The Microsatellite Instability Phenotype

描述（由申请人提供）：微卫星不稳定性（MSI）是一种 组织（通常是肿瘤）中基因组不稳定性的重要量度。它有 与癌症易感性和进展有关，并归因于 遗传性非息肉病性结肠癌中的错配修复（MMR）基因缺陷 （HNPCC）。MSI通常通过跨微卫星进行PCR来确定 基因座和观察片段（或等位基因），具有不同数量的 比祖先等位基因重复--即，突变等位基因为了成为 通过标准基因组PCR检测，任何一个突变片段必须存在于 大量的频率（大于30%）-一个显着的突变体 任何体细胞遗传标准的频率。 我们的假设是，基因中存在各种各样的扰动， 与修复和DNA代谢有关，而不是导致 MMR基因的功能完全丧失。这些事件可能会导致大量的 MSI频率水平（小于0.3 -大于0.05），不可观察 通过标准的PCR，但它易患癌症。因此，我们主张， 这种MSI表型的存在具有相当大的临床意义， 用现在的方法无法检测到 一种灵敏、有效的检测和定量MSI的方法 表型下降到约0.05突变频率的水平， 微卫星位点的开发--小池1 PCR与多重PCR相结合 GENESCAN分析。在这里，我们将SP/PCR应用于两个类（MSI高与 MSI-低或稳定）的HNPCC肿瘤和组成性组织以及 有限的一组“散发性”结直肠患者材料， 结果与年龄、等位基因大小和性别匹配的对照组进行比较。我们期望 相对于MMR，确定和分层肿瘤材料中的MSI表型 基因型;确定组成型组织中是否存在MSI表型， 将有助于在症状前鉴定组织和个体， 发展癌症的风险;并确定MSI的变化范围 表型在一般人群中相对于祖先等位基因的大小， 性别和年龄。

DESCRIPTION (provided by applicant): Microsatellite instability (MSI) is an important measure of genome instability in tissues (usually tumors). It has been related to cancer susceptibility and progression and is attributed to defects in mismatch repair (MMR) genes in hereditary non-polyposis colon cancer (HNPCC). MSI is generally determined by conducting PCR across a microsatellite locus and observing fragments (or alleles) that have different numbers of repeats than the progenitor alleles -- i.e., mutant alleles. In order to be detected by standard genomic PCR, any one mutant fragment must be present at substantial frequency (greater than 30 percent) -- a remarkable mutant frequency by any somatic cell genetic standard. It is our hypothesis that there are of a wide variety of perturbations in genes associated with repair and DNA metabolism, other than those resulting in complete loss of function of MMR genes. Such events could result in substantial levels of MSI frequencies (less than 0.3 - greater than 0.05), not observable by standard PCR, but which predispose to cancer. Therefore, we contend, the presence of such an MSI phenotype has considerable clinical significance but goes undetected by present methodology. A sensitive and efficient method for detecting and quantifying the MSI phenotype down to levels of approximately 0.05 mutant frequency at specific microsatellite loci has been developed -- small poo1 PCR coupled with multiplex GENESCAN analysis. Here we will apply SP/PCR to the two classes (MSI-high vs. MSI-low or stable) of HNPCC tumors and constitutive tissues as well as a limited set of "sporadic" colorectal patient materials and compare those results to age, allele size, and gender matched controls. We expect to determine and stratify the MSI phenotype in tumor material relative to MMR genotype; determine if there is an MSI phenotype in constitutive tissues that would be useful in presymptomatic identification of tissues and individuals at risk for developing cancer; and determine the range of variation of the MSI phenotype in the general population relative to size of progenitor allele, gender, and age.