Lymphangioleiomyomatosis (LAM) is a rare, debilitating lung disease that predominantly affects women of reproductive age. LAM is characterized by the infiltration of the lungs by abnormally proliferating smooth muscle-like cells of unknown origin via an estrogen-dependent metastatic mechanism. LAM cells carry deleterious mutations of tuberous sclerosis complex (TSC1/TSC2) genes, resulting in hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) and ultimately dysregulated cell growth. Sirolimus, an FDA approved mTORC1 inhibitor and current best-choice medication for LAM stabilizes lung function in most LAM patients. However, it requires sustained application and remains inefficacious in some patients. The greatest barriers to finding a cure for LAM include its undetermined origin and unclear underlying pathogenesis. Our study aims to advance knowledge on the origin of LAM, and ultimately serve as a premise for the development of novel therapeutic targets for LAM. Single cell RNA sequencing (scRNA-seq) is a powerful tool in biomedical research that informs gene expression differences at the cellular level and may provide insights into the most fundamental origin of LAM cells. Our scRNA-seq analysis of LAM cells revealed a unique population of cells (LAMCORE), expressing uterine-similar homeobox transcription factors (HOX) and Pre-B-cell leukemia homeobox 1 (PBX1), which are absent in normal lung, suggesting that the uterus is the primary origin of LAM. PBX1 is a transcription factor critical for female reproductive tract development and maintenance, and its overexpression is implicated in some female reproductive cancers. In this study we hypothesize that PBX1 promotes survival and lung colonization of LAM (TSC2-null) cells. Using LAM patient-derived cells, we validated the transcriptional profile, gene expression and protein levels of PBX1. We have the first functional evidence that PBX1 and its downstream targets are upregulated in LAM cells. In a mouse model of LAM, we monitored the effect of suppression of PBX1 by short hairpin RNA-mediated gene silencing on lung colonization and tumor growth. We also found that pharmacological suppression of PBX1 attenuates LAM lung colonization and promotes death of LAM cells in vivo and vitro. Our data collectively suggests that PBX1 is a critical regulator of LAM progression.

中文翻译：

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综合单细胞多组学分析揭示 HOX-PBX 基因调控网络有助于 mTOR 过度活跃细胞的存活

淋巴管平滑肌瘤病 (LAM) 是一种罕见的、使人衰弱的肺部疾病，主要影响育龄妇女。LAM 的特征是通过雌激素依赖性转移机制异常增殖的未知来源的平滑肌样细胞浸润肺部。LAM 细胞携带结节性硬化症复合物 (TSC1/TSC2) 基因的有害突变，导致雷帕霉素复合物 1 (mTORC1) 的机械靶点过度活化，最终导致细胞生长失调。西罗莫司是 FDA 批准的 mTORC1 抑制剂，也是目前 LAM 的最佳选择药物，可稳定大多数 LAM 患者的肺功能。然而，它需要持续应用并且在一些患者中仍然无效。寻找 LAM 治愈方法的最大障碍包括其未确定的起源和不清楚的潜在发病机制。我们的研究旨在推进对 LAM 起源的认识，并最终为开发 LAM 的新治疗靶点奠定基础。单细胞 RNA 测序 (scRNA-seq) 是生物医学研究中的一种强大工具，可在细胞水平上告知基因表达差异，并可能提供对 LAM 细胞最基本起源的见解。我们对 LAM 细胞的 scRNA-seq 分析揭示了一个独特的细胞群 (LAMCORE)，表达了正常肺中不存在的子宫相似同源框转录因子 (HOX) 和前 B 细胞白血病同源框 1 (PBX1)，这表明子宫是LAM的主要起源。PBX1 是对女性生殖道发育和维持至关重要的转录因子，其过度表达与一些女性生殖癌症有关。在这项研究中，我们假设 PBX1 促进 LAM (TSC2-null) 细胞的存活和肺定植。使用 LAM 患者来源的细胞，我们验证了 PBX1 的转录谱、基因表达和蛋白质水平。我们有第一个功能证据表明 PBX1 及其下游靶标在 LAM 细胞中上调。在 LAM 的小鼠模型中，我们监测了通过短发夹 RNA 介导的基因沉默抑制 PBX1 对肺定植和肿瘤生长的影响。我们还发现 PBX1 的药理学抑制减弱了 LAM 肺定植并促进 LAM 细胞在体内和体外的死亡。我们的数据共同表明 PBX1 是 LAM 进展的关键调节因子。PBX1 的基因表达和蛋白质水平。我们有第一个功能证据表明 PBX1 及其下游靶标在 LAM 细胞中上调。在 LAM 的小鼠模型中，我们监测了通过短发夹 RNA 介导的基因沉默抑制 PBX1 对肺定植和肿瘤生长的影响。我们还发现 PBX1 的药理学抑制减弱了 LAM 肺定植并促进 LAM 细胞在体内和体外的死亡。我们的数据共同表明 PBX1 是 LAM 进展的关键调节因子。PBX1 的基因表达和蛋白质水平。我们有第一个功能证据表明 PBX1 及其下游靶标在 LAM 细胞中上调。在 LAM 的小鼠模型中，我们监测了通过短发夹 RNA 介导的基因沉默抑制 PBX1 对肺定植和肿瘤生长的影响。我们还发现 PBX1 的药理学抑制减弱了 LAM 肺定植并促进 LAM 细胞在体内和体外的死亡。我们的数据共同表明 PBX1 是 LAM 进展的关键调节因子。我们还发现 PBX1 的药理学抑制减弱了 LAM 肺定植并促进 LAM 细胞在体内和体外的死亡。我们的数据共同表明 PBX1 是 LAM 进展的关键调节因子。我们还发现 PBX1 的药理学抑制减弱了 LAM 肺定植并促进 LAM 细胞在体内和体外的死亡。我们的数据共同表明 PBX1 是 LAM 进展的关键调节因子。