Biomedical imaging scientist in preclinical molecular and nuclear imaging, particularly employing PET, CT and optical techniques. Applications include therapeutic development, oncology, immunotherapy, neuroscience, and molecular biology. Active in translational diagnostics research and development. Lead a scientific team and skilled in project management with a portfolio of academic and pharmaceutical/biotechnology partners. Broad foundation in molecular biology assays and in vivo disease models.
Honors & Awards
Molecular Imaging: Training in Oncology (R25T) Postdoctoral Fellowship, Memorial Sloan Kettering Cancer Center (2012-2014)
Dissertation Year Fellowship, David Geffen School of Medicine, UCLA (2011-2012)
2nd place, Center for Molecular Imaging Innovation and Translation (CMIIT) Young Investigator Award, Society of Nuclear Medicine (2011)
3rd place, SNM Young Professionals Committee, Clinical Research abstract, Society of Nuclear Medicine (2011)
Institute for Molecular Imaging (AMI) – WMIC Travel Award, World Molecular Imaging Society (2011)
In Vivo Cellular and Molecular Imaging Center (ICMIC) Career Development Grant, David Geffen School of Medicine, UCLA (2009-2010)
Institute for Molecular Imaging (AMI) – WMIC Travel Award, World Molecular Imaging Society (2009)
UCLA Molecular and Medical Pharmacology Graduate Travel Award, Dept of Molecular and Medical Pharmacology, UCLA (2008)
Education & Certifications
R25T postdoctoral fellow, Memorial Sloan Kettering Cancer Center, Molecular Imaging (2014)
PhD, David Geffen School of Medicine at UCLA, Molecular and Medical Pharmacology (2012)
B.S., University of California, Los Angeles, Electrical Engineering, Biomedical Engineering emphasis (2006)
molecular diagnostics, translational imaging, nuclear medicine, theranostics, cancer biology, immunotherapy
Director, Stanford Center for Innovation in In vivo Imaging (SCi3), Stanford University School of Medicine (9/30/2019 - 5/31/2021)
Assistant Professor, Dept Molecular and Medical Pharmacology, School of Medicine at UCLA, David Geffen School of Medicine, UCLA (2014 - 2020)
UCLA, Los Angeles, California
Director, Preclinical Imaging Technology Center, Crump Institute for Molecular Imaging, Crump Institute for Molecular Imaging, David Geffen School of Medicine at UCLA (2014 - 2019)
UCLA, Los Angeles, California
Co-Director, Small Animal Imaging Shared Resource, Jonsson Comprehensive Cancer Center, UCLA, Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, UCLA (2014 - 2019)
UCLA, Los Angeles, California
Professional Affiliations and Activities
Member, Education Committee, World Molecular Imaging Society (2023 - Present)
External Advisory Board, Shared Resources, Simmons Comprehensive Cancer Center, UTSW Medical Center (2019 - 2020)
Core Advisory Committee, Norris Comprehensive Cancer Center, University of Southern California (2019 - 2019)
Reviewer, Journals: J of Nuclear Medicine, Clinical Cancer Research, Theranostics, Oncotarget, BioMed Res Int (2015 - Present)
Member, World Molecular Imaging Society (2014 - Present)
Member, Society of Nuclear Medicine and Molecular Imaging (2014 - Present)
Member, Shared Resources Committee, Jonsson Comprehensive Cancer Center, UCLA (2014 - 2019)
Spatial mapping of mitochondrial networks and bioenergetics in lung cancer.
Mitochondria are critical to the governance of metabolism and bioenergetics in cancer cells1. The mitochondria form highly organized networks, in which their outer and inner membrane structures define their bioenergetic capacity2,3. However, in vivo studies delineating the relationship between the structural organization of mitochondrial networks and their bioenergetic activity have been limited. Here we present an in vivo structural and functional analysis of mitochondrial networks and bioenergetic phenotypes in non-small cell lung cancer (NSCLC) using an integrated platform consisting of positron emission tomography imaging, respirometry and three-dimensional scanning block-face electron microscopy. The diverse bioenergetic phenotypes and metabolic dependencies we identified in NSCLC tumours align with distinct structural organization of mitochondrial networks present. Further, we discovered that mitochondrial networks are organized into distinct compartments within tumour cells. In tumours with high rates of oxidative phosphorylation (OXPHOSHI) and fatty acid oxidation, we identified peri-droplet mitochondrial networks wherein mitochondria contact and surround lipid droplets. By contrast, we discovered that in tumours with low rates of OXPHOS (OXPHOSLO), high glucose flux regulated perinuclear localization of mitochondria, structural remodelling of cristae and mitochondrial respiratory capacity. Our findings suggest that in NSCLC, mitochondrial networks are compartmentalized into distinct subpopulations that govern the bioenergetic capacity of tumours.
View details for DOI 10.1038/s41586-023-05793-3
View details for PubMedID 36922590
View details for PubMedCentralID 3790458
Multimodal imaging of capsid and cargo reveals differential brain targeting and liver detargeting of systemically-administered AAVs.
The development of gene delivery vehicles with high organ specificity when administered systemically is a critical goal for gene therapy. We combine optical and positron emission tomography (PET) imaging of 1) reporter genes and 2) capsid tags to assess the temporal and spatial distribution and transduction of adeno-associated viruses (AAVs). AAV9 and two engineered AAV vectors (PHP.eB and CAP-B10) that are noteworthy for maximizing blood-brain barrier transport were compared. CAP-B10 shares a modification in the 588 loop with PHP.eB, but also has a modification in the 455 loop, added with the goal of reducing off-target transduction. PET and optical imaging revealed that the additional modifications retained brain receptor affinity. In the liver, the accumulation of AAV9 and the engineered AAV capsids was similar (15% of the injected dose per cc and not significantly different between capsids at 21h). However, the engineered capsids were primarily internalized by Kupffer cells rather than hepatocytes, and liver transduction was greatly reduced. PET reporter gene imaging after engineered AAV systemic injection provided a non-invasive method to monitor AAV-mediated protein expression over time. Through comparison with capsid tagging, differences between brain localization and transduction were revealed. In summary, AAV capsids bearing imaging tags and reporter gene payloads create a unique and powerful platform to assay the pharmacokinetics, cellular specificity and protein expression kinetics of AAV vectors in vivo, a key enabler for the field of gene therapy.
View details for DOI 10.1016/j.biomaterials.2022.121701
View details for PubMedID 35985893
Molecular Imaging of Chimeric Antigen Receptor T Cells by ICOS-ImmunoPET.
Clinical cancer research : an official journal of the American Association for Cancer Research
PURPOSE: Immunomonitoring of chimeric antigen receptor (CAR) T cells relies primarily on their quantification in the peripheral blood, which inadequately quantifies their biodistribution and activation status in the tissues. Non-invasive molecular imaging of CAR T cells by positron emission tomography (PET) is a promising approach with the ability to provide spatial, temporal and functional information. Reported strategies rely on the incorporation of reporter transgenes or ex vivo biolabeling, significantly limiting the application of CAR T cell molecular imaging. In the present study, we assessed the ability of antibody-based PET (immunoPET) to non-invasively visualize CAR T cells.EXPERIMENTAL DESIGN: After analyzing human CAR T cells in vitro and ex vivo from patient samples to identify candidate targets for immunoPET, we employed a syngeneic, orthotopic murine tumor model of lymphoma to assess the feasibility of in vivo tracking of CAR T cells by immunoPET using the 89Zr-DFO-anti-ICOS tracer we previously reported.RESULTS: Analysis of human CD19-CAR T cells during activation identified the Inducible T-cell COStimulator (ICOS) as a potential target for immunoPET. In a preclinical tumor model, 89Zr-DFO-ICOS mAb PET-CT imaging detected significantly higher signal in specific bone marrow-containing skeletal sites of CAR T cell treated mice compared with controls. Importantly, administration of ICOS-targeting antibodies at tracer doses did not interfere with CAR T cell persistence and function.CONCLUSIONS: This study highlights the potential of ICOS-immunoPET imaging for monitoring of CAR T cell therapy, a strategy readily applicable to both commercially available and investigational CAR T cells.
View details for DOI 10.1158/1078-0432.CCR-20-2770
View details for PubMedID 33087332
Performance evaluation of HiPET, a high sensitivity and high resolution preclinical PET tomograph.
Physics in medicine and biology
HiPET is a recently developed prototype preclinical PET scanner dedicated to high sensitivity and high resolution molecular imaging. The HiPET system employs a phoswich depth of interaction (DOI) detector design, which also allows identification of the large majority of the cross layer crystal scatter (CLCS) events. This work evaluates its performance characteristics following the National Electrical Manufacturers Association (NEMA) NU4-2008 protocol.METHODS: The HiPET consists of twenty flat panel type detectors arranged in two rings. The inner diameter is 160 mm and the axial field of view (FOV) is 104 mm. Each detector is comprised of two layers of phoswich scintillator crystal arrays, a tapered, pixelated glass lightguide and a multi anode photomultiplier tube (MAPMT). The front (gamma ray entrance) layer is a 48 * 48 pixelated cerium doped lutetium yttrium orthosilicate (LYSO) scintillator array with individual crystals measuring 1.01 * 1.01 * 6.1 mm. The back (towards the PMT) layer is a 32 * 32 pixelated bismuth germanate (BGO) scintillator array with individual crystals measuring 1.55 * 1.55 * 8.9 mm.RESULTS: For energy windows of 250-650 keV and 350-650 keV, the peak absolute sensitivity at the center of the FOV was 13.5 % and 10.4% including CLCS events, and 11.8% and 8.9% excluding CLCS events, respectively. The average detector energy resolution derived by averaging the individual crystal spectra was 11.7±1.4 % for LYSO and 17.0±1.4 % for BGO. The 3D ordered-subsets expectation maximization (OSEM) reconstructed image of a point source in air, ranged from 0.73 mm to 1.19 mm, with an average value of 0.93±0.09 mm at all measured locations. The peak noise equivalent count rate (NECR) and scatter fraction were 179 kcps at 12.4 MBq and 6.9% for the mouse-sized phantom, and 63 kcps at 11.3 MBq and 18.3% for the rat-sized phantom. For the NEMA image quality phantom, the uniformity was 5.8%, and the spillover ratios measured in the water- and air-filled cold region chambers were 0.047 and 0.044, respectively. The recovery coefficients (RC) ranged from 0.31 to 0.92.CONCLUSION: These results and in vivo evaluation demonstrate that the HiPET can achieve high quality molecular imaging for biomedical applications.
