Tetraploidy is a hallmark of cancer cells, and tetraploidy‐selective cell growth suppression is a potential strategy for targeted cancer therapy. However, how tetraploid cells differ from normal diploids in their sensitivity to anti‐proliferative treatments remains largely unknown. In this study, we found that tetraploid cells are significantly more susceptible to inhibitors of a mitotic kinesin (CENP‐E) than are diploids. Treatment with a CENP‐E inhibitor preferentially diminished the tetraploid cell population in a diploid–tetraploid co‐culture at optimum conditions. Live imaging revealed that a tetraploidy‐linked increase in unsolvable chromosome misalignment caused substantially longer mitotic delay in tetraploids than in diploids upon moderate CENP‐E inhibition. This time gap of mitotic arrest resulted in cohesion fatigue and subsequent cell death, specifically in tetraploids, leading to tetraploidy‐selective cell growth suppression. In contrast, the microtubule‐stabilizing compound paclitaxel caused tetraploidy‐selective suppression through the aggravation of spindle multipolarization. We also found that treatment with a CENP‐E inhibitor had superior generality to paclitaxel in its tetraploidy selectivity across a broader spectrum of cell lines. Our results highlight the unique properties of CENP‐E inhibitors in tetraploidy‐selective suppression and their potential use in the development of tetraploidy‐targeting interventions in cancer.

Tetraploidy caused by whole-genome duplication is a hallmark of cancer cells, and tetraploidy-selective cell growth suppression is a potential strategy for targeted cancer therapy. However, how tetraploid cells differ from normal diploids in their sensitivity to anti-proliferative treatments remains largely unknown. In this study, we found that tetraploid cells are significantly more susceptible to inhibitors of a mitotic kinesin CENP-E than diploids. CENP-E inhibitor preferentially diminished the tetraploid cell population in diploid-tetraploid co-culture at optimum conditions. Live imaging revealed that tetraploidy-linked increase in unsolvable polar chromosome misalignment caused substantially longer mitotic delay in tetraploids than in diploids upon moderate CENP-E inhibition. This time gap of mitotic arrest resulted in cohesion fatigue and subsequent cell death, specifically in tetraploids, leading to tetraploidy-selective cell growth suppression. In contrast, the microtubule-stabilizing compound paclitaxel caused tetraploidy-selective growth suppression through the aggravation of spindle multipolarization. We also found that CENP-E inhibitors had superior generality to paclitaxel in its tetraploidy selectivity across a broader spectrum of cell lines. Our results highlight the unique properties of CENP-E inhibitors in tetraploidy-selective suppression, giving us clues on the further development of tetraploidy-targeting interventions in cancer.

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Haploid embryonic lethality is a common feature in vertebrates. However, the developmental defects and timing of lethality in haploid embryos differ between non-mammalian and mammalian species. Therefore, it remains unknown whether vertebrates share common principles of haploid intolerance. We investigated haploidy-linked defects at the cellular level in gynogenetic haploid zebrafish larvae that manifest characteristic morphogenetic abnormalities. Haploid larvae suffered severe mitotic arrest and irregular upregulation of p53, leading to unscheduled cell death. Either mitigation of mitotic arrest by spindle assembly checkpoint inactivation or depletion of p53 significantly improved organ growth in haploid larvae, indicating the critical contribution of these cellular defects to haploidy-linked morphogenetic defects. Moreover, haploid zebrafish larvae suffered frequent centrosome loss resulting in mitotic spindle monopolarization, a leading cause of mitotic instability in haploid mammalian cells (1, 2). Haploid larvae also suffered ciliopathy associated with severe centrosome loss. Based on our results, we propose the ploidy-linked alteration in centrosome number control as a common principle constraining the allowable ploidy state for normal development in vertebrates.Significance statementHaploid embryos possessing a single chromosome set are invariably lethal in vertebrates. Though haploid intolerance is attributed to imprinting misregulation in mammals, it remains unknown what limits the developmental capacity of haploid non-mammalian vertebrates free from the imprinting constraint. This study revealed the haploidy-linked mitotic misregulation and p53 upregulation as the leading cause of organ growth retardation in haploid zebrafish larvae. Accompanied by these defects, haploid larvae manifested drastic centrosome loss and mitotic spindle monopolarization, defects also limiting the proliferative capacity of haploid mammalian cells. These findings suggest the ploidy-linked alteration in centrosome number control as a common cell-intrinsic principle of haploid intolerance in vertebrates, providing an insight into an evolutionary constraint on allowable ploidy status in animal life cycles.