Prevention of genomic instability by a scavenger of bifunctional electrophiles

 描述(由申请人提供)：从癌前病变进展到临床显著的癌症包括获得体细胞基因组异常，这些异常共同推动具有高度恶性表型的癌症的发展。由环氧合酶-2(COX-2)衍生的反应性二羰基、脂氧合酶和脂质过氧化已知形成DNA和组蛋白的共价加合物。有人建议解决这样的假设，即DNA和组蛋白的这些修饰导致了体细胞基因组异常，这种异常是癌症的特征。这两种COX亚型的直接产物是环状内过氧化前列腺素H2(PGH2)，它是产生前列腺素和血栓素A2的合成酶的底物。PGH2还经历非催化重排形成左旋糖素，即高活性的γ-酮醛。在癌细胞系中，我们已经证明了COX-2衍生的左旋糖素形成DNA和组蛋白的共价加合物。我们的团队研究了一系列左旋糖素的清除剂，它们与这些1，4-二羰基的反应速度比赖氨酸快3个数量级，从而抑制了DNA碱基和组蛋白上细胞胺的左旋糖素加合物的形成。我们已经确定了一种5-乙基水杨胺，它有效地阻止了左旋糖苷赖氨酸的加合物，不抑制COX-2，并作用于细胞核。重要的是，我们发现5-乙基水杨胺是反应性二羰基的一般清除剂，包括丙二醛和4-氧-壬烯醛，这两种物质也形成DNA的共价加合物。为了评估这些反应性二羰基是内源性致癌物的假设，我们将确定5-乙基水杨胺对发生在肺表达Kras突变的小鼠身上的体细胞基因组异常的发展的影响，该突变产生肺癌，肺癌逐渐发展为具有广泛拷贝数变化的基因组不稳定。拷贝数变异将通过小鼠多样性基因分型阵列来确定。还将评估5-乙基水杨胺对肿瘤大小和组织学的影响，以及对肿瘤中DNA和组蛋白的左旋糖苷和丙二醛加合物水平的影响。综上所述，由COX-2、脂质过氧化和脂氧合酶产生的以左旋腺苷、丙二醛和4-氧基-壬烯醛为代表的一些反应性二羰基可以形成DNA和组蛋白的共价加合物，这表明它们可能是内源性致癌物质。据推测，5-乙基水杨胺，这些二羰基的清除剂，将防止在小鼠肺癌模型中发生的基因组不稳定。

 DESCRIPTION (provided by applicant): Progression from pre-malignant lesions to clinically significant cancers involves acquisition of somatic genomic abnormalities that in concert drive the development of cancers with a highly malignant phenotype. Reactive dicarbonyls derived from cyclooxygenase-2 (COX-2), the lipoxygenases and lipid peroxidation are known to form covalent adducts of DNA and histones. It is proposed to address the hypothesis that these modifications of DNA and histones contribute to the somatic genomic abnormalities that characterize cancers. The immediate product of both COX isoforms is the cyclic endoperoxide, prostaglandin H2 (PGH2), the substrate for the synthases that produce the prostaglandins and thromboxane A2. PGH2 also undergoes non-catalytic rearrangement to form the levuglandins, highly reactive γ-ketoaldehydes. In cancer cell lines, we have demonstrated that COX-2 derived levuglandins form covalent adducts of DNA and histones. Our group has investigated a series of scavengers of levuglandins that react with these 1,4-dicarbonyls at a rate 3 orders of magnitude faster than does lysine, thereby inhibiting the formation of the levuglandin adducts of cellular amines on DNA bases and on histones. We have identified one, 5-ethylsalicylamine that is potent in preventing levuglandin adducts of lysine, does not inhibit COX-2 and acts in the cellular nucleus. Importantly, we discovered that 5-ethylsalicylamine is a general scavenger of reactive dicarbonyls, including malondialdehyde and 4-oxo-nonenal, both of which also form covalent adducts of DNA. To evaluate the hypothesis that these reactive dicarbonyls are endogenous carcinogens, we will determine the effects of 5- ethylsalicylamine on the development of the somatic genomic abnormalities that occur in a mouse with lung expression of a Kras mutation that produces lung cancers which progressively develop genomic instability with extensive copy number variations. Copy number variations will be determined with the Mouse Diversity Genotyping Array. The effect of 5-ethylsalicylamine on tumor size and histology also will be evaluated as well as its effect on the levels of levuglandin and malondialdehyde adducts of DNA and histones in the tumors. In summary, a number of reactive dicarbonyls, exemplified by the levuglandins, malondialdehyde and 4-oxo- nonenal, are produced by COX-2, lipid peroxidation and the lipoxygenases and can form covalent adducts of DNA and histone, suggesting that they could be endogenous carcinogens. It is hypothesized that 5- ethylsalicylamine, a scavenger of these dicarbonyls, will prevent the genomic instability that occurs in a mouse model of lung cancer.