HYPOXIA, P53 AND GENETIC INSTABILITY

缺氧、P53 和遗传不稳定

• 批准号: 6300484
• 负责人: Amato J. Giaccia
• 金额: $ 21.86万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-14 至 2001-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6300484
• 关键词: angiogenesis; apoptosis; fluorescent in situ hybridization; gene mutation; genetic library; head /neck neoplasm; hypoxia; neoplasm /cancer genetics; neoplastic growth; nucleic acid probes; nucleic acid sequence; oxygen tension; polymerase chain reaction; thrombospondins; tissue /cell culture; tumor suppressor genes

Cancer is a dynamic disease that results from an imbalance between the deregulated expression of positive growth regulators (oncogenes) and the growth inhibitory effects of negative growth regulators (tumor suppressor genes). The inactivation of negative growth regulators such as p53 and Rb has been found in many tumor types, and in general occurs late in the neoplastic process. Functionally, p53 acts as a negative growth regulator by activating either a G1/S-phase cell-cycle checkpoint or by activating an apoptotic cell death pathway in response to DNA damaging agents or growth limiting conditions. Although it is well established p53's role in activation of a cell-cycle checkpoint in response to DNA damage is through transcriptional activation of downstream effector genes such as p21 and GADD 45, it does not seem that p53's role as a transcription factor is needed for activation of cell death by the same agents. Recent studies by several labs have demonstrated that the introduction of dominant oncogenes such as E1A and ras into embryonic stem cells that still possess functional wild-type p53 will poise them for apoptotic cell death when subsequently exposed to DNA damaging agents or growth restrictive stresses. If these cells possess mutated p53 or are devoid of wild-type p53 activity, they exhibit a significant reduction in their ability to undergo apoptosis when exposed to the same stresses. The predisposition of oncogenically transformed cells that possess wild-type p53 to apoptotic cell death coupled with the knowledge that many p53 mutations occur at the later stages of tumor formation suggests that cells possessing wild-type p53 are somehow selected against during tumor growth. We hypothesize that hypoxia or low oxygen conditions act as a tumor specific stress to select against oncogenically transformed cells that possess wild-type p53. Hypoxia, like ionizing radiation, causes the activation of wild-type p53 protein and induces growth arrest in established cell lines. However, exposure of minimally transformed cells to low oxygen conditions in the presence of serum and glucose induces apoptotic cell death that depends on the presence of wild-type p53. The goals of this study are to investigate the genetics of p53 mediated growth arrest and apoptosis induced by low oxygen conditions. We will examine the p53 dependence of hypoxia induced growth arrest and apoptosis in p53 genetically matched mouse, rat and human cells that are minimally transformed by the introduction of dominant oncogenes. By mixing different ratios of wild-type and mutant p53 cells, we will first attempt to demonstrate in cell culture and then in multicellular spheroids that hypoxia selects against the growth of oncogenically transformed cells that possess wild-type p53, and permits the survival and/or growth of mutant p53 cells. Finally, we will correlate the oxygen status of human head and neck tumors with their p53 genotype to investigate whether there is a correlation between these two parameters in human tumors. We feel that these experiments will provide mechanistic insight into how the tumor microenvironment can play a role in selecting for the clonal expansion of a tumor cell that has lost its ability to modulate cell proliferation.

癌症是一种动态的疾病，它是由癌症患者体内 阳性生长调节因子（癌基因）的表达失调， 负性生长调节因子（肿瘤抑制因子）的生长抑制作用 基因）。 负性生长调节因子如p53和Rb的失活 在许多肿瘤类型中发现，一般发生在晚期， 肿瘤过程 在功能上，p53充当负生长调节剂 通过激活G1/S期细胞周期检查点或通过激活 响应于DNA损伤剂的凋亡细胞死亡途径，或 生长限制条件。 尽管p53在细胞凋亡中的作用已经得到了很好的证实， 响应DNA损伤的细胞周期检查点的激活是通过 下游效应基因如p21和 GADD 45，似乎p53作为转录因子的作用并不重要。 所需的激活细胞死亡由相同的代理。 最近的研究 几个实验室已经证明， 如E1 A和Ras等基因转化为胚胎干细胞， 功能性野生型p53将使它们平衡，使细胞凋亡， 随后暴露于DNA损伤剂或生长限制剂 压力 如果这些细胞具有突变的p53或缺乏野生型p53， p53活性，他们表现出显着降低的能力， 当暴露于相同的压力时经历凋亡。 的倾向 具有野生型p53的致癌转化细胞的凋亡 细胞死亡，加上许多p53突变发生在细胞的知识， 肿瘤形成的后期阶段表明，具有野生型 p53在肿瘤生长期间以某种方式被选择。 我们假设 缺氧或低氧条件作为肿瘤特异性应激来选择 针对具有野生型p53的致癌转化细胞。 缺氧，像电离辐射，导致野生型p53的激活 蛋白质并在建立的细胞系中诱导生长停滞。 然而，在这方面， 将最低限度转化的细胞暴露于低氧条件下， 血清和葡萄糖的存在诱导依赖于 野生型p53的存在。 本研究的目的是调查 p53基因介导的低浓度阿霉素诱导的细胞生长停滞和凋亡的遗传学研究 氧气条件。 我们将研究缺氧诱导的p53依赖性。 在p53基因匹配的小鼠、大鼠和 人类细胞，通过引入占主导地位的 致癌基因 通过混合不同比例的野生型和突变型p53细胞， 我们将首先尝试在细胞培养中证明，然后在 缺氧选择了多细胞球体， 具有野生型p53的致癌转化细胞，并允许 突变型p53细胞的存活和/或生长。 最后我们将 人头颈部肿瘤的氧状态与其p53相关 基因型以调查这两者之间是否存在相关性 人类肿瘤的参数。 我们认为这些实验将提供 对肿瘤微环境如何发挥作用的机制性见解， 选择已经丧失其免疫原性的肿瘤细胞的克隆扩增， 调节细胞增殖的能力。