Role of p53 Missense Mutations on Tumorigenesis in Vivo

描述(申请人提供)：在大多数人类癌症的发生过程中，P53基因本身或P53途径的其他重要组成部分发生了改变。在DNA损伤信号或癌基因不适当激活时，p53水平升高，导致细胞周期停滞或诱导细胞凋亡，从而阻止不适当的DNA复制和细胞分裂。大多数研究集中于了解P53诱导细胞周期停滞的机制，而忽略了P53诱导细胞周期停滞的能力。在之前的资助期间，我们培育了一只小鼠，它包含p53氨基酸172位的Arg-to-Pro突变，这是这些途径的区别。P53(515c)等位基因纯合的细胞不能诱导细胞凋亡，但保留了部分细胞周期停滞途径。淋巴瘤和肉瘤在P53(515c)纯合子小鼠中发展，潜伏期比P53缺失小鼠要晚得多，这表明细胞周期停滞在肿瘤抑制中的重要性。重要的是，在P53(515c)/(515c)小鼠中发展的肿瘤仍然是二倍体，这表明该突变的P53的活性维持了基因组的稳定性。这些小鼠和这些小鼠细胞的产生将使我们能够破译基因组稳定性的机制，以及这一途径在具有其他分子缺陷的肿瘤发生中的重要性。具体来说，我们将：1)确定在肿瘤发生中与p53(515c)/(515c)协同作用的分子变化；2)检测p53(515c)/-小鼠肿瘤的存活率和基因组稳定性；3)确定细胞周期抑制物和p53靶点p21在维持基因组稳定中的重要性并确定p53的其他重要靶点；4)确定p53(515c)/(515c)突变体抑制c-myc诱导的肿瘤的能力；以及5)确定p53(515c)/(515c)在延缓不同肿瘤易感品系小鼠乳腺癌中的重要性。这一独特的模型将进一步加深我们对P53在细胞周期停滞和维持基因组稳定中的作用的理解。

DESCRIPTION (provided by applicant): The p53 gene itself or other important components of the p53 pathway are altered in the genesis of most human cancers. In response to DNA damage signals or inappropriate oncogene activation, p53 levels increase and result in arrest of the cell cycle or induction of apoptosis, p53 surveillance thus prevents inappropriate DNA replication and cell division. Most studies have focused on understanding the mechanisms of apoptosis by p53 while the ability of p53 to induce the cell cycle arrest program has largely been ignored. During the previous funding period, we generated a mouse containing an arg-to-pro mutation at p53 amino acid 172, which distinguishes these pathways. Cells homozygous for the p53(515c) allele are unable to induce apoptosis, yet retain a partial cell cycle arrest pathway. Lymphomas and sarcomas develop in p53(515c) homozygous mice with much later latency than p53-null mice suggesting the importance of cell cycle arrest in tumor suppression. Importantly, tumors that develop in p53(515c)/(515c) mice remain diploid suggesting that the activities of this mutant p53 maintain genomic stability. The generation of these mice and cells from these mice will allow us to decipher the mechanism of genomic stability and the importance of this pathway in the genesis of tumors with other molecular defects. Specifically we will: 1) determine the molecular changes that cooperate with p53(515c)/(515c) in tumorigenesis; 2) examine survival and genomic stability in tumors from p53(515c)/- mice; 3) determine the importance of the cell cycle inhibitor and p53 target p21 in maintaining genomic stability and identify other targets of p53 important in arresting the cell cycle; 4) determine the ability of p53(515c)/(515c) mutant to inhibit c-myc induced tumors; and 5) determine the importance of p53(515c)/(515c) in delaying breast carcinomas in a different tumor prone strain of mice. This unique model will further our understanding of the role of p53 in cell cycle arrest and in maintaining genome stability.