RADIATION INDUCED G2 BLOCK AND ITS RELATIONSHIP TO RADIOSENSITIVITY

辐射诱导的 G2 块及其与辐射敏感性的关系

• 批准号: 6616898
• 负责人: RUTH J MUSCHEL
• 金额: $ 14.07万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-22 至 2003-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6616898
• 关键词: DNA damage; HeLa cells; animal tissue; antisense nucleic acid; cell cycle; cell cycle proteins; cell growth regulation; cellular oncology; cellular pathology; cyclins; enzyme activity; gene expression; genetic manipulation; immunoprecipitation; neoplasm /cancer chemotherapy; neoplasm /cancer radiation therapy; neoplastic process; phosphoprotein phosphatase; phosphorylation; protein kinase; protein structure function; radiation resistance; radiation sensitivity; tissue /cell culture; western blottings

After exposure to irradiation or to other agents that induce DNA damage, mammalian cells delay in cell cycle progression through G2. There is suggestive evidence that the delay at the G2 checkpoint may effect the outcome of cellular survival in response to DNA damage. Since many of the drugs used for cancer chemotherapy, as well as radiation, damage DNA and lead to a G2 delay, understanding the G2 delay may have significant implications for cancer chemotherapy. In this proposal we will explore the mechanisms leading to the G2 delay and evaluate whether the length of the G2 delay affects survival in tumor cells. We have found that the levels of cyclin B1 are greatly reduced in many cell types after exposure to DNA damaging agents. Since cyclin B1 is required for the transition through G2 into mitosis, it seemed plausible that the decrease in cyclin B1 levels induced by radiation might contribute to the G2 delay. We have confirmed this hypothesis by experimentally manipulating the expression of cyclin B1. Decreased expression of cyclin B1 leads to a prolonged G2 delay. Conversely, increased B1 expression after irradiation greatly shortened the G2 delay after irradiation, but did not eliminate it. Enhanced expression of cyclin B1 had no effect on the cell cycle of un-irradiated cells. These data demonstrated that the levels of cyclin B1 regulate the G2 delay after irradiation and suggest that cyclin B1 independent mechanisms may also exist. In this application we propose to extend these observations along three main avenues. First to determine if the levels of cyclin B1 control of G2 delay after other forms of DNA damage in a variety of cellular systems and to determine whether the same multi-factorial mechanisms are also at work; second to determine whether phosphorylation of p34/cdc2 influences the G2 delay and third to determine whether manipulation of the G2 delay can affect sensitivity to chemotherapeutic agents or to radiation can be influence by manipulation of the G2 checkpoint.

暴露于辐射或其他引起 DNA 损伤的物质后， 哺乳动物细胞通过 G2 延迟细胞周期进程。有 有暗示性证据表明 G2 检查点的延误可能会影响 DNA损伤后细胞存活的结果。由于许多 用于癌症化疗和放疗的药物，会损伤 DNA 和 导致 G2 延迟，了解 G2 延迟可能有重大意义 对癌症化疗的影响。在本提案中，我们将探讨 导致 G2 延迟的机制并评估 G2 延迟的长度是否 G2 延迟会影响肿瘤细胞的存活。 我们发现许多细胞中细胞周期蛋白B1的水平大大降低 暴露于 DNA 损伤剂后的细胞类型。由于细胞周期蛋白 B1 从 G2 过渡到有丝分裂所需的，这似乎是合理的 辐射引起的细胞周期蛋白 B1 水平下降可能 导致 G2 延迟。我们通过以下方式证实了这一假设 通过实验操纵细胞周期蛋白 B1 的表达。减少 细胞周期蛋白 B1 的表达导致 G2 延迟延长。反过来， 照射后B1表达增加，大大缩短了G2延迟 照射后，但并没有消除。细胞周期蛋白表达增强 B1对未照射细胞的细胞周期没有影响。这些数据 证明细胞周期蛋白 B1 的水平调节 G2 延迟 辐射并表明细胞周期蛋白 B1 独立机制也可能 存在。 在此应用中，我们建议将这些观察扩展到三个方面 主要途径。首先确定cyclin B1的水平是否控制G2 各种细胞系统中其他形式的 DNA 损伤后的延迟 确定相同的多因素机制是否也在发挥作用； 其次确定 p34/cdc2 的磷酸化是否影响 G2 延迟，第三个确定是否可以操纵 G2 延迟 影响对化疗药物或放射线的敏感性 操纵 G2 检查点的影响。