The primary antimitotic mechanism of action of the synthetic halichondrin E7389 is suppression of microtubule growth
The primary antimitotic mechanism of action of the synthetic halichondrin E7389 is suppression of microtubule growth
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DOI：
10.1158/1535-7163.mct-04-0345
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发表时间：
2005-07-01
影响因子：
5.7
通讯作者：
Wilson, L
中科院分区：
文献类型：
--
作者：
Jordan, MA;Kamath, K;Wilson, L
E7389是一种人工合成的大环酮类化合物，与海绵天然产物何首乌B类似，目前正处于I期和11个临床试验阶段。虽然其作用机制尚未完全阐明，但其主要靶点似乎是微管蛋白和/或负责有丝分裂纺锤体的构建和正常功能的微管。像大多数微管靶向的抗肿瘤药物一样，它抑制肿瘤细胞的增殖与G(2)-M期阻滞有关。它与微管蛋白结合，抑制微管聚合。我们研究了E7389与纯化的微管和在活细胞中的作用机制，发现E7389不同于包括长春花碱和紫杉醇在内的抗有丝分裂药物，后者同时抑制微管动态不稳定的缩短和生长阶段，E7389似乎通过一种末端中毒机制发挥作用，该机制主要导致微管生长抑制，但不是缩短，同时将微管蛋白隔离到聚集体中。在活的MCF7细胞中，E7389对微管动态不稳定的缩短事件、灾难和救援频率没有影响，但显著抑制了微管的生长速度和程度。长春花碱能抑制稀释诱导的微管解体，但不能抑制E7389。结果表明，在其最低有效浓度下，E7389可能通过以未连接的E7389直接与微管末端结合或通过E7389诱导的微管蛋白聚集体与未连接的可溶性微管蛋白竞争生长的微管末端而抑制有丝分裂。其结果是形成不能通过中期/后期检查点的异常有丝分裂纺锤体。
E7389, which is in phase I and 11 clinical trials, is a synthetic macrocyclic ketone analogue of the marine sponge natural product halichondrin B. Whereas its mechanism of action has not been fully elucidated, its main target seems to be tubulin and/or the microtubules responsible for the construction and proper function of the mitotic spindle. Like most microtubule-targeted antitumor drugs, it inhibits tumor cell proliferation in association with G(2)-M arrest. It binds to tubulin and inhibits microtubule polymerization. We examined the mechanism of action of E7389 with purified microtubules and in living cells and found that, unlike antimitotic drugs including vinblastine and paclitaxel that suppress both the shortening and growth phases of microtubule dynamic instability, E7389 seems to work by an end-poisoning mechanism that results predominantly in inhibition of microtubule growth, but not shortening, in association with sequestration of tubulin into aggregates. In living MCF7 cells at the concentration that half-maximally blocked cell proliferation and mitosis (1 nmol/L), E7389 did not affect the shortening events of microtubule dynamic instability nor the catastrophe or rescue frequencies, but it significantly suppressed the rate and extent of microtubule growth. Vinblastine, but not E7389, inhibited the dilution-induced microtubule disassembly rate. The results suggest that, at its lowest effective concentrations, E7389 may suppress mitosis by directly binding to microtubule ends as unliganded E7389 or by competition of E7389-induced tubulin aggregates with unliganded soluble tubulin for addition to growing microtubule ends. The result is formation of abnormal mitotic spindles that cannot pass the metaphase/anaphase checkpoint.