Oncogene (2004) 23, 2825–2837 & 2004 Nature Publishing Group All rights reserved 0950-9232/04 $25.00 www.nature.com/onc Cell death by mitotic catastrophe: a molecular definition Maria Castedo1, Jean-Luc Perfettini1, Thomas Roumier1, Karine Andreau1, Rene Medema2 and Guido Kroemer*,1 1CNRS-UMR 8125, Institut Gustave Roussy, Pavillon de Recherche 1, 39 rue Camille-Desmoulins, Villejuif F-94805, France; 2Division of Molecular Biology H8, Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands The current literature is devoid of a clearcut definition of mutant strains (Molz et al., 1989; Ayscough et al., mitotic catastrophe, a type of cell death that occurs during 1992). Accordingly, some authors view ‘mitotic mitosis. Here, we propose that mitotic catastrophe results catastrophe’ of mammalian cells as the failure to from a combination of deficient cell-cycle checkpoints (in undergo complete mitosis (which would be more particular the DNA structure checkpoints and the spindle accurately called ‘mitotic failure’) after DNA damage assembly checkpoint) and cellular damage. Failure to (coupled to defective checkpoints), a situation that arrest the cell cycle before or at mitosis triggers an would lead to tetraploidy (after a single cell cycle) attempt of aberrant chromosome segregation, which (Andreassen et al., 2001a; Margottin-Goguet et al., culminates in the activation of the apoptotic default 2003) or endopolyploidy (after several cell cycles) with pathway and cellular demise. Cell death occurring during extensive DNA damage and repair, perhaps followed by the metaphase/anaphase transition is characterized by the the selection of apoptosis-resistance cells that will ulti- activation of caspase-2 (which can be activated in response mately survive after endoreduplication (Ivanov et al., to DNA damage) and/or mitochondrial membrane per- 2003). meabilization with the release of cell death effectors such During recent years, the expression of ‘mitotic as apoptosis-inducing factor and the caspase-9 and-3 catastrophe’ has been widely used to describe a form activator cytochrome c. Although the morphological of death affecting mammalian cells. Unfortunately aspect of apoptosis may be incomplete, these alterations enough, there is no broadly accepted definition of the constitute the biochemical hallmarks of apoptosis. Cells term ‘mitotic catastrophe’. Igor Roninson attempted to that fail to execute an apoptotic program in response to define mitotic catastrophe in morphological terms, mitotic failure are likely to divide asymmetrically in the namely, as a type of cell death resulting from abnormal next round of cell division, with the consequent generation mitosis, which usually ends in the formation of large of aneuploid cells. This implies that disabling of the cells with multiple micronuclei and decondensed chro- apoptotic program may actually favor chromosomal matin (Swanson et al., 1995; Ianzini and Mackey, 1997; instability, through the suppression of mitotic catastrophe. Roninson et al., 2001). However, reports describing Mitotic catastrophe thus may be conceived as a molecular ‘mitotic catastrophe’ frequently show cells with some device that prevents aneuploidization, which may partici- phenotypic characteristic of apoptosis (such as hyper- pate in oncogenesis. Mitotic catastrophe is controlled by condensed chromatin aggregates) (Heald et al., 1993), numerous molecular players, in particular, cell-cycle- which previously often was interpreted as ‘premature specific kinases (such as the cyclin B1-dependent kinase chromatin condensation’ (Sperling and Ra, 1974; Cdk1, polo-like kinases and Aurora kinases), cell-cycle Chakrabarti and Chakrabarti, 1987). Thus, there is no checkpoint proteins, survivin, p53, caspases and members consensus on the distinctive morphological appearance of the Bcl-2 family. of mitotic catastrophe as far as the extent of chromatin Oncogene (2004) 23, 2825–2837. doi:10.1038/sj.onc.1207528 condensation (which is the morphological hallmark of apoptosis) (Kerr et al., 1972; Ferri and Kroemer, 2001a) Keywords: apoptosis; Cdk1; Chk2; caspases; Bcl-2 is concerned. It has been argued that mitotic catastrophe would be fundamentally different from apoptosis (Roninson et al., 2001) because, in some paradigms, manipulations that Introduction prevent apoptosis (such as overexpression of Bcl-2 in etoposide-treated HeLa cells or MDR1 overexpression ‘Mitotic catastrophe’ has been first described in in irradiated tumor cells) can actually enhance the Schizosaccharomyces pombe as a temperature-sensitive frequency of catastrophic mitoses (Lock and Stribins- lethal phenotype, linked to gross abnormalities of kiene, 1996; Ruth and Roninson, 2000). It has also been chromosome segregation, that was observed in