title: A comparative study of the cytotoxic and genotoxic effects of ICRF-154 and bimolane, two catalytic inhibitors of topoisomerase II.
abstract: ICRF-154 and bimolane have been used for the treatment of cancer, psoriasis, and uveitis in humans. Previous reports have revealed that the two drugs are topoisomerase II catalytic inhibitors, and patients treated with these agents have developed unique types of secondary leukemia. A study published in 1984 by Camerman and colleagues proposed that the therapeutic effects of bimolane could be due to ICRF-154, an impurity present within the bimolane samples that may also be responsible for the toxic effects attributed to bimolane. To date, this hypothesis has not been evaluated. In addition, little is known about the potential cytotoxic and genotoxic effects of ICRF-154. In this study, a combination of in vitro tests in human TK6 lymphoblastoid cells has been used to characterize the cytotoxic and genotoxic effects of ICRF-154 and bimolane as well as to compare the results for the two chemicals. ICRF-154 and bimolane were both cytotoxic, exhibiting very similar effects in three measures of cytotoxicity and cell proliferation. In the cytokinesis-block micronucleus assay with CREST-antibody staining, the two agents similarly induced chromosome breakage and, to a lesser extent, chromosome loss. Intriguingly, both drugs resulted in the formation of binucleated cells, perhaps as a consequence of an interference with cytokinesis. To further investigate their aneugenic effects, flow cytometry and fluorescence in situ hybridization analyses revealed that both compounds also produced similar levels of non-disjunction and polyploidy. In each of the cellular and cytogenetic assays employed, the responses of the ICRF-154-treated cells were very similar to those observed with the bimolane, and generally occurred at equimolar test concentrations. Our results, combined with those from previous studies, strongly suggest that bimolane degrades to ICRF-154, and that ICRF-154 is most likely the chemical species responsible for the cytotoxic, genotoxic, and leukemogenic effects exerted by bimolane.
authors.affiliation: Environmental Toxicology Graduate Program and Department of Cell Biology & Neuroscience, University of California, Riverside, CA 92521, USA.
authors.forename: Minh C
authors.initials: MC
authors.lastname: Vuong
authors.forename: Leslie S
authors.initials: LS
authors.lastname: Hasegawa
authors.forename: David A
authors.initials: DA
authors.lastname: Eastmond
mesh_terms: D000970:Antineoplastic Agents / Q000633:toxicity*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D002869:Chromosome Aberrations / Q000139:chemically induced*; D048749:Cytokinesis; D006801:Humans; D008214:Lymphocytes / Q000648:ultrastructure*; D015162:Micronucleus Tests; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D011929:Razoxane / Q000031:analogs & derivatives* / Q000633:toxicity; D059005:Topoisomerase II Inhibitors / Q000633:toxicity*
chemical_list: D000970:Antineoplastic Agents; D009153:Mutagens; D059005:Topoisomerase II Inhibitors; C031186:bimolane; D011929:Razoxane; C000283:1,2-bis(3,5-dioxopiperazin-1-yl)ethane