View details for DOI 10.1088/1361-6560/ab6b44
View details for PubMedID 31935693
Performance Evaluation of G8, a High-Sensitivity Benchtop Preclinical PET/CT Tomograph
JOURNAL OF NUCLEAR MEDICINE
2019; 60 (1): 142–49
G8 is a benchtop integrated PET/CT scanner dedicated to high-sensitivity and high-resolution imaging of mice. This work characterizes its National Electrical Manufacturers Association NU 4-2008 performance where applicable and also assesses the basic imaging performance of the CT subsystem. Methods: The PET subsystem in G8 consists of 4 flat-panel detectors arranged in a boxlike geometry. Each panel consists of 2 modules of a 26 × 26 pixelated bismuth germanate scintillator array with individual crystals measuring 1.75 × 1.75 × 7.2 mm. The crystal arrays are coupled to multichannel photomultiplier tubes via a tapered, pixelated glass lightguide. A cone-beam CT scanner consisting of a MicroFocus x-ray source and a complementary metal oxide semiconductor detector provides anatomic information. Sensitivity, spatial resolution, energy resolution, scatter fraction, count-rate performance, and the capability of performing phantom and mouse imaging were evaluated for the PET subsystem. Noise, dose level, contrast, and resolution were evaluated for the CT subsystem. Results: With an energy window of 350-650 keV, the peak sensitivity was 9.0% near the center of the field of view. The crystal energy resolution ranged from 15.0% to 69.6% in full width at half maximum (FWHM), with a mean of 19.3% ± 3.7%. The average intrinsic spatial resolution was 1.30 and 1.38 mm FWHM in the transverse and axial directions, respectively. The maximum-likelihood expectation maximization reconstructed image of a point source in air averaged 0.81 ± 0.11 mm FWHM. The peak noise-equivalent count rate for the mouse-sized phantom was 44 kcps for a total activity of 2.9 MBq (78 μCi), and the scatter fraction was 11%. For the CT subsystem, the value of the modulation transfer function at 10% was 2.05 cycles/mm. Conclusion: The overall performance demonstrates that the G8 can produce high-quality images for molecular imaging-based biomedical research.
View details for DOI 10.2967/jnumed.118.208827
View details for Web of Science ID 000454687800028
View details for PubMedID 29903933
View details for PubMedCentralID PMC6354226
In vivo imaging of mitochondrial membrane potential in non-small-cell lung cancer.
Mitochondria are essential regulators of cellular energy and metabolism, and have a crucial role in sustaining the growth and survival of cancer cells. A central function of mitochondria is the synthesis of ATP by oxidative phosphorylation, known as mitochondrial bioenergetics. Mitochondria maintain oxidative phosphorylation by creating a membrane potential gradient that is generated by the electron transport chain to drive the synthesis of ATP1. Mitochondria are essential for tumour initiation and maintaining tumour cell growth in cell culture and xenografts2,3. However, our understanding of oxidative mitochondrial metabolism in cancer is limited because most studies have been performed in vitro in cell culture models. This highlights a need for in vivo studies to better understand how oxidative metabolism supports tumour growth. Here we measure mitochondrial membrane potential in non-small-cell lung cancer in vivo using a voltage-sensitive, positron emission tomography (PET) radiotracer known as 4-[18F]fluorobenzyl-triphenylphosphonium (18F-BnTP)4. By using PET imaging of 18F-BnTP, we profile mitochondrial membrane potential in autochthonous mouse models of lung cancer, and find distinct functional mitochondrial heterogeneity within subtypes of lung tumours. The use of 18F-BnTP PET imaging enabled us to functionally profile mitochondrial membrane potential in live tumours.
View details for DOI 10.1038/s41586-019-1715-0
View details for PubMedID 31666695
Imaging T Cell Dynamics and Function Using PET and Human Nuclear Reporter Genes
REPORTER GENE IMAGING: METHODS AND PROTOCOLS
2018; 1790: 165–80
Adoptive cell transfer immunotherapy has demonstrated significant promise in the treatment of cancer, with long-term, durable responses. T cells expressing T cell receptors (TCRs) that recognize tumor antigens, or engineered with chimeric antigen receptors (CARs) can recognize and eliminate tumor cells even in advanced disease. Positron emission tomography (PET) imaging with nuclear reporter genes, a noninvasive method to track and monitor function of engineered cells in vivo, allows quantitative, longitudinal monitoring of these cells, including their expansion/contraction, migration, retention at target and off-target sites, and biological state. As an additional advantage, some reporter genes also exhibit "suicide potential" permitting the safe elimination of adoptively transferred T cells in instances of adverse reaction to therapy. Here, we describe the production of human nuclear reporter gene-expressing T cells and noninvasive PET imaging to monitor their cell fate in vivo.
View details for DOI 10.1007/978-1-4939-7860-1_13
View details for Web of Science ID 000448886300014
View details for PubMedID 29858791
Cytoplasmic p53 couples oncogene-driven glucose metabolism to apoptosis and is a therapeutic target in glioblastoma
2017; 23 (11): 1342-+
Cross-talk among oncogenic signaling and metabolic pathways may create opportunities for new therapeutic strategies in cancer. Here we show that although acute inhibition of EGFR-driven glucose metabolism induces only minimal cell death, it lowers the apoptotic threshold in a subset of patient-derived glioblastoma (GBM) cells. Mechanistic studies revealed that after attenuated glucose consumption, Bcl-xL blocks cytoplasmic p53 from triggering intrinsic apoptosis. Consequently, targeting of EGFR-driven glucose metabolism in combination with pharmacological stabilization of p53 with the brain-penetrant small molecule idasanutlin resulted in synthetic lethality in orthotopic glioblastoma xenograft models. Notably, neither the degree of EGFR-signaling inhibition nor genetic analysis of EGFR was sufficient to predict sensitivity to this therapeutic combination. However, detection of rapid inhibitory effects on [18F]fluorodeoxyglucose uptake, assessed through noninvasive positron emission tomography, was an effective predictive biomarker of response in vivo. Together, these studies identify a crucial link among oncogene signaling, glucose metabolism, and cytoplasmic p53, which may potentially be exploited for combination therapy in GBM and possibly other malignancies.
View details for DOI 10.1038/nm.4418
View details for Web of Science ID 000414548300016
View details for PubMedID 29035366
View details for PubMedCentralID PMC5683421
Comparative Analysis of Human Nucleoside Kinase-Based Reporter Systems for PET Imaging
MOLECULAR IMAGING AND BIOLOGY
2017; 19 (1): 100–108
Radionuclide-based reporter gene imaging has the sensitivity to monitor gene- and cell-based therapies in human subjects. Potential immunogenicity of current viral transgenes warrants development of human-based reporter systems. We compared human nucleoside kinase reporters to a panel of nucleoside analogs of FEAU, FMAU, and FIAU, including the first in vivo assessment of L-[18F]FEAU.Human isogenic U87 cell lines were transduced to express different human reporter genes including dCK-R104M/D133A (dCKDM), dCK-R104Q/D133N (dCKep16A), dCK-A100V/R104M/D133A (dCK3M), and TK2-N93D/L109F (TK2DM), and wild-type dCK (dCK) and herpes simplex virus type-1 (HSVTK) reporter gene as references. In vitro cell uptake assays were performed with [18F]FEAU, L-[18F]FEAU, [14C]FMAU, L-[18F]FMAU, and [124I]FIAU. Micro-positron emission tomography/X-ray computed tomography imaging of xenograft-bearing nu/nu mice was conducted with [18F]FEAU, L-[18F]FEAU, L-[18F]FMAU, and [124I]FIAU on consecutive days. A cell viability assay was also performed to assess sensitivities to gemcitabine and bromovinyldeoxyuridine (BVdU).In vitro, dCKep16A and dCKDM with [18F]FEAU exhibited the highest sensitivity and selectivity of the human reporters, second only to HSVTK/[18F]FEAU. L-[18F]FEAU biodistribution in mice was on par with [18F]FEAU and L-[18F]FMAU. L-[18F]FMAU uptake in isogenic xenografts was highest for all human reporter genes. However, [18F]FEAU was the most selective of the short half-life reporter probes due to its minimal recognition by human dCK and relative sensitivity, whereas [124I]FIAU permitted imaging at a later time point, improving signal-to-background ratio. Of the human reporter genes, dCKep16A consistently outperformed the other tested reporters. Reporter genes of interest increased potency to the nucleoside analog prodrugs gemcitabine and BVdU.We demonstrate that human nucleoside kinase reporter systems vary significantly in their sensitivity and selectivity for in vivo imaging. The sufficiently high signal-to-background ratios and enhanced suicide gene potential support clinical translation.
