title: Regulation of topoisomerase II by murine mastocytoma cells.
abstract: Nuclei from K21 murine mastocytoma cells do not form topoisomerase II-DNA adducts in response to amsacrine in the absence of a cytoplasmic factor tentatively identified as a type of casein kinase (Darkin, S.J. and Ralph, R.K. (1991) Biochim. Biophys. Acta 1088, 285-291). The stimulatory activity was present in extracts from cells grown in horse serum but not in calf serum. Activity was lost following growth arrest by serum deprivation. In contrast, topoisomerase II activity in isolated nuclei did not decline during growth arrest. These results suggest that the resistance of some non-cycling tumour cells to anti-cancer drugs may result from decreased activation of topoisomerase II.
authors.affiliation: Department of Cellular and Molecular Biology, University of Auckland, New Zealand.
authors.forename: A G
authors.initials: AG
authors.lastname: Collett
authors.forename: R K
authors.initials: RK
authors.lastname: Ralph
mesh_terms: D000677:Amsacrine / Q000494:pharmacology*; D000818:Animals; D001769:Blood; D002455:Cell Division; D003470:Culture Media; D016895:Culture Media, Serum-Free; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D007700:Kinetics; D012515:Mast-Cell Sarcoma / Q000201:enzymology*; D051379:Mice; D014407:Tumor Cells, Cultured
chemical_list: D003470:Culture Media; D016895:Culture Media, Serum-Free; D000677:Amsacrine; D004247:DNA; D004250:DNA Topoisomerases, Type II