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Antiviral Chemistry & Chemotherapy 2023Brivudin, (()-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) can be considered the gold standard for the treatment of varicella-zoster virus (VZV) infections, such as herpes... (Review)
Review
Brivudin, (()-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) can be considered the gold standard for the treatment of varicella-zoster virus (VZV) infections, such as herpes zoster (shingles). It is available for clinical use in most European countries (except for the UK) and over the whole world (except for the US and Canada). Besides VZV its activity spectrum also includes various other herpesviruses, such as herpes simplex virus type 1 (HSV-1). Its activity against VZV and HSV-1 depends on phosphorylation by the virus-encoded thymidine kinase (TK). In its active form (BVDU TP or BVDU 5'-triphosphate), it can act as both substrate and inhibitor of the viral (i.e., HSV-1) DNA polymerase. It has proven to be effective against herpes zoster, including post-herpetic neuralgia (PHN). It is contra-indicated in patients concomitantly treated by 5-fluorouracil (FU), since its degradation product, ()-5-(2-bromovinyl)uracil, is inhibitory to the catabolism of FU, which may enhance the toxicity of the latter. A new compound, the bicyclic nucleoside analogue (BCNA) Cf-1743, has been described, which is a more potent inhibitor of VZV replication than BVDU and which does not interfere with the catabolism of FU. It is applicable orally, as its 5'-valine ester FV-100 (Fermavir), but has not (yet) been marketed for clinical use.
Topics: Humans; Antiviral Agents; Bromodeoxyuridine; Herpesvirus 3, Human; Herpes Zoster; Herpesvirus 1, Human; Fluorouracil; Thymidine Kinase
PubMed: 36710501
DOI: 10.1177/20402066231152971 -
Journal of Neuromuscular Diseases 2022Defects in the replication, maintenance, and repair of mitochondrial DNA (mtDNA) constitute a growing and genetically heterogeneous group of mitochondrial disorders.... (Review)
Review
Defects in the replication, maintenance, and repair of mitochondrial DNA (mtDNA) constitute a growing and genetically heterogeneous group of mitochondrial disorders. Multiple genes participate in these processes, including thymidine kinase 2 (TK2) encoding the mitochondrial matrix protein TK2, a critical component of the mitochondrial nucleotide salvage pathway. TK2 deficiency (TK2d) causes mtDNA depletion, multiple deletions, or both, which manifest predominantly as mitochondrial myopathy. A wide clinical spectrum phenotype includes a severe, rapidly progressive, early onset form (median survival: < 2 years); a less severe childhood-onset form; and a late-onset form with a variably slower rate of progression. Clinical presentation typically includes progressive weakness of limb, neck, facial, oropharyngeal, and respiratory muscle, whereas limb myopathy with ptosis, ophthalmoparesis, and respiratory involvement is more common in the late-onset form. Deoxynucleoside monophosphates and deoxynucleosides that can bypass the TK2 enzyme defect have been assessed in a mouse model, as well as under open-label compassionate use (expanded access) in TK2d patients, indicating clinical efficacy with a favorable side-effect profile. This treatment is currently undergoing testing in clinical trials intended to support approval in the US and European Union (EU). In the early expanded access program, growth differentiation factor 15 (GDF-15) appears to be a useful biomarker that correlates with therapeutic response. With the advent of a specific treatment and given the high morbidity and mortality associated with TK2d, clinicians need to know how to recognize and diagnose this disorder. Here, we summarize translational research about this rare condition emphasizing clinical aspects.
Topics: Animals; Child; DNA, Mitochondrial; Humans; Mice; Mitochondrial Myopathies; Muscular Diseases; Thymidine Kinase
PubMed: 35094997
DOI: 10.3233/JND-210786 -
BMC Veterinary Research Sep 2021Thymidine kinase 1 (TK1) catalyzes the initial phosphorylation of thymidine in the salvage pathway synthesis of dTTP, an essential building block of DNA. TK1 is a...