View details for DOI 10.1007/s11307-016-0981-6
View details for Web of Science ID 000392205000012
View details for PubMedID 27393689
View details for PubMedCentralID PMC5345744
Stratification of nucleoside analog chemotherapy using 1-(2'-deoxy-2'-18F-fluoro-β-D-arabinofuranosyl)cytosine and 1-(2'-deoxy-2'-18F-fluoro-β-L-arabinofuranosyl)-5-methylcytosine PET.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
2012; 53 (2): 275–80
The ability to measure tumor determinants of response to nucleoside analog (NA) chemotherapy agents such as gemcitabine and related compounds could significantly affect the management of several types of cancer. Previously we showed that the accumulation in tumors of the new PET tracer 1-(2'-deoxy-2'-(18)F-fluoro-β-d-arabinofuranosyl)cytosine ((18)F-FAC) is predictive of responses to gemcitabine. (18)F-FAC retention in cells requires deoxycytidine kinase (dCK), a rate-limiting enzyme in the deoxyribonucleoside salvage metabolism and in gemcitabine conversion from an inactive prodrug to a cytotoxic compound. The objectives of the current study were to determine whether (18)F-FAC tumor uptake is also influenced by cytidine deaminase (CDA), a determinant of resistance to gemcitabine; to develop a new PET assay using (18)F-FAC and the related probe 1-(2'-deoxy-2'-(18)F-fluoro-β-l-arabinofuranosyl)-5-methylcytosine (l-(18)F-FMAC) to profile tumor lesions for both dCK and CDA enzymatic activities; and to determine whether this PET assay can identify the most effective NA chemotherapy against tumors with differential expression of dCK and CDA.Isogenic murine leukemic cell lines with defined dCK and CDA activities were generated by retroviral transduction. A cell viability assay was used to determine the sensitivity of the isogenic cell lines to the dCK-dependent NA prodrugs gemcitabine and clofarabine. In vitro enzymatic and cell-based tracer uptake assays and in vivo PET with (18)F-FAC and l-(18)F-FMAC were used to predict tumor responses to gemcitabine and clofarabine.dCK and CDA activities measured by kinase and tracer uptake assays correlated with the sensitivity of isogenic cell lines to gemcitabine and clofarabine. Coexpression of CDA decreased the sensitivity of dCK-positive cells to gemcitabine treatment in vitro by 15-fold but did not affect responses to clofarabine. Coexpression of CDA decreased (18)F-FAC but not l-(18)F-FMAC, phosphorylation, and uptake by dCK-positive cells. (18)F-FAC and l-(18)F-FMAC PET estimates of the enzymatic activities of dCK and CDA in tumor implants in mice were predictive of responses to gemcitabine and clofarabine treatment in vivo.These findings support the utility of PET-based phenotyping of tumor nucleoside metabolism for guiding the selection of NA prodrugs.
View details for DOI 10.2967/jnumed.111.090407
View details for PubMedID 22302964
View details for PubMedCentralID PMC3431619
Heterogeneous cardiac sympathetic innervation gradients promote arrhythmogenesis in murine dilated cardiomyopathy.
Ventricular arrhythmias (VAs) in heart failure are enhanced by sympathoexcitation. However, radiotracer studies of catecholamine uptake in failing human hearts demonstrate a proclivity for VAs in patients with reduced cardiac sympathetic innervation. We hypothesized that this counterintuitive finding is explained by heterogeneous loss of sympathetic nerves in the failing heart. In a murine model of dilated cardiomyopathy (DCM), delayed PET imaging of sympathetic nerve density using the catecholamine analog [11C]meta-Hydroxyephedrine ([11C]-mHED) demonstrated global hypoinnervation in ventricular myocardium. Although reduced, sympathetic innervation in two distinct DCM models invariably exhibited transmural (epicardial to endocardial) gradients, with the endocardium being devoid of sympathetic nerve fibers vs. controls. Further, the severity of transmural innervation gradients was correlated with VAs (r = 0.6, P < 0.05). Transmural innervation gradients were also identified in human left ventricular free wall samples from DCM vs controls. We investigated mechanisms underlying this relationship by in silico studies in 1-D, 2-D, and 3-D models of failing and normal human hearts, finding that arrhythmogenesis increased as heterogeneity in sympathetic innervation worsened. Specifically, both DCM-induced myocyte electrical remodeling and spatially inhomogeneous innervation gradients synergistically worsened arrhythmogenesis. Thus, heterogeneous innervation gradients in DCM promoted arrhythmogenesis. Restoration of homogeneous sympathetic innervation in the failing heart may reduce VAs.
View details for DOI 10.1172/jci.insight.157956
View details for PubMedID 37815863
Safety and Biodistribution Profile of Poly(styrenyl acetal trehalose) and Its Granulocyte Colony Stimulating Factor Conjugate
Poly(styrenyl acetal trehalose) (pSAT), composed of trehalose side chains linked to a polystyrene backbone via acetals, stabilizes a variety of proteins and enzymes against fluctuations in temperature. A promising application of pSAT is conjugation of the polymer to therapeutic proteins to reduce renal clearance. To explore this possibility, the safety of the polymer was first studied. Investigation of acute toxicity of pSAT in mice showed that there were no adverse effects of the polymer at a high (10 mg/kg) concentration. The immune response (antipolymer antibody and cytokine production) in mice was also studied. No significant antipolymer IgG was detected for pSAT, and only a transient and low level of IgM was elicited. pSAT was also safe in terms of cytokine response. The polymer was then conjugated to a granulocyte colony stimulating factor (GCSF), a therapeutic protein that is approved by the Federal Drug Administration, in order to study the biodistribution of a pSAT conjugate. A site-selective, two-step synthesis approach was developed for efficient conjugate preparation for the biodistribution study resulting in 90% conjugation efficiency. The organ distribution of GCSF-pSAT was measured by positron emission tomography and compared to controls GCSF and GCSF-poly(ethylene glycol), which confirmed that the trehalose polymer conjugate improved the in vivo half-life of the protein by reducing renal clearance. These findings suggest that trehalose styrenyl polymers are promising for use in therapeutic protein-polymer conjugates for reduced renal clearance of the biomolecule.
View details for DOI 10.1021/acs.biomac.2c00511
View details for Web of Science ID 000823117700001
View details for PubMedID 35767465
Introducing a new reporter gene, membrane-anchored Cypridina luciferase, for multiplex bioluminescence imaging.
Molecular therapy oncolytics
2021; 21: 15-22
Bioluminescence reporter gene imaging is a robust, high-throughput imaging modality that is useful for tracking cells and monitoring biological processes, both in cell culture and in small animals. We introduced and characterized a novel bioluminescence reporter-membrane-anchored Cypridina luciferase (maCLuc)-paired with a unique vargulin substrate. This luciferase-substrate pair has no cross-reactivity with established d-luciferin- or coelenterazine-based luciferase reporters. We compare maCLuc with several established luciferase-based reporter systems (firefly, click beetle, Renilla, and Gaussia luciferases), using both in vitro and in vivo models. We demonstrate the different imaging characteristics of these reporter systems, which allow for multiplexed-luciferase imaging of 3 and 4 separate targets concurrently in the same animal within 24 h. The imaging paradigms described here can be directly applied for simultaneous in vivo monitoring of multiple cell populations, the activity of selected signal transduction pathways, or a combination of both constitutive and inducible reporter imaging.
View details for DOI 10.1016/j.omto.2021.03.004
View details for PubMedID 33851009
View details for PubMedCentralID PMC8020342
Identification of miRNA signatures associated with radiation-induced late lung injury in mice
2020; 15 (5): e0232411
Acute radiation exposure of the thorax can lead to late serious, and even life-threatening, pulmonary and cardiac damage. Sporadic in nature, late complications tend to be difficult to predict, which prompted this investigation into identifying non-invasive, tissue-specific biomarkers for the early detection of late radiation injury. Levels of circulating microRNA (miRNA) were measured in C3H and C57Bl/6 mice after whole thorax irradiation at doses yielding approximately 70% mortality in 120 or 180 days, respectively (LD70/120 or 180). Within the first two weeks after exposure, weight gain slowed compared to sham treated mice along with a temporary drop in white blood cell counts. 52% of C3H (33 of 64) and 72% of C57Bl/6 (46 of 64) irradiated mice died due to late radiation injury. Lung and heart damage, as assessed by computed tomography (CT) and histology at 150 (C3H mice) and 180 (C57Bl/6 mice) days, correlated well with the appearance of a local, miRNA signature in the lung and heart tissue of irradiated animals, consistent with inherent differences in the C3H and C57Bl/6 strains in their propensity for developing radiation-induced pneumonitis or fibrosis, respectively. Radiation-induced changes in the circulating miRNA profile were most prominent within the first 30 days after exposure and included miRNA known to regulate inflammation and fibrosis. Importantly, early changes in plasma miRNA expression predicted survival with reasonable accuracy (88-92%). The miRNA signature that predicted survival in C3H mice, including miR-34a-5p, -100-5p, and -150-5p, were associated with pro-inflammatory NF-κB-mediated signaling pathways, whereas the signature identified in C57Bl/6 mice (miR-34b-3p, -96-5p, and -802-5p) was associated with TGF-β/SMAD signaling. This study supports the hypothesis that plasma miRNA profiles could be used to identify individuals at high risk of organ-specific late radiation damage, with applications for radiation oncology clinical practice or in the context of a radiological incident.
View details for DOI 10.1371/journal.pone.0232411
View details for Web of Science ID 000537470300005
View details for PubMedID 32392259
View details for PubMedCentralID PMC7213687
Modeling Mixed Vascular and Alzheimer's Dementia Using Focal Subcortical Ischemic Stroke in Human ApoE4-TR:5XFAD Transgenic Mice.
