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Zhao Q, Zhou X, Yan J, Kuiper R, Curbo S, Karlsson A. Long term survival and abnormal liver fat accumulation in mice with specific thymidine kinase 2 deficiency in liver tissue. PLoS One 2023; 18:e0285242. [PMID: 37796969 PMCID: PMC10553353 DOI: 10.1371/journal.pone.0285242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 08/11/2023] [Indexed: 10/07/2023] Open
Abstract
Deficiency in thymidine kinase 2 (TK2) causes mitochondrial DNA depletion. Liver mitochondria are severely affected in Tk2 complete knockout models and have been suggested to play a role in the pathogenesis of the Tk2 knockout phenotype, characterized by loss of hypodermal fat tissue, growth retardation and reduced life span. Here we report a liver specific Tk2 knockout (KO) model to further study mechanisms contributing to the phenotypic changes associated with Tk2 deficiency. Interestingly, the liver specific Tk2 KO mice had a normal life span despite a much lower mtDNA level in liver tissue. Mitochondrial DNA encoded peptide COXI did not differ between the Tk2 KO and control mice. However, the relative liver weight was significantly increased in the male Tk2 KO mouse model. Histology analysis indicated an increased lipid accumulation. We conclude that other enzyme activities can partly compensate Tk2 deficiency to maintain mtDNA at a low but stable level throughout the life span of the liver specific Tk2 KO mice. The lower level of mtDNA was sufficient for survival but led to an abnormal lipid accumulation in liver tissue.
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Affiliation(s)
- Qian Zhao
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
| | - Xiaoshan Zhou
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
| | - Jingyi Yan
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
| | - Raoul Kuiper
- Division of Biomolecular and Cellular Medicine, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
- Norwegian Veterinary Institute, Ås, Norway
| | - Sophie Curbo
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
| | - Anna Karlsson
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
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2
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Ward AS, Hsiung CH, Kesterson DG, Kamath VG, McKee EE. Entecavir competitively inhibits deoxyguanosine and deoxyadenosine phosphorylation in isolated mitochondria and the perfused rat heart. J Biol Chem 2022; 298:101876. [PMID: 35358513 PMCID: PMC9097457 DOI: 10.1016/j.jbc.2022.101876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 03/21/2022] [Accepted: 03/24/2022] [Indexed: 10/26/2022] Open
Abstract
Deoxyguanosine kinase (dGK) is reported responsible for the phosphorylation of deoxyadenosine (dA) and deoxyguanosine (dG) in the mitochondrial purine salvage pathway. Antiviral nucleoside analogs known as nucleoside reverse transcriptase inhibitors (NRTIs) must be phosphorylated by host enzymes for the analog to become active. We address the possibility that NRTI purine analogs may be competitive inhibitors of dGK. From a group of such analogs, we demonstrate that entecavir (ETV) competitively inhibited the phosphorylation of dG and dA in rat mitochondria. Mitochondria from the brain, heart, kidney, and liver showed a marked preference for phosphorylation of dG over dA (10-30-fold) and ETV over dA (2.5-4-fold). We found that ETV inhibited the phosphorylation of dG with an IC50 of 15.3 ± 2.2 μM and that ETV and dG were both potent inhibitors of dA phosphorylation with IC50s of 0.034 ± 0.007 and 0.028 ± 0.006 μM, respectively. In addition, the phosphorylation of dG and ETV followed Michaelis-Menten kinetics and each competitively inhibited the phosphorylation of the other. We observed that the kinetics of dA phosphorylation were strikingly different from those of dG phosphorylation, with an exponentially lower affinity for dGK and no effect of dA on dG or ETV phosphorylation. Finally, in an isolated heart perfusion model, we demonstrated that dG, dA, and ETV were phosphorylated and dG phosphorylation was inhibited by ETV. Taken together, these data demonstrate that dGK is inhibited by ETV and that the primary role of dGK is in the phosphorylation of dG rather than dA.
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Affiliation(s)
- Avery S Ward
- Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan, USA
| | - Chia-Heng Hsiung
- Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan, USA; School of Science, Westlake Institute for Advanced Study, Westlake University, Hangzhou, Zhejiang Province, China
| | - Daniel G Kesterson
- Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan, USA; Department of Health Management and Policy, University of Michigan School of Public Health, University of Michigan, Ann Arbor, Michigan, USA
| | - Vasudeva G Kamath
- Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan, USA; Department of Basic Medical Sciences, Touro College of Osteopathic Medicine, Middletown, New York, USA
| | - Edward E McKee
- Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan, USA.