BACKGROUND
Thymidine kinase 1 (TK1) catalyzes the initial phosphorylation of thymidine in the salvage pathway synthesis of dTTP, an essential building block of DNA. TK1 is a cytosolic enzyme with its highest level during the S-phase of the cell cycle. In cancer cells TK1 is upregulated and excess TK1 is leaked into the blood. Therefore, serum TK1 has been used as biomarker for cancer diagnosis and prognosis in human medicine. Feline TK1 shows high sequence similarity to TK1 from other species. The aim of this study was to characterize feline TK1 and evaluate if serum TK1 can be used as a diagnostic biomarker.
RESULTS
Feline TK1 was cloned, expressed and affinity purified. The purified feline TK1 phosphorylated not only pyrimidine deoxyribonucleosides but also pyrimidine ribonucleosides and to some extent purine deoxynucleosides. A number of anticancer and antiviral nucleoside analogs also served as substrates with fairly high efficiency. ATP and dATP were the preferred phosphate donor. Serum TK1 activity in felines with malignant diseases was significantly higher than that in healthy individuals. ROC analysis revealed an area under the curve (AUC) of 0.98 with a sensitivity of 0.83 and a specificity of 0.95 for felines with lymphoma. Serum TK1 activity in felines with IBD or inflammatory disease was within the same range as healthy ones. Furthermore, in felines with lymphoma serum TK1 activity returned to normal levels in response to treatment.
CONCLUSION
Feline TK1 has high specific activity and a broader substrate specificity in comparison with TK1 from other species. Serum TK1 activity in felines with malignant diseases is significantly higher than that in normal felines and in felines with inflammatory diseases. These results suggest that serum TK1 may be a promising biomarker for the diagnosis and monitoring of malignant diseases and for the differential diagnosis of certain inflammatory disease.
Topics: Animals; Biomarkers; Cat Diseases; Cats; Inflammation; Neoplasms; Sensitivity and Specificity; Thymidine Kinase
PubMed: 34579716
DOI: 10.1186/s12917-021-03030-5 -
Current Pharmaceutical Design 2012Thymidine kinase 2 (TK2), encoded on chromosome 16q22 of the human genome, is a deoxynucleoside kinase (dNK) that catalyzes the phosphorylation of the pyrimidine... (Review)
Review
Thymidine kinase 2 (TK2), encoded on chromosome 16q22 of the human genome, is a deoxynucleoside kinase (dNK) that catalyzes the phosphorylation of the pyrimidine deoxynucleosides 2'-deoxythymidine (dThd), 2'-deoxyuridine (dUrd) and 2'- deoxycytidine (dCyd) to the corresponding deoxynucleoside 5'-monophosphate derivatives. In contrast to the S-phase-specific thymidine kinase 1 (TK1), TK2 is constitutively expressed in the mitochondria and plays an important role in providing dNTPs for the replication and maintenance of mitochondrial DNA (mtDNA). The severe mitochondrial DNA depletion syndrome (MDS) has been associated with mutations in TK2, resulting in mtDNA depletion, isolated skeletal myopathy, and death of the individual at an early stage of life. Some antiviral nucleoside analogs, such as 3'-azido-dThd (AZT) that is targeting the human immunodeficiency virus (HIV)-encoded reverse transcriptase, are substrates for TK2 and it has been proposed that the mitochondrial toxicity observed after prolonged treatment with such drugs could be due to their interaction with TK2. Therefore, the design of specific TK2 inhibitors may be useful to investigate the role of TK2 in the maintenance and homeostasis of mitochondrial dNTP pools and its contribution to the mitochondrial toxicity of several antiviral and anticancer drugs. Since 2000, several potent and selective TK2 inhibitors have been described. Besides bringing together previously reported inhibitors, special attention will be paid in this review to the new families of TK2 inhibitors more recently described, together with modeling studies and biological assays. Moreover, the last section will be focused on several recent investigations that suggest that depletion of mtDNA can take place both in tumorigenesis and during cancer treatment with certain nucleoside analogues.
