Department of Anatomy and Cell Biology, University of Florida College of Medicine, Gainesville, FL, USA.
Cell Cycle. 2013 Aug 15;12(16):2598-607. doi: 10.4161/cc.25591. Epub 2013 Jul 9.
Microtubule-poisoning drugs, such as Paclitaxel (or Taxol, PTX), are powerful and commonly used anti-neoplastic agents for the treatment of several malignancies. PTX triggers cell death, mainly through a mitotic arrest following the activation of the spindle assembly checkpoint (SAC). Cells treated with PTX slowly slip from this mitotic block and die by mitotic catastrophe. However, cancer cells can acquire or are intrinsically resistant to this drug, posing one of the main obstacles for PTX clinical effectiveness. In order to override PTX resistance and increase its efficacy, we investigated both the enhancement of mitotic slippage and the block of mitotic exit. To test these opposing strategies, we used physiological hyperthermia (HT) to force exit from PTX-induced mitotic block and the anaphase-promoting complex/cyclosome (APC/C) inhibitor, proTAME, to block mitotic exit. We observed that application of HT on PTX-treated cells forced mitotic slippage, as shown by the rapid decline of cyclin B levels and by microscopy analysis. Similarly, HT induced mitotic exit in cells blocked in mitosis by other antimitotic drugs, such as Nocodazole and the Aurora A inhibitor MLN8054, indicating a common effect of HT on mitotic cells. On the other hand, proTAME prevented mitotic exit of PTX and MLN8054 arrested cells, prolonged mitosis, and induced apoptosis. In addition, we showed that proTAME prevented HT-mediated mitotic exit, indicating that stress-induced APC/C activation is necessary for HT-induced mitotic slippage. Finally, HT significantly increased PTX cytotoxicity, regardless of cancer cells' sensitivity to PTX, and this activity was superior to the combination of PTX with pro-TAME. Our data suggested that forced mitotic exit of cells arrested in mitosis by anti-mitotic drugs, such as PTX, can be a more successful anticancer strategy than blocking mitotic exit by inactivation of the APC/C.
微管毒素药物，如紫杉醇（或 Taxol，PTX），是治疗多种恶性肿瘤的强效且常用的抗肿瘤药物。PTX 通过激活纺锤体组装检查点（SAC）引起有丝分裂停滞，从而引发细胞死亡。用 PTX 处理的细胞会缓慢地从有丝分裂阻滞中滑脱，并通过有丝分裂灾难而死亡。然而，癌细胞可以获得或固有地对这种药物产生抗性，这是 PTX 临床疗效的主要障碍之一。为了克服 PTX 耐药性并提高其疗效，我们研究了促进有丝分裂滑脱和阻止有丝分裂退出的方法。为了测试这些相反的策略，我们使用生理高温（HT）迫使细胞从 PTX 诱导的有丝分裂阻滞中退出，并使用 APC/C 抑制剂 proTAME 阻止有丝分裂退出。我们观察到，将 HT 应用于 PTX 处理的细胞会迫使有丝分裂滑脱，这表现为 cyclin B 水平的迅速下降和显微镜分析。同样，HT 诱导了其他抗有丝分裂药物，如诺考达唑和 Aurora A 抑制剂 MLN8054 阻滞的细胞中的有丝分裂退出，表明 HT 对有丝分裂细胞有共同的作用。另一方面，proTAME 阻止了 PTX 和 MLN8054 阻滞细胞的有丝分裂退出，延长了有丝分裂并诱导了细胞凋亡。此外，我们表明 proTAME 阻止了 HT 介导的有丝分裂退出，表明应激诱导的 APC/C 激活是 HT 诱导的有丝分裂滑脱所必需的。最后，HT 显著增加了 PTX 的细胞毒性，无论癌细胞对 PTX 的敏感性如何，并且这种活性优于 PTX 与 proTAME 的组合。我们的数据表明，对于由抗有丝分裂药物（如 PTX）阻滞的有丝分裂细胞，强制有丝分裂退出可能是比通过 APC/C 失活阻止有丝分裂退出更成功的抗癌策略。
