Mechanisms of nuclear Mcl-1 mediated chemoresistance

摘要 抗凋亡Bcl-2蛋白的过表达是肿瘤保护自身的主要机制 化疗干预。该领域的大多数努力集中在特定的分子结构域， 与抗凋亡Bcl-2家族蛋白共同，其结合并阻止促凋亡家族成员 通过线粒体途径启动程序性细胞死亡。然而，我们的初步数据表明， Mcl-1通过第二种机制保护肿瘤免受治疗干预，独立于其抗凋亡作用。 活动具体地说，我们的数据表明，Mcl-1含有一个独特的环结构域，该结构域结合调节 当分子从细胞核转位到细胞核时， 化疗具体地说，数据表明，一旦定位到细胞核，Mcl-1与 已知调节RNA稳定性的机制，并直接抑制正常转录本的表达。 在化学敏感细胞中上调，包括参与活性氧物质产生的基因， NOX4我们使用结直肠癌作为我们的模型，实体瘤，因为：1）它仍然是最致命的肿瘤之一 人类癌症; 2）越来越多的数据表明Mcl-1在调节结肠中的化学抗性中起主要作用 癌症; 3）我们可以访问一个非常大的结直肠癌肿瘤库， 许多患者衍生模型。我们假设Mcl-1在化疗耐药性中的作用取决于它的能力， 离开线粒体并转移到细胞核，并在转录后协调应激， 以科普化疗引起的氧化应激反应。因此，我们假设，为了优化靶向， 对于Mcl-1，一种组合方法是必要的，由此其抗凋亡机制和 协调其核活动的环域将提供克服 肿瘤的耐药性我们提出以下三个相关但独立的目标来检验我们的假设： 1)确定化疗诱导Mcl-1核转位的机制。2)探讨 核Mcl-1介导化学抗性的机制。3)制定针对Mcl-1的多个 化学抗性的机制。这些目标的成功完成将产生新的目标，使肿瘤 化学敏感性，并将提供抗Mcl-1药物设计所需的理解， 最终导致其他形式的癌症。由于在设计Mcl-1的抑制剂方面存在显著的药学兴趣， 对于实体瘤治疗，我们的建议对于获得分子的分子理解非常及时。 成功实现这一目标的必要条件。

Abstract The overexpression of anti-apoptotic Bcl-2 proteins is a primary mechanism by which tumors protect themselves from chemotherapeutic interventions. Most effort in the field has focused on a specific molecular domain that is common to the anti-apoptotic Bcl-2 family proteins, which binds and prevents pro- apoptotic family members from initiating programmed cell death by the mitochondrial pathway. Our preliminary data, however, indicate that Mcl-1 protects tumors from therapeutic interventions by a second mechanism, independent of its anti-apoptotic activities. Specifically, our data indicate that Mcl-1 contains a unique loop domain that binds proteins that regulate gene expression when the molecule is translocated from the mitochondrion to the nucleus in response to chemotherapy. Specifically, the data demonstrate that once localized to the nucleus, Mcl-1 interacts with machinery known to regulate RNA stability, and directly suppresses the expression of transcripts normally upregulated in chemosensitive cells, including genes involved in the production of reactive oxygens species such as NOX4. We use colorectal cancer as our model, solid tumor because: 1) it continues to be one of the deadliest human cancers; 2) mounting data indicates that Mcl-1 plays a major role in regulating chemoresistance in colon cancer; and 3) we have access to a very large colorectal cancer tumor bank, from which we have generated numerous patient-derived models. It is our hypothesis that Mcl-1’s role in chemoresistance depends on its ability to leave the mitochondria and translocate to the nucleus, and to post-transcriptionally coordinate a stress response to cope with chemotherapy-induced oxidative stress. We thus hypothesize that to optimize targeting of Mcl-1, a combinatorial approach is necessary, whereby inhibitors of both its anti-apoptotic mechanism and the loop domains mediating its nuclear activities will provide the comprehensive strategy needed to overcome the tumor’s chemoresistance. We propose the following three related but independent aims to test our hypothesis: 1) Determine the mechanism by which chemotherapy induces Mcl-1 nuclear translocation. 2) Investigate the mechanism by which nuclear Mcl-1 mediates chemoresistance. 3) Develop strategies that target Mcl-1’s multiple mechanisms of chemoresistance. Successful completion of these aims will yield new targets for rendering tumors chemosensitive and will provide the understanding needed for anti-Mcl-1 drug design for colorectal- and ultimately other forms of cancer. As there is significant pharmaceutical interest in designing inhibitors of Mcl-1 for solid tumor therapy, our proposal is extremely timely for attaining the molecular understanding of the molecule requisite for successfully accomplishing that goal.