A Novel BRCA1 Heterozygosity Driven Breast Cancer Mouse Model to Identify Tumor Initiating Events and Therapeutic Strategies

项目摘要 携带BRCA 1（B1）突变的女性患乳腺癌的风险极高（按年龄计算为70- 80 70 y）。B1突变型癌症是三阴性的，这使得它对激素治疗很难治疗。铂金和PARP 抑制剂（PARPi）对这些肿瘤有效，但这些药物的成功受到高风险的影响。 随着时间的推移对这些药物的耐药性发生率。此外，目前唯一有效的预防战略 为这些妇女提供的是改变生活的预防性乳房切除术，以消除乳房组织。鉴于有限的 尽管目前有各种治疗选择，但确定新的治疗和预防战略至关重要。设计 这种策略需要了解乳腺细胞中导致肿瘤发生的早期事件。B1 杂合子小鼠模型可以帮助我们识别乳腺上皮细胞群的这些早期变化， 这些细胞就变成了肿瘤细胞。然而，尽管B1杂合性与 尽管在人类中存在癌症易感性，但目前还没有这样的B1杂合小鼠模型， 概括了B1杂合性时肿瘤形成的高风险。B1杂合子小鼠不具有肿瘤倾向。 这使得使用这些模型来研究B1杂合性的作用和识别早期肿瘤变得困难 促进乳房组织的变化。我们现在已经建立了B1杂合子小鼠癌症模型， 能够解决这些问题。我们的方法是基于我们已发表的工作和初步数据 这揭示了B1杂合子细胞中复制应激抑制的单倍不足。我们最近的工作 显示B1杂合乳腺上皮细胞在复制中特别有缺陷/单倍不足 应激（RS）抑制。鉴于RS发展在肿瘤发生中的重要性，这种效应将是合乎逻辑的。 B1突变型癌症的发展。我们已经发现，在RS抑制中B1单倍不足是 通过暴露于4-硝基喹啉-1-氧化物（4 NQO 1）而增强。在B1杂合型组织中，而非B1野生型组织中，RS 作为一个有效的和异常快速的驱动程序的肿瘤形成。这种加速的肿瘤模型系统 可能被证明是非常宝贵的了解在B1突变乳腺癌的最早期事件。我们进一步 我用这种小鼠模型记录了乳腺组织中发生的早期变化，这些变化表现为不同的细胞类型（管腔细胞）。 和基础）对复制应激作出反应，并确定了只在B1中出现的新细胞群 杂合子乳腺组织我们计划使用这种小鼠模型和人类B1突变乳腺类器官， 提出两个关键问题- i）B1杂合子乳腺组织中的早期事件是什么， 肿瘤发生（AIM 1）？和ii）PARPi可用作具有B1突变（AIM 2）的妇女的预防剂。 PARPi已用于维持治疗（初始缓解后继续使用），并显示出在以下方面的潜力： 这种背景。然而，目前尚不清楚它是否也可用作妇女的预防剂， BRCA 1突变。我们将在本申请中回答这些问题。本研究将为 广泛的未来研究，将确定新的治疗和预防战略的妇女与B1突变。

PROJECT SUMMARY Women with BRCA1 (B1) mutation have an exceptionally high risk of developing breast cancer (70-80% by age 70y). B1 mutant cancer is triple negative which makes it refractory to hormone therapy. Platinum and PARP inhibitors (PARPi) have been effective against these tumors but the success of these drugs is marred by high incidence of resistance to these drugs over time. Furthermore, the only effective preventive strategy currently offered to these women is the life altering prophylactic mastectomy to remove the breast tissue. In light of limited treatment options available, it is critical that new therapeutic and preventive strategies be identified. Design of such strategies requires an understanding of early events in the breast cells that drive tumorigenesis. B1 heterozygous mouse models can help us identify these early changes in mammary epithelial cell populations as the cells become tumor cells. However, despite the well-established association between B1 heterozygosity and cancer predisposition in humans, there are currently no such B1 heterozygous mouse models that faithfully recapitulate this high risk of tumor formation upon B1 heterozygosity. B1 heterozygous mice are not tumor-prone. This makes it difficult to use these models to study the role of B1 heterozygosity and to identify early tumor promoting changes in the breast tissue. We have now established a B1 heterozygous mouse cancer model that is capable of addressing these questions. Our approach is based on our published work and preliminary data that reveals haploinsufficiency for replication stress suppression in B1 heterozygous cells. Our recent work has shown that B1 heterozygous mammary epithelial cells are especially defective/haploinsufficient in replication stress (RS) suppression. Given the importance of RS development in tumorigenesis, this effect would be a logical contributor to B1 mutant cancer development. We have found that B1 haploinsufficiency in RS suppression is enhanced by exposure to 4-nitroquinoline-1-oxide (4NQO1). In B1 heterozygous, but not B1 wild type tissue, RS serves as an efficient and abnormally rapid driver of tumor formation. Such an accelerated tumor model system could prove to be invaluable in understanding the earliest events in B1 mutant breast cancer. We have further used this mouse model to document early changes that occur in the breast tissue as different cell types (luminal and basal) respond to replication stress, and have identified new cell populations that emerge exclusively in B1 heterozygous mammary tissue. We plan to use this mouse model and human B1 mutant mammary organoids to ask two critical questions– i) what are the early events in the B1 heterozygous breast tissue that drives tumorigenesis (AIM1)? and ii) can PARPi be used as a preventive agent for women with B1 mutation (AIM2). PARPi has been used for maintenance therapy (continued use after initial response) and has shown potential in that context. However, it is not yet clear whether it can also be used as a preventive agent for women with BRCA1 mutation. We will address these questions in this grant application. This study will lay the foundation for extensive future studies that will identify novel therapeutic and preventive strategies for women with B1 mutation.