针对BRCA1相关乳腺干细胞和乳腺癌干细胞异质性的单细胞蛋白质谱分析

Heterogeneity in cellular populations plays an important role in many normal biological processes, including developmental induction, cell fate determination, pattern formation, and organogenesis. Heterogeneity of breast cancers is one of the major factors that prevent a complete response of cancer cells to drug treatment, and consequently many resistant colonies appear after the treatment. Recent progresses in identification of normal mammary gland stem cells (MaSCs) and cancer stem cells (CSCs) provide a great opportunity for the understanding of heterogeneity of these cells for the development of targeted treatment of the tumorigenic population of breast cancers. In this study, we specifically investigate the following issues: 1) what is heterogeneity of MaSCs? 2) Does the breast cancer associated gene-1 (BRCA1) play a role in the formation of MaSCs? 3) What are molecular pathways, through which the normal MaSCs undergo malignant transformation to form CSCs? We plan to provide answers for these questions through researches using our mouse model for BRCA1-associated breast cancer. We hypothesize that heterogeneity plays an important role in the formation of MaSCs and mammary CSCs and the loss of BRCA1 may yield a big impact on this process and tumorigenesis. We further hypothesize that transcriptome and mass cytometry analysis of MaSCs and mammary CSCs at single cell level should provide a powerful approach for illustrating the heterogeneity among each type of the cells, and the differences between these two types of cells. Through careful data analysis and validation, we aim to identify molecular pathways, through which normal stem cells undergo malignant transformation to CSCs. These data should provide valuable first-hand information and molecular markers to facilitate prevention and early detection of breast cancer, and develop more efficient therapeutics for the elimination of breast cancers.

细胞异质性是指在一个细胞群体中诸多细胞间的不同。细胞异质性在很多生物过程中发挥着重要作用。乳腺癌细胞的异质性被认为是妨碍癌细胞响应药物治疗，因而产生抗性细胞的主要因素之一。近年来在鉴定正常乳腺干细胞和乳腺癌干细胞研究领域的新进展为研究细胞异质性从而治疗乳腺癌提供了极大的机遇。这里我们将研究以下问题：1 ）什么是乳腺干细胞的异质性？ 2 ）乳腺癌相关基因-1（BRCA1)在正常乳腺干细胞形成中起什么作用？3）正常的乳腺干细胞是通过何种分子途径，经历恶性转化而形成肿瘤干细胞的？在本项目中，我们计划利用BRCA1相关乳腺癌的小鼠模型，在单细胞水平对乳腺干细胞和乳腺肿瘤干细胞进行转录分析和蛋白质谱分析。通过细致的数据分析和验证，我们的目标是找出正常乳腺干细胞恶性转化为肿瘤干细胞的分子途径。这些数据将为找到预防和早期发现乳腺癌的分子标记,并开发出根治乳腺癌的更有效的治疗方法提供有价值的第一手资料。

作为哺乳动物特有的器官，乳腺通过合成及分泌乳汁对于繁衍后代发挥非常重要的作用。乳腺由多种不同类型的细胞组成，包括上皮细胞、脂肪细胞、血管内皮细胞以及各种免疫细胞等。而包括乳腺癌在内的多种乳腺疾病都与乳腺上皮细胞的功能异常密切相关。其中，乳腺癌相关基因-1（BRCA1）的突变或缺失会极大地提升女性罹患乳腺癌的风险。BRCA1缺失所导致的乳腺癌的发生存在一定随机性，并且该类乳腺癌在不同个体间存在较高程度的异质性。为了更好地理解乳腺上皮细胞的异质性构成以及BRCA1缺失引发乳腺癌地致病机理，我们以野生型及Brca1基因敲除小鼠为研究对象，通过整体及单细胞转录本测序以及单细胞蛋白质谱分析，阐明了乳腺上皮的细胞组成情况，鉴定了一批乳腺干细胞的分子标志物，解析了Brca1基因敲除小鼠的乳腺上皮细胞及乳腺肿瘤细胞的异质性构成，并重构了乳腺干细胞定向分化以及Brca1基因敲除引发的乳腺上皮细胞向肿瘤细胞恶性转化的分子路径并深入分析了这些非常重要的生物学过程中的基因调控变化。此外，我们还初步探讨了Brca1缺失引发乳腺肿瘤过程中乳腺免疫细胞的异质性变化。总之，本研究项目极大地拓展了我们对乳腺上皮细胞及肿瘤细胞异质性的理解，加深了我们对Brca1相关乳腺肿瘤发病机制的认识，并为乳腺癌的临床诊断及治疗提供了全新的理论视角、科学依据及分子靶标，因而具备广阔的转化应用前景。