Paclitaxel-Induced Apoptosis Is BAK-Dependent, but BAX and BIM-Independent in Breast Tumor
Paclitaxel-Induced Apoptosis Is BAK-Dependent, but BAX and BIM-Independent in Breast Tumor
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DOI：
10.1371/journal.pone.0060685
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发表时间：
2013-04-05
期刊：
影响因子：
3.7
通讯作者：
Harada, Hisashi
中科院分区：
文献类型：
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作者：
Miller, Anna V.;Hicks, Mark A.;Harada, Hisashi
紫杉醇（Taxol）诱导的细胞死亡需要内在的细胞死亡途径，但具体的参与者和确切的机制知之甚少。以前的研究表明，BH 3-only蛋白BIM（BCL-2细胞死亡相互作用介导剂）在紫杉醇诱导的细胞凋亡中起作用。我们在这里使用bim（-/-）MEFs（小鼠胚胎成纤维细胞）、bim（-/-）小鼠乳腺肿瘤模型和人乳腺癌细胞中shRNA介导的BIM下调显示，BIM在紫杉醇治疗的细胞凋亡中被抑制。相反，巴克（-/-）MEFs和巴克被shRNA下调的人乳腺癌细胞对紫杉醇更耐药。然而，紫杉醇的敏感性没有受到影响，在bax（-/-）MEFs或在人乳腺癌细胞中，BAX下调，表明紫杉醇诱导的细胞凋亡是BAK依赖性的，但BAX的独立。在人乳腺癌细胞中，紫杉醇治疗导致MCL-1降解，这被蛋白酶体抑制剂MG 132阻止。Cdk抑制剂roscovitine可阻断紫杉醇诱导的MCL-1降解和细胞凋亡，表明Cdk在有丝分裂阻滞时的激活可诱导随后的MCL-1降解，并以蛋白酶体依赖的方式进行。在未处理的细胞中，巴克与MCL-1相关，并随着MCL-1表达的丧失及其从复合物中的释放而被激活。我们的数据表明，巴克是紫杉醇诱导的细胞凋亡的介质，并可能成为克服紫杉醇耐药的替代靶点。
Paclitaxel (Taxol)-induced cell death requires the intrinsic cell death pathway, but the specific participants and the precise mechanisms are poorly understood. Previous studies indicate that a BH3-only protein BIM (BCL-2 Interacting Mediator of cell death) plays a role in paclitaxel-induced apoptosis. We show here that BIM is dispensable in apoptosis with paclitaxel treatment using bim(-/-) MEFs (mouse embryonic fibroblasts), the bim(-/-) mouse breast tumor model, and shRNA-mediated down-regulation of BIM in human breast cancer cells. In contrast, both bak(-/-) MEFs and human breast cancer cells in which BAK was down-regulated by shRNA were more resistant to paclitaxel. However, paclitaxel sensitivity was not affected in bax(-/-) MEFs or in human breast cancer cells in which BAX was down-regulated, suggesting that paclitaxel-induced apoptosis is BAK-dependent, but BAX-independent. In human breast cancer cells, paclitaxel treatment resulted in MCL-1 degradation which was prevented by a proteasome inhibitor, MG132. A Cdk inhibitor, roscovitine, blocked paclitaxel-induced MCL-1 degradation and apoptosis, suggesting that Cdk activation at mitotic arrest could induce subsequent MCL-1 degradation in a proteasome-dependent manner. BAK was associated with MCL-1 in untreated cells and became activated in concert with loss of MCL-1 expression and its release from the complex. Our data suggest that BAK is the mediator of paclitaxel-induced apoptosis and could be an alternative target for overcoming paclitaxel resistance.