High molar activity [18F]tetrafluoroborate synthesis for sodium iodide symporter imaging by PET

Background: Sodium iodide symporter (NIS) imaging by positron emission tomography (PET) is gaining traction in nuclear medicine, with an increasing number of human studies being published using fluorine-18 radiolabelled tetrafluoroborate ([18F]TFB). Clinical success of any radiotracer relies heavily on its accessibility, which in turn depends on the availability of robust radiolabelling procedures providing a radiotracer in large quantities and of high radiopharmaceutical quality. Results: Here we publish an improved radiolabelling method and quality control procedures for high molar activity [18F]TFB. The use of ammonium hydroxide for [18F]fluoride elution, commercially available boron trifluoride-methanol complex dissolved in acetonitrile as precursor and removal of unreacted [18F]fluoride on Florisil solid-phase extraction cartridges resulted in the reliable production of [18F]TFB on SYNTHRA and TRACERLAB FXFN automated synthesizers with radiochemical yields in excess of 30%, radiochemical purities in excess of 98% and molar activities in the range of 34–217 GBq/µmol at the end of synthesis. PET scanning of a mouse lung tumour model carrying a NIS reporter gene rendered images of high quality and improved sensitivity. Conclusions: A novel automated radiosynthesis procedure for [18F]tetrafluoroborate has been developed that provides the radiotracer with high molar activity, suitable for preclinical imaging of NIS reporter gene

(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

Collective Management Organisations, Creativity and Cultural Diversity

Glycogen synthase kinase 3 (GSK3) is a central regulator of cellular metabolism, development and growth. GSK3 activity was thought to oppose tumourigenesis, yet recent studies indicate that it may support tumour growth in some cancer types including in non-small cell lung carcinoma (NSCLC). We examined the undefined role of GSK3 protein kinase activity in tissue from human NSCLC.The expression and protein kinase activity of GSK3 was determined in 29 fresh frozen samples of human NSCLC and patient-matched normal lung tissue by quantitative immunoassay and western blotting for the phosphorylation of three distinct GSK3 substrates in situ (glycogen synthase, RelA and CRMP-2). The proliferation and sensitivity to the small-molecule GSK3 inhibitor; CHIR99021, of NSCLC cell lines (Hcc193, H1975, PC9 and A549) and non-neoplastic type II pneumocytes was further assessed in adherent culture.Expression and protein kinase activity of GSK3 was elevated in 41% of human NSCLC samples when compared to patient-matched control tissue. Phosphorylation of GSK3α/β at the inhibitory S21/9 residue was a poor biomarker for activity in tumour samples. The GSK3 inhibitor, CHIR99021 dose-dependently reduced the proliferation of three NSCLC cell lines yet was ineffective against type II pneumocytes.NSCLC tumours with elevated GSK3 protein kinase activity may have evolved dependence on the kinase for sustained growth. Our results provide further important rationale for exploring the use of GSK3 inhibitors in treating NSCLC

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

Following Metabolism in Living Microorganisms by Hyperpolarized ¹H NMR

Dissolution dynamic nuclear polarization (dDNP) is used to enhance the sensitivity of nuclear magnetic resonance (NMR), enabling monitoring of metabolism and specific enzymatic reactions in vivo. dDNP involves rapid sample dissolution and transfer to a spectrometer/scanner for subsequent signal detection. So far, most biologically oriented dDNP studies have relied on hyperpolarizing long-lived nuclear spin species such as ¹³C in small molecules. While advantages could also arise from observing hyperpolarized ¹H, short relaxation times limit the utility of prepolarizing this sensitive but fast relaxing nucleus. Recently, it has been reported that ¹H NMR peaks in solution-phase experiments could be hyperpolarized by spontaneous magnetization transfers from bound ¹³C nuclei following dDNP. This work demonstrates the potential of this sensitivity-enhancing approach to probe the enzymatic process that could not be suitably resolved by ¹³C dDNP MR. Here we measured, in microorganisms, the action of pyruvate decarboxylase (PDC) and pyruvate formate lyase (PFL)enzymes that catalyze the decarboxylation of pyruvate to form acetaldehyde and formate, respectively. While ¹³C NMR did not possess the resolution to distinguish the starting pyruvate precursor from the carbonyl resonances in the resulting products, these processes could be monitored by ¹H NMR at 500 MHz. These observations were possible in both yeast and bacteria in minute-long kinetic measurements where the hyperpolarized ¹³C enhanced, via ¹³C → ¹H cross-relaxation, the signals of protons binding to the ¹³C over the course of enzymatic reactions. In addition to these spontaneous heteronuclear enhancement experiments, single-shot acquisitions based on <i>J</i>-driven ¹³C → ¹H polarization transfers were also carried out. These resulted in higher signal enhancements of the ¹H resonances but were not suitable for multishot kinetic studies. The potential of these ¹H-based approaches for measurements in vivo is briefly discussed

