Potential Clinical Roles for Metabolic Imaging with Hyperpolarized [1-(13)C]Pyruvate.

Work in KMB’s laboratory is supported by a Cancer Research UK Programme grant (17242) and the CRUK-EPSRC Imaging Centre in Cambridge and Manchester (16465). Clinical studies are funded by a Strategic Award from the Wellcome Trust (095962). E.M.S. was a recipient of a fellowship from the European Union Seventh Framework Programme (FP7/2007-2013) under the Marie Curie Initial Training Network METAFLUX (project number 264780). E.M.S. also acknowledges the educational support of the Programme for Advanced Medical Education from Calouste Gulbenkian Foundation, Champalimaud Foundation, Ministerio de Saude and Fundacao para a Ciencia e Tecnologia, Portugal.This is the final version of the article. It first appeared from Frontiers via http://dx.doi.org/10.3389/fonc.2016.0005

Effects of fasting on serial measurements of hyperpolarized [1-(13) C]pyruvate metabolism in tumors.

Imaging of the metabolism of hyperpolarized [1-(13) C]pyruvate has shown considerable promise in preclinical studies in oncology, particularly for the assessment of early treatment response. The repeatability of measurements of (13) C label exchange between pyruvate and lactate was determined in a murine lymphoma model in fasted and non-fasted animals. The fasted state showed lower intra-individual variability, although the [1-(13) C]lactate/[1-(13) C]pyruvate signal ratio was significantly greater in fasted than in non-fasted mice, which may be explained by the higher tumor lactate concentrations in fasted animals. These results indicate that the fasted state may be preferable for the measurement of (13) C label exchange between pyruvate and lactate, as it reduces the variability and therefore should make it easier to detect the effects of therapy. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.Cancer Research UK (Grant ID: 17242)This is the final version of the article. It first appeared from Wiley via https://doi.org/10.1002/nbm.356

(13) C magnetic resonance spectroscopy measurements with hyperpolarized [1-(13) C] pyruvate can be used to detect the expression of transgenic pyruvate decarboxylase activity in vivo.

PURPOSE: Dissolution dynamic nuclear polarization can increase the sensitivity of the (13) C magnetic resonance spectroscopy experiment by at least four orders of magnitude and offers a novel approach to the development of MRI gene reporters based on enzymes that metabolize (13) C-labeled tracers. We describe here a gene reporter based on the enzyme pyruvate decarboxylase (EC 4.1.1.1), which catalyzes the decarboxylation of pyruvate to produce acetaldehyde and carbon dioxide. METHODS: Pyruvate decarboxylase from Zymomonas mobilis (zmPDC) and a mutant that lacked enzyme activity were expressed using an inducible promoter in human embryonic kidney (HEK293T) cells. Enzyme activity was measured in the cells and in xenografts derived from the cells using (13) C MRS measurements of the conversion of hyperpolarized [1-(13) C] pyruvate to H(13) CO3-. RESULTS: Induction of zmPDC expression in the cells and in the xenografts derived from them resulted in an approximately two-fold increase in the H(13) CO3-/[1-(13) C] pyruvate signal ratio following intravenous injection of hyperpolarized [1-(13) C] pyruvate. CONCLUSION: We have demonstrated the feasibility of using zmPDC as an in vivo reporter gene for use with hyperpolarized (13) C MRS. Magn Reson Med 76:391-401, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.PD was in receipt of a studentship funded by CRUK and S.-S.T. a Yousef Jameel studentship. TBR was in receipt of an Intra-European Marie Curie (FP7-PEOPLE- 2009-IEF, Imaging Lymphoma) and Long-term EMBO (EMBO-ALT-1145-2009) fellowships and E.M.S. and I.M.R were recipients of fellowships from the European Union Seventh Framework Programme (FP7/2007-2013) under the Marie Curie Initial Training Network METAFLUX (project number 264780). E.M.S. also acknowledges the educational support of Programme for Advanced Medical Education from Calouste Gulbenkian Foundation, Champalimaud Foundation, Ministerio de Saude and Fundacao para a Ciencia e Tecnologia, Portugal. The work was supported by a CRUK Programme Grant (17242) to KMB. The polarizer and related materials were provided by GE-Healthcare.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/mrm.2587

Investigating the ability of multiparametric MRI to exclude significant prostate cancer prior to transperineal biopsy.