Translational stroke research
Subcortical white matter ischemic lesions are increasingly recognized to have pathologic overlap in individuals with Alzheimer's disease (AD). The interaction of white matter ischemic lesions with amyloid pathology seen in AD is poorly characterized. We designed a novel mouse model of subcortical white matter ischemic stroke and AD that can inform our understanding of the cellular and molecular mechanisms of mixed vascular and AD dementia. Subcortical white matter ischemic stroke underlying forelimb motor cortex was induced by local stereotactic injection of an irreversible eNOS inhibitor. Subcortical white matter ischemic stroke or sham procedures were performed on human ApoE4-targeted-replacement (TR):5XFAD mice at 8weeks of age. Behavioral tests were done at 7, 10, 15, and 20weeks. A subset of animals underwent 18FDG-PET/CT. At 20weeks of age, brain tissue was examined for amyloid plaque accumulation and cellular changes. Compared with sham E4-TR:5XFAD mice, those with an early subcortical ischemic stroke showed a significant reduction in amyloid plaque burden in the region of cortex overlying the subcortical stroke. Cognitive performance was improved in E4-TR:5XFAD mice with stroke compared with sham E4-TR:5XFAD animals. Iba-1+ microglial cells in the region of cortex overlying the subcortical stroke were increased in number and morphologic complexity compared with sham E4-TR:5XFAD mice, suggesting that amyloid clearance may be promoted by an interaction between activated microglia and cortical neurons in response to subcortical stroke. This novel approach to modeling mixed vascular and AD dementia provides a valuable tool for dissecting the molecular interactions between these two common pathologies.
View details for DOI 10.1007/s12975-020-00786-0
View details for PubMedID 32086779
- Publisher Correction: In vivo imaging of mitochondrial membrane potential in non-small-cell lung cancer. Nature 2020
Molecular Imaging of Chimeric Antigen Receptor T Cells by ICOS-ImmunoPET
Clinical cancer research: an official journal of the American Association for Cancer Research
Immunomonitoring of chimeric antigen receptor (CAR) T cells relies primarily on their quantification in the peripheral blood, which inadequately quantifies their biodistribution and activation status in the tissues. Noninvasive molecular imaging of CAR T cells by PET is a promising approach with the ability to provide spatial, temporal, and functional information. Reported strategies rely on the incorporation of reporter transgenes or ex vivo biolabeling, significantly limiting the application of CAR T-cell molecular imaging. In this study, we assessed the ability of antibody-based PET (immunoPET) to noninvasively visualize CAR T cells.After analyzing human CAR T cells in vitro and ex vivo from patient samples to identify candidate targets for immunoPET, we employed a syngeneic, orthotopic murine tumor model of lymphoma to assess the feasibility of in vivo tracking of CAR T cells by immunoPET using the 89Zr-DFO-anti-ICOS tracer, which we have previously reported.Analysis of human CD19-CAR T cells during activation identified the Inducible T-cell COStimulator (ICOS) as a potential target for immunoPET. In a preclinical tumor model, 89Zr-DFO-ICOS mAb PET-CT imaging detected significantly higher signal in specific bone marrow-containing skeletal sites of CAR T-cell-treated mice compared with controls. Importantly, administration of ICOS-targeting antibodies at tracer doses did not interfere with CAR T-cell persistence and function.This study highlights the potential of ICOS-immunoPET imaging for monitoring of CAR T-cell therapy, a strategy readily applicable to both commercially available and investigational CAR T cells.See related commentary by Volpe et al., p. 911.
View details for DOI 10.1158/1078-0432.CCR-20-2770
View details for PubMedCentralID PMC7887027
Estrogen receptor α controls metabolism in white and brown adipocytes by regulating Polg1 and mitochondrial remodeling.
Science translational medicine
2020; 12 (555)
Obesity is heightened during aging, and although the estrogen receptor α (ERα) has been implicated in the prevention of obesity, its molecular actions in adipocytes remain inadequately understood. Here, we show that adipose tissue ESR1/Esr1 expression inversely associated with adiposity and positively associated with genes involved in mitochondrial metabolism and markers of metabolic health in 700 Finnish men and 100 strains of inbred mice from the UCLA Hybrid Mouse Diversity Panel. To determine the anti-obesity actions of ERα in fat, we selectively deleted Esr1 from white and brown adipocytes in mice. In white adipose tissue, Esr1 controlled oxidative metabolism by restraining the targeted elimination of mitochondria via the E3 ubiquitin ligase parkin. mtDNA content was elevated, and adipose tissue mass was reduced in adipose-selective parkin knockout mice. In brown fat centrally involved in body temperature maintenance, Esr1 was requisite for both mitochondrial remodeling by dynamin-related protein 1 (Drp1) and uncoupled respiration thermogenesis by uncoupled protein 1 (Ucp1). In both white and brown fat of female mice and adipocytes in culture, mitochondrial dysfunction in the context of Esr1 deletion was paralleled by a reduction in the expression of the mtDNA polymerase γ subunit Polg1 We identified Polg1 as an ERα target gene by showing that ERα binds the Polg1 promoter to control its expression in 3T3L1 adipocytes. These findings support strategies leveraging ERα action on mitochondrial function in adipocytes to combat obesity and metabolic dysfunction.
View details for DOI 10.1126/scitranslmed.aax8096
View details for PubMedID 32759275
BIRC5 is a target for molecular imaging and detection of human pancreatic cancer.
2019; 457: 10-19
Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer mortality with a dismal overall survival rate and an urgent need for detection of minute tumors. Current diagnostic modalities have high sensitivity and specificity for larger tumors, but not for minute PDAC. In this study, we test the feasibility of a precision diagnostic platform for detecting and localizing minute human PDAC in mice. This platform includes: 1) defining BIRC5 as an early PDAC-upregulated gene and utilizing an enhanced BIRC5 super-promoter to drive expression of dual Gaussia luciferase (GLuc) and sr39 thymidine kinase (sr39TK) reporter genes exponentially and specifically in PDAC; 2) utilizing a genetically-engineered AAV2RGD to ensure targeted delivery of GLuc and sr39TK specifically to PDAC; 3) using serologic GLuc and sr39TK microPET/CT imaging to detect and localize minute human PDAC in mice. The study demonstrates feasibility of a precision diagnostic platform using an integrated technology through a multiple-stage amplification strategy of dual reporter genes to enhance the specificity and sensitivity of detection and localization of minute PDAC tumors and currently undetectable disease.
View details for DOI 10.1016/j.canlet.2019.04.036
View details for PubMedID 31059751
Multimodal imaging guides surgical management in a preclinical spinal implant infection model
2019; 4 (3)
Spine implant infections portend disastrous outcomes, as diagnosis is challenging and surgical eradication is at odds with mechanical spinal stability. Current imaging modalities can detect anatomical alterations and anomalies but cannot differentiate between infection and aseptic loosening, diagnose specific pathogens, or delineate the extent of an infection. Herein, a fully human monoclonal antibody 1D9, recognizing the immunodominant staphylococcal antigen A on the surface of Staphylococcus aureus, was assessed as a nuclear and fluorescent imaging probe in a preclinical model of S. aureus spinal implant infection, utilizing bioluminescently labeled bacteria to confirm the specificity and sensitivity of this targeting. Postoperative mice were administered 1D9 probe dual labeled with 89-zirconium (89Zr) and a bars represent SEM dye (NIR680) (89Zr-NIR680-1D9), and PET-CT and in vivo fluorescence and bioluminescence imaging were performed. The 89Zr-NIR680-1D9 probe accurately diagnosed both acute and subacute implant infection and permitted fluorescent image-guided surgery for selective debridement of infected tissue. Therefore, a single probe could noninvasively diagnose an infection and facilitate image-guided surgery to improve the clinical management of implant infections.
View details for DOI 10.1172/jci.insight.124813
View details for Web of Science ID 000458037000008
View details for PubMedID 30728332
View details for PubMedCentralID PMC6413782
An HK2 Antisense Oligonucleotide Induces Synthetic Lethality in HK1-HK2+ Multiple Myeloma.
2019; 79 (10): 2748–60
Although the majority of adult tissues express only hexokinase 1 (HK1) for glycolysis, most cancers express hexokinase 2 (HK2) and many coexpress HK1 and HK2. In contrast to HK1+HK2+ cancers, HK1-HK2+ cancer subsets are sensitive to cytostasis induced by HK2shRNA knockdown and are also sensitive to synthetic lethality in response to the combination of HK2shRNA knockdown, an oxidative phosphorylation (OXPHOS) inhibitor diphenyleneiodonium (DPI), and a fatty acid oxidation (FAO) inhibitor perhexiline (PER). The majority of human multiple myeloma cell lines are HK1-HK2+. Here we describe an antisense oligonucleotide (ASO) directed against human HK2 (HK2-ASO1), which suppressed HK2 expression in human multiple myeloma cell cultures and human multiple myeloma mouse xenograft models. The HK2-ASO1/DPI/PER triple-combination achieved synthetic lethality in multiple myeloma cells in culture and prevented HK1-HK2+ multiple myeloma tumor xenograft progression. DPI was replaceable by the FDA-approved OXPHOS inhibitor metformin (MET), both for synthetic lethality in culture and for inhibition of tumor xenograft progression. In addition, we used an ASO targeting murine HK2 (mHK2-ASO1) to validate the safety of mHK2-ASO1/MET/PER combination therapy in mice bearing murine multiple myeloma tumors. HK2-ASO1 is the first agent that shows selective HK2 inhibition and therapeutic efficacy in cell culture and in animal models, supporting clinical development of this synthetically lethal combination as a therapy for HK1-HK2+ multiple myeloma. SIGNIFICANCE: A first-in-class HK2 antisense oligonucleotide suppresses HK2 expression in cell culture and in in vivo, presenting an effective, tolerated combination therapy for preventing progression of HK1-HK2+ multiple myeloma tumors. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/10/2748/F1.large.jpg.
View details for DOI 10.1158/0008-5472.CAN-18-2799
View details for PubMedID 30885978
View details for PubMedCentralID PMC6522331
In vivo characterization of [18F]AVT-011 as a radiotracer for PET imaging of multidrug resistance.
