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

项目总结 携带BRCA1(B1)突变的女性患乳腺癌的风险极高(年龄时为70-80% 70y)。B1突变的癌症是三重阴性的，这使得它对激素治疗无效。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 随着时间的推移，对这些药物的耐药性的发生率。此外，目前唯一有效的预防战略 为这些女性提供的是改变生活的预防性乳房切除术，以移除乳房组织。鉴于有限的 在现有治疗选择的情况下，至关重要的是确定新的治疗和预防战略。的设计 这样的策略需要了解推动肿瘤发生的乳腺细胞的早期事件。B1 杂合子小鼠模型可以帮助我们识别乳腺上皮细胞群体的这些早期变化 这些细胞会变成肿瘤细胞。然而，尽管B1杂合性和 在人类癌症易感性方面，目前还没有这种B1杂合子的小鼠模型忠实地 将这种肿瘤形成的高风险归结为B1杂合性。B1杂合子小鼠不容易患肿瘤。 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一种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 这揭示了在B1杂合细胞中抑制复制应激的单倍性不足。我们最近的工作是 结果显示，B1杂合子乳腺上皮细胞在复制方面尤其有缺陷/单倍性不足 应激(RS)抑制。鉴于RS的发展在肿瘤发生中的重要性，这种效应是合乎逻辑的 B1突变癌症发展的贡献者。我们发现在RS抑制中B1单倍体不足是 通过接触4-硝基喹啉-1-氧化物(4NQO1)而增强。在B1杂合子组织中，但不是B1野生型组织中，RS 是肿瘤形成的有效和异常快速的驱动力。这样一个加速的肿瘤模型系统 可能被证明对了解B1突变乳腺癌的最早事件是非常有价值的。我们还有更多 使用此小鼠模型将乳房组织中发生的早期变化记录为不同的细胞类型(腔 和基础)对复制压力作出反应，并已鉴定出仅在B1中出现的新细胞群 杂合的乳房组织。我们计划使用这个小鼠模型和人类B1突变的乳腺有机化合物 问两个关键问题-i)在B1杂合子乳腺组织中有哪些早期事件 肿瘤发生(AIM1)？以及ii)PARPI是否可以作为B1突变妇女的预防性药物(AIM2)。 PARPI已用于维持治疗(在初始反应后继续使用)，并在 那就是背景。然而，目前还不清楚它是否也可以用来预防患有 BRCA1突变。我们将在这份拨款申请中解决这些问题。这项研究将为以下工作奠定基础 广泛的未来研究，将确定B1突变女性的新治疗和预防策略。

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.