INTRODUCTION: We characterized false negative prostate magnetic resonance imaging (MRI) reporting by using histology derived from MRI-transrectal ultrasound (TRUS)-guided transperineal (MTTP) fusion biopsies. METHODS: In total, 148 consecutive patients were retrospectively reviewed. Men underwent multiparametric MRI (mpMRI), reported by a consultant/attending radiologist in line with European Society of Urogenital Radiology (ESUR) standards. MTTP biopsy of the lesions was performed according to the Ginsburg recommendations. Cases with an MRI-histology mismatch were identified and underwent a second read by an experienced radiologist. A third review was performed with direct histology comparison to determine a true miss from an MRI-occult cancer. Statistical analysis was performed with McNemar's test. RESULTS: False negative lesions were identified in 29 MRI examinations (19.6%), with a total of 46 lesions. Most false negative lesions (21/46) were located in the anterior sectors of the prostate. The second read led to a significant decrease of false-negative lesions with 7/29 further studies identified as positive on a patient-by-patient basis (24.1% of studies, p = 0.016) and 11/46 lesions (23.9%; p = 0.001). Of these, 30 lesions following the first read and 23 lesions after the second read were considered significant cancer according to the University College London criteria. However, on direct comparison with histology, most lesions were MRI occult. CONCLUSION: We demonstrate that MRI can fail to detect clinically relevant lesions. Improved results were achieved with a second read but despite this, a number of lesions remain MRI-occult. Further advances in imaging are required to reduce false negative results.National Institute of Health Research Cambridge Biomedical Research Centre, Cancer Research UK, Cancer Research UK and the Engineering and Physical Sciences Research Council Imaging Centre in Cambridge and Manchester, Cambridge Experimental Cancer Medicine CentreThis is the final version of the article. It first appeared from the Canadian Urological Association via http://dx.doi.org/10.5489/cuaj.289

Carbonic Anhydrase Activity Monitored In Vivo by Hyperpolarized 13C-Magnetic Resonance Spectroscopy Demonstrates Its Importance for pH Regulation in Tumors.

Carbonic anhydrase buffers tissue pH by catalyzing the rapid interconversion of carbon dioxide (CO2) and bicarbonate (HCO3 (-)). We assessed the functional activity of CAIX in two colorectal tumor models, expressing different levels of the enzyme, by measuring the rate of exchange of hyperpolarized (13)C label between bicarbonate (H(13)CO3(-)) and carbon dioxide ((13)CO2), following injection of hyperpolarized H(13)CO3(-), using (13)C-magnetic resonance spectroscopy ((13)C-MRS) magnetization transfer measurements. (31)P-MRS measurements of the chemical shift of the pH probe, 3-aminopropylphosphonate, and (13)C-MRS measurements of the H(13)CO3(-)/(13)CO2 peak intensity ratio showed that CAIX overexpression lowered extracellular pH in these tumors. However, the (13)C measurements overestimated pH due to incomplete equilibration of the hyperpolarized (13)C label between the H(13)CO3(-) and (13)CO2 pools. Paradoxically, tumors overexpressing CAIX showed lower enzyme activity using magnetization transfer measurements, which can be explained by the more acidic extracellular pH in these tumors and the decreased activity of the enzyme at low pH. This explanation was confirmed by administration of bicarbonate in the drinking water, which elevated tumor extracellular pH and restored enzyme activity to control levels. These results suggest that CAIX expression is increased in hypoxia to compensate for the decrease in its activity produced by a low extracellular pH and supports the hypothesis that a major function of CAIX is to lower the extracellular pH.The authors acknowledge funding support from Cancer Research UK (CRUK; C19212/A16628; C19212/A911376), the National Institute for Health Research Cambridge Biomedical Research Centre and the School of Clinical Medicine at the University of Cambridge, the CRUK and Engineering and Physical Sciences Research Council (EPSRC) Cancer Imaging Centre in Cambridge and Manchester. E.M.S. is a recipient of funding from the European Union Seventh Framework Programme (FP7/2007-2013) under the Marie Curie Initial Training Network METAFLUX and has support from the Calouste Gulbenkian Foundation, Champalimaud Foundation, Ministerio de Saude and Fundacao para a Ciencia e Tecnologia, Portugal.This is the author accepted manuscript. The final version is available from American Association for Cancer Research via http://dx.doi.org/10.1158/0008-5472.CAN-15-085

Magnetic resonance imaging with hyperpolarized [1-13C]pyruvate detects advanced pancreatic preneoplasia prior to invasive disease in a mouse model