European journal of nuclear medicine and molecular imaging
Multidrug resistance (MDR) impedes cancer treatment. Two efflux transporters from the ATP-binding cassette (ABC) family, ABCB1 and ABCG2, may contribute to MDR by restricting the entry of therapeutic drugs into tumor cells. Although a higher expression of these transporters has been correlated with an unfavorable response to chemotherapy, transporter expression does not necessarily correlate with function. In this study, we characterized the pharmacological properties of [18F]AVT-011, a new PET radiotracer for imaging transporter-mediated MDR in tumors.AVT-011 was radiolabeled with 18F and evaluated with PET imaging in preclinical models. Transport of [18F]AVT-011 by ABCB1 and/or ABCG2 was assessed by measuring its uptake in the brains of wild-type, Abcb1a/b-/-, and Abcg2-/- mice at baseline and after administration of the ABCB1 inhibitor tariquidar (n = 5/group). Metabolism and biodistribution of [18F]AVT-011 were also measured. To measure ABCB1 function in tumors, we performed PET experiments using both [18F]AVT-011 and [18F]FDG in mice bearing orthotopic breast tumors (n = 7-10/group) expressing clinically relevant levels of ABCB1.At baseline, brain uptake was highest in Abcb1a/b-/- mice. After tariquidar administration, brain uptake increased 3-fold and 8-fold in wild-type and Abcg2-/- mice, respectively, but did not increase further in Abcb1a/b-/- mice. At 30 min after injection, the radiotracer was > 90% in its parent form and had highest uptake in organs of the hepatobiliary system. Compared with that in drug-sensitive tumors, uptake of [18F]AVT-011 was 32% lower in doxorubicin-resistant tumors with highest ABCB1 expression and increased by 40% with tariquidar administration. Tumor uptake of [18F]FDG did not significantly differ among groups.[18F]AVT-011 is a dual ABCB1/ABCG2 substrate radiotracer that can quantify transporter function at the blood-brain barrier and in ABCB1-expressing tumors, making it potentially suitable for clinical imaging of ABCB1-mediated MDR in tumors.
View details for DOI 10.1007/s00259-019-04589-w
View details for PubMedID 31729540
Utilizing F-18-FDG PET/CT Imaging and Quantitative Histology to Measure Dynamic Changes in the Glucose Metabolism in Mouse Models of Lung Cancer
JOVE-JOURNAL OF VISUALIZED EXPERIMENTS
A hallmark of advanced tumors is a switch to aerobic glycolysis that is readily measured by [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG PET) imaging. Co-mutations in the KRAS proto-oncogene and the LKB1 tumor suppressor gene are frequent events in lung cancer that drive hypermetabolic, glycolytic tumor growth. A critical pathway regulating the growth and metabolism of these tumors is the mechanistic target of the rapamycin (mTOR) pathway, which can be effectively targeted using selective catalytic mTOR kinase inhibitors. The mTOR inhibitor MLN0128 suppresses glycolysis in mice bearing tumors with Kras and Lkb1 co-mutations, referred to as KL mice. The therapy response in KL mice is first measured by 18F-FDG PET and computed tomography (CT) imaging before and after the delivery of MLN0128. By utilizing 18F-FDG PET/CT, researchers are able to measure dynamic changes in the glucose metabolism in genetically engineered mouse models (GEMMs) of lung cancer following a therapeutic intervention with targeted therapies. This is followed by ex vivo autoradiography and a quantitative immunohistochemical (qIHC) analysis using morphometric software. The use of qIHC enables the detection and quantification of distinct changes in the biomarker profiles following treatment as well as the characterization of distinct tumor pathologies. The coupling of PET imaging to quantitative histology is an effective strategy to identify metabolic and therapeutic responses in vivo in mouse models of disease.
View details for DOI 10.3791/57167
View details for Web of Science ID 000444836300011
View details for PubMedID 30080208
View details for PubMedCentralID PMC6126521
A precision therapeutic strategy for hexokinase 1-null, hexokinase 2-positive cancers
CANCER & METABOLISM
2018; 6: 7
Precision medicine therapies require identification of unique molecular cancer characteristics. Hexokinase (HK) activity has been proposed as a therapeutic target; however, different hexokinase isoforms have not been well characterized as alternative targets. While HK2 is highly expressed in the majority of cancers, cancer subtypes with differential HK1 and HK2 expression have not been characterized for their sensitivities to HK2 silencing.HK1 and HK2 expression in the Cancer Cell Line Encyclopedia dataset was analyzed. A doxycycline-inducible shRNA silencing system was used to examine the effect of HK2 knockdown in cultured cells and in xenograft models of HK1-HK2+ and HK1+HK2+ cancers. Glucose consumption and lactate production rates were measured to monitor HK activity in cell culture, and 18F-FDG PET/CT was used to monitor HK activity in xenograft tumors. A high-throughput screen was performed to search for synthetically lethal compounds in combination with HK2 inhibition in HK1-HK2+ liver cancer cells, and a combination therapy for liver cancers with this phenotype was developed. A metabolomic analysis was performed to examine changes in cellular energy levels and key metabolites in HK1-HK2+ cells treated with this combination therapy. The CRISPR Cas9 method was used to establish isogenic HK1+HK2+ and HK1-HK2+ cell lines to evaluate HK1-HK2+ cancer cell sensitivity to the combination therapy.Most tumors express both HK1 and HK2, and subsets of cancers from a wide variety of tissues of origin express only HK2. Unlike HK1+HK2+ cancers, HK1-HK2+ cancers are sensitive to HK2 silencing-induced cytostasis. Synthetic lethality was achieved in HK1-HK2+ liver cancer cells, by the combination of DPI, a mitochondrial complex I inhibitor, and HK2 inhibition, in HK1-HK2+ liver cancer cells. Perhexiline, a fatty acid oxidation inhibitor, further sensitizes HK1-HK2+ liver cancer cells to the complex I/HK2-targeted therapeutic combination. Although HK1+HK2+ lung cancer H460 cells are resistant to this therapeutic combination, isogenic HK1KOHK2+ cells are sensitive to this therapy.The HK1-HK2+ cancer subsets exist among a wide variety of cancer types. Selective inhibition of the HK1-HK2+ cancer cell-specific energy production pathways (HK2-driven glycolysis, oxidative phosphorylation and fatty acid oxidation), due to the unique presence of only the HK2 isoform, appears promising to treat HK1-HK2+ cancers. This therapeutic strategy will likely be tolerated by most normal tissues, where only HK1 is expressed.
View details for DOI 10.1186/s40170-018-0181-8
View details for Web of Science ID 000437119600001
View details for PubMedID 29988332
View details for PubMedCentralID PMC6022704
Effects of teriparatide on morphology of aortic calcification in aged hyperlipidemic mice
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
2018; 314 (6): H1203–H1213
Calcific aortic vasculopathy correlates with bone loss in osteoporosis in an age-independent manner. Prior work suggests that teriparatide, the bone anabolic treatment for postmenopausal osteoporosis, may inhibit the onset of aortic calcification. Whether teriparatide affects the progression of preexisting aortic calcification, widespread among this patient population, is unknown. Female apolipoprotein E-deficient mice were aged for over 1 yr to induce aortic calcification, treated for 4.5 wk with daily injections of control vehicle (PBS), 40 µg/kg teriparatide (PTH40), or 400 µg/kg teriparatide (PTH400), and assayed for aortic calcification by microcomputed tomography (microCT) before and after treatment. In a followup cohort, aged female apolipoprotein E-deficient mice were treated with PBS or PTH400 and assayed for aortic calcification by serial microCT and micropositron emission tomography. In both cohorts, aortic calcification detected by microCT progressed similarly in all groups. Mean aortic 18F-NaF incorporation, detected by serial micropositron emission tomography, increased in the PBS-treated group (+14 ± 5%). In contrast, 18F-NaF incorporation decreased in the PTH400-treated group (-33 ± 20%, P = 0.03). Quantitative histochemical analysis by Alizarin red staining revealed a lower mineral surface area index in the PTH400-treated group compared with the PBS-treated group ( P = 0.04). Furthermore, Masson trichrome staining showed a significant increase in collagen deposition in the left ventricular myocardium of mice that received PTH400 [2.1 ± 0.6% vs. control mice (0.5 ± 0.1%), P = 0.02]. In summary, although teriparatide may not affect the calcium mineral content of aortic calcification, it reduces 18F-NaF uptake in calcified lesions, suggesting the possibility that it may reduce mineral surface area with potential impact on plaque stability. NEW & NOTEWORTHY Parathyroid hormone regulates bone mineralization and may also affect vascular calcification, which is an important issue, given that its active fragment, teriparatide, is widely used for the treatment of osteoporosis. To determine whether teriparatide alters vascular calcification, we imaged aortic calcification in mice treated with teriparatide and control mice. Although teriparatide did not affect the calcium content of cardiovascular deposits, it reduced their fluoride tracer uptake.
View details for DOI 10.1152/ajpheart.00718.2017
View details for Web of Science ID 000441143800010
View details for PubMedID 29451816
View details for PubMedCentralID PMC6032086
Microscale radiosynthesis, preclinical imaging and dosimetry study of [F-18]AMBF(3)-TATE: A potential PET tracer for clinical imaging of somatostatin receptors
NUCLEAR MEDICINE AND BIOLOGY
2018; 61: 36–44
Peptides labeled with positron-emitting isotopes are emerging as a versatile class of compounds for the development of highly specific, targeted imaging agents for diagnostic imaging via positron-emission tomography (PET) and for precision medicine via theranostic applications. Despite the success of peptides labeled with gallium-68 (for imaging) or lutetium-177 (for therapy) in the clinical management of patients with neuroendocrine tumors or prostate cancer, there are significant advantages of using fluorine-18 for imaging. Recent developments have greatly simplified such labeling: in particular, labeling of organotrifluoroborates via isotopic exchange can readily be performed in a single-step under aqueous conditions and without the need for HPLC purification. Though an automated synthesis has not yet been explored, microfluidic approaches have emerged for 18F-labeling with high speed, minimal reagents, and high molar activity compared to conventional approaches. As a proof-of-concept, we performed microfluidic labeling of an octreotate analog ([18F]AMBF3-TATE), a promising 18F-labeled analog that could compete with [68Ga]Ga-DOTATATE with the advantage of providing a greater number of patient doses per batch produced.Both [18F]AMBF3-TATE and [68Ga]Ga-DOTATATE were labeled, the former by microscale methods adapted from manual labeling, and were imaged in mice bearing human SSTR2-overexpressing, rat SSTR2 wildtype, and SSTR2-negative xenografts. Furthermore, a dosimetry analysis was performed for [18F]AMBF3-TATE.The micro-synthesis exhibited highly-repeatable performance with radiochemical conversion of 50 ± 6% (n = 15), overall decay-corrected radiochemical yield of 16 ± 1% (n = 5) in ~40 min, radiochemical purity >99%, and high molar activity. Preclinical imaging with [18F]AMBF3-TATE in SSTR2 tumor models correlated well with [68Ga]Ga-DOTATATE. The favorable biodistribution, with the highest tracer accumulation in the bladder followed distantly by gastrointestinal tissues, resulted in 1.26 × 10-2 mSv/MBq maximal estimated effective dose in human, a value lower than that reported for current clinical 18F- and 68Ga-labeled compounds.The combination of novel chemical approaches to 18F-labeling and microdroplet radiochemistry have the potential to serve as a platform for greatly simplified development and production of 18F-labeled peptide tracers. Favorable preclinical imaging and dosimetry of [18F]AMBF3-TATE, combined with a convenient synthesis, validate this assertion and suggest strong potential for clinical translation.
