title: Drug-induced cell cycle modulation leading to cell-cycle arrest, nuclear mis-segregation, or endoreplication.
abstract: BACKGROUND
  Cancer cell responses to chemotherapeutic agents vary, and this may reflect different defects in DNA repair, cell-cycle checkpoints, and apoptosis control. Cytometry analysis only quantifies dye-incorporation to examine DNA content and does not reflect the biological complexity of the cell cycle in drug discovery screens.
  
  
  RESULTS
  Using population and time-lapse imaging analyses of cultured immortalized cells expressing a new version of the fluorescent cell-cycle indicator, Fucci (Fluorescent Ubiquitination-based Cell Cycle Indicator), we found great diversity in the cell-cycle alterations induced by two anticancer drugs. When treated with etoposide, an inhibitor of DNA topoisomerase II, HeLa and NMuMG cells halted at the G2/M checkpoint. HeLa cells remained there, but NMuMG cells then overrode the checkpoint and underwent nuclear mis-segregation or avoided the checkpoint and entered the endoreplication cycle in a drug concentration dependent manner. In contrast, an inhibitor of Cdk4 led to G1 arrest or endoreplication in NMuMG cells depending upon the initial cell-cycle phase of drug exposure.
  
  
  CONCLUSIONS
  Drug-induced cell cycle modulation varied not only between different cell types or following treatment with different drugs, but also between cells treated with different concentrations of the same drug or following drug addition during different phases of the cell cycle. By combining cytometry analysis with the Fucci probe, we have developed a novel assay that fully integrates the complexity of cell cycle regulation into drug discovery screens. This assay system will represent a powerful drug-discovery tool for the development of the next generation of anti-cancer therapies.
authors.affiliation: Life Function and Dynamics, ERATO, JST, 2-1 Hirosawa, Wako-city, Saitama 351-0198, Japan.
authors.forename: Asako
authors.initials: A
authors.lastname: Sakaue-Sawano
authors.forename: Tamiyo
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Kenji
authors.initials: K
authors.lastname: Ohtawa
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyawaki
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002227:Carbazoles / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects; D049109:Cell Proliferation; D020090:Chromosome Segregation; D051358:Cyclin-Dependent Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000737:chemistry / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology*; D016195:G2 Phase; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D016196:S Phase; D059008:Time-Lapse Imaging; D000097573:Red Fluorescent Protein
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D002227:Carbazoles; D018797:Cell Cycle Proteins; D051358:Cyclin-Dependent Kinase 4; D004250:DNA Topoisomerases, Type II; D005047:Etoposide; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D000097573:Red Fluorescent Protein; C521501:2-bromo-12,13-dihydro-5-indolo(2,3-a)pyrrolo(3,4-c)carbazole-5,7(6H)-dione; C485192:green fluorescent protein, Aequorea victoria