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3
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Wang H, Han Y, Li S, Chen Y, Chen Y, Wang J, Zhang Y, Zhang Y, Wang J, Xia Y, Yuan J. Mitochondrial DNA Depletion Syndrome and Its Associated Cardiac Disease. Front Cardiovasc Med 2022; 8:808115. [PMID: 35237671 PMCID: PMC8882844 DOI: 10.3389/fcvm.2021.808115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 12/23/2021] [Indexed: 12/06/2022] Open
Abstract
Mitochondria is a ubiquitous, energy-supplying (ATP-based) organelle found in nearly all eukaryotes. It acts as a “power plant” by producing ATP through oxidative phosphorylation, providing energy for the cell. The bioenergetic functions of mitochondria are regulated by nuclear genes (nDNA). Mitochondrial DNA (mtDNA) and respiratory enzymes lose normal structure and function when nuclear genes encoding the related mitochondrial factors are impaired, resulting in deficiency in energy production. Massive generation of reactive oxygen species and calcium overload are common causes of mitochondrial diseases. The mitochondrial depletion syndrome (MDS) is associated with the mutations of mitochondrial genes in the nucleus. It is a heterogeneous group of progressive disorders characterized by the low mtDNA copy number. TK2, FBXL4, TYPM, and AGK are genes known to be related to MDS. More recent studies identified new mutation loci associated with this disease. Herein, we first summarize the structure and function of mitochondria, and then discuss the characteristics of various types of MDS and its association with cardiac diseases.
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Affiliation(s)
- Haiying Wang
- Department of Physiology, Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yijun Han
- Clinical Medical College, Jining Medical University, Jining, China
| | - Shenwei Li
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yunan Chen
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yafen Chen
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Jing Wang
- Dongying Fifth People's Hospital, Dongying, China
| | - Yuqing Zhang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yawen Zhang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Jingsuo Wang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yong Xia
- Key Laboratory of Precision Oncology of Shandong Higher Education, Institute of Precision Medicine, Jining Medical University, Jining, China
- Yong Xia
| | - Jinxiang Yuan
- The Collaborative Innovation Center, Jining Medical University, Jining, China
- *Correspondence: Jinxiang Yuan
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Frisk J, Vanoevelen JM, Bierau J, Pejler G, Eriksson S, Wang L. Biochemical Characterizations of Human TMPK Mutations Identified in Patients with Severe Microcephaly: Single Amino Acid Substitutions Impair Dimerization and Abolish Their Catalytic Activity. ACS OMEGA 2021; 6:33943-33952. [PMID: 34926941 PMCID: PMC8679000 DOI: 10.1021/acsomega.1c05288] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 11/19/2021] [Indexed: 06/14/2023]
Abstract
Deoxythymidylate kinase (TMPK) is a key enzyme in the synthesis of deoxythymidine triphosphate (dTTP). Four TMPK variants (P81L, A99T, D128N, and a frameshift) have been identified in human patients who suffered from severe neurodegenerative diseases. However, the impact of these mutations on TMPK function has not been clarified. Here we show that in fibroblasts derived from a patient, the P81L and D128N mutations led to a complete loss of TMPK activity in mitochondria and extremely low and unstable TMPK activity in cytosol. Despite the lack of TMPK activity, the patient-derived fibroblasts apparently grew normal. To investigate the impact of the mutations on the enzyme function, the mutant TMPKs were expressed, purified, and characterized. The wild-type TMPK mainly exists as a dimer with high substrate binding affinity, that is, low K M value and high catalytic efficiency, that is, k cat/K M. In contrast, all mutants were present as monomers with dramatically reduced substrate binding affinity and catalytic efficiencies. Based on the human TMPK structure, none of the mutated amino acids interacted directly with the substrates. By structural analysis, we could explain why the respective amino acid substitutions could drastically alter the enzyme structure and catalytic function. In conclusion, TMPK mutations identified in patients represent loss of function mutations but surprisingly the proliferation rate of the patient-derived fibroblasts was normal, suggesting the existence of an alternative and hitherto unknown compensatory TMPK-like enzyme for dTTP synthesis. Further studies of the TMPK enzymes will help to elucidate the role of TMPK in neuropathology.
