Mouse Models for Li Fraumeni Syndrome

在一些Li-Fraumeni综合征(LFS)患者中遗传的P53突变是一种关键事件 阐述了许多不同来源的肿瘤。大多数P53基因突变都是单核苷酸改变 DNA结合域中的关键氨基酸，而不是删除p53基因的改变。这个 P53错义突变的流行加上体外数据导致了这样的假设：突变型P53 具有其他特性，使其对适当的细胞周期调节更有害，以及更多 有利于细胞分裂。为了在活体内验证这一假设并更准确地模拟人类LFS，我们 已经生成了继承p53R172H突变的小鼠模型(对应于p53R175H热点 人类癌症)。这种突变扰乱了p53的构象，导致了一种在 与ras合作，并很容易使细胞永生。携带p53R172H突变的小鼠获得了 另外的致瘤特性，也表现出显性-阴性表型。转移猖獗于 P53R172H/+小鼠，而不是缺少一个p53等位基因的小鼠。还需要更多的实验来 确定导致肿瘤发生、转移、突变型p53的稳定性和显性阴性的事件 突变的本质。为了检测p53R172H协同Brcal缺失的能力， 另一种导致乳腺癌的常见突变与背景中的BRCA1+/-小鼠交叉 对兽类癌症敏感的人将被执行。这些研究中将解决的一个重要问题是 通过CGH和AFFYMETRY阵列检查，还有哪些分子变化与突变型p53在 不同种类癌症的起源。最后，由于P53错义突变的类型也可能导致 不同的表型，另一种P53错义突变会在小鼠身上产生。P53R245W突变 代表一个DMA接触突变体，它改变了与DNA直接接触的精氨酸氨基酸。 P53R245W在转录上也是不活跃的，但不能使细胞永生化。中国人群中p53R245W基因突变 另一个在LFS患者中遗传的热点突变。两类突变型p53基因的比较 (构象与接触)应该能深入了解这些突变体在肿瘤发生中的作用。我们的 研究表明，对患者的治疗不仅要针对发生的肿瘤进行量身定制， 但肿瘤中发现的特定的P53错义突变也是如此。 这项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 突变和与此缺陷相关的其他变化。这些研究可能会发现新的治疗方法 目标。

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.