View details for DOI 10.1016/j.nucmedbio.2018.04.001
View details for Web of Science ID 000437551700005
View details for PubMedID 29747035
View details for PubMedCentralID PMC6015542
The GSK3 Signaling Axis Regulates Adaptive Glutamine Metabolism in Lung Squamous Cell Carcinoma
2018; 33 (5): 905-+
Altered metabolism is a hallmark of cancer growth, forming the conceptual basis for development of metabolic therapies as cancer treatments. We performed in vivo metabolic profiling and molecular analysis of lung squamous cell carcinoma (SCC) to identify metabolic nodes for therapeutic targeting. Lung SCCs adapt to chronic mTOR inhibition and suppression of glycolysis through the GSK3α/β signaling pathway, which upregulates glutaminolysis. Phospho-GSK3α/β protein levels are predictive of response to single-therapy mTOR inhibition while combinatorial treatment with the glutaminase inhibitor CB-839 effectively overcomes therapy resistance. In addition, we identified a conserved metabolic signature in a broad spectrum of hypermetabolic human tumors that may be predictive of patient outcome and response to combined metabolic therapies targeting mTOR and glutaminase.
View details for DOI 10.1016/j.ccell.2018.04.002
View details for Web of Science ID 000432494500014
View details for PubMedID 29763624
View details for PubMedCentralID PMC6451645
The 4-N-acyl and 4-N-alkyl gemcitabine analogues with silicon-fluoride-acceptor: Application to F-18-Radiolabeling
EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY
2018; 148: 314–24
The coupling of gemcitabine with functionalized carboxylic acids using peptide coupling conditions afforded 4-N-alkanoyl analogues with a terminal alkyne or azido moiety. Reaction of 4-N-tosylgemcitabine with azidoalkyl amine provided 4-N-alkyl gemcitabine with a terminal azido group. Click reaction with silane building blocks afforded 4-N-alkanoyl or 4-N-alkyl gemcitabine analogues suitable for fluorination. RP-HPLC analysis indicated better chemical stability of 4-N-alkyl gemcitabine analogues versus 4-N-alkanoyl analogues in acidic aqueous conditions. The 4-N-alkanoyl gemcitabine analogues showed potent cytostatic activity against L1210 cell line, but cytotoxicity of the 4-N-alkylgemcitabine analogues was low. However, 4-N-alkanoyl and 4-N-alkyl analogues had comparable antiproliferative activities in the HEK293 cells. The 4-N-alkyl analogue with a terminal azide group was shown to be localized inside HEK293 cells by fluorescence microscopy after labelling with Fluor 488-alkyne. The [18F]4-N-alkyl or alkanoyl silane gemcitabine analogues were successfully synthesized using microscale and conventional silane-labeling radiochemical protocols. Preliminary positron-emission tomography (PET) imaging in mice showed the biodistribution of [18F]4-N-alkyl to have initial concentration in the liver, kidneys and GI tract followed by increasing signal in the bone.
View details for DOI 10.1016/j.ejmech.2018.02.017
View details for Web of Science ID 000428824700025
View details for PubMedID 29471120
View details for PubMedCentralID PMC5841594
- Performing radiosynthesis in microvolumes to maximize molar activity of tracers for positron emission tomography COMMUNICATIONS CHEMISTRY 2018; 1
Performing radiosynthesis in microvolumes to maximize molar activity of tracers for positron emission tomography.
2018; 1 (1)
Positron emission tomography (PET) is a molecular diagnostic imaging technology to quantitatively visualize biological processes in vivo. For many applications, including imaging of low tissue density targets (e.g. neuroreceptors), imaging in small animals, and evaluation of novel tracers, the injected PET tracer must be produced with high molar activity to ensure low occupancy of biological targets and avoid pharmacologic effects. Additionally, high molar activity is essential for tracers with lengthy syntheses or tracers transported to distant imaging sites. We show that radiosynthesis of PET tracers in microliter volumes instead of conventional milliliter volumes results in substantially increased molar activity, and we identify the most relevant variables affecting this parameter. Furthermore, using the PET tracer [18F]fallypride, we illustrate that molar activity can have a significant impact on biodistribution. With full automation, microdroplet platforms could provide a means for radiochemists to routinely, conveniently, and safely produce PET tracers with high molar activity.
View details for DOI 10.1038/s42004-018-0009-z
View details for PubMedID 34291178
View details for PubMedCentralID PMC8291036
Hexokinase 2 is targetable for HK1 negative, HK2 positive tumors from a wide variety of tissues of origin.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Although absent in most adult tissues, hexokinase 2 (HK2) is expressed in a majority of tumors and contributes to increased glucose consumption and to in vivo tumor 18F-FDG PET signaling. Methods: Both HK2 knockdown and knockout approaches were used to investigate the role of HK2 in cancer cell proliferation, in vivo xenograft tumor progression and 18F-FDG tumor accumulation. BioProfiler analysis monitored cell culture glucose consumption and lactate production; 18F-FDG PET/CT monitored in vivo tumor glucose accumulation. Cancer Cell Line Encyclopedia data were analyzed for HK1 and HK2 expression. Results: Neither cell proliferation in culture nor xenograft tumor progression are inhibited by HK2 knockdown or knockout in cancer cells that express HK1 and HK2. However, cancer subsets from a variety of tissues of origin express only HK2, but not HK1. In contrast to HK1+HK2+ cancers, HK2 knockdown in HK1-HK2+ cancer cells results in inhibition of cell proliferation, colony formation and xenograft tumor progression. Moreover, HK1KOHK2+ cancer cells are susceptible to HK2 inhibition, in contrast to their isogenic HK1+HK2+ parental cells. Conclusion: HK1 and HK2 expression are redundant in tumors; either can provide sufficient aerobic glycolysis for tumor growth; despite a reduction in 18F-FDG PET signal. Therapeutic HK2 inhibition is likely to be restricted to HK1-HK2+ tumor subsets, but stratification of tumors that express HK2, but not HK1, should identify tumors treatable with emerging HK2 specific inhibitors.
View details for DOI 10.2967/jnumed.118.212365
View details for PubMedID 29880505
Ex Vivo Radiolabeling and In Vivo PET Imaging of T Cells Expressing Nuclear Reporter Genes
REPORTER GENE IMAGING: METHODS AND PROTOCOLS
2018; 1790: 153–63
Recent advances in T cell-based immunotherapies from bench to bedside have highlighted the need for improved diagnostic imaging of T cell trafficking in vivo and the means to noninvasively investigate failures in treatment response. T cells expressing tumor-associated T cell receptors (TCRs) or engineered with chimeric antigen receptors (CARs) face multiple challenges, including possible influence of genetic engineering on T cell efficacy, inhibitory effects of the tumor microenvironment, tumor checkpoint proteins and on-target, off-tissue toxicities (Kershaw et al., Nat Rev Cancer 13:525-541, 2013; Corrigan-Curay et al., Mol Ther 22:1564-1574, 2014; June et al., Sci Trans Med 7:280-287, 2015; Whiteside et al., Clin Cancer Res 22:1845-1855, 2016; Rosenberg and Restifo, Science 348:62-68, 2015). Positron emission tomography (PET) imaging with nuclear reporter genes is potentially one of the most sensitive and noninvasive methods to quantitatively track and monitor function of adoptively transferred cells in vivo. However, in vivo PET detection of T cells after administration into patients is limited by the degree of tracer accumulation per cell in situ and cell density in target tissues. We describe here a method for ex vivo radiolabeling of T cells, a reliable and robust technique for PET imaging of the kinetics of T cell biodistribution from the time of administration to subsequent localization in targeted tumors and other tissues of the body. This noninvasive technique can provide valuable information to monitor and identify the potential efficacy of adoptive cell therapies.
