INHIBITION OF SPONTANEOUS MUTATION IN MISMATCH MUTATORS

科学和公众对“健康饮食”在预防癌症中的作用的兴趣引发了许多关于饮食抗癌的研究。然而，大多数研究都集中在减少特定致癌物引起的诱变效应上。很少有研究人员试图确定有效地减少自发突变的抗诱变剂可能与整体终生疾病预防更相关，而不是减轻特定的致癌物影响。在遗传性非息肉病性结直肠癌(HNPCC，Lynch综合征II)患者中发现了错配修复缺陷，这种疾病的特征是自发突变率增加和基因组高度不稳定。这项建议旨在研究几种抗癌物质，如番茄类胡萝卜素番茄红素、大豆提取物和绿茶多酚表没食子儿茶素没食子酸酯(EGCG)的能力，以降低错配修复缺陷细胞中观察到的高水平自发突变。该项目使用了一种新的错配修复细胞系和一种人HNPCC结肠癌细胞系来研究这些药物。我们在测量低水平自发突变率方面的专业知识使我们能够调查这样一种假设，即人类细胞功能错配修复丢失所导致的自发突变率增加可能会被某些饮食成分缓解。在目标1和2中，我们将直接测量番茄红素、大豆制品和EGCG在两个细胞系中自发突变率的降低，每个细胞系都存在一个错配修复基因hPMS2或Hmlh1缺陷。目的3将确定相同的抗癌物质是否也可以减少观察到的微卫星不稳定性，这种不稳定性与这些修复缺陷细胞中高水平的自发突变相协调。目的4将评估我们的新型hPMS2突变细胞系是否获得了在软琼脂中生长所证明的致瘤能力，并将协调评估这种表型是否可以通过添加抗癌物质来逆转。这些研究将提供科学证据，证明饮食成分可能对一种重要的突变表型具有保护作用，这种表型是许多癌症的特征。

Scientific and public interest in the role of a "healthy diet" for prevention of cancer has sparked research on numerous dietary anti-carcinogenesis. However most studies have focused on reduction of mutagenic effects elicited by specific carcinogens. Few investigators have attempted to identify anti-mutagens that are effective in reducing spontaneous mutations may be more relevant to overall lifetime disease prevention than mitigating specific carcinogen effects. Defects in mismatch repair have been identified in patients with hereditary non-polyposis colorectal cancer (HNPCC, Lynch Syndrome II), a condition characterized by an increased spontaneous mutation rate and a high degree of genome instability. This proposal aims to study the ability of several anti- carcinogens, the tomato carotenoid lycopene, soybean extracts, and the green tea polyphenol epigallocatechin-3-gallate (EGCG), to reduce the the high levels of spontaneous mutations observed in mismatch repair deficient human cells. The project uses a novel mismatch repair cell line and a human HNPCC colon cancer cell line to study these agents. Our expertise in measuring low levels of spontaneous mutation rates allows us to investigate the hypothesis that increased spontaneous mutation rates conferred by loss of functional mismatch repair in humans cells may be mitigated by certain dietary components. In aims 1 and 2 we will directly measure the reduction of spontaneous mutation rates by lycopene, soybean products, and EGCG in two cell lines, each defective in one mismatch repair gene, hPMS2 or Hmlh1. Aim 3 will determine whether the same anti-carcinogens can also reduce the observed microsatellite instability that is coordinate with high levels of spontaneous mutations in these repair deficient cells. Aim 4 will evaluate whether our novel hPMS2 mutant cell line has acquired tumorigenic capacity as evidenced by growth in soft agar, and will coordinately evaluate whether this phenotype can be reversed by the addition of anti-carcinogens. These studies will provide scientific evidence that dietary components may have protective effects against an important mutator phenotype that is characteristic of many cancers.