Topics: Animals; Antineoplastic Agents; Antiviral Agents; DNA, Mitochondrial; Drug Design; Enzyme Inhibitors; Humans; Mitochondria; Neoplasms; Phosphorylation; Thymidine Kinase
PubMed: 22571666
DOI: 10.2174/138161212800672787 -
The Journal of Biological Chemistry Jun 2022Giardiasis is a diarrheal disease caused by the unicellular parasite Giardia intestinalis, for which metronidazole is the main treatment option. The parasite is...
Giardiasis is a diarrheal disease caused by the unicellular parasite Giardia intestinalis, for which metronidazole is the main treatment option. The parasite is dependent on exogenous deoxyribonucleosides for DNA replication and thus is also potentially vulnerable to deoxyribonucleoside analogs. Here, we characterized the G. intestinalis thymidine kinase, a divergent member of the thymidine kinase 1 family that consists of two weakly homologous parts within one polypeptide. We found that the recombinantly expressed enzyme is monomeric, with 100-fold higher catalytic efficiency for thymidine compared to its second-best substrate, deoxyuridine, and is furthermore subject to feedback inhibition by dTTP. This efficient substrate discrimination is in line with the lack of thymidylate synthase and dUTPase in the parasite, which makes deoxy-UMP a dead-end product that is potentially harmful if converted to deoxy-UTP. We also found that the antiretroviral drug azidothymidine (AZT) was an equally good substrate as thymidine and was active against WT as well as metronidazole-resistant G. intestinalis trophozoites. This drug inhibited DNA synthesis in the parasite and efficiently decreased cyst production in vitro, which suggests that it could reduce infectivity. AZT also showed a good effect in G. intestinalis-infected gerbils, reducing both the number of trophozoites in the small intestine and the number of viable cysts in the stool. Taken together, these results suggest that the absolute dependency of the parasite on thymidine kinase for its DNA synthesis can be exploited by AZT, which has promise as a future medication effective against metronidazole-refractory giardiasis.
Topics: Animals; DNA Replication; Drug Discovery; Gerbillinae; Giardia lamblia; Giardiasis; Metronidazole; Protozoan Proteins; Thymidine; Thymidine Kinase; Zidovudine
PubMed: 35568200
DOI: 10.1016/j.jbc.2022.102028 -
International Journal of Molecular... Sep 2022Pseudorabies (also called Aujeszky's disease) is a highly infectious viral disease caused by the pseudorabies virus (PRV, or Suid herpesvirus 1). Although the disease...
Pseudorabies (also called Aujeszky's disease) is a highly infectious viral disease caused by the pseudorabies virus (PRV, or Suid herpesvirus 1). Although the disease has been controlled by immunization with the PRV-attenuated vaccine, the emerging PRV variants can escape the immune surveillance in the vaccinated pig, resulting in recent outbreaks. Furthermore, the virus has been detected in other animals and humans, indicating cross-transmission of PRV. However, the mechanism of PRV cross-species transmission needs further study. In this study, we compared the amino acid sequences of glycoproteins (gD), gL, and thymidine kinase (TK) of PRV strains, human PRV hSD-1 2019 strain, and the attenuated strain Bartha-K61, followed by predication of their spatial conformation. In addition, the interactions between the viral gD protein and host nectin-1, nectin-2, and HS were also evaluated via molecular docking. The results showed that the amino acid sequence homology of the gD, gL, and TK proteins of hSD-1 2019 and JL-CC was 97.5%, 94.4%, and 99.1%, respectively. Moreover, there were mutations in the amino acid sequences of gD, gL, and TK proteins of hSD-1 2019 and JL-CC compared with the corresponding reference sequences of the Bartha strain. The mutations of gD, gL, and TK might not affect the spatial conformation of the protein domain but may affect the recognition of antibodies and antigen epitopes. Moreover, the gD protein of JL-CC, isolated previously, can bind to human nectin-1, nectin-2, and HS, suggesting the virus may be highly infectious and pathogenic to human beings.
