Molecular Genetic Analysis of Colorectal Cancer

在过去的五年中，我们在结直肠肿瘤中发现了几种新的遗传改变， 是其发病机制的核心。其中最有趣的是影响PIK3CA，一种脂质激酶突变， 超过30%的肿瘤这些突变聚集在两个热点中，并且在相似的温度下发生改变。 其他几种常见肿瘤类型的频率和位置。因此，PIK3CA基因是其中一个。 两种在人类癌症中发现的最高度突变的癌基因。我们今后的工作将致力于 它将包括四个主要组成部分： 1.我们将使用靶向同源重组来破坏似乎是介导细胞凋亡的基因。 PIK3CA在结直肠癌细胞中的生物学作用。通过比较这些细胞的特性 其中突变型或野生型形式的PIK3CA已被破坏，我们将定义每个基因的作用， 每种表型与PIK3CA突变相关。 2.我们将使用SAGE确定与PIK3CA突变相关的转录变化， 微阵列技术。通过表达分析鉴定的基因本身将受到 靶向破坏以测试它们在结肠直肠癌细胞中的生理作用。 3.我们将开发由PIK3CA编码的p110 a酶的小分子抑制剂，优选 特异于突变体形式，但至少特异于α同种型。其中PIK3CA途径基因 将提供此类化合物特异性的独特测试。 4.我们将确定PIK3CA基因产物的野生型和突变形式的分子结构， 无论是单独使用还是与小分子抑制剂复合使用。这种结构将用于指导药物 发现以及提供深入了解PIK3CA突变影响的机制 酶的功能 与公共卫生的相关性：这些研究代表了一个综合的研究计划， 导致人类肿瘤形成的最重要途径之一的关键特征。很可能已经 这对癌症患者的诊断和治疗具有重大意义。

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.