Carcinoma cell radiosensitization by MAPK inhibition

本申请的中心目标是为采用破坏丝裂原活化蛋白激酶（MAPK）信号转导途径的试剂以增强电离辐射的抗肿瘤活性开发合理的机制基础。这种策略是基于最近的证据表明，特异性的MAPK通路抑制剂与辐射协同作用，启动凋亡蛋白酶级联反应。我们的基本假设是，MAPK，一种参与G2/M进程的酶的抑制，导致辐射介导的细胞死亡的增强。我们推测这种现象源于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损伤的存活能力降低，或者受到这些因素的深刻影响。我们已经在人类癌细胞中显示，通过ErbB 1和TGF α相互作用自分泌调节，以MAPK依赖的方式在辐射中存活。辐射引起MAPK通路的激活和MAPK激活的钝化增加了在辐射后24小时发现的G2/M期细胞的比例，这与增加的凋亡有关。在这个建议中，我们将研究MAPK信号通路是如何负责细胞周期控制，半胱天冬酶的调节和生存，在癌细胞中的细胞凋亡和细胞周期调控蛋白的表达的测量。在目标1和2中，我们将检验MAPK抑制通过增强半胱天冬酶8、9和3的活化来增强辐射诱导的细胞杀伤的假设。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设。我们认为MAPK信号是细胞对DNA损伤反应中的一个重要生存因子。总的来说，这些研究将确定MAPK抑制增强细胞凋亡和放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.