Glutathione reductase and tumor sensitivity to radiation

描述(申请人提供)：癌症对辐射的抵抗通常是放射治疗失败的原因；细胞内谷胱甘肽(GSH)被认为是造成抵抗的主要原因之一。GSH通过终止辐射产生的自由基和活性氧物种(ROS)来破坏癌细胞，从而提高癌症对辐射的抵抗力。通过降低细胞内GSH水平来增加癌症对辐射的敏感性已经做出了广泛的努力。最广泛研究的降低细胞内GSH的方法是使用GSH合成的抑制剂丁硫氨酸亚磺胺(BSO)。BSO已被证明能有效降低GSH水平，增加癌症对辐射的敏感性。在这项应用中，我们建议通过抑制谷胱甘肽还原酶(GR)来增加癌症对辐射的敏感性。这一提出的假说，即抑制GR可能提供了一种替代的、可能更有效的方式来增强癌症对辐射的反应，这是基于这样一个事实：在终止自由基或ROS的过程中，GSH被氧化为其氧化形式GSSG。GR是负责将GSSG还原为GSH的酶。抑制GR将阻碍细胞将GSSG转换回GSH以维持细胞内GSH水平的能力。因此，抑制GR不仅会降低细胞内GSH水平，还会导致GSSG的积聚。因此，抑制GR可能比抑制GSH合成对肿瘤放射敏感性的影响更大。本实验室用对化疗和放射耐药的人卵巢癌细胞株OVCAR-3细胞进行的初步实验表明，抑制GR确实降低了细胞内GSH，GSH的减少导致OVCAR-3对化疗药物马法兰的敏感性增加。在这一应用中，我们计划扩大工作，以确定抑制GR是否也可以增加OVCAR-3对辐射的敏感性。此外，我们还计划研究GR抑制对细胞氧化还原状态和负责终止自由基和ROS的酶系统的影响，因为这些酶系统将影响癌症对辐射的敏感性。这项研究将提供有关GR抑制对癌症辐射敏感性的影响、细胞氧化还原状态(通过硫醇/二硫键的比率)以及参与终止自由基和ROS的酶系统的信息。长期目标是开发一种新的方法来提高癌症对辐射的敏感性。

DESCRIPTION (provided by applicant): Cancer resistance to radiation is often the cause of failure in radiotherapy; intracellular glutathione (GSH) has been implicated as one of the major causes of the resistance. GSH increases cancer resistance to radiation by terminating free radicals and reactive oxygen species (ROS) that are generated by radiation to destroy cancer cells. Extensive efforts have been made to increase cancer sensitivity to radiation through decreasing intracellular GSH. The most extensively investigated approach in reducing intracellular GSH has been the use of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. BSO has been demonstrated to effectively reduce GSH levels and increase cancer sensitivity to radiation. In this application, we propose to increase cancer sensitivity to radiation through inhibition of glutathione reductase (GR). This proposed hypothesis, that is inhibition of GR may provide an alternative and possibly more effective way to increase cancer response to radiation, is based on the fact that in terminating free radicals or ROS, GSH is oxidized to its oxidized form GSSG. GR is the enzyme responsible for the reduction of GSSG to GSH. Inhibition of GR will hamper the cell's ability to convert GSSG back to GSH to maintain intracellular GSH levels. As a result, inhibition of GR will not only reduce intracellular GSH levels but also cause accumulation of GSSG. Therefore, inhibition of GR may have more impact on cancer sensitivity to radiation than inhibition of GSH synthesis.Preliminary experiments conducted in this laboratory with OVCAR-3 ceils, a human ovarian cancer cell line with resistance to chemotherapy and radiotherapy, have shown that inhibition of GR did reduce intracellular GSH and the reduction of GSH led to an increase in the sensitivity of OVCAR-3 to melphalan, a chemotherapeutic agent. In this application, we are planning to extend the work to determine if inhibition of GR can also increase the sensitivity of OVCAR-3 to radiation. In addition, we are also planning to investigate the effect of GR inhibition on the cellular redox state and the enzyme systems responsible for terminating free radicals and ROS, since these enzyme systems will affect cancer sensitivity to radiation. This investigation will provide information on the effect of GR inhibition on cancer sensitivity to radiation, cellular redox state (via the ratio of thiol/disulfide), and enzyme systems involved in terminating radicals and ROS. The long-term objective is to develop a novel approach to increase cancer sensitivity to radiation.