Wang Zhanxiang, Sampath Janardhan, Fukuda Seiji, Pelus Louis M
Department of Microbiology and Immunology and the Walther Oncology Center, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Cancer Res. 2005 Sep 15;65(18):8224-32. doi: 10.1158/0008-5472.CAN-05-0303.
The Bcr-abl oncogene induces hematopoietic cell transformation and protects cells from apoptosis; however, the mechanisms whereby Bcr-abl blocks apoptosis are poorly defined. We examined whether the inhibitor of apoptosis protein (IAP) family, in particular survivin, are regulated by Bcr-abl. Overexpression of Bcr-abl in Mo7e or BaF3 hematopoietic cells elevated survivin mRNA and protein concomitant with a 4-fold increase in survivin promoter activity. The region of the survivin promoter responding to Bcr-abl was narrowed down to a 116 bp fragment between nucleotides -1,194 and -1,078. The IAP family member IAP-like protein-2 was also up-regulated by Bcr-abl. Disruption of Bcr-abl in Bcr-abl-transduced BaF3 cells by small interfering RNA resulted in 3- to 4-fold reduction in survivin protein confirming the link between Bcr-abl and survivin. Survivin disruption in Bcr-abl-transduced Mo7e cells, or in K562 cells that endogenously express Bcr-abl, by transfection with dominant-negative or antisense survivin constructs promoted apoptosis induced by the Bcr-abl tyrosine kinase inhibitor STI571, which was accompanied by caspase-dependent cleavage of Bcr-abl, mitochondrial membrane potential disruption, and enhanced mitochondrial cytochrome c release. Although ectopic survivin protected K562 cells from apoptosis induced by STI571, it did not protect cells from apoptosis induced either by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or the combination of TRAIL plus Hemin. Our results identify a new signal pathway downstream of Bcr-abl, in addition to the Bcl-2 family involved in the antiapoptotic effects of Bcr-abl, and suggest that anti-survivin therapy may have utility in patients with chronic myelogenous leukemia.
Bcr-abl癌基因可诱导造血细胞转化并保护细胞免于凋亡；然而，Bcr-abl阻断凋亡的机制尚不清楚。我们研究了凋亡抑制蛋白（IAP）家族，尤其是生存素，是否受Bcr-abl调控。在Mo7e或BaF3造血细胞中过表达Bcr-abl可使生存素mRNA和蛋白水平升高，同时生存素启动子活性增加4倍。生存素启动子对Bcr-abl作出反应的区域被缩小至核苷酸-1194至-1078之间的116 bp片段。IAP家族成员IAP样蛋白-2也被Bcr-abl上调。用小干扰RNA破坏转导了Bcr-abl的BaF3细胞中的Bcr-abl，可使生存素蛋白水平降低3至4倍，证实了Bcr-abl与生存素之间的联系。通过转染显性阴性或反义生存素构建体，破坏转导了Bcr-abl的Mo7e细胞或内源性表达Bcr-abl的K562细胞中的生存素，可促进Bcr-abl酪氨酸激酶抑制剂STI571诱导的凋亡，这伴随着Bcr-abl的半胱天冬酶依赖性切割、线粒体膜电位破坏以及线粒体细胞色素c释放增加。虽然异位表达的生存素可保护K562细胞免于STI571诱导的凋亡，但它不能保护细胞免于肿瘤坏死因子相关凋亡诱导配体（TRAIL）或TRAIL加血红素联合诱导的凋亡。我们的结果确定了Bcr-abl下游的一条新信号通路，除了参与Bcr-abl抗凋亡作用的Bcl-2家族外，还表明抗生存素疗法可能对慢性粒细胞白血病患者有用。
