The Mitotic Spindle Checkpoint Is a Critical Determinant for Topoisomerase-based Chemotherapy

Abstract

A novel strategy in cancer therapy is the induction of mitotic cell death by the pharmacological abrogation of cell cycle checkpoints. UCN-01 is such a compound that overrides the G 2 cell cycle arrest induced by DNA damage and forces cells into a deleterious mitosis. The molecular pathways leading to mitotic cell death are largely unknown although recent evidence indicates that mitotic cell death represents a special case of apoptosis. Here, we demonstrate that the mitotic spindle checkpoint is activated upon chemotherapeutic treatment with topoisomerase II poisons and UCN-01. Cells that are forced to enter mitosis in the presence of topoisomerase inhibition arrest transiently in a prometaphase like state. By using a novel pharmacological inhibitor of the spindle checkpoint and spindle checkpoint-deficient cells we show that the spindle checkpoint function is required for the mitotic arrest and, most importantly, for efficient induction of mitotic cell death. Thus, our results demonstrate that the mitotic spindle checkpoint is an important determinant for the outcome of a chemotherapy based on the induction of mitotic cell death. Its frequent inactivation in human cancer might contribute to the observed resistance of tumor cells to these chemotherapeutic drugs.

Determinants of Mitotic Catastrophe on Abrogation of the G2 DNA Damage Checkpoint by UCN-01

“…S6). These results are in agreement with the findings that the spindle-assembly checkpoint is important for mitotic catastrophe induced by topoisomerase II inhibitors followed by UCN-01 treatment (8,35), or for cell death in cases where the DNA damage checkpoint has been weakened (36).…”

Partial downregulation of MAD1 causes spindle checkpoint inactivation and aneuploidy, but does not confer resistance towards taxol

“…To date, it is unclear if a moderate downregulation of other spindle checkpoint genes directly contributes to aneuploidy and tumorigenesis; however, a reduced expression of MAD2 and BUBR1, but also of BUB1 and MAD1, has been found in different human cancers (Li and Benezra, 1996;Shichiri et al, 2002;Wang et al, 2002). Surprisingly, spindle checkpoint defects have recently been associated with resistance to spindle damaging anticancer drugs, for example, paclitaxel/taxol (Kasai et al, 2002;Anand et al, 2003;Masuda et al, 2003;Sudo et al, 2004) and with the resistance to topoisomerase poisons, for example, etoposide, adriamycin/ doxorubicin (Vogel et al, 2004b). These findings indicate that the spindle checkpoint might be directly involved in the induction of apoptosis upon mitotic damage and imply that tumors harboring a compromised spindle checkpoint are resistant to such chemotherapeutic treatments.…”

The N-terminus of rodent and human MAD1 confers species-specific stringency to spindle assembly checkpoint

“…Bub1-3, Mad1-3, and Mps1) (Hoyt and Geiser, 1996;Rudner and Murray, 1996;Weiss and Winey, 1996); additional factors such as CENP-E, ZW10, Rod and Rae1 (Abrieu et al, 2000;Basto et al, 2000;Babu et al, 2003) were later proposed for metazoan SAC. The importance of SAC in normal cellular metabolism is reflected in its frequent dysfunction in human cancers (Draviam et al, 2004;Lengauer and Wang, 2004), and in its role for dictating cellular responsiveness to chemotherapeutic agents Vogel et al, 2005). Accordingly, a better understanding of the molecular bases, which influence SAC stringency in higher eukaryotes, could uncover novel targets for treating neoplasia.…”