RNASEH2B loss to predict response to PARP inhibitor in prostate cancer

摘要 转移性去势抵抗性前列腺癌（CRPC）是一种无法治愈的疾病，预计将占 在美国每年约有31,000人死亡。转移性CRPC的治疗选择有限 患者可以延长生命。迫切需要开发新的靶向治疗，特别是 基于肿瘤基因组改变的个性化治疗。最近的基因组研究显示， 具有潜在基因组改变的多种可操作的分子靶标。值得注意的是， 参与DNA损伤反应（DDR）的基因是最常见的遗传事件之一， 转移性CRPC。这些改变与前列腺的特殊治疗脆弱性相关 癌细胞（PCa）。具体而言，同源重组（HR）修复中的缺陷将预测对 抑制聚（ADP-核糖）聚合酶（PARP）。PARP抑制剂（PARPi）是一种新型的靶向药物， 这种疗法通过阻止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BRCA 1/2的癌细胞依赖于PARP调节的 DNA修复，对PARPi过敏。美国FDA已经批准了两种PARP抑制剂（奥拉帕尼和 rucaparib）用于治疗具有HR修复突变（或有害BRCA）的转移性CRPC患者 突变）的基础上，从最近的临床试验结果。 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 从PARP抑制中获益。BRCA突变可以预测PARPi反应，准确率为50 - 60%。然而，在这方面， 具有非BCRA基因组改变的患者对PARPi的反应程度仍不清楚。通过 在全基因组CRISPR筛选中，我们最近发现PCa细胞中RNASEH 2B的缺失可能会导致PCa细胞中RNASEH 2B的缺失。 预测对PARP抑制的反应。RNASEH2B是三种RNA酶H2亚基之一，被认为是 在DNA复制中发挥作用。最近的一项研究已经证明了它在核糖核苷酸切除修复中的功能， 这可能导致PARP捕获性病变。重要的是，TCGA数据集的分析揭示了RNASEH2B 17%的PCa肿瘤存在深度缺失。RNASEH 2B和RB 1在染色体13q14上的共缺失频繁发生， 发生。此外，我们的CRISPR筛选结果进一步表明，TP53的缺失可能使PCa 细胞对PARPi的抗性。因此，本项目的目标是确定（1）在多大程度上损失 RNASEH2B在临床前PCa模型中赋予对PARPi的细胞应答;（2）RNASEH2B的失活程度 TP53和RB1影响对PARPi的反应。该项目的成功实施将为 RNASEH 2B/TP 53/RB 1改变的PCa患者未来临床试验的阶段， 符合PARP抑制条件的患者池。

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.