BIOLOGY AND DIAGNOSIS OF HNPCC

遗传性非息肉病性结直肠癌是一种常染色体显性遗传病。 会增加早发风险的遗传性疾病 结直肠癌。这种综合征最近被认为与四个 鉴定了DNA错配修复(MMR)基因。每一种基因的生殖系突变 这四个MMR基因在少数HNPCC家族中被发现， 但这些基因异常导致癌症的机制并不是 很清楚，关于MMR基因的具体突变是如何发生的，人们知之甚少 与疾病的临床表现相关。 在这个提议中，我们假设MMR基因是功能性肿瘤 作为DNA监测的“传入肢体”的抑制基因 一种不仅识别和修复DNA错配，而且调解 G2逮捕，以回应过度的DNA损伤。我们已经开发了一个模型在 我们可能会检验MMR基因是功能性肿瘤的假设 抑制者。我们已经鉴定出了缺陷的结肠癌细胞系 在错配修复中，确定了有缺陷的基因，并恢复了它们的 通过稳定的转移检测和修复DNA错配的能力 相关基因重新进入细胞。我们建议研究两个MMR HMSH2和hMLH1基因--确定它们在错配中的独立作用 修复，并研究这些基因中每一个识别的能力 特定类型的DNA损伤。与合作者一起，我们拥有 开发了检测人类生殖系突变的改进方法 怀疑患有HNPCC的患者，这将使我们能够确定 肿瘤发生的临床特征及其与遗传基因的关系 所涉及的突变类型。我们还建议确定是否 DNA错配修复基因在体内发挥肿瘤抑制基因的作用 寻找MMR缺乏症是否提供内在的生长优势。 因为识别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 具有MMR缺陷的肿瘤是否固有地对 化疗药物5-氟尿嘧啶。最后，使用概念，即 我们认为，DNA错配修复基因可能具有肿瘤抑制因子的功能 建立HNPCC基因携带者体外筛选试验的策略。 这项申请是一次尝试，将重要的进步应用于我们的 了解DNA错配修复基因与临床的关系 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.