Molecular Genetic Analysis of Colorectal Cancer

描述（由申请人提供）：在过去的五年中，我们在结直肠肿瘤中发现了一些新的基因改变，这些改变是其发病机制的核心。其中最有趣的影响PIK3CA，一种脂质激酶在超过30%的肿瘤中发生突变。突变集中在两个热点，并且在其他几种常见肿瘤类型中以相似的频率和位置发生改变。因此，PIK3CA基因是人类癌症中发现的两个高度突变的致癌基因之一。我们今后的努力将致力于进一步探索它，并将包括四个主要组成部分：我们将使用靶向同源重组来破坏似乎介导结直肠癌细胞中PIK3CA生物学效应的基因。通过比较这些细胞与突变型或野生型PIK3CA被破坏的细胞的特性，我们将定义与PIK3CA突变相关的每种表型中每个基因的作用。2. 我们将使用SAGE和微阵列技术确定与PIK3CA突变相关的转录变化。通过表达分析鉴定的基因本身将受到有针对性的破坏，以测试其在结直肠癌细胞中的生理作用。3. 我们将开发由PIK3CA编码的p110a酶的小分子抑制剂，最好对突变形式特异性，但至少对a亚型特异性。PIK3CA通路基因被破坏的细胞将提供这种化合物特异性的独特测试。4. 我们将确定野生型和突变型PIK3CA基因产物的分子结构，无论是单独的还是与小分子抑制剂的复合。这种结构将用于指导药物发现，并提供对PIK3CA突变影响酶功能的机制的见解。与公共卫生的相关性：这些研究代表了一个综合的研究项目，将阐明导致人类肿瘤的最重要途径之一的关键特征。它很可能对癌症患者的诊断和治疗产生重大影响。

DESCRIPTION (provided by applicant): During the past five years, we have discovered several novel genetic alterations in colorectal tumors that are central to its pathogenesis. The most interesting of these affected PIK3CA, a lipid kinase mutated in more than 30% of the tumors. The mutations were clustered in two hot-spots and were altered at similar frequencies and positions in several other common tumor types. The PIK3CA gene is therefore one of the two most highly mutated oncogenes ever identified in human cancers. Our future efforts will be devoted to its further exploration and will incorporate four major components: 1. We will use targeted homologous recombination to disrupt the genes that appear to mediate the biologic effects of PIK3CA in colorectal cancer cells. By comparison of the properties of these cells to those in which mutant or wild-type forms of PIK3CA have been disrupted, we will define the role of each gene in each phenotype associated with PIK3CA mutation. 2. We will determine the changes in transcription associated with PIK3CA mutation using SAGE and microarray technologies. Genes identified through the expression analyses will themselves be subject to targeted disruption to test their physiologic roles in colorectal cancer cells. 3. We will develop small molecular inhibitors of the p110a enzyme encoded by PIK3CA, preferably specific for the mutant form but at minimum specific for the a isoform. Cells in which PIK3CA pathway genes have been disrupted will provide unique tests of specificity of such compounds. 4. We will determine the molecular structure of wild-type and mutant forms of the PIK3CA gene product, both alone and in complex with small molecule inhibitors. Such structures will be used to guide drug discovery as well as to provide insights into the mechanisms through which PIK3CA mutations affect enzymatic function. Relevance to Public Health: These studies represent an integrated program of research that will illuminate key features of one of the most important pathways contributing to human neoplasia. It is likely to have substantial implications for the diagnosis and treatment of cancer patients.