RESUMO
HOE 15030 inhibited the growth of BHK cells at concentrations that did not inhibit their nuclear DNA and RNA syntheses. When BHK cells were cultured in the presence of 30 micrograms/ml of HOE 15030, cells were arrested in the G1 phase after one or two cell divisions. After removal of the drug, cells progressed through the G1 to the S phase. HOE 15030 inhibited the activities of both topoisomerases I and II in vitro. To determine the target molecule of HOE 15030 in cells, we isolated a HOE 15030-resistant (HOEr) mutant of BHK cells. The HOEr cells exhibited cross-resistance to ethidium bromide, acriflavine, and rhodamine 123, and slight cross-resistance to 4'-dimethylepipodophyllotoxin-4-(4,6-O-ethylidine-beta-D-glu copyranoside) (VP-16) and adriamycin, but not to chloramphenicol, oligomycin, novobiocin, colchicine, or vinblastine. The uptake and retention of rhodamine 123 by HOEr cells were lower than those by BHK cells. Mitochondrial DNA synthesis of HOEr cells was more resistant to HOE 15030 and ethidium bromide than that of wild-type cells. These results indicate that the resistance of HOEr cells to drugs is due to reduced uptake or accumulation of the drugs by mitochondria and suggest that the mitochondria are the main target of HOE 15030 in cells.