Induction of BIM is essential for apoptosis triggered by EGFR kinase inhibitors in mutant EGFR-dependent lung adenocarcinomas.
Induction of BIM is essential for apoptosis triggered by EGFR kinase inhibitors in mutant EGFR-dependent lung adenocarcinomas.
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BIM的诱导对于突变体EGFR依赖性肺腺癌中EGFR激酶抑制剂触发的凋亡至关重要。
DOI：
10.1371/journal.pmed.0040294
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发表时间：
2007-10-09
期刊：
影响因子：
15.8
通讯作者：
Pao, William
中科院分区：
文献类型：
--
作者：
Gong, Yixuan;Somwar, Romel;Politi, Katerina;Balak, Marissa;Chmielecki, Juliann;Jiang, Xuejun;Pao, William
表皮生长因子受体（EGFR）基因突变与肺癌对厄洛替尼等激酶抑制剂的敏感性增加有关。在这些致癌基因依赖性肿瘤中激酶抑制后发生的细胞死亡机制尚未得到很好的阐明。我们试图加深对这一过程的理解，以便深入了解酪氨酸激酶抑制剂的敏感性和/或耐药机制，并发现新的治疗靶点。使用一组含有 EGFR 突变的人类肺癌细胞系和各种生化、分子和细胞技术，我们证明药物敏感细胞中的 EGFR 激酶抑制可通过 caspase 激活的内在途径引发细胞凋亡。该过程需要诱导促凋亡的 BH3 BCL2 家族成员 BIM（即 BCL2 样 11 或 BCL2L11）；厄洛替尼在敏感细胞系中显着诱导 BIM 水平，但在耐药细胞系中则不然，并且通过 RNA 干扰敲低 BIM 表达实际上消除了药物诱导的体外细胞杀伤。 BIM 状态在转录和转录后水平上受到调节，并受到 EGFR 下游的细胞外信号调节激酶 (ERK) 信号级联的影响。与这些发现一致的是，厄洛替尼治疗后，携带突变 EGFR 依赖性肺腺癌的小鼠的肺肿瘤和异种移植物显示出 Bim 浓度增加。此外，抗凋亡蛋白抑制剂 ABT-737 可在体外增强厄洛替尼诱导的细胞死亡。在药物敏感的 EGFR 突变型肺癌细胞中，BIM 的诱导对于 EGFR 激酶抑制剂触发的细胞凋亡至关重要。这一发现意味着 caspase 激活的内在途径可能影响 EGFR 突变型肺肿瘤细胞对 EGFR 激酶抑制的敏感性和/或耐药性。操纵内在途径可能是一种治疗策略，可进一步增强 EGFR 突变肺肿瘤患者的临床结果。 William Pao 及其同事使用一组人类药物敏感 EGFR 突变型肺癌细胞表明，BCL2 家族成员 BIM 的诱导对于 EGFR 激酶抑制剂触发的细胞凋亡至关重要。肺癌是一种常见的癌症，治愈率非常低。与所有癌症一样，当细胞由于基因变化（突变）而开始不受控制地分裂时，就会发生癌症。化疗药物杀死这些快速分裂的细胞，但由于一些正常组织对这些药物敏感，因此很难在不引起严重副作用的情况下消灭癌症。最近，“靶向”治疗给一些癌症患者带来了新的希望。这些疗法攻击癌细胞的变化，使它们不受控制地分裂，但正常细胞毫发无伤。表皮生长因子受体（EGFR）是最早开发出靶向治疗的分子之一。在正常细胞中，信使蛋白与 EGFR 结合并激活其“酪氨酸激酶”，这种酶将磷酸基团粘附在其他蛋白质的酪氨酸（一种氨基酸）上。然后这些蛋白质告诉细胞分裂。这种信号系统的改变会导致某些癌症中不受控制的细胞分裂，因此阻断 EGFR 信号通路应该会阻止这些癌症的生长。事实上，当使用吉非替尼或厄洛替尼这两种酪氨酸激酶抑制剂 (TKI) 治疗时，一些 EGFR 酪氨酸激酶发生突变的肺癌会显着缩小。由于药物诱导的细胞死亡，TKI 敏感的肺癌在使用 TKI 治疗时会缩小，但这种死亡背后的分子机制是什么？更好地了解 TKI 如何杀死癌细胞可能会为为什么并非所有 EGFR（构成 EGFR 的基因）突变的癌细胞都对 TKI 敏感提供新的见解。它还可能发现新的治疗靶点。 TKI 并不能完全杀死肺癌，但如果了解 TKI 诱导的细胞死亡的机制，就有可能增强其效果。在这项研究中，研究人员研究了一组携带 EGFR 突变的人类肺癌细胞系（从人类肿瘤中分离出来的细胞，在培养皿中无限期生长的细胞）在激酶抑制后如何发生细胞死亡。研究人员首先表明，厄洛替尼在厄洛替尼敏感细胞系中诱导一种称为细胞凋亡的细胞死亡，但在耐药细胞系中则不然。细胞凋亡可以通过两种主要途径激活。研究人员报告说，在这种情况下，所谓的“内在”途径会激活细胞凋亡。该通路受到 BCL2 蛋白家族促凋亡成员的刺激，并被抗凋亡成员阻断，因此研究人员检查了厄洛替尼治疗对 EGFR 突变细胞系中 BCL2 家族成员表达的影响。厄洛替尼治疗增加了敏感细胞系中促凋亡蛋白 BIM 的表达，但在耐药细胞系中却没有增加。它还去除了 BIM 中的磷酸基团——去磷酸化的 BIM 是一种更有效的促凋亡蛋白。相反，使用一种称为 RNA 干扰的技术阻断 BIM 表达，实际上消除了厄洛替尼杀死 EGFR 突变细胞系的能力。研究人员还报告说，厄洛替尼治疗增加了小鼠体内生长的厄洛替尼敏感肺肿瘤中的 BIM 表达，并且抗凋亡蛋白 BCL2 的抑制剂增强了厄洛替尼诱导的培养皿中生长的药物敏感细胞的死亡。这些发现表明，在携带 EGFR 突变的药物敏感肺癌细胞中，BIM 活性对于 TKI 引发的细胞凋亡至关重要，并且用 TKI 处理这些细胞会诱导 BIM 的表达和去磷酸化。凋亡激活的内在途径参与 TKI 诱导的细胞死亡这一发现表明，该途径的变化（可能是其某些成分的突变）可能会影响 EGFR 突变肺癌对 TKI 的敏感性。最后，这些发现表明，在 TKI 的同时给予影响细胞凋亡激活内在途径的药物可能会进一步改善 EGFR 突变肿瘤患者的临床结果。此类组合在常规使用之前必须经过临床试验测试。请通过此摘要的在线版本访问这些网站：http://dx.doi.org/10.1371/journal.pmed.0040294。美国国家癌症研究所为患者和专业人员提供的有关肺癌的信息（英语和西班牙语） 英国癌症研究中心为患者提供的有关肺癌的信息，包括 TKI 治疗的信息 有关细胞凋亡、表皮生长因子受体和 BCL-2 蛋白的维基百科页面（请注意，维基百科是任何人都可以编辑的免费在线百科全书；有多种语言版本） Cancerbackup 为患者提供的有关厄洛替尼和吉非替尼的信息
