三阴乳腺癌(TNBC)是最难治的乳腺癌亚型之一，严重威胁妇女健康。TNBC与乳腺癌干细胞(BrCSCs)密切相关，部分BrCSCs亚群就是TNBC。然而，病人体内恶性程度最高的TNBC/BrCSCs源自何种细胞，如何进展成为TNBC，其体内动态演变的过程和调控机制尚未知晓。我们前期工作发现Kindlin-2经细胞重编程机制在体外产生了TNBC/BrCSCs。本申请中，我们将综合利用小鼠转基因、基因敲除和敲入的技术，在小鼠体内建立动态追踪Kindlin-2诱导产生TNBC/BrCSCs的谱系变化模型。进一步，我们将在小鼠乳腺内建立人源化乳腺癌的移植物(PDX)，在PDX中以近似人体的环境对Kindlin-2诱导产生的TNBC/BrCSCs进行谱系追踪。研究将揭示乳腺癌中TNBC/BrCSCs的起源和谱系变化规律，有助于抗TNBC/BrCSCs的药物筛选和新临床对策的建立，从而惠及乳腺癌病人。

Triple-negative breast cancer (TNBC) is one of the breast cancer subtype that is very difficult to be cured and is also quite lethal to women worldwide. TNBC tightly connected to breast cancer stem cells (BrCSCs) and some of the BrCSCs are triple-negetive. However, there is almost no clues for where these highly malignant TNBC/BrCSCs originate from, and how these cells progress to TNBC stage.Up to now nothing has been known for the in vivo dynamic conversion of these cells and the corresponding regulatory mechanisms. In our previous investigations, we found that integrin-interacting protein Kindlin-2 could generate TNBC/BrCSCs in vitro by an epigenetic reprogramming process. In the present proposal, we aim to establish a model system for TNBC/BrCSCs in vivo generation and lineage changes by tracing them in the mice mammary glands that are genetically modified by Kindlin-2 transgenic and null mice, in corporaton with the use of Lgr5 knock-in mice.In addition, we will also establish a model with humanized mouse mammary gland by transplantation of patient-derived xenogrant (PDX) from breast cancer patients. Within PDX model that is close to the tumor microenvironment in human body we will trace the TNBC/BrCSCs generation and lineage changes. By means of these models in mouse mammary glands and the transplanted PDX we anticipate to uncover the origin of TNBC/BrCSCs and the commom mechanisms accounting for BrCSCs lineage changes. Therefore, the execution of this research plan will help to set up new systems for anti-TNBC/BrCSCs drug screenings and will formulate new therapeutic strategies for TNBC, which will no doubt be beneficial to the breast cancer patients.