Mitochondrial Heat Shock Protein 90 as a Novel Target for Radiation Resistant Prostate Cancer Treatment

放射治疗广泛用于治疗局部前列腺肿瘤。然而，癌细胞经常通过未知的机制产生对辐射的抵抗力，并构成棘手的挑战。放射抗性是高度不可预测的，导致许多患者的治疗效果较差，并经常导致癌症复发。为了改善放射治疗，迫切需要揭示导致细胞产生耐药性的分子事件。在我们对抗辐射前列腺癌 (RR-PCa) 的深入研究中，我们发现与放射敏感的 PCa 相比，线粒体热休克蛋白 90 (mtHsp90) 水平和线粒体代谢异常高。 mtHsp90 是一种伴侣蛋白，可维持许多不同蛋白质的稳定性，包括肿瘤生存和代谢所必需的蛋白质。我们进一步证明，降低 mtHsp90 蛋白水平可显着恢复 RR-PCa 细胞对辐射的敏感性。因此，我们的首要假设是 mtHsp90 定义了前列腺癌细胞对辐射的抵抗力，这是本提案中将接受严格测试的前提。已知活性氧 (ROS) 通过干扰 mtHsp90 的转录和翻译后水平来降低 mtHsp90 的水平。我们筛选了 768 种 FDA 批准的药物，寻找一种可以提高 ROS 水平但对正常细胞无毒性的有效药物。我们发现阿奇霉素（AZM）是一种大环内酯类抗生素，是选择性增加线粒体 ROS 并降低 mtHsp90 蛋白水平的最有效药物。我们进一步证明，AZM 通过放射治疗可增强癌细胞的死亡。受到稳健结果的鼓舞，我们的目标是推进我们在该项目中的发现，检验我们的假设，并开发辅助治疗范例，最终将增强放射治疗作为一种更有效的治疗方法。目标是：目标 1，确定 mtHsp90 在 RR-PCa 细胞存活和适应性代谢中的功能重要性；目标 2，确定 ROS 如何下调 mtHsp90 蛋白水平并使 RR-PCa 敏感的机制；目标 3，在临床前模型中验证 AZM 生成的 ROS 是否下调 mtHsp90 并增强放射治疗。结果将在 mtHsp90 和 RR-PCa 之间建立新的联系。这项研究使用最先进的代谢组学、成像技术和模型系统，并且有可能转化为临床实践，因为 AZM 已经拥有良好的安全记录。在精准医学时代，我们对我们密切关注的研究的前景充满信心，这将突破界限并使放射治疗成为更好的治疗方法，我们的方法将为许多首选放射治疗的癌症治疗树立先例。

Radiation therapy is widely used to treat localized prostate tumors. However, cancer cells often develop resistance to radiation through unknown mechanisms and pose an intractable challenge. Radiation resistance is highly unpredictable, rendering the treatment less effective in many patients and frequently resulting in cancer recurrence. There is a dire need to uncover the molecular events that cause cells to become resistant in order to improve radiation therapy. In our in-depth investigations of radiation-resistant prostate cancer (RR-PCa), we found that mitochondrial heat shock protein 90 (mtHsp90) level and mitochondrial metabolism were aberrantly high when compared to radiosensitive PCa. mtHsp90 is a chaperone that maintains the stability of many diverse proteins, including those that are necessary for tumor survival and metabolism. We further demonstrated that decreasing mtHsp90 protein level significantly restored the sensitivity of RR-PCa cells to radiation. Hence, our overarching hypothesis is that mtHsp90 defines resistance of prostate cancer cells to radiation, a premise that will be put under stringent testing in this proposal. Reactive oxygen species (ROS) are known to reduce the level of mtHsp90 by interfering with its transcriptional and post-translational levels. We screened 768 FDA-approved drugs in search of a potent drug that could raise the level of ROS, but not be toxic to normal cells. We found Azithromycin (AZM), a macrolide antibiotic, to be the most effective drug that selectively increases mitochondrial ROS and reduces mtHsp90 protein level. We further demonstrated that AZM enhances the death of cancer cells with radiation treatment. Encouraged by robust results, we aim to advance our findings in this project, test our hypotheses, and develop a paradigm for adjuvant treatment that will ultimately enhance radiation therapy as a more effective procedure. The goals are: Aim 1, to determine the functional importance of mtHsp90 in RR-PCa cell survival and adaptive metabolisms, Aim 2, to determine mechanistically how ROS down-regulates mtHsp90 protein level and sensitizes RR-PCa, and Aim 3, to validate in preclinical models if AZM-generated ROS down-regulates mtHsp90 and enhances radiation treatment. The results will establish a novel link between mtHsp90 and RR-PCa. This study using state-of-the art metabolomics, imaging techniques, and model systems and has the potential to be translated into a clinical practice because AZM already has a good safety record. In the era of precision medicine, we are confident of the prospects of our closely-focused studies, which will push boundaries and make radiation therapy a better procedure, and our approach will set a precedent for many cancer treatments where radiation therapy is preferred.