Mutations in the epidermal growth factor receptor (EGFR) gene are associated with increased sensitivity of lung cancers to kinase inhibitors like erlotinib. Mechanisms of cell death that occur after kinase inhibition in these oncogene-dependent tumors have not been well delineated. We sought to improve understanding of this process in order to provide insight into mechanisms of sensitivity and/or resistance to tyrosine kinase inhibitors and to uncover new targets for therapy. Using a panel of human lung cancer cell lines that harbor EGFR mutations and a variety of biochemical, molecular, and cellular techniques, we show that EGFR kinase inhibition in drug-sensitive cells provokes apoptosis via the intrinsic pathway of caspase activation. The process requires induction of the proapoptotic BH3-only BCL2 family member BIM (i.e., BCL2-like 11, or BCL2L11); erlotinib dramatically induces BIM levels in sensitive but not in resistant cell lines, and knockdown of BIM expression by RNA interference virtually eliminates drug-induced cell killing in vitro. BIM status is regulated at both transcriptional and posttranscriptional levels and is influenced by the extracellular signal-regulated kinase (ERK) signaling cascade downstream of EGFR. Consistent with these findings, lung tumors and xenografts from mice bearing mutant EGFR-dependent lung adenocarcinomas display increased concentrations of Bim after erlotinib treatment. Moreover, an inhibitor of antiapoptotic proteins, ABT-737, enhances erlotinib-induced cell death in vitro. In drug-sensitive EGFR mutant lung cancer cells, induction of BIM is essential for apoptosis triggered by EGFR kinase inhibitors. This finding implies that the intrinsic pathway of caspase activation may influence sensitivity and/or resistance of EGFR mutant lung tumor cells to EGFR kinase inhibition. Manipulation of the intrinsic pathway could be a therapeutic strategy to enhance further the clinical outcomes of patients with EGFR mutant lung tumors. Using a panel of human drug-sensitive EGFR mutant lung cancer cells, William Pao and colleagues show that induction of BIM, a member of the BCL2 family, is essential for apoptosis triggered by EGFR kinase inhibitors. Lung cancer, a common type of cancer, has a very low cure rate. Like all cancers, it occurs when cells begin to divide uncontrollably because of changes (mutations) in their genes. Chemotherapy drugs kill these rapidly dividing cells but, because some normal tissues are sensitive to these agents, it is hard to destroy the cancer without causing serious side effects. Recently, “targeted” therapies have brought new hope to some patients with cancer. These therapies attack the changes in cancer cells that allow them to divide uncontrollably but leave normal cells unscathed. One of the first molecules for which a targeted therapy was developed was the epidermal growth factor receptor (EGFR). In normal cells, messenger proteins bind to EGFR and activate its “tyrosine kinase,” an enzyme that sticks phosphate groups on tyrosine (an amino acid) in other proteins. These proteins then tell the cell to divide. Alterations to this signaling system drive uncontrolled cell division in some cancers so blocking the EGFR signaling pathway should stop these cancers growing. Indeed, some lung cancers with mutations in the tyrosine kinase of EGFR shrink dramatically when treated with gefitinib or erlotinib, two tyrosine kinase inhibitors (TKIs). TKI-sensitive lung cancers shrink when treated with TKIs because of drug-induced cell death, but what are the molecular mechanisms underlying this death? A better understanding of how TKIs kill cancer cells might provide new insights into why not all cancer cells with mutations in EGFR (the gene from which EGFR is made) are sensitive to TKIs. It might also uncover new targets for