Carcinoma cell radiosensitization by MAPK inhibition

本应用程序的中心目标是建立一个合理的机制基础，利用破坏有丝分裂原活化蛋白激酶（MAPK）信号转导途径的药物，以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途径的特异性抑制剂与辐射协同作用，启动凋亡蛋白酶级联。我们的基本假设是，抑制MAPK（一种参与G2/M进展的酶）导致辐射介导的细胞死亡增强。我们假设，这种现象源于细胞周期调节的扰动，线粒体功能障碍耐受阈值的降低，以及辐射诱导的DNA损伤存活能力的降低，或受到其深刻影响。我们已经证明，通过ErbB 1和TGFalpha相互作用自分泌调节的人类癌细胞，以MAPK依赖的方式在照射下存活。辐射激活MAPK通路，MAPK激活的钝化增加了照射后24h G2/M期细胞的比例，这与凋亡增加有关。在本提案中，我们将研究MAPK信号通路如何负责细胞周期控制、caspase调节和存活，并测量癌细胞的凋亡和细胞周期调节蛋白的表达。在目标1和目标2中，我们将验证MAPK抑制通过增强半胱天蛋白酶8、9和3的激活来增强辐射诱导的细胞杀伤的假设。在Aim 3中，我们将验证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损伤反应的重要生存因子。总的来说，这些研究将确定抑制MAPK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.