Molecular Species Responsible for Tumor Suppressive Effect of MnSOD

描述(申请人提供)：线粒体抗氧化酶含锰超氧化物歧化酶(MnSOD)已被证明在多种不同类型的癌细胞中是一种肿瘤抑制因子。在这一应用中，我们建议研究MnSOD的肿瘤抑制机制。我们将检查哪些活性氧或氮物种参与其中。我们提出只有三种逻辑上的可能性：超氧自由基、过氧化氢或一氧化氮自由基。我们将把影响这些分子的蛋白质的cDNA导入过表达MnSOD的人乳腺癌和胶质瘤细胞系，并确定其对恶性表型的影响。其他将过度表达的蛋白质包括两种形式的谷胱甘肽过氧化物酶、过氧化氢酶和一氧化氮合酶。此外，还将确定抑制这些蛋白质活性的效果。谷胱甘肽过氧化物酶、过氧化氢酶和一氧化氮合酶的抑制将通过化学抑制剂以及反义寡核苷酸和siRNA来实现。我们还将把葡萄糖氧化酶导入癌细胞，并检测其对恶性表型的影响。当葡萄糖作为底物存在时，葡萄糖氧化酶会产生过氧化氢，因此本实验将进一步研究过氧化氢是否是效应分子。如果我们能够确定MnSOD过表达抑制生长的分子效应分子，那么我们就可以利用这一知识来开发基于MnSOD过表达和抑制效应分子去除途径的新的抗癌治疗方法。例如，我们已经有数据表明过氧化氢参与了MnSOD过表达的生长抑制作用，因此我们计划研究MnSOD过表达与过氧化氢清除抑制剂联合使用的抗肿瘤作用。通过这种方式，我们希望能够开发出令人兴奋的癌症新疗法。

DESCRIPTION (provided by applicant): The mitochondrial antioxidant enzyme manganese-containing superoxide dismutase (MnSOD) has been shown to be a tumor suppressor in a wide variety of different cancer cell types. In this application, we propose to examine the mechanism of tumor suppression by MnSOD. We will examine which reactive oxygen or nitrogen species is involved. We propose that there are only three logical possibilities: superoxide radical, hydrogen peroxide, or nitric oxide radical. We will transfect the cDNA for proteins that affect these molecules into MnSOD over-expressing human breast cancer and glioma cell lines and determine the effect on the malignant phenotype. The other proteins that will be over-expressed include two forms of glutathione peroxidase, catalase, and nitric oxide synthase. Moreover, the effect of inhibiting the activity of these proteins will be determined. Inhibition of glutathione peroxidase, catalase, and nitric oxide synthase will be accomplished by chemical inhibitors as well as antisense oligodeoxynucleotides and siRNAs. We will also transfect glucose oxidase into cancer cells and examine the effect on the malignant phenotype. Glucose oxidase produces hydrogen peroxide when glucose is present as substrate and thus this experiment will examine further if hydrogen peroxide is the effector molecule. If we can determine the molecular effector of the growth inhibitory effect of MnSOD over-expression, then we can use that knowledge to develop new anticancer treatments based on MnSOD over-expression and inhibition of the effector removal pathway. For example, we already have data showing hydrogen peroxide is involved in the growth suppressive effect of MnSOD over-expression and so we plan to study the antitumor effect of MnSOD over-expression combined with inhibitors of hydrogen peroxide removal. In this way, we hope to be able to develop exciting new cancer therapies.