title: Inhibition of Eg5 acts synergistically with checkpoint abrogation in promoting mitotic catastrophe.
abstract: The G(2) DNA damage checkpoint is activated by genotoxic agents and is particularly important for cancer therapies. Overriding the checkpoint can trigger precocious entry into mitosis, causing cells to undergo mitotic catastrophe. But some checkpoint-abrogated cells can remain viable and progress into G(1) phase, which may contribute to further genome instability. Our previous studies reveal that the effectiveness of the spindle assembly checkpoint and the duration of mitosis are pivotal determinants of mitotic catastrophe after checkpoint abrogation. In this study, we tested the hypothesis whether mitotic catastrophe could be enhanced by combining genotoxic stress, checkpoint abrogation, and the inhibition of the mitotic kinesin protein Eg5. We found that mitotic catastrophe induced by ionizing radiation and a CHK1 inhibitor (UCN-01) was exacerbated after Eg5 was inhibited with either siRNAs or monastrol. The combination of DNA damage, UCN-01, and monastrol sensitized cancer cells that were normally resistant to checkpoint abrogation. Importantly, a relatively low concentration of monastrol, alone not sufficient in causing mitotic arrest, was already effective in promoting mitotic catastrophe. These experiments suggest that it is possible to use sublethal concentrations of Eg5 inhibitors in combination with G(2) DNA damage checkpoint abrogation as an effective therapeutic approach.
authors.affiliation: Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.forename: Jeremy P H
authors.initials: JP
authors.lastname: Chow
authors.forename: Randy Y C
authors.initials: RY
authors.lastname: Poon
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D059447:Cell Cycle Checkpoints / Q000235:genetics* / Q000528:radiation effects; D000071877:Checkpoint Kinase 1; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D042822:Genomic Instability / Q000187:drug effects / Q000528:radiation effects; D045325:HCT116 Cells; D006367:HeLa Cells; D006801:Humans; D016547:Kinesins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D008938:Mitosis / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D011494:Protein Kinases / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering; D011839:Radiation, Ionizing; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology; D013871:Thiones / Q000494:pharmacology
chemical_list: C470243:KIF11 protein, human; D011743:Pyrimidines; D034741:RNA, Small Interfering; D013871:Thiones; C400223:monastrol; C054852:7-hydroxystaurosporine; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D016547:Kinesins; D019311:Staurosporine