重编程产生Claudin-low/三阴乳腺癌干细胞：乳腺癌可塑性的分子机制及转化医学意义

Little is known about the mechanisms of the plasticity of breast cancer stem cells (BrCSCs). Triple-negative breast cancer (TNBC) is the subgroup of tumors that do not express clinically significant levels of the estrogen receptor ? (ER??), progesterone receptor (PgR) and HER2. TNBC has been connected to the early onset of breast cancer and is often accompanied with BRCA1 gene mutations, which represents a refractory subgroup of breast cancer. We recently converted luminal A subtype of breast cancer cells to Claudin-low/TNBC BrCSCs, which is at the end stage of breast cancer cell dedifferentiation, by a mechanism of the integrin-interacting protein Kindlin-2-regulated epigenetic reprogramming. For the first time, we proved that the luminal A subtype of breast cancer cells can be directly transmitted to Claudin-low/TNBC BrCSCs without undergoing the hierarchical progression. In the present proposal, we aim to investigate the network regulation of signaling pathways on the hormonal receptors in TNBC and to uncover the relationship between BrCSCs and the maintenance of triple-negative status. We also want to understand the molecular mechanism accounting for Claudin-low subtype. Towards translational research, on one hand we aim to screen the potential drug leads that could block Claudin-low/TNBC BrCSCs using the stable cell line we established; on the other hand, we try to link the molecules that promote TNBC with the outcomes in breast cancer patients. This study anticipates to unravel the molecular mechanism underlying the generation of Claudin-low/TNBC BrCSCs, and to create new clinical strategies that will no doubt be beneficial to the breast cancer patients.

对乳腺癌干细胞(BrCSCs)可塑性的产生机制知之甚少。雌激素受体,孕激素受体和表皮生长因子受体2均呈阴性的乳腺癌称为三阴乳腺癌(TNBC)，其发病年龄轻，常伴有BRCA1基因突变，是最难治的乳腺癌亚型。我们近期将luminal A亚型的乳腺癌细胞籍整合素结合蛋白Kindlin-2调控的重编程机制，产生了Claudin-low/TNBC BrCSCs。率先证实，luminal A亚型乳腺癌可跨越中间演变环节而直接产生Claudin-low/TNBC BrCSCs。本申请中，我们将在信号通路对激素受体的网络调控、BrCSCs与三阴状态之间的关系、Claudin-low产生的分子机制、抗TNBC药物新靶点的筛选以及促TNBC表型的分子在乳腺癌病人中的表达对病人预后的影响等方面开展研究。预期将揭示Claudin-low/TNBC BrCSCs的产生机制并建立新的临床对策，从而惠及乳腺癌病人。

三阴乳腺癌约占乳腺癌的15-20%，是目前最难治的乳腺癌之一，尚无有效的治疗方法，肺转移和肝转移的发生率高，病人预后差。三阴乳腺癌细胞具有干细胞的特征。我们研究了整合素结合蛋白Kindlin-2在三阴乳腺癌中的表达调控，Kindlin-2 诱导产生 Claudin-low/TNBC 乳腺癌干细胞的重编程，及其抑制雌激素受体 ERa及Claudin的分子机制。我们的研究结果揭示出Kindlin-2通过与β-catenin 及TCF4 形成复合物促进Wnt信号通路，从而调节乳腺癌细胞的重编程产生具有三阴乳腺癌表型特征的癌干细胞。通过对雌激素受体ERa及Claudin基因启动子的甲基化而产生的Claudin-low/TNBC的表型、通过对肿瘤干细胞干性维持因子EZH2，Slug的调节促成乳腺癌细胞的重编程。 Kindlin-2 在乳腺癌细胞中诱导基因组不稳定性促进乳腺癌的肿瘤形成、并通过使microRNA-200b 启动子的CpG岛高度甲基化，从而抑制microRNA-200b的表达，进而促进乳腺癌的侵袭转移。尤为重要的是我们发现，Kindlin-2 - EZH2 - Slug轴控制乳腺癌干细胞的干性。靶向这一调控轴可以抑制乳腺癌干细胞的干性。因此，我们还积极探讨了靶向乳腺癌干细胞的药物筛选和耐药机制的研究。我们的研究成果具有重要的理论意义和较高的应用前景，将对三阴性乳腺癌治疗的药物选择和新药筛选及病人的耐药性预警起到重要的推动作用。