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Affiliation(s)
- Junmei
Hu Frisk
- Department
of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala SE-750 07, Sweden
| | - Jo M. Vanoevelen
- Department
of Clinical Genetics, Maastricht University
Medical Centre+ and GROW School for Oncology and Developmental Biology, Maastricht 6202 AZ, The Netherlands
| | - Jörgen Bierau
- Department
of Clinical Genetics, Maastricht University
Medical Centre+ and GROW School for Oncology and Developmental Biology, Maastricht 6202 AZ, The Netherlands
| | - Gunnar Pejler
- Department
of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala SE-750 07, Sweden
- Department
of Medical Biochemistry and Microbiology, Uppsala University, Uppsala SE-750 07, Sweden
| | - Staffan Eriksson
- Department
of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala SE-750 07, Sweden
| | - Liya Wang
- Department
of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala SE-750 07, Sweden
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Jasper L, Scarcia P, Rust S, Reunert J, Palmieri F, Marquardt T. Uridine Treatment of the First Known Case of SLC25A36 Deficiency. Int J Mol Sci 2021; 22:ijms22189929. [PMID: 34576089 PMCID: PMC8470663 DOI: 10.3390/ijms22189929] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 09/05/2021] [Accepted: 09/06/2021] [Indexed: 11/16/2022] Open
Abstract
SLC25A36 is a pyrimidine nucleotide carrier playing an important role in maintaining mitochondrial biogenesis. Deficiencies in SLC25A36 in mouse embryonic stem cells have been associated with mtDNA depletion as well as mitochondrial dysfunction. In human beings, diseases triggered by SLC25A36 mutations have not been described yet. We report the first known case of SLC25A36 deficiency in a 12-year-old patient with hypothyroidism, hyperinsulinism, hyperammonemia, chronical obstipation, short stature, along with language and general developmental delay. Whole exome analysis identified the homozygous mutation c.803dupT, p.Ser269llefs*35 in the SLC25A36 gene. Functional analysis of mutant SLC25A36 protein in proteoliposomes showed a virtually abolished transport activity. Immunoblotting results suggest that the mutant SLC25A36 protein in the patient undergoes fast degradation. Supplementation with oral uridine led to an improvement of thyroid function and obstipation, increase of growth and developmental progress. Our findings suggest an important role of SLC25A36 in hormonal regulations and oral uridine as a safe and effective treatment.
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Affiliation(s)
- Luisa Jasper
- Department of Pediatrics, University Hospital of Münster, Albert-Schweitzer-Campus 1, Gebäude A13, 48149 Münster, Germany; (L.J.); (S.R.); (J.R.)
| | - Pasquale Scarcia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125 Bari, Italy;
| | - Stephan Rust
- Department of Pediatrics, University Hospital of Münster, Albert-Schweitzer-Campus 1, Gebäude A13, 48149 Münster, Germany; (L.J.); (S.R.); (J.R.)
| | - Janine Reunert
- Department of Pediatrics, University Hospital of Münster, Albert-Schweitzer-Campus 1, Gebäude A13, 48149 Münster, Germany; (L.J.); (S.R.); (J.R.)
| | - Ferdinando Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125 Bari, Italy;
- Correspondence: (F.P.); (T.M.)
| | - Thorsten Marquardt
- Department of Pediatrics, University Hospital of Münster, Albert-Schweitzer-Campus 1, Gebäude A13, 48149 Münster, Germany; (L.J.); (S.R.); (J.R.)
- Correspondence: (F.P.); (T.M.)
