BIOLOGY AND DIAGNOSIS OF HNPCC

遗传性非息肉病性结直肠癌（HNPCC）是一种常染色体显性遗传， 一种遗传性疾病，会增加早发性疾病的风险 结肠直肠癌最近，这种综合症与四种疾病有关 DNA错配修复（MMR）基因。每一种基因的种系突变 这四个MMR基因已在少数HNPCC家族中发现， 但这些遗传变异导致癌症的机制并不 清楚，很少有人知道MMR基因中的特定突变是如何发生的。 与疾病的临床表现相关。 在这个建议中，我们假设MMR基因在功能上是肿瘤， 抑制基因，作为DNA监测的“传入肢”， 一种不仅能识别和修复DNA错配， G2期阻滞是对过度DNA损伤的反应。我们开发了一个模型， 我们可以验证MMR基因在功能上是肿瘤的假设， 抑制剂我们已经鉴定出结肠癌细胞系， 在错配修复中，确定了有缺陷的基因，并恢复了它们的功能。 检测和修复DNA错配的能力，通过稳定的转移， 将相关基因带回细胞。我们建议审查两个产妇死亡率 基因hMSH 2和hMLH 1-以确定它们在错配中的独立作用 修复，并研究这些基因中的每一个的能力， 特定类型的DNA损伤。与合作者一起，我们有 开发了检测生殖系突变的改进方法， 怀疑患有HNPCC的患者，这将使我们能够描述 基于遗传位点的肿瘤发展的临床特征， 所涉及的突变类型我们亦建议决定 DNA错配修复基因作为肿瘤抑制基因在体内发挥作用， 寻找MMR缺陷是否提供了内在的生长优势。 由于识别DNA损伤和诱导细胞周期停滞的能力是 部分由DNA错配修复基因介导，我们建议确定 MMR缺陷的肿瘤是否对MMR具有内在抗性， 化疗剂5-氟尿嘧啶。最后，利用 DNA错配修复基因的功能可能类似于肿瘤抑制因子， 建立HNPCC基因携带者的体外筛选方法。 这一应用是将我们的重要进展应用于 了解DNA错配修复基因与临床相关 与家族性和散发性结直肠癌有关的问题。

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant inherited disease that confers an increased risk for early onset colorectal cancer. This syndrome has been linked to four recently identified DNA mismatch repair (MMR) genes. Germline mutations in each of the four MMR genes have been found in a small number of HNPCC families, but the mechanism by which these genetic aberrations cause cancers is not clear, and little is known about how specific mutations in the MMR genes correlate with the clinical manifestations of the disease. In this proposal, we hypothesize that the MMR genes are functionally tumor suppressor genes, that serve as the "afferent limb" of a DNA-monitoring system that not only recognizes and repairs DNA mismatches, but mediates G2 arrest in response to excess DNA damage. We have developed a model in which we may test the hypothesis that the MMR genes are functionally tumor suppressors. We have identified colon cancer cell lines that are deficient in mismatch repair, identified the defective gene, and have restored their ability to detect and repair DNA mismatches by the stable transfer of the relevant gene back into the cell. We propose to examine two of the MMR genes hMSH2 and hMLH1 - to determine their independent roles in mismatch repair, and to study the ability of each of these genes to recognize specific types of DNA damage. Together with collaborators, we have developed improved methods for the detection of germline mutations in patients suspected to have HNPCC, which will permit us to characterize the clinical features of tumor development based upon the genetic locus and the type of mutation involved. We also propose to determine whether the DNA mismatch repair genes function as tumor suppressor genes in vivo by looking for whether MMR deficiency provides an intrinsic growth advantage. Since the ability to recognize DNA damage and induct cell cycle arrest is mediated in part by the DNA mismatch repair genes, we propose to determine whether tumors with MMR deficiency are intrinsically resistant to the chemotherapeutic agent 5-fluorouracil. Finally, using the concept that the DNA mismatch repair gene may function like tumor suppressors, we propose a strategy to develop an in vitro screening test for HNPCC gene carriers. This application is an attempt to apply important advances in our understanding of the DNA mismatch repair genes to clinically relevant problems related to familial and sporadic colorectal cancer.