title: Rapid induction of apoptosis during Kinesin-5 inhibitor-induced mitotic arrest in HL60 cells.
abstract: Small molecule inhibitors of Kinesin-5 (K5Is) that arrest cells in mitosis with monopolar spindles are promising anti-cancer drug candidates. Clinical trials of K5Is revealed dose-limiting neutropenia, or loss of neutrophils, for which the molecular mechanism is unclear. We investigated the effects of a K5I on HL60 cells, a human promyelocytic leukemia cell line that is often used to model dividing neutrophil progenitors in cell culture. We found K5I treatment caused unusually rapid death of HL60 cells exclusively during mitotic arrest. This mitotic death occurred via the intrinsic apoptosis pathway with molecular events that include cytochrome c leakage into the cytoplasm, caspase activation, and Parp1 cleavage. Bcl-2 overexpression protected from death. We probed mitochondrial physiology to find candidate triggers of cytochrome c release, and observed a decrease of membrane potential (ΔΨm) before mitochondrial outer membrane permeabilization (MOMP). Interestingly, this loss of ΔΨm was not blocked by overexpressing Bcl-2, suggesting it might be a cause of Bax/Bak activation, not a consequence. Taken together, these results show that K5I induces intrinsic apoptosis during mitotic arrest in HL60 with loss of ΔΨm as an upstream event of MOMP.
authors.affiliation: Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA. yangzhong_tan@hms.harvard.edu
authors.forename: Yangzhong
authors.initials: Y
authors.lastname: Tang
authors.forename: James D
authors.initials: JD
authors.lastname: Orth
authors.forename: Tiao
authors.initials: T
authors.lastname: Xie
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mitchison
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D016547:Kinesins / Q000037:antagonists & inhibitors / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008938:Mitosis / Q000187:drug effects*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011804:Quinolines / Q000494:pharmacology; D034622:RNA Interference
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; D000072224:Bcl-2-Like Protein 11; C561944:EMD 534085; D004791:Enzyme Inhibitors; C470243:KIF11 protein, human; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D011804:Quinolines; D000251:Adenosine Triphosphatases; D016547:Kinesins