An MRI Investigation of the Effect of Active Site Mutant DDAH1 in C6 Glioma Xenografts in Vivo
Jessica Katherine Rowena Boult¹, Simon Walker-Samuel¹, Yann Jamin¹, James M. Leiper², Guy St.John Whitley³, Simon P. Robinson^1
1CRUK and EPSRC Cancer Imaging Centre, The Institute of Cancer Research and Royal Marsden NHS Trust, Sutton, Surrey, United Kingdom; ²MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London, United Kingdom; ³Department of Basic Medical Sciences, St. Georges, University of London, London, United Kingdom

Dimethylarginine dimethylaminohydrolase (DDAH) metabolizes the endogenous inhibitor of nitric oxide synthesis, asymmetric dimethylarginine (ADMA), indirectly leading to an increase in nitric oxide. Diffusion-weighted and dynamic contract enhanced MRI were used to evaluate the vascular phenotypes of C6 glioma xenografts overexpressing either wildtype DDAH1 or an active site mutant DDAH1 incapable of metabolizing ADMA. Tumours expressing mDDAH1 demonstrated an intermediate phenotype between control and wtDDAH1 expressing tumours. Differences in ADC and native T1 and T2 times were consistent with higher cellularity/lower necrosis in the DDAH1 expressing tumours. Despite differences in VEGF expression and perfusion, no significant alterations in Ktrans or ve were observed between the 3 tumour groups.

Microscopic Morphology of Brain and Bone Metastases in a Rat Breast Cancer Model by Diffusion MRI
Matthew D. Budde¹, Molly Resnick¹, Eric Gold¹, E Kay Jordan¹, Joseph A. Frank^1
1Radiology and Imaging Sciences, National Institutes of Health, Bethesda, MD, United States

The apparent diffusion coefficient (ADC) measured with diffusion MRI has shown promise as an early marker of therapeutic response in malignant gliomas.  However, metastatic tumors are the primary cause of intracranial tumors, and it is unknown whether brain metastases exhibit similar diffusion characteristics as the preclinical implanted brain tumor model.  A rat model of metastatic breast cancer was used to examine the diffusion properties of brain and bone metastases.  The results demonstrate that ADC is sensitive to the microscopic growth patterns of brain and bone metastases that result from their differing microenvironments.

Vessel Size Index (VSI) MRI in Solid Tumours - Validation with Microvascular Corrosion Casts
Jake Samuel Burrell¹, Jane Halliday², Simon Walker-Samuel³, John C. Waterton², Philip J. Withers⁴, Robert S. Bradley⁴, Jessica Boult¹, Yann Jamin¹, Lauren C. Baker¹, Simon P. Robinson^1
1The Institute of Cancer Research, Sutton, Surrey, United Kingdom; ²AstraZeneca, Manchester, United Kingdom; ³UCL, London, United Kingdom; ⁴School of Materials, University of Manchester, Manchester, United Kingdom

Susceptibility contrast MRI vessel size index (VSI) derived vessel diameters were compared with vessel diameters measured from vascular corrosion casts of the same SW1222 colorectal tumours. Good agreement was found between the MRI and vascular corrosion cast derived vessel sizes, reported as 38 ± 6µm and 39 ± 2µm respectively. This work helps to qualify non-invasive MRI vessel size measurements with appropriate histology.

Gas Challenge-Blood Oxygen Level Dependent (BOLD) MRI in Monitoring Tumor Angiogenesis of a Rodent Novikoff Hepatoma Model
Yang Guo¹, Ning Jin^1,2, Rachel Klein¹, Guang-Yu Yang³, Reed Omary^1,2, Andrew Larson^1,2
1Department of Radiology, Northwestern University, Chicago, IL, United States; ²Department of Biomedical Engineering , Northwestern University, Chicago, IL, United States; ³Department of Pathology, Northwestern University, Chicago, IL, United States

Angiogenesis is fundamental for tumor growth, invasion and metastasis. Non-invasive methods to monitor tumor neo-vascular changes during tumor progression and/or in response to anti-angiogenic therapy may be critical. The purpose of our study was to investigate the relationship between gas-challenge (GC)-BOLD response and degree of tumor angiogenesis during tumor progression in rodent hepatoma model. A positive correlation was found between GC-BOLD response and tumor microvessel density and a negative correlation was between GC-BOLD response and tumor size. GC-BOLD MRI may offer the potential to serve as a non-invasive method for evaluating angiogenesis and monitoring anti-angiogenic therapy response in hepatic tumors.

Hypoxia Detected with Phase Contrast MRI Is an Early Event in Micrometastatic Breast Cancer Development in the Rat Brain
Matthew D. Budde¹, Eric Gold¹, E Kay Jordan¹, Melissa Smith-Brown¹, Joseph A. Frank^1
1Radiology and Imaging Sciences, National Institutes of Health, Bethesda, MD, United States

Hypoxia is an important prognostic factor in tumor growth and therapeutic response and is a driving force in the angiogenic cascade. Blood oxygen level dependent (BOLD) MRI contrast is related to the oxygenation status of tumors, but brain tumors can have significant edema that can complicate measurements of magnetic field inhomogeneities caused by deoxygenated hemoglobin.  The purpose of this study was to determine if phase contrast MRI was more sensitive to vascular abnormalities than BOLD MRI in a rat model of breast cancer metastases to the brain and whether these changes were indicative of hypoxic changes that precede angiogenesis.