therapy. TKIs do not completely kill lung cancers, but if the mechanism of TKI-induced cell death were understood, it might be possible to enhance their effects. In this study, the researchers have investigated how cell death occurs after kinase inhibition in a panel of human lung cancer cell lines (cells isolated from human tumors that grow indefinitely in dishes) that carry EGFR mutations. The researchers show, first, that erlotinib induces a type of cell death called apoptosis in erlotinib-sensitive cell lines but not in resistant cell lines. Apoptosis can be activated by two major pathways. In this instance, the researchers report, the so-called “intrinsic” pathway activates apoptosis. This pathway is stimulated by proapoptotic members of the BCL2 family of proteins and is blocked by antiapoptotic members, so the researchers examined the effect of erlotinib treatment on the expression of BCL2 family members in the EGFR mutant cell lines. Erlotinib treatment increased the expression of the proapoptotic protein BIM in sensitive but not in resistant cell lines. It also removed phosphate groups from BIM—dephosphorylated BIM is a more potent proapoptotic protein. Conversely, blocking BIM expression using a technique called RNA interference virtually eliminated the ability of erlotinib to kill EGFR mutant cell lines. The researchers also report that erlotinib treatment increased BIM expression in erlotinib-sensitive lung tumors growing in mice and that an inhibitor of the anti-apoptotic protein BCL2 enhanced erlotinib-induced death in drug-sensitive cells growing in dishes. These findings indicate that BIM activity is essential for the apoptosis triggered by TKIs in drug-sensitive lung cancer cells that carry EGFR mutations, and that treatment of these cells with TKIs induces both the expression and dephosphorylation of BIM. The finding that the intrinsic pathway of apoptosis activation is involved in TKI-induced cell death suggests that changes in this pathway (possibly mutations in some of its components) might influence the sensitivity of EGFR mutant lung cancers to TKIs. Finally, these findings suggest that giving drugs that affect the intrinsic pathway of apoptosis activation at the same time as TKIs might further improve the clinical outcome for patients with EGFR mutant tumors. Such combinations will have to be tested in clinical trials before being used routinely. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040294. US National Cancer Institute information for patients and professionals on lung cancer (in English and Spanish) Information for patients from Cancer Research UK on lung cancer including information on treatment with TKIs Wikipedia pages on apoptosis, epidermal growth factor receptor, and BCL-2 proteins (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages) Information for patients from Cancerbackup on erlotinib and gefitinib
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影响因子：
158.5
作者：
Lynch, TJ;Bell, DW;Haber, DA
通讯作者：
Haber, DA
影响因子：
20.3
作者：
Ekert, Paul G.;Jabbour, Anissa M.;Vaux, David L.
通讯作者：
Vaux, David L.
影响因子：
15.8
作者：
Greulich H;Chen TH;Feng W;Jänne PA;Alvarez JV;Zappaterra M;Bulmer SE;Frank DA;Hahn WC;Sellers WR;Meyerson M
通讯作者：
Meyerson M
影响因子：
6.4
作者：
Janmaat, ML;Rodriguez, JA;Giaccone, G
通讯作者：
Giaccone, G
影响因子：
4.8
作者：
Qi, XJ;Wildey, GM;Howe, PH
通讯作者：
Howe, PH