Project 1 - PARP Project

项目摘要--项目1 高级别浆液性卵巢癌(HGSOC)是最常见和最致命的亚型，主要是一种疾病 基因组的不稳定性。肿瘤抑制基因TP53在95%以上的病例中失活；Fanconi ANEM- IA/同源重组(FA/HR)通路有30-40%发生突变失活，导致进一步的基因突变。 体型不稳定性。DNA修复蛋白多聚(ADP-核糖)聚合酶(PARP)的抑制剂已显示出PROM-... Ising在HR缺乏的临床前模型中的活性，导致了开发PARP抑制剂的广泛努力 HGSOC和其他HR缺陷癌症。尽管II期临床试验表明，PARP抑制剂有利于 Duce I)在BRCA1或BRCA2(BRCA1/2)突变携带者中，铂类药物的客观应答率为30%-45%。 敏感的复发性卵巢癌和II)显著延长患者的无进展生存期。 BRCA1或BRCA2突变的HGSOC对含铂治疗的反应后的ANCE设置，FDA 强调了更好地识别最有可能对PARP抑制剂产生反应的卵巢癌的必要性。 在上一个供资期间取得的成果的基础上，本研究旨在 更好地理解为什么一些HR缺陷型卵巢癌对PARP抑制剂有反应，而另一些则会 不。我们的初步结果表明，PARP抑制剂在HR缺陷卵巢癌中的细胞毒作用 反映了非同源末端连接(NHEJ)的激活，这是一种容易出错的修复途径，而不是中断 其他人最初假设的单链断裂修复。重要的是，抑制NHEJ相关的 激酶DNA-PK或下调任何一种NHEJ蛋白同时抑制这种容易出错的 修复和减少PARP抑制剂的细胞毒性作用。对PARP抑制剂作用的新认识 提出这样一种假设，即只有当HR有缺陷时，卵巢癌才会对PARP抑制剂产生反应 NHEJ途径保持完好。与这一假设一致，我们对BRCA2突变体的进一步研究 临床前卵巢癌模型显示，对PARP抑制剂耐药的选择导致 NHEJ蛋白的下调或BRCA2下游的HR蛋白RAD51的过度表达 通过BRCA1/2突变以外的其他方式禁用NHEJ或恢复HR会导致PARP抑制 抵抗。为了建立在这些发现的基础上，我们现在建议：i)确定RAD51过度表达是如何起作用的 为了提高PARP抑制剂的抗性，II)确定了HR缺陷的PARP抑制剂抗性的变化 体内患者来源的卵巢癌异种移植瘤和III)开发多参数分类器，包括 RAD51和NHEJ蛋白表达检测、修复基因测序及基因组检测 瘢痕形成：在一项大型多中心II期临床试验中预测PARP抑制剂鲁卡帕利的疗效 患有复发的卵巢癌。影响：总的来说，这些研究将提供对 并同时测试修复路径的多方面评估的概念- 方法完整性将确定卵巢癌患者最有可能受益于这一有前途的新药类别。

PROJECT SUMMARY – Project 1 High grade serous ovarian cancer (HGSOC), the most common and most lethal subtype, is largely a disease of genomic instability. The tumor suppressor TP53 is inactivated in over 95% of cases; and the Fanconi anem- ia/homologous recombination (FA/HR) pathway is mutationally inactivated in 30-40%, leading to further gen- omic instability. Inhibitors of the DNA repair protein poly(ADP-ribose) polymerase (PARP) have exhibited prom- ising activity in HR-deficient preclinical models, leading to extensive efforts to develop PARP inhibitors for HGSOC and other HR-deficient cancers. Although phase II clinical trials have shown that PARP inhibitors pro- duce i) objective response rates of 30-45% in BRCA1 or BRCA2 (BRCA1/2) mutation carriers with platinum- sensitive relapsed ovarian cancer and ii) substantial prolongation of progression-free survival in the mainten- ance setting after response of BRCA1- or BRCA2-mutant HGSOCs to platinum-containing therapy, the FDA has highlighted the need to better identify ovarian cancers that are most likely to respond to PARP inhibitors. Building on results generated during the previous funding period, the present studies are designed to better understand why some HR-deficient ovarian cancers respond to PARP inhibitors and others do not. Our preliminary results show that the cytotoxic effects of PARP inhibitors in HR-deficient ovarian cancer reflect activation of nonhomologous end-joining (NHEJ), an error-prone repair pathway, rather than interruption of single-strand break repair as originally postulated by others. Importantly, inhibition of the NHEJ-associated kinase DNA-PK or downregulation of any of a number of NHEJ proteins simultaneously inhibits this error-prone repair and diminishes the cytotoxic effects of PARP inhibitors. This new understanding of PARP inhibitor action suggests the hypothesis that ovarian cancers will respond to PARP inhibitors only if HR is defective and the NHEJ pathway remains intact. Consistent with this hypothesis, our further studies in a BRCA2-mutant preclinical ovarian cancer model have revealed that selection for PARP inhibitor resistance results in either downregulation of NHEJ proteins or overexpression of Rad51, an HR protein downstream of BRCA2, sug- gesting that disabling NHEJ or restoring HR by means other than BRCA1/2 mutations confers PARP inhibitor resistance. To build on these findings we now propose to: i) determine how Rad51 overexpression contributes to PARP inhibitor resistance, ii) identify the changes that confer PARP inhibitor resistance in HR-deficient patient-derived ovarian cancer xenografts in vivo and iii) develop a multi-parameter classifier that includes assays of Rad51 and NHEJ protein expression, sequencing of repair genes and measurements of genomic scarring, to predict responses to the PARP inhibitor rucaparib in a large multicenter phase II trial in patients with relapsed ovarian cancer. Impact: Collectively, these studies will provide new insight into mechanisms of PARP inhibitor resistance and simultaneously test the concept that a multifaceted assessment of repair path- way integrity will identify ovarian cancer patients most likely to benefit from this promising new class of drugs.