Induction of apoptosis by enediyne antibiotic calicheamicin θII proceeds through a caspase-mediated mitochondrial amplification loop in an entirely Bax-dependent manner
Induction of apoptosis by enediyne antibiotic calicheamicin θII proceeds through a caspase-mediated mitochondrial amplification loop in an entirely Bax-dependent manner
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DOI：
10.1038/sj.onc.1207196
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发表时间：
2003-12-11
期刊：
影响因子：
8
通讯作者：
Daniel, PT
中科院分区：
文献类型：
--
作者：
Prokop, A;Wrasidlo, W;Daniel, PT
卡利奇霉素（Calicheamicin thetaII）是一种与DNA结合并诱导细胞凋亡的烯二炔类抗肿瘤抗生素。然而，这些化合物与传统的抗癌药物不同，因为它们以序列特异性的方式与DNA非共价结合，并导致脱氧核糖序列选择性氧化和DNA螺旋弯曲。Calicheamicin在临床上被用作针对抗体的免疫偶联物，例如，在gemtuzumab ozogamicin的情况下，CD33。在这里，我们通过使用非偶联药物表明，卡利奇霉素诱导的细胞凋亡不依赖于死亡受体/ fadd介导的信号。此外，calicheamicin通过p53敲除细胞以p53不依赖的方式触发细胞凋亡。细胞死亡通过激活线粒体通透性转变、细胞色素c释放和激活caspase-9和-3进行。过表达Bcl-x(L)或Bcl-2强烈抑制卡利奇霉素诱导的细胞凋亡。敲除Bax可消除calicheamicin处理后的细胞死亡。因此，线粒体的激活和细胞死亡是通过完全依赖bax的机制发生的。有趣的是，caspase抑制剂zVAD-fmk对caspase的抑制会干扰calicheamicin对线粒体的激活。这将caspase激活置于线粒体的上游，并表明calicheamicin触发的凋亡通过不依赖于死亡受体的caspase级联的激活而增强，即一个完全激活线粒体途径所需的扩增环。
Calicheamicin thetaII is a member of the enediyne class of antitumor antibiotics that bind to DNA and induce apoptosis. These compounds differ, however, from conventional anticancer drugs as they bind in a sequence-specific manner noncovalently to DNA and cause sequence-selective oxidation of deoxyriboses and bending of the DNA helix. Calicheamicin is clinically employed as immunoconjugate to antibodies directed against, for example, CD33 in the case of gemtuzumab ozogamicin. Here, we show by the use of the unconjugated drug that calicheamicin-induced apoptosis is independent from death-receptor/FADD-mediated signals. Moreover, calicheamicin triggers apoptosis in a p53-independent manner as shown by the use of p53 knockout cells. Cell death proceeds via activation of mitochondrial permeability transition, cytochrome c release and activation of caspase-9 and -3. The overexpression of Bcl-x(L) or Bcl-2 strongly inhibited calicheamicin-induced apoptosis. Knockout of Bax abrogated cell death after calicheamicin treatment. Thus, the activation of mitochondria and execution of cell death occur through a fully Bax-dependent mechanism. Interestingly, caspase inhibition by the pancaspase-inhibitor zVAD-fmk interfered with mitochondrial activation by calicheamicin. This places caspase activation upstream of the mitochondria and indicates that calicheamicin-triggered apoptosis is enhanced through death receptor-independent activation of the caspase cascade, that is, an amplification loop that is required for full activation of the mitochondrial pathway.