title: Instability of Mex- phenotype in human lymphoblastoid cell lines.
abstract: Three lymphoblastoid cell lines (LCLs) had extremely low activities of O6-alkylguanine-DNA alkyltransferase (O6-AGT), and were classified as Mex-. They were highly sensitive to cell killing by 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoure a hydrochloride (ACNU), whereas NMO2, a Mex+ LCL with a high O6-AGT activity, was resistant to the agent. Small fractions of these Mex- LCLs survived the treatment with 10 micrograms/ml of ACNU for 24 h, and the surviving cells were found to be resistant to subsequent treatments with the agent. In addition, they contained O6-AGT activities comparable to that of NMO2 and were therefore regarded as Mex+. These results suggest that the Mex- phenotype in LCLs is unstable.
authors.affiliation: Department of Molecular Oncology, Faculty of Medicine, Kyoto University, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Arita
authors.forename: K
authors.initials: K
authors.lastname: Tatsumi
authors.forename: A
authors.initials: A
authors.lastname: Tachibana
authors.forename: M
authors.initials: M
authors.lastname: Toyoda
authors.forename: H
authors.initials: H
authors.lastname: Takebe
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair; D004351:Drug Resistance; D005720:Gamma Rays; D006801:Humans; D008214:Lymphocytes / Q000502:physiology*; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism*; D015376:Nimustine; D009607:Nitrosourea Compounds / Q000633:toxicity; D019853:O(6)-Methylguanine-DNA Methyltransferase; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics
chemical_list: D009607:Nitrosourea Compounds; D015376:Nimustine; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase