Preferential killing of tetraploid tumor cells by targeting the mitotic kinesin Eg5

Abstract

Tetraploid cells may constitute a metastable intermediate between normal euploidy and cancer-associated aneuploidy.Tetraploid cells are relatively more resistant against DNA damaging agents and are genetically unstable, due to their tendency towards multipolar, asymmetric division. Therefore, it is important to develop strategies for the selective removal of tetraploid cells. Here, we show that targeting the mitotic kinesin Eg5 (also known as kinesin spindle protein, KSP) by a small interfering RNA (siRNA) or by the pharmacological inhibitor dimethylenastron (DIMEN) kills tetraploid tumor cells more efficiently than their diploid precursors. Cell death occurs after an attempt of monoastral mitosis that, in diploid cells, is followed by a prolonged mitotic arrest and morphological reversion to the interphase, with a 4n DNA content. In contrast, DIMEN-treated tetraploid cells exhibit a shorter mitotic arrest, bipolar or multipolar karyokinesis, followed by apoptosis of the daughter cells, as assessed by fluorescence videomicroscopy of cells that express a histone 2B-GFP fusion construct to monitor their chromosomes. Cell death occurred with hallmarks of apoptosis, namely loss of the mitochondrial transmembrane potential and terminal chromatin compaction. In conclusion, tetraploid cells are particular vulnerable to undergo mitotic catastrophe after genetic or pharmacological inhibition of Eg5.

Docetaxel-Resistant Prostate Cancer Cells Remain Sensitive toS-Trityl-l-Cysteine–Mediated Eg5 Inhibition

“…These polyploid cells were found to undergo a slow and delayed death after the process of endo-reduplication. In addition, Eg5 inhibition by a number of methods has been reported to preferentially kill tetraploid human colon carcinoma (24). The importance of sequential activation of the spindle assembly checkpoint followed by mitotic slippage has been suggested for the induction of apoptosis by the Eg5 inhibitor KSP-1A (25).…”

Caspase 2 in mitotic catastrophe: The terminator of aneuploid and tetraploid cells

“…29 In this context it appears intriguing that non-diploid cancer cells are peculiarly sensitive to mitotic catastrophe inducers, such as inhibitors of checkpoint kinase 1 (CHEK1, best known as CHK1), 30 kinesin family member 11 (KIF11, best known as EG5), 31 or TTK protein kinase (TTK, best known as MPS1). 32 Altogether, it appears important for cancer research to further elucidate the molecular mechanisms of mitotic catastrophe involved in the suppression of non-diploidy and how this process (1) is subverted during oncogenesis, (2) contributes to tumor evolution and intra-tumor heterogeneity, (3) confers resistance to cancer therapy, (4) is modulated by the tumor microenvironment, and (5) may be exploited for the eradication of cancer cells.…”

Learning about cancer from frogs: analysis of mitotic spindles in Xenopus egg extracts

“…Overexpression of the molecular motor Eg5, a contributor to microtubule dynamics in the spindle, increases tumorigenesis in mouse models (Castillo et al, 2007;Hansen and Justice, 1999). Recently, Eg5 emerged as a promising target of small molecule inhibitors that are under evaluation as new cancer therapeutics (Groen et al, 2008;Liu et al, 2008;Nakai et al, 2009;Rello-Varona et al, 2009). …”