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6
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Molecular signature pathway of gene protein interaction in human mitochondrial DNA (mtDNA) metabolism linked disease. INDIAN JOURNAL OF MEDICAL SPECIALITIES 2018. [DOI: 10.1016/j.injms.2018.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Lopez-Gomez C, Levy RJ, Sanchez-Quintero MJ, Juanola-Falgarona M, Barca E, Garcia-Diaz B, Tadesse S, Garone C, Hirano M. Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency. Ann Neurol 2017; 81:641-652. [PMID: 28318037 DOI: 10.1002/ana.24922] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 03/09/2017] [Accepted: 03/09/2017] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Thymidine kinase 2 (TK2), a critical enzyme in the mitochondrial pyrimidine salvage pathway, is essential for mitochondrial DNA (mtDNA) maintenance. Mutations in the nuclear gene, TK2, cause TK2 deficiency, which manifests predominantly in children as myopathy with mtDNA depletion. Molecular bypass therapy with the TK2 products, deoxycytidine monophosphate (dCMP) and deoxythymidine monophosphate (dTMP), prolongs the life span of Tk2-deficient (Tk2-/- ) mice by 2- to 3-fold. Because we observed rapid catabolism of the deoxynucleoside monophosphates to deoxythymidine (dT) and deoxycytidine (dC), we hypothesized that: (1) deoxynucleosides might be the major active agents and (2) inhibition of deoxycytidine deamination might enhance dTMP+dCMP therapy. METHODS To test these hypotheses, we assessed two therapies in Tk2-/- mice: (1) dT+dC and (2) coadministration of the deaminase inhibitor, tetrahydrouridine (THU), with dTMP+dCMP. RESULTS We observed that dC+dT delayed disease onset, prolonged life span of Tk2-deficient mice and restored mtDNA copy number as well as respiratory chain enzyme activities and levels. In contrast, dCMP+dTMP+THU therapy decreased life span of Tk2-/- animals compared to dCMP+dTMP. INTERPRETATION Our studies demonstrate that deoxynucleoside substrate enhancement is a novel therapy, which may ameliorate TK2 deficiency in patients. Ann Neurol 2017;81:641-652.
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Affiliation(s)
- Carlos Lopez-Gomez
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Rebecca J Levy
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Maria J Sanchez-Quintero
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Martí Juanola-Falgarona
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Emanuele Barca
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY.,Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Beatriz Garcia-Diaz
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY.,Unidad de Gestión Clínica de Neurociencias, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain
| | - Saba Tadesse
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Caterina Garone
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY.,MRC Mitochondrial Biology Unit, Cambridge University, Cambridge, United Kingdom
| | - Michio Hirano
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
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Wang L. Mitochondrial purine and pyrimidine metabolism and beyond. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2017; 35:578-594. [PMID: 27906631 DOI: 10.1080/15257770.2015.1125001] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Carefully balanced deoxynucleoside triphosphate (dNTP) pools are essential for both nuclear and mitochondrial genome replication and repair. Two synthetic pathways operate in cells to produce dNTPs, e.g., the de novo and the salvage pathways. The key regulatory enzymes for de novo synthesis are ribonucleotide reductase (RNR) and thymidylate synthase (TS), and this process is considered to be cytosolic. The salvage pathway operates both in the cytosol (TK1 and dCK) and the mitochondria (TK2 and dGK). Mitochondrial dNTP pools are separated from the cytosolic ones owing to the double membrane structure of the mitochondria, and are formed by the salvage enzymes TK2 and dGK together with NMPKs and NDPK in postmitotic tissues, while in proliferating cells the mitochondrial dNTPs are mainly imported from the cytosol produced by the cytosolic pathways. Imbalanced mitochondrial dNTP pools lead to mtDNA depletion and/or deletions resulting in serious mitochondrial diseases. The mtDNA depletion syndrome is caused by deficiencies not only in enzymes in dNTP synthesis (TK2, dGK, p53R2, and TP) and mtDNA replication (mtDNA polymerase and twinkle helicase), but also in enzymes in other metabolic pathways such as SUCLA2 and SUCLG1, ABAT and MPV17. Basic questions are why defects in these enzymes affect dNTP synthesis and how important is mitochondrial nucleotide synthesis in the whole cell/organism perspective? This review will focus on recent studies on purine and pyrimidine metabolism, which have revealed several important links that connect mitochondrial nucleotide metabolism with amino acids, glucose, and fatty acid metabolism.
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Affiliation(s)
- Liya Wang
- a Department of Anatomy, Physiology and Biochemistry , Swedish University of Agricultural Sciences , Uppsala , Sweden
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[18F]CFA as a clinically translatable probe for PET imaging of deoxycytidine kinase activity. Proc Natl Acad Sci U S A 2016; 113:4027-32. [PMID: 27035974 DOI: 10.1073/pnas.1524212113] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
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.
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