Mutant p53 Gain of Function in Tumorigenesis

突变体 p53 在肿瘤发生中获得功能

• 批准号: 6843087
• 负责人: GERARD PAUL ZAMBETTI
• 金额: $ 31.73万
• 依托单位: ST. JUDE CHILDREN'S RESEARCH HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-04-01 至 2008-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6843087
• 关键词: Mutant; p53; Gain; Function; Tumorigenesis

EXCEED THE SPACE PROVIDED. Mutation of p53 occurs in more than 50% of all tumors, including those of colon, breast and lung. Tumors expressing elevated levels of mutant p53 may be associated with a worse prognosis than p53-null cancers. The long.term goal of this research program continues to focus on the mechanisms by which mutant p53 contributes to tumorigenesis. Mutant p53 enhances the tumorigenic potential of p53-negative cell lines and this activity has long been considered to be linked to its ability to selectively transactivate the human multi-drug resistance (MDR1) promoter. We previously established that mutant p53 regulates endogenous MDR1 and c-myc gene expression and that this activity requires an intact C-terminus. In the previous funding period we identified key lysines in this domain, which normally become acetylated in wild-type p53 during cell stress, that are required for mutant p53-transactivation. Most importantly but paradoxically, we demonstrated that this region is dispensable for mutant p53 to promote tumorigenicity. These results uncouple transactivation from tumorigenicity and represent a paradigm shift in considering models for mutant p53 gain of function. Rather, our data support a mechanism by which mutant p53 binds and stabilizes the Mdm2 proto- oncogene protein, which could lead to aneuploidy, hyperplasia and ultimately tumor cell growth. Consistent with this reasoning, we generated a triple knockout mouse model that lacks p19 ARF,Mdm2 and p53. Mouse embryo fibroblasts (MEFs) derived from these mice are not tumorigenic, but remarkably, double knockout MEFs lacking both p53 and ARF readily form tumors in nude mice. These results suggest that Mdm2 may be required for tumor cell growth. The experiments proposed in this study are designed to test this hypothesis using cell and animal based approaches by addressing the following specific questions: 1) Does Mdm2 cooperate with mutant p53 in tumorigenicity?; 2) What is the in vivo contribution of Mdm2 to mutant p53 gain of function?; and 3) Do post-translational modifications influence mutant p53 gain of function? Our findings demonstrate significant differences in the structural requirements for wild-type and mutant p53 function, which may provide an exploitable basis for developing therapeutic approaches to treating cancer. PERFORMANCE SITE ========================================Section End===========================================

超出所提供的空间。 p53 突变发生在超过 50% 的肿瘤中，包括结肠癌、乳腺癌和肺癌。表达突变 p53 水平升高的肿瘤可能比 p53 缺失癌症的预后更差。该研究计划的长期目标继续关注突变型 p53 促进肿瘤发生的机制。突变的 p53 增强了 p53 阴性细胞系的致瘤潜力，并且这种活性长期以来被认为与其选择性反式激活人类多药耐药性 (MDR1) 启动子的能力有关。我们之前确定突变型 p53 调节内源性 MDR1 和 c-myc 基因表达，并且这种活性需要完整的 C 末端。在之前的资助期间，我们确定了该结构域中的关键赖氨酸，这些赖氨酸通常在细胞应激期间在野生型 p53 中被乙酰化，这是突变型 p53 反式激活所必需的。最重要但矛盾的是，我们证明该区域对于突变 p53 促进致瘤性是可有可无的。这些结果将反式激活与致瘤性分开，代表了考虑突变型 p53 功能获得模型的范式转变。相反，我们的数据支持突变型 p53 结合并稳定 Mdm2 原癌基因蛋白的机制，这可能导致非整倍性、增生并最终导致肿瘤细胞生长。与此推理一致，我们生成了缺乏 p19 ARF、Mdm2 和 p53 的三重敲除小鼠模型。来自这些小鼠的小鼠胚胎成纤维细胞 (MEF) 不具有致瘤性，但值得注意的是，同时缺乏 p53 和 ARF 的双敲除 MEF 很容易在裸鼠中形成肿瘤。这些结果表明 Mdm2 可能是肿瘤细胞生长所必需的。本研究中提出的实验旨在使用基于细胞和动物的方法通过解决以下具体问题来检验这一假设：1）Mdm2 在致瘤性方面是否与突变体 p53 合作？ 2) Mdm2 对突变 p53 功能获得的体内贡献是什么？ 3) 翻译后修饰是否会影响突变型 p53 的功能获得？我们的研究结果表明野生型和突变型 p53 功能的结构要求存在显着差异，这可能为开发癌症治疗方法提供可利用的基础。表演网站==========================================部分结束====== =======================================