Topics: Animals; Epitopes; Glycoproteins; Herpesvirus 1, Suid; Humans; Molecular Docking Simulation; Mutation; Nectins; Pseudorabies; Swine; Swine Diseases; Thymidine Kinase; Vaccines, Attenuated; Viral Envelope Proteins; Viral Proteins
PubMed: 36232898
DOI: 10.3390/ijms231911597 -
BMC Molecular and Cell Biology Dec 2021Thymidine kinase 1 (TK1) plays a key role in the synthesis of deoxythymidine triphosphate (dTTP) and is thus important for DNA replication and cell proliferation. The...
BACKGROUND
Thymidine kinase 1 (TK1) plays a key role in the synthesis of deoxythymidine triphosphate (dTTP) and is thus important for DNA replication and cell proliferation. The expression of TK1 is highest during S-phase, and it is rapidly degraded after mitosis. In cancer cells, TK1 is upregulated, resulting in leakage of excess TK1 into the blood. Consequently, serum TK1 has been used as a diagnostic and prognostic cancer biomarker, mainly in human medicine. The aims of this work were to characterize equine TK1 and to evaluate its suitability as a serum biomarker for equine lymphoma.
RESULTS
Equine TK1 was cloned, expressed in E. coli and affinity purified. The purified recombinant horse TK1 showed broad substrate specificity, phosphorylating pyrimidine deoxyribo- and ribonucleosides and, to some extent, purine deoxynucleosides, including anticancer and antiviral nucleoside analogues. ATP was the preferred phosphate donor. Serum TK1 activity was measured in samples collected from horses with confirmed or suspected lymphoma and control horses with and without concurrent diseases. Serum TK1 activity levels were significantly higher in horses with lymphoma (p < 0.0005) and suspected lymphoma (p < 0.02) and in tumour-free groups with diverse diseases (p < 0.03) than in controls without concurrent diseases. There was a significant difference between the lymphoma group and the tumour-free group with diverse diseases (p < 0.0006). Furthermore, receiver operating characteristic analysis revealed a sensitivity of 0.86, a specificity of 0.95 and an AUC (area under the curve) of 0.92 compared to the controls without concurrent diseases, with a sensitivity of 0.97, a specificity of 0.71 and an AUC of 0.88 when compared with the tumour-free group with diverse diseases.
CONCLUSION
Equine TK1 showed high specific activity and broader substrate specificity than human TK1. Anticancer and antiviral thymidine analogues were efficiently phosphorylated by horse TK1, suggesting that these analogues might be good candidates for chemotherapy in horses. Serum TK1 activity was significantly higher in horses with lymphoma than in controls. ROC analysis indicated that serum TK1 could serve as a promising cancer biomarker in horses.
Topics: Animals; Biomarkers, Tumor; Horse Diseases; Horses; Lymphoma; Thymidine Kinase
PubMed: 34906077
DOI: 10.1186/s12860-021-00399-x -
Cells Jan 2022Cell therapies based on pluripotent stem cells (PSC), have opened new therapeutic strategies for neurodegenerative diseases. However, insufficiently differentiated PSC...
Cell therapies based on pluripotent stem cells (PSC), have opened new therapeutic strategies for neurodegenerative diseases. However, insufficiently differentiated PSC can lead to tumor formation. Ideally, safety switch therapies should selectively kill proliferative transplant cells while preserving post-mitotic neurons. In this study, we evaluated the potential of nucleoside analogs and thymidine kinase-based suicide genes. Among tested thymidine kinase variants, the humanized SR39 (SR39h) variant rendered cells most sensitive to suicide induction. Unexpectedly, post-mitotic neurons with ubiquitous SR39h expression were killed by ganciclovir, but were spared when SR39h was expressed under the control of the cell cycle-dependent Ki67 promoter. The efficacy of six different nucleoside analogs to induce cell death was then evaluated. Penciclovir (PCV) showed the most interesting properties with an efficiency comparable to ganciclovir (GCV), but low toxicity. We tested three nucleoside analogs in vivo: at concentrations of 40 mg/kg/day, PCV and GCV prevented tumor formation, while acyclovir (ACV) did not. In summary, SR39h under the control of a cell cycle-dependent promoter appears most efficient and selective as safety switch for neural transplants. In this setting, PCV and GCV are efficient inducers of cell death. Because of its low toxicity, PCV might become a preferred alternative to GCV.
