| Summary: | 碩士 === 高雄醫學大學 === 生物科技學系碩士班 === 99 === A polo-like kinase 1 inhibitor, BI-2023, accompanied with three microtubule-targeting agents, paclitaxel, nocodazole and CIL-102, have been introduced to explore their anti-mitotic actions in two prostate cancer cell lines, LNCaP and PC3. Flow cytometry analysis first revealed that four compounds cause cell cycle arrest at G2/M. Chromosome condensation for the cells treated by three microtubule-targeting agents, paclitaxel, nocodazole and CIL-102, occurs simultaneously, but the cells treated by BI-2536, a PLK1 inhibitor, show much late in this event. By considering their effects on microtubule assembly system, paclitaxel, nocodazole and CIL-102 exert their activities on microtubules far before the beginning of mitosis, whereas BI-2536, a PLK1 inhibitor, seems no effect on microtubules. After entering into mitosis, condensed chromosomes attaching with paclitaxel-stabilized microtubule and with CIL-102-destabilized microtubule appear as dense-multipolar- and light-multipolar-spindle complex, respectively. Interestingly, BI-2536 does not interact with microtubules directly, but affects spindle assembly after entering into mitosis, resulting in light-multipolar spindles with similar appearance as CIL-102 did. Apparently, cell cycle arrest induced by these compounds exactly occurs at formation of chromosome-spindle complex, prometaphase but not G2/M phase. Further PARP degradation and annexin-V assay indicated that BI-2536 showed more sensitive apoptotic response in prostate cancer cell lines than that of microtubule-targeting agents. Flow cytometry analysis on the adherent and detached cells revealed that BI-2536 drove relatively late cell death in comparison with microtubule-targeting agents in LNCaP and PC3 cells. Moreover, paclitaxel, nocodazole or CIL-102 seemed much easily to cause mitosis slippage to form polyploidy cells in PC3 cells, in comparison with BI-2536. In conclusion, our results indicated that a PLK1 inhibitor and microtubule-targeting agents could efficiently kill prostate cancer cells mainly through spindle disruption at prometaphase. Moreover, we demonstrated that the PLK1 inhibitor such as BI-2536 might drive cell death by distinct pathway from the classical microtubule-targeting agents.
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