title: Selection of human leukemic CEM cells for resistance to the DNA topoisomerase II catalytic inhibitor ICRF-187 results in increased levels of topoisomerase IIalpha and altered G(2)/M checkpoint and apoptotic responses.
abstract: ICRF-187 is a bisdioxopiperazine anticancer drug that inhibits the catalytic activity of DNA topoisomerase (topo) II without stabilizing DNA-topoII cleavable complexes. To better understand the mechanisms of action of and resistance to topoII catalytic inhibitors, human leukemic CEM cells were selected for resistance to ICRF-187. The clones CEM/ICRF-8 and CEM/ICRF-18 are approximately 40- and 69-fold resistant to ICRF-187, and 12- and 67-fold cross-resistant to ICRF-193, respectively, but are sensitive to other topoII catalytic inhibitors (merbarone and aclarubicin), as well as collaterally sensitive to the DNA-topoII complex-stabilizing drug etoposide (VP-16). Both the number of VP-16- induced DNA-topoII complexes formed and the amount of in vitro topoII catalytic activity are enhanced in the drug-resistant cells. The ICRF-187-resistant clones contain approximately 5-fold increase in topoIIalpha protein levels and approximately 2.2-fold increase in topoIIalpha mRNA levels. Furthermore, CEM/ICRF-8 expresses approximately 3.5-fold increase in topoIIalpha promoter activity, suggesting that up-regulation of topoIIalpha in this clone occurs at the transcriptional level. Treatment of the drug-resistant or -sensitive cells with equitoxic doses of merbarone or teniposide results in a G(2)/M arrest. In marked contrast, when treated with equitoxic ICRF-187 doses, the drug-resistant clones exhibit either a transient arrest or completely lack the G(2)/M checkpoint compared with the drug-sensitive cells. This aberrant cell cycle profile is associated with a 48-h delay in drug-induced apoptotic cell death, as revealed by fluorescent-end labeling of DNA and poly (ADP-ribose) polymerase cleavage. In summary, resistance to ICRF-187 in CEM cells is associated with increased levels of catalytically active topoIIalpha and altered G(2)/M checkpoint and apoptotic responses.
authors.affiliation: Department of Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Morgan
authors.forename: R S
authors.initials: RS
authors.lastname: Cadena
authors.forename: S C
authors.initials: SC
authors.lastname: Raimondi
authors.forename: W T
authors.initials: WT
authors.lastname: Beck
mesh_terms: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D053938:DNA Fragmentation / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D018076:DNA, Complementary / Q000032:analysis; D004268:DNA-Binding Proteins; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005047:Etoposide / Q000494:pharmacology; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D011929:Razoxane / Q000494:pharmacology*; D016196:S Phase / Q000187:drug effects; D017421:Sequence Analysis; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D012333:RNA, Messenger; D059005:Topoisomerase II Inhibitors; D011929:Razoxane; D005047:Etoposide; D004250:DNA Topoisomerases, Type II