Topics: Cell- and Tissue-Based Therapy; Ganciclovir; Humans; Neurons; Nucleosides; Thymidine Kinase
PubMed: 35159311
DOI: 10.3390/cells11030502 -
Future Medicinal Chemistry Apr 2013The compound class of 3-carboranyl thymidine analogues (3CTAs) are boron delivery agents for boron neutron capture therapy (BNCT), a binary treatment modality for... (Review)
Review
The compound class of 3-carboranyl thymidine analogues (3CTAs) are boron delivery agents for boron neutron capture therapy (BNCT), a binary treatment modality for cancer. Presumably, these compounds accumulate selectively in tumor cells via intracellular trapping, which is mediated by hTK1. Favorable in vivo biodistribution profiles of 3CTAs led to promising results in preclinical BNCT of rats with intracerebral brain tumors. This review presents an overview on the design, synthesis, and biological evaluation of first- and second-generation 3CTAs. Boronated nucleosides developed prior to 3CTAs for BNCT and non-boronated N3-substituted thymidine conjugates for other areas of cancer therapy and imaging are also described. In addition, basic features of carborane clusters, which are used as boron moieties in the design and synthesis of 3CTAs, and the biological and structural features of TK1-like enzymes, which are the molecular targets of 3CTAs, are discussed.
Topics: Animals; Boranes; Boron Neutron Capture Therapy; Humans; Molecular Docking Simulation; Neoplasms; Nitrogen; Prodrugs; Thymidine; Thymidine Kinase
PubMed: 23617430
DOI: 10.4155/fmc.13.31 -
European Journal of Cell Biology 2022Early discover of risk progression of invisible carcinomas is important for a prerequisite successful treatment. Here, we investigated whether concentration of human...
Early discover of risk progression of invisible carcinomas is important for a prerequisite successful treatment. Here, we investigated whether concentration of human thymidine kinase 1 (HTK1) discover invisible malignant human tumours. The HTK1 concentration of tumour cellular based on HTK1 IgY-polyclonal-antibody (HTK1-IgY-pAb) was determined by using a novel automatic chemiluminescence analyser with sandwich biotin-streptavidin (SBSA) platform. Minimum number of cells able to be detected by this technology used cells with low and high concentration of HTK1. The limit visibility by tumour imaging is approximately 1 mm in diameter, corresponding to approximately 10 cells with a cell diameter of 1 µm. Based on a HTK1 standard curve and a molecular weight of HTK1 of 96 kD, the HTK1protein (HTK1p) concentration per cell was calculated to be 0.021 pg. Assuming 200 pg in total protein/cell, approximately 50 × 10 growing malignant cells in the body were calculated to releases HTK1 into 5-liter blood. A HTK1 values of 3.914, 0.435 and 0.009 pmol/L corresponds to 10 × 10, 2 × 10 and 1 × 10 growing malignant cells, respectively. The lowest detectable sensitivity of HTK1 is 0.009 pmol/L in 1 × 10 growing malignant cells and 0.01 pmol/L in blood serum, detectable in health screening. Comparing the novel automatic chemiluminescence analyser with the original ECL dot-blot assay using serum HTK1p (health screening, n = 265) showed high correlation (r = 0.8743, P < .000). In conclusion, the novel automatic chemiluminescence analyser with SBSA platform is a reliable method with high accuracy to determine carcinoma invisible.
Topics: Humans; Thymidine Kinase; Neoplasms
PubMed: 36334559
DOI: 10.1016/j.ejcb.2022.151280