title: Increased methotrexate-induced DNA strand breaks and cytotoxicity following mutational loss of thymidine kinase.
abstract: The cytotoxicity and DNA lesions induced by methotrexate (MTX) were compared in wild-type, hypoxanthine-guanine phosphoribosyltransferase-deficient (HGPRT-) and thymidine-kinase-deficient (TK-) HL-60 cells. TK- and HGPRT- cells were approximately 10 and 3 times more sensitive to MTX than wild-type cells, respectively. Following incubation with 2 microM MTX for 16 hr, TK- cells showed a significantly higher number of DNA strand breaks. Concomitantly, DNA fragmentation at the nucleosomal linker region was detected more prominently in TK- cells. Although MTX tended to decrease TTP pools similarly in all 3 cells types, the initial TTP level in TK- cells was only about one-fifth of that found in the wild type. These results indicate that the thymidine salvage pathway has a pivotal role in mediating MTX-induced toxicity and DNA lesions.
authors.affiliation: Department of Pediatrics, Kyoto University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sano
authors.forename: M
authors.initials: M
authors.lastname: Kubota
authors.forename: Y
authors.initials: Y
authors.lastname: Kasai
authors.forename: H
authors.initials: H
authors.lastname: Hashimoto
authors.forename: T
authors.initials: T
authors.lastname: Shimizu
authors.forename: S
authors.initials: S
authors.lastname: Adachi
authors.forename: H
authors.initials: H
authors.lastname: Mikawa
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D008727:Methotrexate / Q000494:pharmacology*; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology*; D016296:Mutagenesis; D013937:Thymidine Kinase / Q000235:genetics*; D013942:Thymine Nucleotides / Q000378:metabolism
chemical_list: D004273:DNA, Neoplasm; D013942:Thymine Nucleotides; D008769:Methylnitronitrosoguanidine; D007041:Hypoxanthine Phosphoribosyltransferase; D013937:Thymidine Kinase; C024157:thymidine 5'-triphosphate; D008727:Methotrexate