RNASEH2B loss to predict response to PARP inhibitor in prostate cancer

摘要 转移性去势抵抗前列腺癌(CRPC)是一种不治之症，预计将占 在美国每年约有3.1万人死亡。转移性CRPC的治疗选择有限 延长生命的病人。迫切需要开发新的靶向疗法，特别是 基于肿瘤基因组改变的个性化治疗。最近的基因组研究揭示了 具有潜在基因组改变的各种可操作的分子靶点。值得注意的是，基因的改变 参与DNA损伤反应(DDR)是最常见的遗传事件之一，并在 转移性CRPC。这些变化与前列腺癌的特殊治疗脆弱性有关。 癌症(PCA)细胞。具体地说，同源重组(HR)修复中的缺陷将预测对 抑制多(ADP-核糖)聚合酶(PARP)。PARP抑制剂(PARPI)是一种新型的靶向药物 治疗，通过阻止PARP酶修复肿瘤细胞中受损的DNA来发挥作用。BRCA1/2 编码HR修复所必需的蛋白质。缺乏BRCA1/2的癌细胞依赖于PARP调节 DNA修复，对PARPI超敏。美国FDA批准了两种PARP抑制剂(奥拉帕利和 Rucaparib)治疗HR修复突变(或恶性BRCA)的转移性CRPC患者 突变)基于最近临床试验的结果。 使用PARPI进行有效治疗的主要障碍之一是如何选择最有可能 受益于PARP抑制。BRCA突变预测PARPI反应的准确率为50-60%。然而， 非BCRA基因组改变的患者对PARPI的反应程度尚不清楚。穿过 在全基因组CRISPR筛查中，我们最近发现在PCa细胞中RNASEH2 B的丢失可能 预测对PARP抑制的反应。RNASEH2B是被认为是三个RNaseH2亚基之一 在DNA复制中发挥作用。最近的一项研究证明了它在核苷酸切除修复中的作用， 这可能有助于PARP捕获性损伤。重要的是，对TCGA数据集的分析揭示了RNASEH2 B 17%的前列腺癌组织中存在深度缺失。染色体13q14上RNASE_2B和RB1的共同缺失频率 发生。此外，我们CRISPR筛查的结果进一步表明，TP53的丢失可能会导致前列腺癌 细胞对PARPI的抗性。因此，本项目的目标是确定(1)损失到什么程度 在临床前PCa模型中，RNASEH2B对PARPI有细胞反应；(2)在多大程度上失活 TP53和RB1影响对PARPI的反应。这一项目的成功实施将为 RNASEH2B/TP53/RB1改变的PCa患者的未来临床试验阶段，并显著扩大 PARP抑制的合格患者池。

ABSTRACT Metastatic castration-resistant prostate cancer (CRPC) is an incurable disease that is expected to account for ~ 31,000 deaths each year in the United States. There are limited therapeutic options for metastatic CRPC patients that extend life. There is an urgent need for developing novel targeted therapies, especially personalized therapies based on genomic alterations in tumors. Recent genomic studies have revealed a variety of actionable molecular targets with underlying genomic alterations. Notably, alterations in genes involved in DNA damage response (DDR) are among the most common genetic events and enriched in metastatic CRPC. These alterations have been correlated with particular therapeutic vulnerabilities in prostate cancer (PCa) cells. Specifically, defects in homologous recombination (HR) repair would predict sensitivity to inhibition of Poly (ADP-ribose) polymerase (PARP). PARP inhibitors (PARPi) are a new type of targeted therapy, which works by preventing the enzyme PARP from repairing damaged DNA in tumor cells. BRCA1/2 encode proteins essential for HR repair. Cancer cells lacking BRCA1/2 depend instead on PARP-regulated DNA repair and are hypersensitive to PARPi. The U.S. FDA has approved two PARP inhibitors (olaparib and rucaparib) for treatment of metastatic CRPC patients with HR repair mutations (or deleterious BRCA mutations) based on the results from recent clinical trials. One of the major barriers to effective treatment using PARPi is how to select patients who most likely benefit from PARP inhibition. BRCA mutations can predict PARPi response with 50-60% accuracy. However, the degree to which patients with non-BCRA genomic alterations respond to PARPi remains unclear. Through a genome-wide CRISPR screen, we have recently discovered that loss of RNASEH2B in PCa cells may predict response to PARP inhibition. RNASEH2B is one of the three RNase H2 subunits that are thought to play a role in DNA replication. A recent study has demonstrated its function in ribonucleotide excision repair, which may contribute to PARP-trapping lesions. Importantly, analysis of TCGA datasets revealed RNASEH2B deep deletions in 17% of PCa tumors. Co-deletion of RNASEH2B and RB1 on chromosome13q14 frequently occurs. In addition, the results from our CRISPR screening further suggest that loss of TP53 may render PCa cells resistance to PARPi. Therefore, the goal of this project is to determine (1) to what extent loss of RNASEH2B confers a cellular response to PARPi in preclinical PCa models; (2) to what extent inactivation of TP53 and RB1 influences the response to PARPi. The successful implementation of this project will set the stage for future clinical trials in PCa patients with RNASEH2B/TP53/RB1 alterations and significantly expand the pool of eligible patients for PARP inhibition.