Hyperpolarized Amino Acid Derivatives as Multivalent Magnetic Resonance pH Sensor Molecules

pH is a tightly regulated physiological parameter that is often altered in diseased states like cancer. The development of biosensors that can be used to non-invasively image pH with hyperpolarized (HP) magnetic resonance spectroscopic imaging has therefore recently gained tremendous interest. However, most of the known HP-sensors have only individually and not comprehensively been analyzed for their biocompatibility, their pH sensitivity under physiological conditions, and the effects of chemical derivatization on their logarithmic acid dissociation constant (pKa). Proteinogenic amino acids are biocompatible, can be hyperpolarized and have at least two pH sensitive moieties. However, they do not exhibit a pH sensitivity in the physiologically relevant pH range. Here, we developed a systematic approach to tailor the pKa of molecules using modifications of carbon chain length and derivatization rendering these molecules interesting for pH biosensing. Notably, we identified several derivatives such as [1-13C]serine amide and [1-13C]-2,3-diaminopropionic acid as novel pH sensors. They bear several spin-1/2 nuclei (13C, 15N, 31P) with high sensitivity up to 4.8 ppm/pH and we show that 13C spins can be hyperpolarized with dissolution dynamic polarization (DNP). Our findings elucidate the molecular mechanisms of chemical shift pH sensors that might help to design tailored probes for specific pH in vivo imaging applications

Positron emission tomography imaging of the sodium iodide symporter senses real-time energy stress in vivo

Abstract Background Tissue environment is critical in determining tumour metabolic vulnerability. However, in vivo drug testing is slow and waiting for tumour growth delay may not be the most appropriate endpoint for metabolic treatments. An in vivo method for measuring energy stress would rapidly determine tumour targeting in a physiologically relevant environment. The sodium-iodide symporter (NIS) is an imaging reporter gene whose protein product co-transports sodium and iodide, and positron emission tomography (PET) radiolabelled anions into the cell. Here, we show that PET imaging of NIS-mediated radiotracer uptake can rapidly visualise tumour energy stress within minutes following in vivo treatment. Methods We modified HEK293T human embryonic kidney cells, and A549 and H358 lung cancer cells to express transgenic NIS. Next, we subjected these cells and implanted tumours to drugs known to induce metabolic stress to observe the impact on NIS activity and energy charge. We used [18F]tetrafluoroborate positron emission tomography (PET) imaging to non-invasively image NIS activity in vivo. Results NIS activity was ablated by treating HEK293T cells in vitro, with the Na+/K+ ATPase inhibitor digoxin, confirming that radiotracer uptake was dependent on the sodium–potassium concentration gradient. NIS-mediated radiotracer uptake was significantly reduced (− 58.2%) following disruptions to ATP re-synthesis by combined glycolysis and oxidative phosphorylation inhibition in HEK293T cells and by oxidative phosphorylation inhibition (− 16.6%) in A549 cells in vitro. PET signal was significantly decreased (− 56.5%) within 90 min from the onset of treatment with IACS-010759, an oxidative phosphorylation inhibitor, in subcutaneous transgenic A549 tumours in vivo, showing that NIS could rapidly and sensitively detect energy stress non-invasively, before more widespread changes to phosphorylated AMP-activated protein kinase, phosphorylated pyruvate dehydrogenase, and GLUT1 were detectable. Conclusions NIS acts as a rapid metabolic sensor for drugs that lead to ATP depletion. PET imaging of NIS could facilitate in vivo testing of treatments targeting energetic pathways, determine drug potency, and expedite metabolic drug development

Hyperpolarized Amino Acid Derivatives as Multivalent Magnetic Resonance pH Sensor Molecules.

pH is a tightly regulated physiological parameter that is often altered in diseased states like cancer. The development of biosensors that can be used to non-invasively image pH with hyperpolarized (HP) magnetic resonance spectroscopic imaging has therefore recently gained tremendous interest. However, most of the known HP-sensors have only individually and not comprehensively been analyzed for their biocompatibility, their pH sensitivity under physiological conditions, and the effects of chemical derivatization on their logarithmic acid dissociation constant (pKa). Proteinogenic amino acids are biocompatible, can be hyperpolarized and have at least two pH sensitive moieties. However, they do not exhibit a pH sensitivity in the physiologically relevant pH range. Here, we developed a systematic approach to tailor the pKa of molecules using modifications of carbon chain length and derivatization rendering these molecules interesting for pH biosensing. Notably, we identified several derivatives such as [1-13C]serine amide and [1-13C]-2,3-diaminopropionic acid as novel pH sensors. They bear several spin-1/2 nuclei (13C, 15N, 31P) with high sensitivity up to 4.8 ppm/pH and we show that 13C spins can be hyperpolarized with dissolution dynamic polarization (DNP). Our findings elucidate the molecular mechanisms of chemical shift pH sensors that might help to design tailored probes for specific pH in vivo imaging applications

Additional file 1 of Positron emission tomography imaging of the sodium iodide symporter senses real-time energy stress in vivo

Additional file 1: Supplementary Figure 1. Illustrative images showing H&E staining of tumour tissue fixed shortly after the completion of vehicle or IACS-10759 treatment, as stated on the label in the left-hand corner of the image (Vehiclex1, IACSx1: fixed 2 hours from the administration of a single dose; Vehiclex6, IACSx6: fixed 24 hours from the administration of the last one of six, once-daily doses). Supplementary Figure 2. [18F]TFB PET imaging of sodium iodide symporter (NIS) expressing sensitive (A549-LN; n = 4) and resistant (H358-LN; n = 3) tumours at baseline and 24 hours later, immediately after oral administration of a single dose of 20mg/kg IACS-10759. Two-way, repeated measures ANOVA with Šídák's multiple comparisons analysis was performed to test statistical significance of the results. P value classifications are summarized as follows: **, P∈(0.001–0.01 〉. Each data point represents SUVmax calculated for a single tumour/animal and time-point

GSK3α/β expression in selected patients.

<p>Three distinct samples from normal (N1-3) and patient-matched tumour (T1-3) tissues were separated on SDS-PAGE gels. Expression of GSK3α/β was determined by western blotting. An anti-F₁-ATPase antibody was used as a control for protein loading.</p