Thymidine kinase activity and trifluorothymidine resistance of spontaneous and mutagen-induced L5178Y cells in RPMI 1640 medium.
L5178Y/TK+/- cells were treated with 3-methylcholanthrene (3MC) in order to obtain thymidine-kinase-deficient mutants (TK-/-) which were resistant to trifluorothymidine (TFTr). Clones of TK-/- cells were harvested from soft agar and adapted to growth in suspension culture. The phenotype of the TK-/- and TK+/- clones was confirmed by measuring thymidine kinase activity. These studies were undertaken with cells from 16 3MC-induced large colony clones (lambda TK-/-), 21 3MC-induced small colony clones (sigma TK-/-), and 51 spontaneous sigma TK-/- clones. Thymidine kinase activity was absent in all of the lambda TK-/- and sigma TK-/- 3MC-induced clones and also in 49 of 51 sigma TK-/- spontaneous clones. After at least 50 generations in suspension culture, TFTr was retained by 80% of the 3MC-induced lambda TK-/- cells, by 75% of the 3MC-induced sigma TK-/- cells, and by 89% of the spontaneous sigma TK-/- cells. The collective results showed that 86 of the 88 TFTr colonies examined lacked thymidine kinase activity and indicate that at least 98% of all TFTr colonies seen in the L5178Y assay are true TK-/- mutants.
D000818:Animals; D002460:Cell Line; D003470:Culture Media; D004351:Drug Resistance; D007940:Leukemia L5178 / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D007942:Leukemia, Experimental / Q000378:metabolism*; D008748:Methylcholanthrene / Q000494:pharmacology*; D051379:Mice; D009152:Mutagenicity Tests; D009363:Neoplasm Proteins / Q000235:genetics*; D013936:Thymidine / Q000031:analogs & derivatives*; D013937:Thymidine Kinase / Q000235:genetics*; D014271:Trifluridine / Q000494:pharmacology*; D014410:Tumor Stem Cell Assay
D003470:Culture Media; D009363:Neoplasm Proteins; D008748:Methylcholanthrene; D013937:Thymidine Kinase; D014271:Trifluridine; D013936:Thymidine