Reduced DNA topoisomerase II activity and drug-stimulated DNA cleavage in 9-hydroxyellipticine resistant cells.
We have isolated a Chinese hamster lung cell line resistant to 9-hydroxyellipticine (DC-3F/9-OH-E) which is also cross-resistant to topoisomerase II inhibitors such as amsacrine and etoposide. In this work we have studied quantitatively both DNA topoisomerase II activity by decatenation of kinetoplast DNA and drug-stimulated DNA cleavage of pBR 322. DNA topoisomerase II activity of DC-3F/9-OH-E nuclear extract was reduced by 3.5-fold as compared to that from DC-3F (sensitive parent) nuclear extract. We also found that DC-3F/9-OH-E nuclear extracts have a reduced capacity to induce in vitro topoisomerase II-mediated DNA cleavage upon stimulation by etoposide and amsacrine (7- and 10-fold respectively). Besides, mixing nuclear extracts from both sensitive and resistant cells indicates that either the enzyme in resistant cells is modified or a modulating factor is associated to it. Our results suggest that the resistance of the DC-3F/9-OH-E cell line to topoisomerase II inhibitors might be due to both a reduced amount of the enzyme and its reduced ability to form the cleavable complex in the presence of drugs.
Charcosset
J Y
JY
Unité de Biochimie et Enzymologie (UA 147 CNRS), Institut Gustave Roussy, Villejuif, France.
Saucier
J M
JM
Jacquemin-Sablon
A
A
D000470:Alkaloids / Q000494:pharmacology*; D000677:Amsacrine / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000187:drug effects*; D004351:Drug Resistance; D004611:Ellipticines / Q000494:pharmacology*; D011034:Podophyllotoxin / Q000494:pharmacology; D059005:Topoisomerase II Inhibitors
D000470:Alkaloids; D000970:Antineoplastic Agents; D004611:Ellipticines; D059005:Topoisomerase II Inhibitors; D000677:Amsacrine; D004247:DNA; C008009:9-hydroxyellipticine; D011034:Podophyllotoxin