Targeting RNA Polymerase I Transcription Machinery in Chemoresistant Ovarian Cancer

项目总结 事实上，每一种夺走患者生命的癌症都是由于先天或后天的化疗耐药性。这 尤其在上皮性卵巢癌(EOC)中，大多数肿瘤最初对铂类药物敏感 化疗，但大多数会复发并死于耐药疾病。为了实现持久的治疗，我们必须 了解化疗耐药的分子机制。通过对多个模型的深入分析， 接受治疗的患者化疗前后(卡铂/紫杉醇)匹配的卵巢癌，患者- 来源的异种移植(PDX)和耐药细胞系，我们已经发现并验证了化疗耐药肿瘤 显著上调核糖体生物发生途径。我们进一步检查了两种药物的疗效 RNA聚合酶I的抑制物(POL I)，rRNA产生的主要调节因子。这些药物是CX-5461和 BMH-21对卵巢癌细胞株和PDX模型具有显著(但经常可变)的活性 所有的组织学，在许多情况下，在耐药模型中甚至更有效。CX-5461目前处于 I期试验，但我们是第一个证明和探索化疗耐药细胞的特殊敏感性的人 靶向核糖体生物发生，以及为什么这一过程可能是发展化疗耐药性的关键。几个 问题仍然没有得到回答，包括靶向Pol I是否可以杀死化疗后残留的显微镜 人口实现持久治愈；核糖体机制上调如何增强化疗耐药性；什么 转录组被化疗激活；无论是紫杉醇、卡铂还是 以及假设的TP53在这些药物的疗效中的关键作用是否能够 使Pol I目标更加有效的战略。这项建议的总体目标是 了解核糖体生物生成上调如何使癌细胞在化疗中存活，确定 将Pol I作为治疗目标的最有效环境，并确定联合使用的最佳药物 与Pol I达成治疗协同效应。为达致这些目标，我们会更详细地调查 化疗诱导化疗敏感和耐药细胞核糖体合成的差异 使用多个模型的人群，并确定这些差异如何调节POL I抑制剂的敏感性。 化疗耐药的PDX模型将用于确定Pol I靶向是否可以防止复发或增强 卡波/紫杉醇疗效。我们将研究化疗敏感细胞和耐药细胞之间的差异。 在染色质结构、rRNA DNA转录位点的占据和核糖体组织的水平上。我们 将利用7000个可药物靶标的CRISPR基因文库来确定联合使用的候选药物 如果能更好地了解核糖体生物发生在化疗耐药细胞中的作用，它可能 打开一种治疗多种癌症的全新方法的大门，专注于 癌症-进化为一种化疗耐药表型，目前尚无治愈方法。

PROJECT SUMMARY Virtually every cancer that takes the life of a patient is due to innate or acquired chemoresistance. This is especially true in epithelial ovarian cancer (EOC), in which most tumors are initially sensitive to platinum-based chemotherapy, but most will recur and succumb to chemoresistant disease. To achieve durable cures we must understand the molecular mechanisms of chemoresistance. Through in-depth analysis of multiple models of matched pre- and post-chemotherapy (carboplatin/paclitaxel) ovarian cancers from treated patients, patient- derived xenografts (PDX), and resistant cell lines, we have discovered and validated that chemoresistant tumors have significant upregulation of the ribosomal biogenesis pathway. We have further examined efficacy of two inhibitors of RNA Polymerase I (Pol I), the primary regulator of rRNA production. These agents, CX-5461 and BMH-21, have significant (but frequently variable) activity against ovarian cancer cell lines and PDX models of all histologies, and in many cases is even more effective in chemoresistant models. CX-5461 is currently in a phase I trial, but we are the first to demonstrate and explore the particular susceptibility of chemoresistant cells to targeting ribosomal biogenesis, and why this process might be key to developing chemoresistance. Several questions remain unanswered, including whether targeting Pol I can kill the post-chemo microscopic remaining population to achieve durable cures; how upregulation of ribosomal machinery enhances chemoresistance; what transcriptome is activated by chemotherapy; whether the effects are specific to paclitaxel, carboplatin, or the combination; and whether the hypothesized critical role of TP53 in the efficacy of these agents can allow strategies to allow targeting Pol I to be even more effective. The overall objectives of this proposal are to understand how upregulation of ribosome biogenesis allows cancer cells to survive chemotherapy, identify the most effective setting in which to target Pol I as a therapy, and identify the best agents to use in combination with Pol I for therapeutic synergy. To achieve these objectives, we will investigate in greater detail the chemotherapy-induced differences in ribosome synthesis between the chemosensitive and chemoresistant cell populations using multiple models, and identify how these differences are mediating Pol I inhibitor sensitivity. Chemoresistant PDX models will be used to determine if Pol I targeting can prevent recurrence, or enhance carbo/paclitaxel efficacy. We will investigate the differences between chemosensitive and chemoresistant cells at the level of chromatin structure, occupancy of rRNA DNA transcription sites, and ribosomal organization. We will utilize a 7,000-gene CRISPR library of druggable targets to identify candidate drugs to use in combination with targeting Pol I. If the role of ribosomal biogenesis in chemoresistant cells can be better understood, it could open the door to an entirely new approach to treating many cancers, and focus on the most deadly aspect of cancer – evolution to a chemoresistant phenotype for which there is no cure.