Song Jin H, Kandasamy Karthikeyan, Kraft Andrew S
Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
J Biol Chem. 2008 Sep 5;283(36):25003-13. doi: 10.1074/jbc.M802511200. Epub 2008 Jul 3.
Because Bcl-2 family members inhibit the ability of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to induce apoptosis, we investigated whether ABT-737, a small molecule Bcl-2 inhibitor, enhances TRAIL killing. We demonstrate that a combination of ABT-737 and TRAIL induced significant cell death in multiple cancer types, including renal, prostate, and lung cancers, although each agent individually had little activity in these tumor cells. All of these cell lines expressed the Mcl-1 protein that is known to block the activity of ABT-737 and TRAIL but did not block the synergy between these agents. However, Bax-deficient cell lines, including DU145 and HCT116 cells and those cell lines expressing low levels of TRAIL receptor, were resistant to apoptosis induced by these agents. To understand how ABT-737 functions to markedly increase TRAIL sensitivity, the levels of specific death-inducing signaling complex components were evaluated. Treatment with ABT-737 did not change the levels of c-FLIP, FADD, and caspase-8 but up-regulated the levels of the TRAIL receptor DR5. DR5 up-regulation induced by ABT-737 treatment occurred through a transcriptional mechanism, and mutagenesis studies demonstrated that the NF-kappaB site found in the DR5 promoter was essential for the ability of ABT-737 to increase the levels of this mRNA. Using luciferase reporter plasmids, ABT-737 was shown to stimulate NF-kappaB activity. Together, these results demonstrate that the ability of ABT-737 and TRAIL to induce apoptosis is mediated through activation of both the extrinsic and intrinsic pathways. Combinations of ABT-737 and TRAIL can be exploited therapeutically where antiapoptotic Bcl-2 family members drive tumor cell resistance to current anticancer therapies.
由于Bcl-2家族成员会抑制肿瘤坏死因子相关凋亡诱导配体（TRAIL）诱导凋亡的能力，我们研究了小分子Bcl-2抑制剂ABT-737是否能增强TRAIL的杀伤作用。我们证明，ABT-737与TRAIL联合使用可在多种癌症类型中诱导显著的细胞死亡，包括肾癌、前列腺癌和肺癌，尽管每种药物单独使用时在这些肿瘤细胞中活性很小。所有这些细胞系均表达Mcl-1蛋白，已知该蛋白可阻断ABT-737和TRAIL的活性，但不会阻断这些药物之间的协同作用。然而，Bax缺陷细胞系，包括DU145和HCT116细胞以及那些表达低水平TRAIL受体的细胞系，对这些药物诱导的凋亡具有抗性。为了了解ABT-737如何发挥作用以显著提高TRAIL敏感性，我们评估了特定死亡诱导信号复合物成分的水平。用ABT-737处理不会改变c-FLIP、FADD和半胱天冬酶-8的水平，但会上调TRAIL受体DR5的水平。ABT-737处理诱导的DR5上调是通过转录机制发生的，诱变研究表明，DR5启动子中发现的NF-κB位点对于ABT-737增加该mRNA水平的能力至关重要。使用荧光素酶报告质粒，显示ABT-737可刺激NF-κB活性。总之，这些结果表明，ABT-737和TRAIL诱导凋亡的能力是通过激活外源性和内源性途径介导的。在抗凋亡Bcl-2家族成员导致肿瘤细胞对当前抗癌疗法产生抗性的情况下，ABT-737和TRAIL的联合使用可用于治疗。
