title: Deoxynucleoside salvage facilitates DNA repair during ribonucleotide reductase blockade in human cervical cancers.
abstract: Cells generate 2'-deoxyribonucleoside triphosphates (dNTPs) for both replication and repair of damaged DNA predominantly through de novo reduction of intracellular ribonucleotides by ribonucleotide reductase (RNR). Cells can also salvage deoxynucleosides by deoxycytidine kinase/thymidine kinase 1 in the cytosol or by deoxyguanosine kinase/thymidine kinase 2 in mitochondria. In this study we investigated whether the salvage dNTP supply pathway facilitates DNA damage repair, promoting cell survival, when pharmacological inhibition of RNR by 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC no. 663249) impairs the de novo pathway. Human cervical cancer cells were subjected to radiation with or without 3-AP under medium deoxynucleoside concentrations of 0, 0.05, 0.5 and 5.0 µM. Efficacy of DNA damage repair was assessed by γ-H2AX flow cytometry and focus counts, by single cell electrophoresis (Comet assay), and by caspase 3 cleavage assay as a marker of treatment-induced apoptosis. Cell survival was assessed by colony formation. We found that deoxyribonucleotide salvage facilitates DNA repair during RNR inhibition by 3-AP and that salvage reduces the radiochemosensitivity of human cervical cancer cells.
authors.affiliation: Department of Radiation Oncology, University Hospitals of Cleveland, 11100 Euclid Avenue, Cleveland, OH 44106, USA. charles.kunos@UHhospitals.org
authors.forename: Charles A
authors.initials: CA
authors.lastname: Kunos
authors.forename: Gina
authors.initials: G
authors.lastname: Ferris
authors.forename: Natalie
authors.initials: N
authors.lastname: Pyatka
authors.forename: John
authors.initials: J
authors.lastname: Pink
authors.forename: Tomas
authors.initials: T
authors.lastname: Radivoyevitch
mesh_terms: D003470:Culture Media / Q000494:pharmacology; D004260:DNA Repair / Q000187:drug effects* / Q000528:radiation effects*; D003853:Deoxyribonucleosides / Q000378:metabolism* / Q000494:pharmacology*; D003854:Deoxyribonucleotides / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D011725:Pyridines / Q000494:pharmacology; D011836:Radiation Tolerance / Q000187:drug effects / Q000528:radiation effects; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors*; D013882:Thiosemicarbazones / Q000494:pharmacology; D002583:Uterine Cervical Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism
chemical_list: D003470:Culture Media; D003853:Deoxyribonucleosides; D003854:Deoxyribonucleotides; D004791:Enzyme Inhibitors; D011725:Pyridines; D013882:Thiosemicarbazones; C078157:3-aminopyridine-2-carboxaldehyde thiosemicarbazone; D012264:Ribonucleotide Reductases