Mechanism of LSD1 in breast cancer metastasis suppression

原发性肿瘤及其相应转移灶中发现的基因突变的比较， 目前还没有确定导致转移的基因突变。这提出了一个概念，即它是表观遗传 机制，与癌症类型特异性致癌和/或细胞类型特异性谱系程序一起工作， 这可能会导致转移性进展。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策略来阻止 乳腺癌转移LSD 1（KDM 1A）是第一个被发现的组蛋白去甲基化酶。在人类癌症中， LSD 1的遗传异常主要包括缺失和突变。这样的缺失/突变也具有 在转移性乳腺癌中被发现，提高了LSD 1是乳腺癌转移的可能性。 抑制器。事实上，在初步研究中，我们发现LSD 1在管腔型乳腺肿瘤细胞中的诱导丢失， 或LSD 1抑制剂治疗导致肺转移的显著增加。 从机制上讲，在管腔乳腺细胞中，我们发现LSD 1与GATA 3相互作用，GATA 3是一种关键的管腔特异性蛋白。 转录因子，以控制它们与细胞-细胞粘附和细胞周期相关的共同程序。LSD1 正调节GATA 3的表达，并抑制TRIM 37的表达，TRIM 37是LSD 1和 GATA 3，其编码参与基因阻遏的组蛋白H2 A泛素连接酶。重要的是，TRIM 37可以 有助于通过抑制LSD 1缺失增加管腔乳腺癌细胞的侵袭和迁移， 几种细胞粘附基因（例如，CDH1、VCL、CTNNA1）。这种表达的变化也观察到， 具有LSD 1缺失的鼠PyMT肿瘤细胞。总之，这些数据表明LSD 1可能抑制乳腺癌的发生， 通过调节其靶基因（例如，TRIM 37）在管腔细胞中的脱甲基酶活性- 依赖的方式。有趣的是，用LSD 1消融的PyMT肿瘤细胞也表现出显著的变化， 免疫相关基因，表明LSD 1也可能通过细胞外， 免疫相关机制。为了测试这些，我们将继续建立小鼠导管内注射（MIND） 作为我们的研究对象，PyMT肿瘤细胞和人雌激素受体+乳腺癌细胞系的移植模型， 体内系统在目标1中，我们将进行基于CRISPR的筛选，以映射LSD 1的功能结构域 负责其转移抑制与增殖/生存支持作用，并测试LSD 1 在患者中发现的突变通过破坏脱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LSD 1目标的作用（例如，TRIM 37及其合作伙伴EZH 2和其他）， 在各种MIND模型中转移级联的不同步骤中的管腔细胞。在目标3中，我们将确定 介导与LSD 1消融相关的PyMT转移增加的免疫机制，特别是， NK细胞和MHC-I分子，因为PyMT肿瘤细胞中的LSD 1缺失导致多种细胞因子的显著上调。 经典和非经典MHC-I，其用作NK细胞中抑制性受体的配体。

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.