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Wang J, Kim E, Dai H, Stefans V, Vogel H, Al Jasmi F, Schrier Vergano SA, Castro D, Bernes S, Bhambhani V, Long C, El-Hattab AW, Wong LJ. Clinical and molecular spectrum of thymidine kinase 2-related mtDNA maintenance defect. Mol Genet Metab 2018; 124:124-130. [PMID: 29735374 DOI: 10.1016/j.ymgme.2018.04.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 04/25/2018] [Accepted: 04/26/2018] [Indexed: 11/29/2022]
Abstract
Mitochondrial DNA maintenance (mtDNA) defects have a wide range of causes, each with a set of phenotypes that overlap with many other neurological or muscular diseases. Clinicians face the challenge of narrowing down a long list of differential diagnosis when encountered with non-specific neuromuscular symptoms. Biallelic pathogenic variants in the Thymidine Kinase 2 (TK2) gene cause a myopathic form of mitochondrial DNA maintenance defect. Since the first description in 2001, there have been 71 patients reported with 42 unique pathogenic variants. Here we are reporting 11 new cases with 5 novel pathogenic variants. We describe and analyze a total of 82 cases with 47 unique TK2 pathogenic variants in effort to formulate a comprehensive molecular and clinical spectrum of TK2-related mtDNA maintenance disorders.
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Affiliation(s)
- Julia Wang
- Medical Scientist Training Program, Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States.
| | - Emily Kim
- Department of BioSciences, Rice University, 6100 Main Street, Houston, TX 77005, United States
| | - Honzheng Dai
- Department of Human and Molecular Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States
| | - Vikki Stefans
- UAMS College of Medicine, Arkansas Children's Hospital, 1 Children's Way, Little Rock, AR 72202, United States
| | - Hannes Vogel
- Pathology, Stanford University School of Medicine, R241 Edwards Building, 300 Pasteur Drive, Palo Alto, CA 94305, United States
| | - Fatma Al Jasmi
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - Samantha A Schrier Vergano
- Division of Medical Genetics and Metabolism, Children's Hospital of The King's Daughters, 601 Children's Lane, Norfolk, VA 23507, United States
| | - Diana Castro
- Department of Pediatric, Neurology and Neurotherapeutics, Children's Health Dallas, University of Texas Southwestern, 2350 N Stemmons Freeway, Dallas, TX 75207, United States
| | - Saunder Bernes
- Department of Neurology, Phoenix Children's Hospital, Barrows Neurological Institute, 1919 East Thomas Road, Phoenix, AZ 85016, United States
| | - Vikas Bhambhani
- Genomics Medicine Program, Children's Hospital Minnesota, 2525 Chicago Ave S, Minneapolis, MN 55404, United States
| | - Catherine Long
- Genomics Medicine Program, Children's Hospital Minnesota, 2525 Chicago Ave S, Minneapolis, MN 55404, United States
| | - Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - Lee-Jun Wong
- Department of Human and Molecular Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States.
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Di Cresce C, Figueredo R, Rytelewski M, Vareki SM, Way C, Ferguson PJ, Vincent MD, Koropatnick J. siRNA knockdown of mitochondrial thymidine kinase 2 (TK2) sensitizes human tumor cells to gemcitabine. Oncotarget 2015; 6:22397-409. [PMID: 26087398 PMCID: PMC4673171 DOI: 10.18632/oncotarget.4272] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 06/03/2015] [Indexed: 11/25/2022] Open
Abstract
Nucleoside metabolism enzymes are determinants of chemotherapeutic drug activity. The nucleoside salvage enzyme deoxycytidine kinase (dCK) activates gemcitabine (2', 2'-difluoro-2'-deoxycytidine) and is negatively regulated by deoxycytidine triphosphate (dCTP). Reduction of dCTP in tumor cells could, therefore, enhance gemcitabine activity. Mitochondrial thymidine kinase 2 (TK2) phosphorylates deoxycytidine to generate dCTP. We hypothesized that: (1) TK2 modulates human tumor cell sensitivity to gemcitabine, and (2) antisense knockdown of TK2 would decrease dCTP and increase dCK activity and gemcitabine activation. siRNA downregulation of TK2 sensitized MCF7 and HeLa cells (high and moderate TK2) but not A549 cells (low TK2) to gemcitabine. Combined treatment with TK2 siRNA and gemcitabine increased dCK. We also hypothesized that TK2 siRNA-induced drug sensitization results in mitochondrial damage that enhances gemcitabine effectiveness. TK2 siRNA and gemcitabine decreased mitochondrial redox status, DNA content, and activity. This is the first demonstration of a direct role for TK2 in gemcitabine resistance, or any independent role in cancer drug resistance, and further distinguishes TK2 function from that of other dTMP-producing enzymes [cytosolic TK1 and thymidylate synthase (TS)]. siRNA knockdown of TK1 and/or TS did not sensitize cancer cells to gemcitabine indicating that, among the 3 enzymes, only TK2 is a candidate therapeutic target for combination with gemcitabine.