View details for DOI 10.1007/978-1-4939-7860-1_12
View details for Web of Science ID 000448886300013
View details for PubMedID 29858790
Detection of immune responses after immunotherapy in glioblastoma using PET and MRI
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2017; 114 (38): 10220–25
Contrast-enhanced MRI is typically used to follow treatment response and progression in patients with glioblastoma (GBM). However, differentiating tumor progression from pseudoprogression remains a clinical dilemma largely unmitigated by current advances in imaging techniques. Noninvasive imaging techniques capable of distinguishing these two conditions could play an important role in the clinical management of patients with GBM and other brain malignancies. We hypothesized that PET probes for deoxycytidine kinase (dCK) could be used to differentiate immune inflammatory responses from other sources of contrast-enhancement on MRI. Orthotopic malignant gliomas were established in syngeneic immunocompetent mice and then treated with dendritic cell (DC) vaccination and/or PD-1 mAb blockade. Mice were then imaged with [18F]-FAC PET/CT and MRI with i.v. contrast. The ratio of contrast enhancement on MRI to normalized PET probe uptake, which we term the immunotherapeutic response index, delineated specific regions of immune inflammatory activity. On postmortem examination, FACS-based enumeration of intracranial tumor-infiltrating lymphocytes directly correlated with quantitative [18F]-FAC PET probe uptake. Three patients with GBM undergoing treatment with tumor lysate-pulsed DC vaccination and PD-1 mAb blockade were also imaged before and after therapy using MRI and a clinical PET probe for dCK. Unlike in mice, [18F]-FAC is rapidly catabolized in humans; thus, we used another dCK PET probe, [18F]-clofarabine ([18F]-CFA), that may be more clinically relevant. Enhanced [18F]-CFA PET probe accumulation was identified in tumor and secondary lymphoid organs after immunotherapy. Our findings identify a noninvasive modality capable of imaging the host antitumor immune response against intracranial tumors.
View details for DOI 10.1073/pnas.1706689114
View details for Web of Science ID 000411157100075
View details for PubMedID 28874539
View details for PubMedCentralID PMC5617282
Automatic concentration and reformulation of PET tracers via microfluidic membrane distillation
LAB ON A CHIP
2017; 17 (10): 1802–16
Short-lived radiolabeled tracers for positron emission tomography (PET) must be rapidly synthesized, purified, and formulated into injectable solution just prior to imaging. Current radiosynthesizers are generally designed for clinical use, and the HPLC purification and SPE formulation processes often result in a final volume that is too large for preclinical and emerging in vitro applications. Conventional technologies and techniques for reducing this volume tend to be slow, resulting in radioactive decay of the product, and often require manual handling of the radioactive materials. We present a fully-automated microfluidic system based on sweeping gas membrane distillation to rapidly perform the concentration and formulation process. After detailed characterization of the system, we demonstrate fast and efficient concentration and formulation of several PET tracers, evaluate residual solvent content to establish the safety of the formulated tracers for injection, and show that the formulated tracer can be used for in vivo imaging.
View details for DOI 10.1039/c6lc01569g
View details for Web of Science ID 000401551300011
View details for PubMedID 28443841
View details for PubMedCentralID PMC5497730
Radiochemistry on electrodes: Synthesis of an F-18-labelled and in vivo stable COX-2 inhibitor
2017; 12 (5): e0176606
New radiochemistry techniques can yield novel PET tracers for COX-2 and address the shortcomings in in vivo stability and specificity, which have held back clinical translation of tracers to image COX-2 expression. Current techniques limit radiosynthesis to analogs of the COX-2 inhibitors with fluorine-18 added via a carbon chain, or on an aromatic position which renders the radiolabeled analog less specific towards COX-2, resulting in tracers with low in vivo stability or specificity. To solve this problem, we have developed a new high affinity, 18F-labelled COX-2 inhibitor that is radiolabeled directly on a heteroaromatic ring. This molecule exhibits favorable biodistribution and increased metabolic stability. Synthesis of this molecule cannot be achieved by traditional means; consequently, we have developed an automated electrochemical radiosynthesis platform to synthesize up to 5 mCi of radiochemically pure 18F-COX-2ib in 4 hours (2% decay-corrected radiochemical yield). In vitro studies demonstrated clear correlation between COX-2 expression and uptake of the tracer. PET imaging of healthy animals confirmed that the molecule is excreted from blood within an hour, mainly through the hepatobiliary excretion pathway. In vivo metabolism data demonstrated that > 95% of the injected radioactivity remains in the form of the parent molecule 1 hour after injection.
View details for DOI 10.1371/journal.pone.0176606
View details for Web of Science ID 000400646300037
View details for PubMedID 28464017
View details for PubMedCentralID PMC5413030
- Rigor and Reproducibility in Analysis of Vascular Calcification CIRCULATION RESEARCH 2017; 120 (8): 1240–42
Cardiac Fibroblasts Adopt Osteogenic Fates and Can Be Targeted to Attenuate Pathological Heart Calcification
CELL STEM CELL
2017; 20 (2): 218-+
Mammalian tissues calcify with age and injury. Analogous to bone formation, osteogenic cells are thought to be recruited to the affected tissue and induce mineralization. In the heart, calcification of cardiac muscle leads to conduction system disturbances and is one of the most common pathologies underlying heart blocks. However the cell identity and mechanisms contributing to pathological heart muscle calcification remain unknown. Using lineage tracing, murine models of heart calcification and in vivo transplantation assays, we show that cardiac fibroblasts (CFs) adopt an osteoblast cell-like fate and contribute directly to heart muscle calcification. Small-molecule inhibition of ENPP1, an enzyme that is induced upon injury and regulates bone mineralization, significantly attenuated cardiac calcification. Inhibitors of bone mineralization completely prevented ectopic cardiac calcification and improved post injury heart function. Taken together, these findings highlight the plasticity of fibroblasts in contributing to ectopic calcification and identify pharmacological targets for therapeutic development.
View details for PubMedID 27867037
View details for PubMedCentralID PMC5291784
Targeted Inhibition of EGFR and Glutaminase Induces Metabolic Crisis in EGFR Mutant Lung Cancer
2017; 18 (3): 601–10
Cancer cells exhibit increased use of nutrients, including glucose and glutamine, to support the bioenergetic and biosynthetic demands of proliferation. We tested the small-molecule inhibitor of glutaminase CB-839 in combination with erlotinib on epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC) as a therapeutic strategy to simultaneously impair cancer glucose and glutamine utilization and thereby suppress tumor growth. Here, we show that CB-839 cooperates with erlotinib to drive energetic stress and activate the AMP-activated protein kinase (AMPK) pathway in EGFR (del19) lung tumors. Tumor cells undergo metabolic crisis and cell death, resulting in rapid tumor regression in vivo in mouse NSCLC xenografts. Consistently, positron emission tomography (PET) imaging with 18F-fluoro-2-deoxyglucose (18F-FDG) and 11C-glutamine (11C-Gln) of xenografts indicated reduced glucose and glutamine uptake in tumors following treatment with CB-839 + erlotinib. Therefore, PET imaging with 18F-FDG and 11C-Gln tracers can be used to non-invasively measure metabolic response to CB-839 and erlotinib combination therapy.
View details for DOI 10.1016/j.celrep.2016.12.061
View details for Web of Science ID 000396470600003
View details for PubMedID 28099841
View details for PubMedCentralID PMC5260616
Synthesis and preclinical evaluation of an (AlF)-F-18 radiofluorinated GLU-UREA-LYS(AHX)-HBED-CC PSMA ligand
EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
2016; 43 (12): 2122–30
The aim of this study was to synthesize and preclinically evaluate an 18F-PSMA positron emission tomography (PET) tracer. Prostate-specific membrane antigen (PSMA) specificity, biodistribution, and dosimetry in healthy and tumor-bearing mice were determined.Several conditions for the labeling of 18F-PSMA-11 via 18F-AlF-complexation were screened to study the influence of reaction temperature, peptide amount, ethanol volume, and reaction time. After synthesis optimization, biodistribution and dosimetry studies were performed in C57BL6 mice. For proof of PSMA-specificity, mice were implanted with PSMA-negative (PC3) and PSMA-positive (LNCaP) tumors in contralateral flanks. Static and dynamic microPET/computed tomography (CT) imaging was performed.Quantitative labeling yields could be achieved with >97 % radiochemical purity. The 18F-PSMA-11 uptake was more than 24-fold higher in PSMA-high LNCaP than in PSMA-low PC3 tumors (18.4 ± 3.3 %ID/g and 0.795 ± 0.260 %ID/g, respectively; p < 4.2e-5). Results were confirmed by ex vivo gamma counter analysis of tissues after the last imaging time point. The highest absorbed dose was reported for the kidneys. The maximum effective dose for an administered activity of 200 MBq was 1.72 mSv.18F-PSMA-11 using direct labeling of chelate-attached peptide with aluminum-fluoride detected PSMA-expressing tumors with high tumor-to-liver ratios. The kidneys were the dose-limiting organs. Even by applying the most stringent dosimetric calculations, injected activities of up to 0.56 GBq are feasible.
View details for DOI 10.1007/s00259-016-3437-y
View details for Web of Science ID 000385161100004
View details for PubMedID 27329046
View details for PubMedCentralID PMC5050145
[18F]CFA as a clinically translatable probe for PET imaging of deoxycytidine kinase activity.
Proceedings of the National Academy of Sciences of the United States of America
2016; 113 (15): 4027–32
Deoxycytidine kinase (dCK), a rate-limiting enzyme in the cytosolic deoxyribonucleoside (dN) salvage pathway, is an important therapeutic and positron emission tomography (PET) imaging target in cancer. PET probes for dCK have been developed and are effective in mice but have suboptimal specificity and sensitivity in humans. To identify a more suitable probe for clinical dCK PET imaging, we compared the selectivity of two candidate compounds-[(18)F]Clofarabine; 2-chloro-2'-deoxy-2'-[(18)F]fluoro-9-β-d-arabinofuranosyl-adenine ([(18)F]CFA) and 2'-deoxy-2'-[(18)F]fluoro-9-β-d-arabinofuranosyl-guanine ([(18)F]F-AraG)-for dCK and deoxyguanosine kinase (dGK), a dCK-related mitochondrial enzyme. We demonstrate that, in the tracer concentration range used for PET imaging, [(18)F]CFA is primarily a substrate for dCK, with minimal cross-reactivity. In contrast, [(18)F]F-AraG is a better substrate for dGK than for dCK. [(18)F]CFA accumulation in leukemia cells correlated with dCK expression and was abrogated by treatment with a dCK inhibitor. Although [(18)F]CFA uptake was reduced by deoxycytidine (dC) competition, this inhibition required high dC concentrations present in murine, but not human, plasma. Expression of cytidine deaminase, a dC-catabolizing enzyme, in leukemia cells both in cell culture and in mice reduced the competition between dC and [(18)F]CFA, leading to increased dCK-dependent probe accumulation. First-in-human, to our knowledge, [(18)F]CFA PET/CT studies showed probe accumulation in tissues with high dCK expression: e.g., hematopoietic bone marrow and secondary lymphoid organs. The selectivity of [(18)F]CFA for dCK and its favorable biodistribution in humans justify further studies to validate [(18)F]CFA PET as a new cancer biomarker for treatment stratification and monitoring.
