CD20-induced B cell death can bypass mitochondria and caspase activation
CD20-induced B cell death can bypass mitochondria and caspase activation
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DOI：
10.1038/sj.leu.2402559
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发表时间：
2002-09-01
期刊：
影响因子：
11.4
通讯作者：
Eldering, E
中科院分区：
文献类型：
--
作者：
van der Kolk, LE;Evers, LM;Eldering, E
以Burkitt淋巴瘤细胞株Ramos为研究对象，分析了抗CD20嵌合单抗(美罗华，IDEC.C2B8)诱导的细胞凋亡途径。CD20(CD20XL)可诱导Ramos细胞发生凋亡，包括线粒体膜电位降低(M)、细胞色素-c(cyt-c)释放以及caspase-9和-3的激活。然而，几条证据表明，细胞凋亡的结果并不取决于这些事件。首先，在RAMOS细胞对CD95或B细胞受体(BCR)诱导的凋亡表现出抵抗的情况下，CD20XL诱导的凋亡不受影响，这表明了一种独特的途径。第二，广谱caspase抑制剂zVAD-fmk阻止caspase-9、-3和PARP的加工以及DNA片段化，但不能阻止Annin V染色、细胞大小和膜完整性检测的细胞凋亡。最后，Bcl2过表达可阻断Cyt-c的释放和DelTapsi(M)的降低，并完全阻止CD95或BCR介导的细胞凋亡，但不影响CD20XL诱导的细胞死亡。我们的结论是，虽然CD20XL可以启动线粒体的凋亡途径，但CD20诱导的细胞凋亡并不一定需要激活的caspase，也不能被Bcl-2阻断。由于大多数化疗药物需要激活caspase才能发挥其细胞毒作用，这些发现为CD20单抗用于化疗耐药恶性肿瘤提供了重要的理论基础。
The apoptotic pathway activated by chimeric anti-CD20 monoclonal antibodies (rituximab, IDEC.C2B8) was analyzed using the Burkitt lymphoma cell line Ramos. Crosslinking of CD20 (CD20XL) induced apoptosis in Ramos cells, which involved loss of mitochondrial membrane potential (Deltapsi(m)), the release of cytochrome-c (cyt-c), and activation of caspases-9 and -3. Nevertheless, several lines of evidence showed that the apoptotic outcome did not depend on these events. First, under circumstances where Ramos cells display resistance to either CD95- or B cell receptor (BCR)-induced apoptosis, CD20XL-induced apoptosis was not affected, pointing to a distinct pathway. Second, the broad-spectrum caspase inhibitor zVAD-fmk prevented processing of caspase-9, -3 and PARP as well as DNA fragmentation, but did not block apoptosis as measured by annexin V staining, cell size and membrane integrity. Lastly, Bcl-2 overexpression blocked cyt-c release and the decrease in Deltapsi(m), and completely prevented CD95- or BCR-mediated apoptosis; however, it did not affect CD20XL-induced cell death. We conclude that although CD20XL can initiate the mitochondrial apoptosis pathway, CD20-induced apoptosis does not necessarily require active caspases and cannot be blocked by Bcl-2. Since most chemotherapeutic drugs require the activation of caspases to exert their cytotoxicity, these findings provide an important rationale for the use of CD20 mAbs in chemoresistant malignancies.