OBJECTIVES: Pancreatic cancer (PCa) is treatable by surgery when detected at an early stage. Non-invasive imaging methods able to detect both established tumours and their precursor lesions are needed to select patients for surgery. We investigated here whether pancreatic preneoplasia could be detected prior to the development of invasive cancers in genetically engineered mouse models of PCa using metabolic imaging. DESIGN: The concentrations of alanine and lactate and the activities of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT) were measured in extracts prepared from the pancreas of animals at different stages of disease progression; from pancreatitis, through tissue with predominantly low-grade and then high-grade pancreatic intraepithelial neoplasia and then tumour. (13)C magnetic resonance spectroscopic imaging ((13)C-MRSI) was used to measure non-invasively changes in (13)C labelling of alanine and lactate with disease progression, following injection of hyperpolarised [1-(13)C]pyruvate. RESULTS: Progressive decreases in the alanine/lactate concentration ratio and ALT/LDH activity ratio with disease progression were accompanied by a corresponding decrease in the [1-(13)C]alanine/[1-(13)C]lactate signal ratio observed in (13)C-MRSI images of the pancreas. CONCLUSIONS: Metabolic imaging with hyperpolarised [1-(13)C]pyruvate enables detection and monitoring of the progression of PCa precursor lesions. Translation of this MRI technique to the clinic has the potential to improve the management of patients at high risk of developing PCa.The work was supported by a Cancer Research UK Programme grant (17242) to K.M.B.. E.M.S. is a recipient of a fellowship from the European Union Seventh Framework Programme (FP7/2007-2013) under the Marie Curie Initial Training Network METAFLUX (project number 264780). T.B.R. is a recipient of an Intra- European Marie Curie (FP7-PEOPLE-2009-IEF, Imaging Lymphoma) fellowship and a Long-term European Molecular Biology Organization (EMBO-ALT-1145-2009) fellowship. E.M.S. and J.A. acknowledge the educational support of Programme for Advanced Medical Education from Calouste Gulbenkian Foundation, Champalimaud Foundation, Ministerio de Saude and Fundacao para a Ciencia e Tecnologia, Portugal. The polarizer and related materials were provided by GE Healthcare. The polarimeter was provided by NIHR Cambridge Biomedical Centre. The laboratory is a member of and receives support from the Cancer Research UK & Engineering and Physical Science Research Council Cancer Imaging Center in Cambridge and Manchester. The authors would also like to acknowledge Dr. Judit Espana, Dr. Athena Matakidou, Dr. Madhu Basetti, Dr. Jose Sandoval and Sarah McGuire for their help with experiments as well as the Tumor Models Core of Cancer Research UK-Cambridge Institute.This is the final version of the article. It first appeared from BMJ Group via http://dx.doi.org/10.1136/gutjnl-2015-31011

Magnetic resonance fingerprinting of the pancreas at 1.5 T and 3.0 T

Funder: GlaxoSmithKline; doi: http://dx.doi.org/10.13039/100004330Funder: National Institute of Health Research (NIHR) Cambridge Biomedical Research CentreFunder: Addenbrooke's Charitable Trust, Cambridge University Hospitals; doi: http://dx.doi.org/10.13039/501100002927Abstract: Magnetic resonance imaging of the pancreas is increasingly used as an important diagnostic modality for characterisation of pancreatic lesions. Pancreatic MRI protocols are mostly qualitative due to time constraints and motion sensitivity. MR Fingerprinting is an innovative acquisition technique that provides qualitative data and quantitative parameter maps from a single free‐breathing acquisition with the potential to reduce exam times. This work investigates the feasibility of MRF parameter mapping for pancreatic imaging in the presence of free-breathing exam. Sixteen healthy participants were prospectively imaged using MRF framework. Regions-of-interest were drawn in multiple solid organs including the pancreas and T1 and T2 values determined. MRF T1 and T2 mapping was performed successfully in all participants (acquisition time:2.4–3.6 min). Mean pancreatic T1 values were 37–43% lower than those of the muscle, spleen, and kidney at both 1.5 and 3.0 T. For these organs, the mean pancreatic T2 values were nearly 40% at 1.5 T and < 12% at 3.0 T. The feasibility of MRF at 1.5 T and 3 T was demonstrated in the pancreas. By enabling fast and free-breathing quantitation, MRF has the potential to add value during the clinical characterisation and grading of pathological conditions, such as pancreatitis or cancer

Metabolic profiling of induced acute pancreatitis and pancreatic cancer progression in a mutant Kras mouse model.

Untargeted Nuclear Magnetic Resonance (NMR) metabolomics of polar extracts from the pancreata of a caerulin-induced mouse model of pancreatitis (Pt) and of a transgenic mouse model of pancreatic cancer (PCa) were used to find metabolic markers of Pt and to characterize the metabolic changes accompanying PCa progression. Using multivariate analysis a 10-metabolite metabolic signature specific to Pt tissue was found to distinguish the benign condition from both normal tissue and precancerous tissue (low grade pancreatic intraepithelial neoplasia, PanIN, lesions). The mice pancreata showed significant changes in the progression from normal tissue, through low-grade and high-grade PanIN lesions to pancreatic ductal adenocarcinoma (PDA). These included increased lactate production, amino acid changes consistent with enhanced anaplerosis, decreased concentrations of intermediates in membrane biosynthesis (phosphocholine and phosphoethanolamine) and decreased glycosylated uridine phosphates, reflecting activation of the hexosamine biosynthesis pathway and protein glycosylation

Hyperpolarized singlet lifetimes of pyruvate in human blood and in the mouse

Hyperpolarized NMR is a promising technique for non-invasive imaging of tissue metabolism in vivo. However, the pathways that can be studied are limited by the fast T1 decay of the nuclear spin order. In metabolites containing pairs of coupled nuclear spins-1/2, the spin order may be maintained by exploiting the non-magnetic singlet (spin-0) state of the pair. This may allow preservation of the hyperpolarization in vivo during transport to tissues of interest, such as tumors, or to detect slower metabolic reactions. We show here that in human blood and in a mouse in vivo at millitesla fields the 13C singlet lifetime of [1,2-13C2]pyruvate was significantly longer than the 13C T1, although it was shorter than the T1 at field strengths of several tesla. We also examine the singlet-derived NMR spectrum observed for hyperpolarized [1,2-13C2]lactate, originating from the metabolism of [1,2-13C2]pyruvate