View details for DOI 10.1073/pnas.1524212113
View details for PubMedID 27035974
View details for PubMedCentralID PMC4839461
Comparative Analysis of T Cell Imaging with Human Nuclear Reporter Genes.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
2015; 56 (7): 1055-60
Monitoring genetically altered T cells is an important component of adoptive T cell therapy in patients, and the ability to visualize their trafficking/targeting, proliferation/expansion, and retention/death using highly sensitive reporter systems that do not induce an immunologic response would provide useful information. Therefore, we focused on human reporter gene systems that have the potential for translation to clinical studies. The objective of the in vivo imaging studies was to determine the minimum number of T cells that could be visualized with the different nuclear reporter systems. We determined the imaging sensitivity (lower limit of T cell detection) of each reporter using appropriate radiolabeled probes for PET or SPECT imaging.Human T cells were transduced with retroviral vectors encoding for the human norepinephrine transporter (hNET), human sodium-iodide symporter (hNIS), a human deoxycytidine kinase double mutant (hdCKDM), and herpes simplex virus type 1 thymidine kinase (hsvTK) reporter genes. After viability and growth were assessed, 10(5) to 3 × 10(6) reporter T cells were injected subcutaneously on the shoulder area. The corresponding radiolabeled probe was injected intravenously 30 min later, followed by sequential PET or SPECT imaging. Radioactivity at the T cell injection sites and in the thigh (background) was measured.The viability and growth of experimental cells were unaffected by transduction. The hNET/meta-(18)F-fluorobenzylguanidine ((18)F-MFBG) reporter system could detect less than 1 × 10(5) T cells because of its high uptake in the transduced T cells and low background activity. The hNIS/(124)I-iodide reporter system could detect approximately 1 × 10(6) T cells; (124)I-iodide uptake at the T cell injection site was time-dependent and associated with high background. The hdCKDM/2'-(18)F-fluoro-5-ethyl-1-β-d-arabinofuranosyluracil ((18)F-FEAU) and hsvTK/(18)F-FEAU reporter systems detected approximately 3 × 10(5) T cells, respectively. (18)F-FEAU was a more efficient probe (higher uptake, lower background) than (124)I-1-(2-deoxy-2-fluoro-1-d-arabinofuranosyl)-5-iodouracil for both hdCKDM and hsvTK.A comparison of different reporter gene-reporter probe systems for imaging of T cell number was performed, and the hNET/(18)F-MFBG PET reporter system was found to be the most sensitive and capable of detecting approximately 35-40 × 10(3) T cells at the site of T cell injection in the animal model.
View details for DOI 10.2967/jnumed.115.159855
View details for PubMedID 26025962
View details for PubMedCentralID PMC4511596
Co-targeting of convergent nucleotide biosynthetic pathways for leukemia eradication.
The Journal of experimental medicine
2014; 211 (3): 473-86
Pharmacological targeting of metabolic processes in cancer must overcome redundancy in biosynthetic pathways. Deoxycytidine (dC) triphosphate (dCTP) can be produced both by the de novo pathway (DNP) and by the nucleoside salvage pathway (NSP). However, the role of the NSP in dCTP production and DNA synthesis in cancer cells is currently not well understood. We show that acute lymphoblastic leukemia (ALL) cells avoid lethal replication stress after thymidine (dT)-induced inhibition of DNP dCTP synthesis by switching to NSP-mediated dCTP production. The metabolic switch in dCTP production triggered by DNP inhibition is accompanied by NSP up-regulation and can be prevented using DI-39, a new high-affinity small-molecule inhibitor of the NSP rate-limiting enzyme dC kinase (dCK). Positron emission tomography (PET) imaging was useful for following both the duration and degree of dCK inhibition by DI-39 treatment in vivo, thus providing a companion pharmacodynamic biomarker. Pharmacological co-targeting of the DNP with dT and the NSP with DI-39 was efficacious against ALL models in mice, without detectable host toxicity. These findings advance our understanding of nucleotide metabolism in leukemic cells, and identify dCTP biosynthesis as a potential new therapeutic target for metabolic interventions in ALL and possibly other hematological malignancies.
View details for DOI 10.1084/jem.20131738
View details for PubMedID 24567448
View details for PubMedCentralID PMC3949575
Development of new deoxycytidine kinase inhibitors and noninvasive in vivo evaluation using positron emission tomography.
Journal of medicinal chemistry
2013; 56 (17): 6696-708
Combined inhibition of ribonucleotide reductase and deoxycytidine kinase (dCK) in multiple cancer cell lines depletes deoxycytidine triphosphate pools leading to DNA replication stress, cell cycle arrest, and apoptosis. Evidence implicating dCK in cancer cell proliferation and survival stimulated our interest in developing small molecule dCK inhibitors. Following a high throughput screen of a diverse chemical library, a structure-activity relationship study was carried out. Positron Emission Tomography (PET) using (18)F-L-1-(2'-deoxy-2'-FluoroArabinofuranosyl) Cytosine ((18)F-L-FAC), a dCK-specific substrate, was used to rapidly rank lead compounds based on their ability to inhibit dCK activity in vivo. Evaluation of a subset of the most potent compounds in cell culture (IC50 = ∼1-12 nM) using the (18)F-L-FAC PET pharmacodynamic assay identified compounds demonstrating superior in vivo efficacy.
View details for DOI 10.1021/jm400457y
View details for PubMedID 23947754
View details for PubMedCentralID PMC3789385
Structure-guided engineering of human thymidine kinase 2 as a positron emission tomography reporter gene for enhanced phosphorylation of non-natural thymidine analog reporter probe.
The Journal of biological chemistry
2012; 287 (1): 446–54
Positron emission tomography (PET) reporter gene imaging can be used to non-invasively monitor cell-based therapies. Therapeutic cells engineered to express a PET reporter gene (PRG) specifically accumulate a PET reporter probe (PRP) and can be detected by PET imaging. Expanding the utility of this technology requires the development of new non-immunogenic PRGs. Here we describe a new PRG-PRP system that employs, as the PRG, a mutated form of human thymidine kinase 2 (TK2) and 2'-deoxy-2'-18F-5-methyl-1-β-L-arabinofuranosyluracil (L-18F-FMAU) as the PRP. We identified L-18F-FMAU as a candidate PRP and determined its biodistribution in mice and humans. Using structure-guided enzyme engineering, we generated a TK2 double mutant (TK2-N93D/L109F) that efficiently phosphorylates L-18F-FMAU. The N93D/L109F TK2 mutant has lower activity for the endogenous nucleosides thymidine and deoxycytidine than wild type TK2, and its ectopic expression in therapeutic cells is not expected to alter nucleotide metabolism. Imaging studies in mice indicate that the sensitivity of the new human TK2-N93D/L109F PRG is comparable with that of a widely used PRG based on the herpes simplex virus 1 thymidine kinase. These findings suggest that the TK2-N93D/L109F/L-18F-FMAU PRG-PRP system warrants further evaluation in preclinical and clinical applications of cell-based therapies.
View details for DOI 10.1074/jbc.M111.314666
View details for PubMedID 22074768
View details for PubMedCentralID PMC3249097
- Imaging in Immunology Research SMALL ANIMAL IMAGING: BASICS AND PRACTICAL GUIDE 2011: 565–83
Novel PET probes specific for deoxycytidine kinase.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
2010; 51 (7): 1092-8
Deoxycytidine kinase (dCK) is a rate-limiting enzyme in the deoxyribonucleoside salvage pathway and a critical determinant of therapeutic activity for several nucleoside analog prodrugs. We have previously reported the development of 1-(2'-deoxy-2'-(18)F-fluoro-beta-D-arabinofuranosyl)cytosine ((18)F-FAC), a new probe for PET of dCK activity in immune disorders and certain cancers. The objective of the current study was to develop PET probes with improved metabolic stability and specificity for dCK. Toward this goal, several candidate PET probes were synthesized and evaluated in vitro and in vivo.High-pressure liquid chromatography was used to analyze the metabolic stability of (18)F-FAC and several newly synthesized analogs with the natural D-enantiomeric sugar configuration or the corresponding unnatural L-configuration. In vitro kinase and uptake assays were used to determine the affinity of the (18)F-FAC L-nucleoside analogs for dCK. The biodistribution of selected L-analogs in mice was determined by small-animal PET/CT.Candidate PET probes were selected using the following criteria: low susceptibility to deamination, high affinity for purified recombinant dCK, high uptake in dCK-expressing cell lines, and biodistribution in mice reflective of the tissue-expression pattern of dCK. Among the 10 newly developed candidate probes, 1-(2'-deoxy-2'-(18)F-fluoro-beta-L-arabinofuranosyl)cytosine (L-(18)F-FAC) and 1-(2'-deoxy-2'-(18)F-fluoro-beta-L-arabinofuranosyl)-5-methylcytosine (L-(18)F-FMAC) most closely matched the selection criteria. The selection of L-(18)F-FAC and L-(18)F-FMAC was validated by showing that these two PET probes could be used to image animal models of leukemia and autoimmunity.Promising in vitro and in vivo data warrant biodistribution and dosimetry studies of L-(18)F-FAC and L-(18)F-FMAC in humans.
View details for DOI 10.2967/jnumed.109.073361
View details for PubMedID 20554721
View details for PubMedCentralID PMC3119947