Mouse Models for Li Fraumeni Syndrome

在某些患有Li-Fraumeni综合征（LFS）的个体中遗传的p53突变是在LFS中的关键事件。 许多不同来源的肿瘤。大多数p53突变是单核苷酸改变， DNA结合域中的关键氨基酸，而不是缺失p53基因的改变。的 p53错义突变的普遍性加上体外数据导致了突变型p53 具有额外的特性，使其对适当的细胞周期调节更有害， 有利于细胞分裂。为了在体内验证这一假设并更准确地模拟人类LFS，我们 已经产生了遗传p53 R172 H突变（对应于p53 R175 H热点）的小鼠模型 在人类癌症中）。这种突变破坏了p53的构象，导致蛋白质的致瘤性。 与ras合作，并容易使细胞永生化。携带p53 R172 H突变的小鼠 另外的致瘤特性并且还表现出显性阴性表型。肿瘤转移在 p53 R172 H/+小鼠与缺乏一个p53等位基因的小鼠相反。需要更多的实验来 确定导致肿瘤发生、转移、突变型p53的稳定性和显性负性的事件。 突变的性质。为了检测p53 R172 H与Brcal缺失协同作用的能力， 另一种导致乳腺癌的常见变异，与背景中的Brca 1 +/-小鼠杂交， 对癌症敏感的动物将被执行。在这些研究中要解决的一个重要问题是 通过CGH和Affymetric阵列检测，还有哪些其他分子变化与突变型p53协同作用， 不同种类癌症的起源。最后，由于p53错义突变的类型也可能有助于 不同的表型，另一个p53错义突变将在小鼠中产生。p53 R245 W突变 代表改变参与与DNA直接接触的精氨酸氨基酸的DMA接触突变体。 p53 R245 W也是转录失活的，但不能使细胞永生化。p53 R245 W突变在 LFS患者中遗传的另一个热点突变。两类p53突变体的比较 （构象与接触）应产生洞察这些突变体在肿瘤发生中的作用。我们 研究表明，对患者的治疗不仅要针对所发展的肿瘤类型， 而且还与肿瘤中鉴定的特异性p53错义突变有关。 本申请中概述的研究与公共卫生直接相关，因为它建议研究一种 p53基因在不同类型的癌症中经常发生改变。这项研究旨在了解p53的性质， 突变和其他变化，配合这一缺陷。这些研究可能会发现新的治疗方法 目标的

Mutation of p53, inherited in some individuals with Li-Fraumeni syndrome (LFS), is a critical event in the elaboration of many tumors of diverse origin. Most mutations of p53 are single nucleotide changes that alter critical amino acids in the DNA-binding domain rather than alterations that delete the p53 gene. The prevalence of p53 missense mutations coupled with in vitro data has led to the hypothesis that mutant p53 has additional properties that make it more detrimental for proper cell cycle regulation and more advantageous to the dividing cell. To test this hypothesis in vivo and model human LFS more accurately, we have generated mouse models inheriting the p53R172H mutation (corresponding to the p53R175H hotspot in human cancers). This mutation disrupts the conformation of p53 resulting in a protein that is tumorigenic in cooperation with ras, and readily immortalizes cells. Mice with the p53R172H mutation have gained additional tumorigenic properties and also exhibit a dominant-negative phenotype. Metastasis is rampant in p53R172H/+ mice as opposed to mice lacking one p53 allele. Additional experiments are needed to ascertain the events leading to tumorigenesis, metastasis, stability of the mutant p53, and the dominantnegative nature of the mutation. To examine the ability of p53R172H to cooperate with Brcal deletion, another common alteration that leads to breast cancer, crosses with Brca1+/- mice in a background sensitive to beast cancer will be performed. An important question that will be addressed in these studies is what other molecular changes, examined by CGH and Affymetric arrays, cooperate with mutant p53 in the genesis of different kinds of cancers. Lastly, since the type of p53 missense mutation may also contribute to different phenotypes, another p53 missense mutation will be generated in mice. The p53R245W mutation represents a DMA contact mutant that alters an arginine amino acid involved in direct contact to DNA. p53R245W is also transcriptionally inactive, but cannot immortalize cells. The p53R245W mutation in another hot spot mutation inherited in LFS patients. Comparison of the two classes of p53 mutants (conformation versus contact) should yield insights into the role of these mutants in tumorigenesis. Our studies suggest that treatment of a patient will have to be tailored not only to the kind of tumor that develops, but to the specific p53 missense mutation identified in the tumor as well. The research outlined in this application is directly relevant to public health in that it proposes to study a gene, p53, that is often altered in different kinds of cancers. The study aims to understand the nature of p53 mutations and of other changes that cooperate with this defect. These studies may identify novel therapeutic targets.