Biology and Diagnosis of HNPCC

描述（由申请人提供）：遗传性非息肉病性结直肠癌（HNPCC或Lynch综合征）是一种遗传性结直肠癌（CRC），由DNA错配修复（MMR）基因的生殖系突变引起。这导致CRC具有称为微卫星不稳定性（MSI）的表型，并且由此产生的肿瘤具有几个独特的临床特征。HNPCC患者患CRC和其他器官癌症的风险非常高，通常在非典型的年轻年龄发生癌症，并有患多种原发性恶性肿瘤的风险。HNPCC目前面临的挑战包括我们无法在所有患有该疾病的家庭中找到生殖系突变，对该疾病在细胞水平上的演变的不完全理解，以及不确定缺陷DNA错配修复机制如何导致肿瘤形成。本申请提出开发新的方法，其将扩展我们诊断DNA MMR基因hMSH 2中的大基因组缺失的能力，所述大基因组缺失是由DNA重组事件介导的。提出研究以确定在已经发展癌症的靶结肠直肠组织中发生“第二次打击”的机制。提出了一个新的模型来研究如何不适当的“放松”的DNA MMR发生在氧化应激反应，通过测量MMR蛋白的合成和降解速率。已经设计了对DNA MMR活性下调的研究以提供对负责神秘的MS 1-低表型的机制的深入了解，其不同于HNPCC，但可以解释在慢性发炎的粘膜中发生的具有MSI形式的癌症。最后，一个计划概述了选择性地抑制主要的DNA MMR基因hMSH 2和hMLH 1使用siRNA技术，以确定对突变率，细胞生长，突变损伤的耐受性和细胞周期的改变的影响。这是一项全面的研究计划，其长期目标是了解肿瘤如何在HNPCC中发展，并将这些见解转化为改善CRC风险患者的预防策略。

DESCRIPTION (provided by applicant): Hereditary Non-Polyposis Colorectal Cancer (HNPCC or Lynch syndrome) is an inherited form of colorectal cancer (CRC) caused by germ line mutations in DNA mismatch repair (MMR) genes. This leads to CRCs with a phenotype called microsatellite instability (MSI), and the resulting tumors have several unique clinical characteristics. Patients with HNPCC are at very high risk for CRC and cancers of other organs, often develop cancers at uncharacteristically young ages, and are at risk for multiple primary malignancies. Current challenges in HNPCC include our inability to find a germ line mutation in all families with the disease an incomplete understanding of the evolution of the disease at the cellular level, and uncertainty about how defective DNA mismatch repair mechanistically leads to tumor formation. This application proposes to develop novel methods that will extend our ability to diagnose large genomic deletions in the DNA MMR gene hMSH2, which are mediated by Alu-recombination events. Studies are proposed to determine the mechanism(s) by which the "second hit" occurs in target colorectal tissues that have developed cancer. A new model is proposed to study how inappropriate "relaxation" of DNA MMR occurs in response to oxidative stress, by measuring rates of synthesis and degradation of MMR proteins. Studies on the down regulation of DNA MMR activity have been designed to provide insight into the mechanism responsible for the enigmatic MSl-low phenotype, which is distinct from HNPCC, but may account for cancers with a form of MSI that occur in chronically inflamed mucosa. Finally, a plan is outlined to selectively inhibit the major DNA MMR genes hMSH2 and hMLH1 using siRNA technology, to determine the effects on mutation rates, cell growth, tolerance of mutational damage, and alterations in the cell cycle. This is a comprehensive research plan developed with a long-term aim of understanding how tumors develop in HNPCC, towards an overall goal of translating these insights into improved preventive strategies for patients at risk for CRC.