some argued that the assessment of micronucleation (which would indicate mitotic catastrophe) can yield a more accurate picture of cell death induction in vivo than *Correspondence: G Kroemer; E-mail: [email protected] the quantitation of apoptosis (Driessens et al., 2003). Mitotic catastrophe M Castedo et al 2826 Moreover, the fact that caspase inhibitors such as Molecules and processes involved in mitotic catastrophe Z-VAD.fmk can fail to prevent the appearance of dying giant multinucleated cells (induced, for instance, Cdk1/cyclin B1 complex: essential for mitosis and mitotic by treatment with spindle poisons) has been used to catastrophe conclude that mitotic catastrophe would be unrelated to apoptosis (Nabha et al., 2002), assuming that apop- The cyclin-dependent kinase 1 (Cdk1), formerly called tosis must be mediated by caspases. However, it is Cdc2 (or p34Cdc2), interacts with its obligate allosteric now well established that apoptosis may occur in a activator, cyclin B1 to form an active heterodimer, the caspase-independent manner (Susin et al., 1999, 2000; ‘mitosis-promoting factor’. Progression from G2 to Joza et al., 2001), meaning that failure to prevent M phase is driven by the activation of the Cdk1/cyclin cell death by caspase inhibitors cannot be used as B1 complex, whose activity must be sustained from an argument to define this type of cell death as prophase to metaphase. Subsequent entry into the nonapoptotic. anaphase critically relies on the sudden destruction of An alternative definition of mitotic catastrophe the Cdk1/cyclin B1 activity by the anaphase-promoting may be considered as near-to-tautological. Mitotic complex (APC) (Nigg, 2001; Smits and Medema, 2001) catastrophe would be a type of cell death occurring (Figure 1). Accordingly, the activity of Cdk1 is regulated during mitosis, as a result of DNA damage or deran- in a complex spatiotemporal pattern at several levels, ged spindle formation coupled to the debilitation of namely, (i) the transcription of cyclin B1 and (to a lower different checkpoint mechanisms that would normally extent) that of Cdk1, (ii) regulatory Cdk1 (de)pho- arrest progression into mitosis and hence suppress sphorylations by multiple kinases and phosphatases, (iii) catastrophic events until repair has been achieved. endogenous Cdk1 inhibitors, (iv) the subcellular dis- The ‘DNA structure checkpoint’ arrests cells at the tribution of cylin B1, and (v) the regulated degradation G2/M transition in response to unreplicated DNA of cyclin B1. or DNA damage, and the ‘spindle assembly check- The transcription of Cdk1 is modulated in conditions point’ prevents anaphase until all chromosomes have of genotoxic stress. For instance, p53 negatively obtained bipolar attachment. The combination of regulates the transcription of Cdk1 (Yun et al., 1999) checkpoint deficiencies and specific types of damage and cyclin B1 (Taylor et al., 1999), while enhancing the would lead to mitotic catastrophe. Thus, the pharma- transcription of three Cdk1 inhibitors (Gadd45, p21 and cological inhibition or genetic suppression of several 14-3-3s) (Taylor and Stark, 2001). The cyclin B1 gene is G2 checkpoint genes such as ATM, ATR, Chk1, transcribed and its mRNA is stabilized from the end of Chk2, polo-like kinase (Plk)1, Plk2, Plk3, Pin1, Mlh1 the S phase. The phosphorylation of Cdk1 on Thr14 and 14-3-3-s can promote DNA-damage-induced mito- (mainly by Myt1 kinase) and Tyr15 (mainly by Wee1 tic catastrophe (Bunz et al., 1998; Chan et al., 1999; kinase) inhibits its activity during the G2 phase of the Roninson et al., 2001; Chen et al., 2003). Damage cell cycle, while dephosphorylation of Cdk1 on Thr14 leading to mitotic catastrophe can be induced, in and Tyr15 by a member of the Cdc25 family of particular, by microtubule-hyperpolymerizing agents phosphatases results in the activation of Cdk1 during (taxanes, elutherobins, epothilones, laulimalide, sarco- early mitosis. The phosphorylation of Thr161 by CAK dictyins, docodermolide) and by microtubule-depoly- (Cdk-activating kinase, a heterodimer of cyclin H and merizing agents (such as the Vinca alkaloids, Cdk7) is strictly required for Cdk1 to be active. The cryptophyscins, halichondrins, estramustine and colchi- Cdk1 inhibitor p21Cip1/Waf1 directly inhibits Cdk1 activity. cine) as well as by DNA damage (Roninson et al., 2001). Cyclin B1 translocates from the cytosol to the nucleus, Since cancer cells are frequently deficient in cell-cycle early during mitosis. The equilibrium between nuclear checkpoints, they may be particularly susceptible to the import and export of cyclin B1 (as well as that of induction of mitotic catastrophe by such drugs. Mitotic Cdc25C, required for the activation of Cdk1) is catastrophe can also be induced by fusion