A novel microtubule-modulating noscapinoid triggers apoptosis by inducing spindle multipolarity via centrosome amplification and declustering.
We have previously shown that a non-toxic noscapinoid, EM011 binds tubulin without altering its monomer/polymer ratio. EM011 is more active than the parent molecule, noscapine, in inducing G2/M arrest, inhibiting cellular proliferation and tumor growth in various human xenograft models. However, the mechanisms of mitotic-block and subsequent cell death have remained elusive. Here, we show that EM011-induced attenuation of microtubule dynamics was associated with impaired association of microtubule plus-end tracking proteins, such as EB1 and CLIP-170. EM011 treatment then led to the formation of multipolar spindles containing 'real' centrioles indicating drug-induced centrosome amplification and persistent centrosome declustering. Centrosome amplification was accompanied by an upregulation of Aurora A and Plk4 protein levels, as well as a surge in the kinase activity of Aurora A, suggesting a deregulation of the centrosome duplication cycle. Cell-cycle phase-specific experiments showed that the 'cytotoxicity-window' of the drug encompasses the late S-G2 period. Drug-treatment, excluding S-phase, not only resulted in lower sub-G1 population but also attenuated centrosome amplification and spindle multipolarity, suggesting that drug-induced centrosome amplification is essential for maximal cell death. Subsequent to a robust mitotic arrest, EM011-treated cells displayed diverse cellular fates suggesting a high degree of intraline variation. Some 'apoptosis-evasive' cells underwent aberrant cytokinesis to generate rampant aneuploidy that perhaps contributed to drug-induced cell death. These data indicate that spindle multipolarity induction by means of centrosome amplification has an exciting chemotherapeutic potential that merits further investigation.
Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
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P
Karna
P C G
PC
Rida
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V
Pannu
K K
KK
Gupta
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Dalton
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H
Joshi
V W
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Yang
J
J
Zhou
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Aneja
D017209:Apoptosis; D064127:Aurora Kinases; D045744:Cell Line, Tumor; D018385:Centrosome / Q000502:physiology*; D004149:Dioxoles / Q000494:pharmacology*; D016193:G1 Phase; D016195:G2 Phase; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008938:Mitosis; D009363:Neoplasm Proteins / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016196:S Phase; D008941:Spindle Apparatus / Q000502:physiology*; D050257:Tubulin Modulators / Q000494:pharmacology*; D015854:Up-Regulation
D004149:Dioxoles; C510553:EM011 compound; D007546:Isoquinolines; C500985:MAPRE1 protein, human; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D050257:Tubulin Modulators; C076744:cytoplasmic linker protein 170; C490219:PLK4 protein, human; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases