Mechanisms of PARP Inhibitor Resistance in Ovarian Cancer

卵巢癌 PARP 抑制剂耐药机制

• 批准号: 9020939
• 负责人: SCOTT H KAUFMANN
• 金额: $ 40.39万
• 依托单位: MAYO CLINIC ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-02-23 至 2020-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9020939
• 关键词: Affect; Antineoplastic Agents; BRCA1 gene; BRCA2 Mutation; BRCA2 gene; Biopsy; Cancer Model; Cancer Patient; Cell Line; Cells; Cessation of life; Cicatrix; Cisplatin; Clinical; Complement; DNA Damage; DNA Double Strand Break; DNA Repair; DNA Repair Gene; DNA Repair Pathway; DNA Single Strand Break; DNA-PKcs; Defect; Diagnosis; Disabled Persons; Disease-Free Survival; Double Strand Break Repair; Down-Regulation; Epigenetic Process; Epithelial ovarian cancer; Fanconi' s Anemia; Future; G22P1 gene; Gene Dosage; Genes; Genomic Instability; Genomics; Half-Life; Health; In Vitro; Ku Protein; LIG4 gene; Maintenance; Maintenance Therapy; Malignant Neoplasms; Malignant neoplasm of ovary; Malignant neoplasm of pancreas; Malignant neoplasm of prostate; Messenger RNA; MicroRNAs; Mutation; New Agents; Newly Diagnosed; Nuclear Export; Oncogenes; Pathway interactions; Patients; Phase II Clinical Trials; Placebo Control; Platinum; Poly(ADP-ribose) Polymerases; Pre-Clinical Model; Protein Tyrosine Kinase; Proteins; Publishing; Randomized; Relapse; Reporting; Resistance; Sampling; Serous; Single Strand Break Repair; Somatic Mutation; Time; Translations; Up-Regulation; Work; XRCC4 gene; artemis; base; cancer cell; cancer subtypes; cancer type; candidate identification; chemotherapy; cytotoxic; design; exome; genome-wide; homologous recombination; in vivo; inhibitor/antagonist; insertion/deletion mutation; insight; interest; mRNA Expression; malignant breast neoplasm; member; mutant; mutation carrier; novel; novel therapeutics; objective response rate; overexpression; p53-binding protein 1; phase 2 study; phase III trial; pre-clinical; predictive marker; protein expression; repaired; research study; resistance mechanism; response; small hairpin RNA; targeted treatment; tumor

DESCRIPTION (provided by applicant): The Fanconi anemia/homologous recombination (FA/HR) pathway is frequently silenced by mutations or epigenetic processes in several types of cancer, including high-grade serous ovarian cancer (HGSOC), basal breast cancer, and a subset of pancreatic and prostate cancers. As a result, high fidelity repair of DNA double- strand breaks is disabled, leading to genomic instability in these cancers. Inhibitors of the DNA repair protein poly(ADP-ribose) polymerase (PARP) have shown promising activity in HR-deficient preclinical models and response rates of 30-45% in BRCA1 or BRCA2 (BRCA1/2) mutation carriers with platinum-sensitive relapsed HGSOC. This project is designed to better understand why some BRCA1/2-mutant cancers respond to PARP inhibitors and others do not. Previous results from members of our investigative team have not only identified BRCA1/2 reversion mutations as a potential cause of platinum resistance in preclinical models and clinical samples, but also demonstrated that the cytotoxic effects of PARP inhibitors reflect activation of nonhomologous end-joining (NHEJ), an error-prone DNA double-strand break repair pathway, rather than inhibition of DNA single-strand break repair as originally thought. Importantly, inhibition or downregulation of any of a number of NHEJ proteins inhibits this error-prone repair and diminishes the cytotoxic effects of PARP inhibitors. This new understanding of PARP inhibitor action leads to the hypothesis that resistance of BRCA1/2-mutant cancers to PARP inhibitors can result from either reversion mutations or changes in DNA repair pathway proteins that abrogate the action of the PARP inhibitors. Consistent with this hypothesis, our further studies in a BRCA2-mutant preclinical ovarian cancer model have demonstrated that selection for PARP inhibitor resistance results in either downregulation of NHEJ proteins or overexpression of Rad51, an HR protein downstream of BRCA2. To build on these findings we now propose to: i) further assess the impact of NHEJ protein downregulation on PARP inhibitor sensitivity in vitro and in vivo, ii) examine how Rad51 is upregulated to induce PARP inhibitor resistance; iii) perform a whole-exome shRNA screen looking for additional mechanisms of PARP inhibitor resistance in BRCA1/2-mutant ovarian cancer lines in vitro; and iv) examine two unique sets of cancer biopsies from patients receiving single-agent PARP inhibitor therapy to evaluate the potential importance of these resistance mechanisms in the clinical setting. Collectively, these studies will provide new insight into mechanisms of PARP inhibitor resistance that will enable future selection of ovarian cancer patients most likely to benefit from these promising new drugs.

描述(申请人提供)：Fanconi贫血/同源重组(FA/HR)途径经常被几种类型的癌症的突变或表观遗传过程所沉默，包括高级别浆液性卵巢癌(HGSOC)、基底乳腺癌以及胰腺癌和前列腺癌的亚组。结果，DNA双链断裂的高保真修复被禁用，导致这些癌症的基因组不稳定。DNA修复蛋白多聚(ADP-核糖)聚合酶(PARP)的抑制剂在HR缺乏的临床前模型中显示出良好的活性，在对铂敏感的复发HGSOC的BRCA1或BRCA2(BRCA1/2)突变携带者中的应答率为30-45%。该项目旨在更好地理解为什么一些BRCA1/2突变的癌症对PARP抑制剂有反应，而另一些则不能。我们研究团队成员之前的结果不仅确定BRCA1/2逆转突变是临床前模型和临床样本中铂耐药的潜在原因，而且还证明PARP抑制剂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DNA双链断裂修复途径，而不是像最初认为的那样抑制DNA单链断裂修复。重要的是，抑制或下调任何一种NHEJ蛋白都会抑制这种容易出错的修复，并减弱PARP抑制剂的细胞毒作用。这种对PARP抑制剂作用的新理解导致了一种假设，即BRCA1/2突变的癌症对PARP抑制剂的耐药性可能是由于逆转突变或DNA修复途径蛋白的变化而导致的，这些变化取消了PARP抑制剂的作用。与这一假设一致，我们在BRCA2突变的临床前卵巢癌模型中的进一步研究表明，选择PARP抑制剂耐药性会导致NHEJ蛋白下调或RAD51过度表达，RAD51是BRCA2下游的HR蛋白。为了进一步了解这些发现，我们现在建议：i)进一步评估NHEJ蛋白下调在体内外对PARP抑制剂敏感性的影响；ii)检测RAD51上调如何诱导PARP抑制剂耐药性；iii)进行全外显子shRNA筛选，以寻找BRCA1/2突变卵巢癌细胞株中PARP抑制剂耐药性的其他机制；以及iv)检测两组独特的癌症活检标本，以评估这些耐药机制在临床上的潜在重要性。总而言之，这些研究将为PARP抑制剂耐药机制提供新的见解，使未来能够选择最有可能从这些有希望的新药中受益的卵巢癌患者。