Regulation of Tumor Cell Migration by Mitochondrial Superoxide Dismutase

描述(申请人提供)：癌症死亡的主要原因是原发肿瘤的细胞扩散形成远处转移。细胞迁移和侵袭的可能性取决于多种信号通路，这些信号通路为抗癌治疗提供了新的靶点。活性氧簇(ROS)越来越多地被认为是肿瘤发生的调节因子，许多癌症类型表现出ROS水平升高。氧化还原平衡的重要调节酶是线粒体表达的锰超氧化物歧化酶(Sod2)，它催化超氧阴离子转化为过氧化氢(H_2O_2)。Sod2的高表达在包括乳腺癌、脑癌和膀胱癌在内的多种浸润性癌症中已被描述。我们已经证明，Sod2的过度表达和伴随的过氧化氢的增加，可以导致纤维肉瘤HT-1080细胞更多的转移和迁移行为。在这项建议中，我们希望阐明Sod2表达的增加和线粒体过氧化氢产生的激增如何导致这种亲迁移表型。为了解决这个问题，我们将使用新型氧化还原感应绿色荧光蛋白探针来确定线粒体过氧化氢的空间定位和作用位置。这将表明ROS是否可以针对移动细胞中的特定区域，在那里它们可以发挥第二信使的作用。ROS在细胞信号转导中的一个新作用是蛋白质酪氨酸磷酸酶的氧化和失活，包括那些参与粘着斑激酶在质膜上动态重排焦点接触的酶。利用生化方法，我们将研究Sod2的表达是否可以通过增强通常抑制这一途径的磷酸酶的氧化/失活来显着增强支持迁移的粘着斑激酶信号。最后，我们将在体内和体外研究抗氧化分子在逆转Sod2表达细胞的亲迁移表型和信号事件中的作用。这将决定基于抗氧化剂的治疗对由于Sod2表达增加而表现出ROS负担增加的癌症的有效性。这项提议的研究旨在解决这样的假设，即Sod2的表达增加导致蛋白质酪氨酸磷酸酶的空间失活，这是通过增加线粒体过氧化氢的产生，导致亲迁移信号和癌细胞转移潜力的增强。这项研究将进一步加深我们对调控转移的细胞内机制的了解。了解活性氧在这些事件中的作用将有助于开发基于抗氧化剂的新型癌症治疗方法。

DESCRIPTION (provided by applicant): The principal cause of cancer mortality is the dissemination of cells from the primary tumor to form distant metastases. The potential for a cell to migrate and invade depends on a multitude of signaling pathways, which present novel targets for anti-cancer therapies. Reactive oxygen species (ROS) have increasingly been implicated as modulators of tumorigenicity and many cancer types exhibit elevated ROS levels. An important regulatory enzyme of Redox balance is the mitochondrially expressed manganese superoxide dismutase (Sod2), which catalyzes the conversion of superoxide anion to hydrogen peroxide (H2O2). Elevated Sod2 expression has been described in a variety of invasive cancers including those of breast, brain and bladder. We have shown that Sod2 overexpression, and a concomitant increase in H2O2, can lead to a more metastatic and migratory behavior of fibrosarcoma HT-1080 cells. In this proposal we hope to elucidate how an increase in Sod2 expression and a surge in mitochondrial H2O2 production leads to this pro-migratory phenotype. To address this we will determine the spatial localization and site of action of mitochondrial H2O2, using novel Redox sensing green fluorescing protein probes. This will indicate if ROS can be targeted to specific areas within a moving cell, where they may carry out their role as second messengers. A novel role for ROS in cellular signaling is the oxidation and inactivation of protein tyrosine phosphatases, including those that are involved in the dynamic rearrangement of focal contacts at the plasma membrane by focal adhesion kinase. Using biochemical approaches we will investigate whether expression of Sod2 can significantly enhance pro-migratory focal adhesion kinase signaling via enhanced oxidation/inactivation of phosphatases that normally inhibit this pathway. Finally, we will investigate the role of anti-oxidant molecules in reversing the pro-migratory phenotype and signaling events of Sod2 expressing cells, both in vivo and in vitro. This will determine the validity of antioxidant based therapies for cancers that display an enhanced ROS burden due to elevated Sod2 expression. The studies of this proposal aim to address the hypothesize that elevated Sod2 expression results in the spatial inactivation of protein tyrosine phosphatases via increased mitochondrial H2O2 production, leading to pro-migratory signaling and an enhancement of the metastatic potential of cancer cells. This research will further our knowledge of the intracellular mechanisms that regulate metastasis. Understanding the role of reactive oxygen species in these events will aid in the development of novel antioxidant based cancer therapies.