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对许多饮食抗癌作用的研究。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。很少有研究者试图确定有效减少自发突变的抗诱变剂可能比减轻特定致癌物的影响更能预防终生疾病。在遗传性非息肉病性结直肠癌（HNPCC，Lynch综合征II）患者中已发现错配修复缺陷，这种疾病的特征是自发突变率增加和基因组高度不稳定。该提议旨在研究几种抗癌物质，番茄类胡萝卜素番茄红素、大豆提取物和绿色茶多酚表没食子儿茶素-3-没食子酸酯（EGCG），降低在错配修复缺陷的人类细胞中观察到的高水平自发突变的能力。该项目使用一种新的错配修复细胞系和人类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研究这样一种假设，即人类细胞中功能性错配修复丧失所导致的自发突变率增加可能会被某些饮食成分所缓解。在目标1和2中，我们将直接测量两种细胞系中番茄红素、大豆制品和EGCG对自发突变率的降低，每种细胞系都有一个错配修复基因hPMS 2或Hmlh 1缺陷。目标3将确定是否相同的抗癌物质也可以减少观察到的微卫星不稳定性，这是协调与高水平的自发突变，在这些修复缺陷细胞。目的4将评估我们的新的hPMS 2突变细胞系是否具有通过在软琼脂中生长证明的致瘤能力，并将协同评估这种表型是否可以通过添加抗癌剂逆转。这些研究将提供科学证据，证明饮食成分可能对许多癌症特有的重要突变表型具有保护作用。

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.