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Affiliation(s)
- Christine Di Cresce
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
| | - Rene Figueredo
- Department of Oncology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
| | - Mateusz Rytelewski
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
| | - Saman Maleki Vareki
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
| | - Colin Way
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
| | - Peter J. Ferguson
- Department of Oncology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
| | - Mark D. Vincent
- Department of Oncology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
| | - James Koropatnick
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- Department of Oncology, The University of Western Ontario, London, Ontario, Canada
- Department of Pathology, The University of Western Ontario, London, Ontario, Canada
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
- Cancer Research Laboratory Program, Lawson Health Research Institute and London Regional Cancer Program, London, Ontario, Canada
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Antiherpesvirus activities of two novel 4'-thiothymidine derivatives, KAY-2-41 and KAH-39-149, are dependent on viral and cellular thymidine kinases. Antimicrob Agents Chemother 2014; 58:4328-40. [PMID: 24820089 DOI: 10.1128/aac.02825-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The emergence of drug-resistant herpesviruses represents a significant problem in clinical practice, primarily in immunocompromised patients. Furthermore, effective antiviral therapies against gammaherpesvirus-associated diseases are lacking. Here, we present two thiothymidine derivatives, KAY-2-41 and KAH-39-149, with different spectra of antiviral activity from those of the reference antiherpetic drugs, showing inhibitory activities against herpes simplex virus, varicella-zoster virus (VZV), and particularly against Epstein-Barr virus, with high selectivity in vitro. While KAY-2-41- and KAH-39-149-resistant herpesviruses were found to harbor mutations in the viral thymidine kinase (TK), these mutations conferred only low levels of resistance to these drugs but high levels to other TK-dependent drugs. Also, antiviral assays in HeLa TK-deficient cells showed a lack of KAY-2-41 and KAH-39-149 activities against herpes simplex virus 1 (HSV-1) and HSV-2 TK-deficient mutants. Furthermore, enzymatic TK assays showed the ability of HSV-1 TK, VZV TK, and cellular TK1 and TK2 to recognize and phosphorylate KAY-2-41 and KAH-39-149. These results demonstrate that the compounds depend on both viral and host TKs to exert antiviral activity. Additionally, the antiviral efficacy of KAH-39-149 proved to be superior to that of KAY-2-41 in a mouse model of gammaherpesvirus infection, highlighting the potential of this class of antiviral agents for further development as selective therapeutics against Epstein-Barr virus.
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Koczor CA, Torres RA, Fields EJ, Boyd A, He S, Patel N, Lee EK, Samarel AM, Lewis W. Thymidine kinase and mtDNA depletion in human cardiomyopathy: epigenetic and translational evidence for energy starvation. Physiol Genomics 2013; 45:590-6. [PMID: 23695887 DOI: 10.1152/physiolgenomics.00014.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
This study addresses how depletion of human cardiac left ventricle (LV) mitochondrial DNA (mtDNA) and epigenetic nuclear DNA methylation promote cardiac dysfunction in human dilated cardiomyopathy (DCM) through regulation of pyrimidine nucleotide kinases. Samples of DCM LV and right ventricle (n = 18) were obtained fresh at heart transplant surgery. Parallel samples from nonfailing (NF) controls (n = 12) were from donor hearts found unsuitable for clinical use. We analyzed abundance of mtDNA and nuclear DNA (nDNA) using qPCR. LV mtDNA was depleted in DCM (50%, P < 0.05 each) compared with NF. No detectable change in RV mtDNA abundance occurred. DNA methylation and gene expression were determined using microarray analysis (GEO accession number: GSE43435). Fifty-seven gene promoters exhibited DNA hypermethylation or hypomethylation in DCM LVs. Among those, cytosolic thymidine kinase 1 (TK1) was hypermethylated. Expression arrays revealed decreased abundance of the TK1 mRNA transcript with no change in transcripts for other relevant thymidine metabolism enzymes. Quantitative immunoblots confirmed decreased TK1 polypeptide steady state abundance. TK1 activity remained unchanged in DCM samples while mitochondrial thymidine kinase (TK2) activity was significantly reduced. Compensatory TK activity was found in cardiac myocytes in the DCM LV. Diminished TK2 activity is mechanistically important to reduced mtDNA abundance and identified in DCM LV samples here. Epigenetic and genetic changes result in changes in mtDNA and in nucleotide substrates for mtDNA replication and underpin energy starvation in DCM.
