title: Correlation between DNA topoisomerase II activity and cytotoxicity in pMC540 and merodantoin sensitive and resistant human breast cancer cells.
abstract: We have shown previously that preactivated merocyanine 540 (pMC540) and merodantoin appear to mediate their cytotoxic effects via interaction with Topo II. Now, we demonstrate a correlation between DNA Topo II activity and drug-sensitive (MCF-7) and -insensitive (MDA-MB-231) breast cancer cell lines. Further studies indicate that MDA-MB-231 cells are insensitive to the cytotoxic and DNA cleavage effects of pMC540 and merodantoin. This loss of sensitivity is not associated with M(r) 170,000 P-glycoprotein over expression. However, in drug insensitive cells, the Topo II catalytic activity in crude nuclear extract was reduced two- to-three-fold and in cellular extracts was virtually absent as determined by decatenation of kDNA. Topoisomerase I activities appeared similar in extracts from MCF-7 and MDA-MB-231 cell lines. Drug-induced DNA cleavage was reduced two-to-threefold in nuclear extracts from MDA-MB-231. m-AMSA was more effective in inhibiting the decatenation activity in the nuclear extracts from MDA-MB-231 as compared to MCF-7 cells. Western blot analysis of whole-cell lysates revealed undetectable immunoreactivity of Topo II in the drug-insensitive cells. These data indicate that insensitivity of MDA-MB-231 to pMC540 and merodantoin is in part due to the reduced drug-induced formation of the cleavage complex and Topo II (170 kD) enzyme content.
authors.affiliation: Baylor Research Institute, Dallas, TX 75226, USA.
authors.forename: R
authors.initials: R
authors.lastname: Sharma
authors.forename: L
authors.initials: L
authors.lastname: Arnold
authors.forename: K S
authors.initials: KS
authors.lastname: Gulliya
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis; D000677:Amsacrine / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D004249:DNA Damage; D004264:DNA Topoisomerases, Type I / Q000502:physiology; D004250:DNA Topoisomerases, Type II / Q000502:physiology*; D004273:DNA, Neoplasm / Q000187:drug effects; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D005031:Ethylenethiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D006801:Humans; D046911:Macromolecular Substances; D009363:Neoplasm Proteins / Q000502:physiology*; D010777:Photochemistry; D011744:Pyrimidinones / Q000494:pharmacology / Q000528:radiation effects; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004273:DNA, Neoplasm; D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D011744:Pyrimidinones; D000677:Amsacrine; C089291:merodantoin; D005031:Ethylenethiourea; C003954:merocyanine dye; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II