Mechanism of LSD1 in breast cancer metastasis suppression

在原发肿瘤及其相应转移灶中发现的基因突变的比较 到目前为止，还没有定义导致转移的基因突变。这提出了一种概念，即它是表观遗传学 机制，与癌症类型特定的致癌和/或细胞类型特定的谱系计划一起工作， 这可能会推动转移性进展。在乳腺癌中，表观遗传异常如何驱动转移 进展在很大程度上仍然难以捉摸。更好地理解这一点可能会导致新的阻止策略 乳腺癌转移。LSD1(KDM1A)是第一个被鉴定的组蛋白去甲基酶。在人类癌症中， LSD1基因异常主要包括缺失和突变。这种缺失/突变也有 在转移性乳腺癌中被发现，增加了LSD1是乳腺癌转移的可能性 抑制者。事实上，在初步研究中，我们发现在腔内乳腺肿瘤细胞中诱导LSD1的丢失 在MMTV-PYMT小鼠模型中，LSD1抑制剂治疗导致肺转移显著增加。 从机制上讲，我们发现在腔内乳腺细胞中，LSD1与GATA3相互作用，GATA3是腔内特有的关键基因 转录因子，控制它们与细胞间黏附和细胞周期相关的共同程序。LSD1 正向调节GATA3的表达并抑制TRIM37的表达，TRIM37是LSD1和TIM37的共同靶点 GATA3，编码组蛋白H_2A泛素连接酶，参与基因抑制。重要的是，TRIM37可能 通过抑制LSD1的表达促进腔内乳腺癌细胞侵袭和迁移的增加 几个细胞黏附基因(如CDH1、VCL、CTNNA1)。这种表达变化也被观察到在 LSD1缺失的小鼠PYMT肿瘤细胞。综上所述，这些数据表明LSD1可能抑制乳房 肿瘤转移通过调节其靶基因(例如，TRIM37)在瘤细胞中的去甲基酶活性-- 依赖的态度。有趣的是，去除LSD1的PYMT肿瘤细胞也显示出深刻的变化 免疫相关基因，提示LSD1也可能通过一种外源性细胞， 与免疫相关的机制。为了测试这些，我们将继续建立小鼠导管内注射(Mind)。 PYMT肿瘤细胞和人雌激素受体+乳腺癌细胞系移植模型的建立 活体系统。在目标1中，我们将进行基于CRISPR的筛选，以定位LSD1的功能结构域(S 负责其抑制转移与增殖/支持生存的作用，并检测LSD1 在患者中发现的突变通过破坏去甲基酶而损害其转移抑制功能 活动。在目标2中，我们将确定LSD1目标(例如，TRIM37及其合作伙伴EZH2和其他)的角色 在不同的心智模型中，处于转移级联不同阶段的腔细胞。在目标3中，我们将确定 与LSD1消融相关的PYMT转移增加的免疫机制，尤其是， NK细胞和MHC-I分子作为LSD1在PYMT肿瘤细胞中的缺失导致多种基因表达的深刻上调 经典和非经典MHC-IS，作为NK细胞抑制性受体的配体。

Comparisons of genetic mutations found in primary tumors and their corresponding metastatic lesions have so far failed to define genetic mutations that lead to metastasis. This raises a notion that it is the epigenetic mechanisms, working together with cancer type-specific oncogenic and/or cell type-specific lineage programs, that may drive metastatic progression. In breast cancer, how epigenetic abnormalities drive metastatic progression remains largely elusive. A better understanding of this may lead to novel strategies to block breast cancer metastasis. LSD1 (KDM1A) is the first identified histone demethylase. In human cancers, genetic abnormalities of LSD1 mainly include deletions and mutations. Such deletions/mutations have also been found in metastatic breast cancer, raising a possibility that LSD1 is a breast cancer metastasis suppressor. Indeed, in preliminary studies, we found induced loss of LSD1 in luminal mammary tumor cells or LSD1 inhibitor treatment in the MMTV-PyMT mouse model led to a dramatic increase in lung metastasis. Mechanistically, in luminal breast cells, we found LSD1 interacts with GATA3, a key luminal-specific transcription factor, to control their common programs related to cell-cell adhesion and cell cycle. LSD1 positively regulates GATA3 expression and represses that of TRIM37, a common target of both LSD1 and GATA3, which encodes a histone H2A ubiquitin ligase involved in gene repression. Importantly, TRIM37 may contribute to increased invasion and migration of luminal breast cancer cells with LSD1-loss via repression of several cell adhesion genes (e.g., CDH1, VCL, CTNNA1). Such expression changes were also observed in murine PyMT tumor cells with LSD1-loss. Together, these data suggest that LSD1 may suppress breast cancer metastasis via regulation of its target genes (e.g., TRIM37) in luminal cells in a demethylase activity- dependent manner. Intriguingly, PyMT tumor cells with LSD1 ablation also exhibited a profound change in immune-related genes, suggesting that LSD1 may also suppress breast cancer metastasis by a cell-extrinsic, immune-related mechanism. To test these, we will continue to establish mouse intraductal injection (MIND) transplantation models for PyMT tumor cells and human estrogen receptor+ breast cancer cell lines as our in vivo system. In Aim 1, we will perform CRISPR-based screens to map functional domain(s) of LSD1 responsible for its metastasis suppression vs. proliferation/survival-supporting roles, and test if LSD1 mutations found in patients impair its metastasis suppression function via disruption of the demethylase activity. In Aim 2, we will determine roles of LSD1 targets (e.g., TRIM37 and its partner EZH2, and others) of luminal cells at different steps of the metastatic cascade in various MIND models. In Aim 3, we will determine the immune mechanism mediating increased PyMT metastasis associated with LSD1 ablation, in particular, NK cells and MHC-I molecules, as LSD1-loss in PyMT tumor cells led to a profound upregulation of various classic and non-classic MHC-Is, which serve as ligands for inhibitory receptors in NK cells.