Carcinoma cell radiosensitization by MAPK inhibition

这一应用的中心目标是开发一种合理的机制基础，以使用干扰丝裂原活化蛋白激酶(MAPK)信号转导途径的药物来增强电离辐射的抗肿瘤活性。这一策略是基于最近的证据表明，MAPK通路的特定抑制剂与辐射协同作用，启动了凋亡蛋白酶级联反应。我们的基本假设是抑制MAPK，一种与G2/M进程有关的酶，导致辐射介导的细胞死亡的增强。我们推测，这种现象源于或深刻影响细胞周期调节的扰动，耐受线粒体功能障碍的阈值降低，以及辐射诱导的DNA损伤生存能力降低。我们已经在人类癌细胞中展示了通过ErbB 1和TGFpha相互作用调节的自分泌，以MAPK依赖的方式在辐射中存活。照射后24小时，MAPK通路的激活和MAPK激活的钝化使处于G2/M期的细胞比例增加，与细胞凋亡率增加有关。在这项提案中，我们将通过测量癌细胞中的凋亡和细胞周期调节蛋白的表达，来研究MAPK信号通路如何参与细胞周期控制、caspase调节和生存。在目标1和目标2中，我们将验证MAPK抑制通过增强caspase8、9和3的激活来增强辐射诱导的细胞杀伤的假说。在目标3中，我们将检验MAPK活性降低改变辐射/ATM/CDC 2相互作用，改变细胞周期进程导致细胞凋亡增强的假说。我们认为MAPK信号在细胞对DNA损伤的反应中是一个必不可少的生存因素。总之，这些研究将确定抑制MAPK增强细胞凋亡和辐射敏感性的分子机制。

The central goal of this application is to develop a rational mechanistic basis for employing agents that disrupt the mitogen activated protein kinase (MAPK) signal transduction pathway in order to potentiate the anti-tumor activity of ionizing radiation. This strategy is based upon recent evidence indicating that specific inhibitors of the MAPK pathway interact synergistically with radiation to initiate the apoptotic protease cascade. Our underlying hypothesis is that inhibition of MAPK, an enzyme implicated in G2/M progression, leads to a potentiation of radiation-mediated cell death. We postulate that this phenomenon stems from, or is profoundly influenced by, perturbations in cell cycle regulation, a diminished threshold for tolerating mitochondria) dysfunction, and a reduced ability to survive radiation-induced DNA damage. We have shown in human carcinoma cells that are autocrine regulated via an ErbB 1 and TGFalpha interaction, survive irradiation in a MAPK- dependent fashion. Radiation causes activation of the MAPK pathway and blunting of MAPK activation enhanced the proportion of cells found in G2/M phase 24h after irradiation, which was associated with increased apoptosis. In this proposal we will examine how the MAPK signaling pathway is responsible for cell cycle control, caspase regulation and survival, with measurements of apoptosis and cell cycle regulatory protein expression in carcinoma cells. In Aims 1 and 2 we will test the hypothesis that MAPK inhibition enhances radiation-induced cell killing by potentiating the activation of caspases 8, 9 and 3. In Aim 3 we will test the hypothesis that reduced MAPK activity modifies the radiation / ATM / cdc 2 interaction, altering cell cycle progression leading to enhanced apoptosis. We propose that MAPK signaling is an essential survival factor in the response of the cell to DNA damage. Collectively, these studies will determine the molecular mechanisms by which inhibition of MAPK enhances apoptosis and radio-sensitivity.