radiotherapy did not impact BBB permeability associated with metastases.

Conclusions: Clinically relevant WBRT is not curative when delivered after MRI-detectable tumors have developed in this model. A dose of 20 Gy in 2 fractions was not sufficient to increase tumor permeability such that it could be used as a method to increase systemic drug uptake in brain metastasis.
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http://dx.doi.org/10.1016/j.tranon.2016.04.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4907987PMC
June 2016

Technical Note: Immunohistochemical evaluation of mouse brain irradiation targeting accuracy with 3D-printed immobilization device.

Med Phys 2015 Nov;42(11):6507-13

Department of Physics and Astronomy, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 3K7, Canada; Department of Medical Biophysics, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 3K7, Canada; Department of Oncology, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 3K7, Canada; and London Regional Cancer Program, London Health Sciences Centre, 800 Commissioners Road East, London, Ontario N6A 5W9, Canada.

Purpose: Small animal immobilization devices facilitate positioning of animals for reproducible imaging and accurate focal radiation therapy. In this study, the authors demonstrate the use of three-dimensional (3D) printing technology to fabricate a custom-designed mouse head restraint. The authors evaluate the accuracy of this device for the purpose of mouse brain irradiation.

Methods: A mouse head holder was designed for a microCT couch using cad software and printed in an acrylic based material. Ten mice received half-brain radiation while positioned in the 3D-printed head holder. Animal placement was achieved using on-board image guidance and computerized asymmetric collimators. To evaluate the precision of beam localization for half-brain irradiation, mice were sacrificed approximately 30 min after treatment and brain sections were stained for γ-H2AX, a marker for DNA breaks. The distance and angle of the γ-H2AX radiation beam border to longitudinal fissure were measured on histological samples. Animals were monitored for any possible trauma from the device.

Results: Visualization of the radiation beam on ex vivo brain sections with γ-H2AX immunohistochemical staining showed a sharp radiation field within the tissue. Measurements showed a mean irradiation targeting error of 0.14±0.09 mm (standard deviation). Rotation between the beam axis and mouse head was 1.2°±1.0° (standard deviation). The immobilization device was easily adjusted to accommodate different sizes of mice. No signs of trauma to the mice were observed from the use of tooth block and ear bars.

Conclusions: The authors designed and built a novel 3D-printed mouse head holder with many desired features for accurate and reproducible radiation targeting. The 3D printing technology was found to be practical and economical for producing a small animal imaging and radiation restraint device and allows for customization for study specific needs.
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http://dx.doi.org/10.1118/1.4933200DOI Listing
November 2015
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