Hypoxic Environments Disrupt Collagen I Fibers and Macromolecular Transport
Samata Kakkad¹, Marie-France Penet¹, Meiyappan Solaiyappan¹, Arvind Pathak¹, Venu Raman¹, Kristine Glunde¹, Zaver M. Bhujwalla^1
1JHU ICMIC Program, The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States

Solid tumors are characterized by hypoxic environments.  Hypoxia stimulates the gene expression of a cluster of hydroxylases used for collagen fiber formation.  Hypoxic environments in tumors may lead to abnormal collagen deposits either by cancer cells or by fibroblasts within the tumor stroma.  In normal tissue collagen fibers direct interstitial fluid into lymphatic channels.  In tumors these fibers may not be structured for efficient flow of fluid, especially in hypoxic areas.  Our purpose was to understand the role of hypoxia in modifying macromolecular fluid transport using MRI, and collagen fiber distribution using second harmonic generation microscopy.

High-Resolution Imaging of Non-Small Cell Lung Cancer in a Mouse Model of Brain Metastasis
Hye-Won Kang¹, Geun-Ho Im², Jung Hee Lee², Alexei A. Bogdanov^1
1Radiology, University of Massachusetts Medical School, Worcester, MA, United States; ²Radiology, Samsung Medical Center, Seoul, Korea, Republic of

A combination of anti-human EGFR antibody-enzyme conjugates and a paramagnetic substrate has been designed for EGFR MR imaging for detecting NSCLC in vivo. The specificity of conjugate to the tumors and the sensitivity to EGFR expression in vivo were examined. The experimental group of mice after the injection of pretargeting conjugates followed by the injection of the paramagnetic substrate showed a strong enhancement of the tumor. The increase of MR signal was higher and the peak of enhancement was reached earlier than in the control group. The higher signal around the tumor periphery was retained for up to 24 h.

Theranostic Imaging of Metastatic Disease
Zhihang Chen¹, Marie-France Penet¹, Sridhar Nimmagadda¹, Cong Li¹, Sangeeta Ray¹, Paul Winnard¹, Dmitri Artemov¹, Kristine Glunde¹, Martin G. Pomper¹, Zaver M. Bhujwalla^1
1JHU ICMIC Program, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States

There is a compelling need to find effective treatments for metastatic disease, as it typically becomes refractory to treatment.  We are developing targeted nanoplexes carrying multimodality imaging reporters together with small interfering RNA (siRNA) and a prodrug enzyme for theranostic imaging of metastatic prostate cancer.  Down-regulation of specific pathways using siRNA provides unique opportunities to target cancer cells selectively while sparing normal tissue.  The targeted nanoplexes we develop will allow us to deliver siRNA together with a prodrug enzyme, under image guidance for developing theranostic imaging of metastatic prostate cancer.

In Vivo Detection of PI3K Pathway Inhibition by Hyperpolarized ¹³C MRSI at 14 Tesla
Myriam Marianne Chaumeil¹, Subramanian Sukumar¹, Humsa Venkatesh¹, Christopher Ward¹, Kristen R. Scott¹, Tomoko Ozawa², C David James², John Kurhanewicz¹, Daniel B. Vigneron¹, Sarah J. Nelson¹, Sabrina M. Ronen^1
1Radiology, UCSF, San Francisco, CA, United States; ²Brain Tumor Research Center, UCSF, San Francisco, CA, United States

In vivo  inhibition of the PI3K pathway by Everolimus was evaluated using hyperpolarized (HP) ¹³C MRSI in subcutaneous tumors in mice at 14 Tesla. Whereas lactate-to-pyruvate ratio was increased in control animals, this ratio was decreased by 78% and 35% in treated animals relative to controls after 2 and 7 days, respectively. The drop in lactate-to-pyruvate ratio following Everolimus treatment is in line with the findings in treated cells and likely indicates a decrease in LDH activity in treated tumors.  This preliminary in vivo  study demonstrates the likely value of HP ¹³C studies of pyruvate for noninvasive monitoring PI3K inhibition.

In Vivo P31 NMR Demonstrates Reduced ATP Synthesis Rate in Skeletal Muscle in a Murine Cancer Cachexia Model
Dionyssios Mintzopoulos^1,2, Cibely Cristine Fontes de Oliveira³, Jianxin He⁴, Caterina Constantinou⁴, Michael N. Mindrinos⁵, Laurence G. Rahme⁴, Josep M. Argiles³, A. Aria Tzika^1,2
1NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA, United States; ²Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA, United States; ³Cancer Research Group, Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona, Spain; ⁴Molecular Surgery Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA, United States; ⁵Stanford Genome Technology Center, Department of Biochemistry, Stanford University School of Medicine, Palo Alto, CA, United States

We employed in vivo P31 NMR on intact mice, in a mouse cancer (Lewis lung carcinoma) cachexia model. We examined ATP synthesis rate and the gene expression of key regulatory genes, involved in regulation of skeletal muscle metabolism. Our in vivo NMR results that showed significantly reduced rate of ATP synthesis rate were cross-validated with genomic analysis, showing aberrant expression levels in key regulatory genes. Our findings implicate that reduction in ATP synthesis rate is linked to mitochondrial dysfunction leading to wasting of skeletal muscle in cancer cachexia.