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

放射治疗被广泛用于治疗局限性前列腺肿瘤。然而，癌细胞往往通过未知的机制产生对辐射的抗性，这是一个棘手的挑战。放射抵抗是高度不可预测的，这使得治疗在许多患者中效果较差，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。在我们对放射抵抗性前列腺癌（RR-PCa）的深入研究中，我们发现与放射敏感性前列腺癌相比，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，维持多种蛋白质的稳定性，包括那些肿瘤生存和代谢所必需的蛋白质。我们进一步证明，降低mtHsp90蛋白水平可显著恢复RR-PCa细胞对辐射的敏感性。因此，我们的首要假设是mtHsp90决定了前列腺癌细胞对辐射的抵抗力，这一前提将在本提案中进行严格的测试。已知活性氧（ROS）通过干扰mtHsp90的转录和翻译后水平来降低其水平。我们筛选了768种fda批准的药物，以寻找一种可以提高ROS水平，但对正常细胞无毒的有效药物。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和降低mtHsp90蛋白水平的最有效药物。我们进一步证明AZM可以促进放射治疗癌细胞的死亡。在强有力的结果的鼓舞下，我们的目标是在这个项目中推进我们的发现，检验我们的假设，并开发一种辅助治疗的范例，最终将使放射治疗成为更有效的治疗方法。目标是：目的1，确定mtHsp90在RR-PCa细胞存活和适应性代谢中的功能重要性；目的2，确定ROS下调mtHsp90蛋白水平和致敏RR-PCa的机制；目的3，在临床前模型中验证azm产生的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。这项研究使用了最先进的代谢组学、成像技术和模型系统，并有可能转化为临床实践，因为AZM已经有了良好的安全记录。在精准医疗时代，我们对我们密切关注的研究前景充满信心，这将突破界限，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开创先例。

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.