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Affiliation(s)
- Christopher A Koczor
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia, USA
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Kunos CA, Radivoyevitch T. Molecular Strategies of Deoxynucleotide Triphosphate Supply Inhibition Used in the Treatment of Gynecologic Malignancies. ACTA ACUST UNITED AC 2012; Suppl 4:001. [PMID: 25392744 DOI: 10.4172/2161-0932.s4-001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Chemotherapies targeting deoxynucleotide triphosphate synthesis are of high medical interest in the treatment of gynecologic malignancies. In this article, we focus on targeted inhibitors of ribonucleotide reductase, an enzyme in charge of ribonucleotide reduction to their corresponding deoxyribonucleotide to be used as the building blocks of DNA. We also discuss human clinical trials have utilized ribonucleotide reductase subunit-specific inhibitors, particularly trials for women with cervical cancer.
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Affiliation(s)
- Charles A Kunos
- Department of Radiation Oncology, University Hospitals Case Medical Center and Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
| | - Tomas Radivoyevitch
- Department of Epidemiology and Biostatistics, University Hospitals Case Medical Center and Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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Cetina M, Makarević J, Nura-Lama A. Self-assembling of dihydroxypropyl 5,6-dihydrothymine derivatives. J Mol Struct 2010. [DOI: 10.1016/j.molstruc.2010.06.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Pérez-Pérez MJ, Priego EM, Hernández AI, Familiar O, Camarasa MJ, Negri A, Gago F, Balzarini J. Structure, physiological role, and specific inhibitors of human thymidine kinase 2 (TK2): present and future. Med Res Rev 2008; 28:797-820. [PMID: 18459168 PMCID: PMC7168489 DOI: 10.1002/med.20124] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Human mitochondrial thymidine kinase (TK2) is a pyrimidine deoxynucleoside kinase (dNK) that catalyzes the phosphorylation of pyrimidine deoxynucleosides to their corresponding deoxynucleoside 5′‐monophosphates by γ‐phosphoryl transfer from ATP. In resting cells, TK2 is suggested to play a key role in the mitochondrial salvage pathway to provide pyrimidine nucleotides for mitochondrial DNA (mtDNA) synthesis and maintenance. However, recently the physiological role of TK2turned out to have direct clinical relevance as well. Point mutations in the gene encoding TK2 have been correlated to mtDNA disorders in a heterogeneous group of patients suffering from the so‐called mtDNA depletion syndrome (MDS). TK2 activity could also be involved in mitochondrial toxicity associated to prolonged treatment with antiviral nucleoside analogues like AZT and FIAU. Therefore, TK2 inhibitors can be considered as valuable tools to unravel the role of TK2 in the maintenance and homeostasis of mitochondrial nucleotide pools and mtDNA, and to clarify the contribution of TK2 activity to mitochondrial toxicity of certain antivirals. Highly selective TK‐2 inhibitors having an acyclic nucleoside structure and efficiently discriminating between TK‐2 and the closely related TK‐1 have already been reported. It is actually unclear whether these agents efficiently reach the inner mitochondrial compartment. In the present review article,structural features of TK2, MDS‐related mutations observed in TK2 and their role in MDS will be discussed. Also, an update on novel and selective TK2 inhibitors will be provided. © 2008 Wiley Periodicals, Inc. Med Res Rev, 28, No. 5, 797–820, 2008
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