Base Excision Repair Deficiency as a Risk Modifier in BRCA2 Associated Cancer

碱基切除修复缺陷作为 BRCA2 相关癌症的风险调节剂

• 批准号: 9813370
• 负责人: Shailja Pathania
• 金额: $ 45.64万
• 依托单位: UNIVERSITY OF MASSACHUSETTS BOSTON
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9813370
• 关键词: Address; Affect; BRCA2 Mutation; BRCA2 gene; Base Excision Repairs; Biological Assay; Breast; Breast Epithelial Cells; Cell Survival; Cells; Chromosome abnormality; Cisplatin; Complex; Cytokinesis; DNA; DNA Damage; DNA Repair; DNA replication fork; Data; Degradation Pathway; Double Strand Break Repair; Epidemiology; Event; Exposure to; Fiber; Foundations; Future; Genetic; Genomic Instability; Germ-Line Mutation; Goals; Immunofluorescence Immunologic; Individual; Lead; Malignant Neoplasms; Malignant neoplasm of esophagus; Malignant neoplasm of ovary; Malignant neoplasm of pancreas; Malignant neoplasm of prostate; Mammary Gland Parenchyma; Mind; Molecular; Mutation; Nature; Nonhomologous DNA End Joining; Ovarian; Pathway interactions; Patients; Phenotype; Play; Predisposition; Prevention strategy; Preventive; Proteins; Reporting; Resistance; Resolution; Risk; Role; Site; Source; Survival Analysis; Therapeutic; Treatment Efficacy; Woman; Work; base; cancer risk; cell type; design; endonuclease; genomic biomarker; high risk; homologous recombination; insight; member; mutant; mutation carrier; neoplastic cell; novel; outcome forecast; repaired; replication stress; response; tumor; tumorigenesis; uracil-DNA glycosylase

Germline mutations in BRCA2 confer exceptionally high risk for breast, ovarian and multiple other cancers. There is strong epidemiological evidence that these risks are modified by genetic factors, however, currently there is no clear understanding of which genetic factors modify the risk of cancer in BRCA2 mutation carriers. An insight into the early driver events will be critical to help design more effective therapeutic, and importantly, preventive strategies for individuals with mutations in BRCA2. In the project outlined here, we will be investigating one such genetic factor that can influence cancer predisposition and/or response to chemotherapeutics in BRCA2 mutation carriers. We have identified members of base excision repair (BER) pathway, which, when lost, alter sensitivity of BRCA2 deficient cells to DNA damaging agents – especially those that cause stalled replication forks. We have identified BER proteins, APE1 (apurinic/apyrimidinic endonuclease) and UNG (Uracil-DNA glycosylase), which, when depleted, rescue sensitivity of BRCA2 deficient cells to stalled fork inducing agents. Depletion of these proteins also reverses chromosomal aberrations, a marker of genomic instability, in BRCA2 depleted cells. Importantly, we find that endogenous base damage is highly elevated in BRCA2 depleted cells. Based on our preliminary data, we hypothesize that altered BER activity and/or APE1 or UNG levels affect cancer risk predisposition in BRCA2 mutation carriers. In keeping with these hypotheses, a 5-year survival analysis of women with BRCA2-mutant ovarian cancer shows that patients with low APE1 levels in their tumor have a far worse prognosis compared to those with high APE1 levels. In order to investigate these hypotheses, we propose to determine whether APE1 and/or UNG affect stalled fork resolution in BRCA2 depleted cells (Aim 1). We will also determine the basis for increased base damage in replicating BRCA2 depleted cells, and the molecular mechanism by which APE1 and UNG affect the resolution of DNA damage in these cells (Aim 2). Finally, we will also determine whether phenotypically normal BRCA2mut/+ mammary epithelial cells (MECs) demonstrate altered stalled fork resolution upon loss of APE1 and/or UNG and how response to therapeutics in BRCA2 mutant cancers is affected by levels of APE1 and/or UNG in those cells (Aim 3). Successful completion of this work will give us an insight into a) a heretofore unknown function of BER proteins in affecting resolution of fork associated DNA damage in BRCA2 depleted cells , b) whether alterations in BER pathway has the ability to influence BRCA2 mutation driven tumorigenesis, and/or the response of BRCA2 tumors to chemotherapeutics, d) source of increased base damage in BRCA2 depleted cells, and c) the mechanism that drives these phenomena. Such work will lay the foundation for targeted, future preventive and therapeutic strategies for BRCA2 mutation associated cancer.

BRCA 2的生殖系突变赋予乳腺癌、卵巢癌和多种其他癌症异常高的风险。那里 强有力的流行病学证据表明，这些风险是由遗传因素改变的，然而，目前有 对于哪些遗传因素改变了BRCA 2突变携带者的癌症风险还没有明确的认识。的洞察 将有助于设计更有效的治疗方法，更重要的是， 针对BRCA 2突变个体的策略。 在这里概述的项目中，我们将调查一种可能影响癌症的遗传因素 BRCA 2突变携带者对化疗药物的易感性和/或反应。我们已经确认了 碱基切除修复（BER）途径，当丢失时，会改变BRCA 2缺陷细胞对DNA的敏感性 破坏代理-特别是那些导致复制分叉停滞的代理。我们已经鉴定了BER蛋白，APE 1 （脱嘌呤/脱嘧啶核酸内切酶）和UNG（尿嘧啶-DNA糖基化酶），当耗尽时，其拯救了 BRCA 2缺陷细胞对停滞叉诱导剂的敏感性。这些蛋白质的消耗也逆转了 染色体畸变，基因组不稳定性的标志。重要的是，我们发现， 内源性碱基损伤在BRCA 2耗尽的细胞中高度升高。根据初步数据，我们 假设BER活性和/或APE 1或UNG水平改变影响BRCA 2中癌症风险易感性 变异携带者与这些假设一致，BRCA 2突变女性的5年生存分析 卵巢癌显示，肿瘤中APE 1水平较低的患者预后要差得多， APE 1水平高的人 为了研究这些假设，我们建议确定APE 1和/或UNG是否影响失速 BRCA 2耗尽细胞中的分叉分辨率（Aim 1）。我们还将确定增加基础伤害的基础， 复制BRCA 2耗尽细胞，以及APE 1和UNG影响分辨率的分子机制 这些细胞中的DNA损伤（目的2）。最后，我们还将确定表型正常的BRCA 2 mut/+ 乳腺上皮细胞（MEC）在APE 1和/或UNG丧失后表现出改变的停滞叉分辨率， BRCA 2突变型癌症对治疗的反应如何受到这些细胞中APE 1和/或UNG水平的影响 (Aim 3）。 这项工作的成功完成将使我们深入了解a）迄今未知的BER功能 在BRCA 2耗尽的细胞中影响叉相关DNA损伤的解决的蛋白质，B）是否改变 在BER通路中，具有影响BRCA 2突变驱动的肿瘤发生和/或 BRCA 2肿瘤与化学治疗剂的关系，d）BRCA 2耗尽的细胞中碱基损伤增加的来源，和c）BRCA 2肿瘤与化学治疗剂的关系。 驱动这些现象的机制。这些工作将为今后有针对性的预防和 BRCA 2突变相关癌症的治疗策略。