Endothelial-to-osteoblast transition in prostate cancer bone metastasis

描述（由申请方提供）：具有致死潜力的前列腺癌（PCa）的一个显著特征是肿瘤细胞能够在去势环境中存活，并在骨中发生具有骨形成表型的转移。我们最近证实，前列腺癌诱导的异常骨过度生长促进骨肿瘤生长。因此，PCa细胞与其错误诱导的骨之间的双向相互作用在骨中的PCa进展中起关键作用。一般认为，转移性PCa细胞通过刺激骨髓中常驻成骨细胞的增殖来诱导新骨形成。然而，人类骨转移标本的组织病理学分析表明，编织骨不是来自相邻的骨表面。因此，通过PCa转化成成骨细胞的细胞的来源尚未确定。我们的目的是确定PCa骨转移中PCa诱导异位骨形成的细胞来源。 虽然成骨细胞PCa骨转移在临床上很普遍，但缺乏 成骨型PCa模型用于PCa骨转移研究。我们的异种移植核心最近成功地从患者样本中产生了骨形成PCa异种移植物MDA-PCa-118 b（PCa-118 b），为我们提供了一个模型来破译PCa诱导的骨形成机制。使用这种异种移植物，我们的初步结果表明：（1）PCa-118 b招募小鼠基质细胞进入肿瘤并将其转化为成骨细胞;（2）PCa-118 b中的成骨细胞也共表达内皮细胞标记物Tie 2;（3）PCa-118 b分泌包括BMP 4和TGF？2在内的因子，这些因子已被证明可促进内皮细胞向间充质细胞转化（EndMT）;（4）BMP 4或TGF β 2能够转化内皮细胞以表达osterix（OSX），一种成骨细胞特异性转录因子;和（5）在人PCa骨转移标本中，我们检测到分别共表达成骨细胞和内皮细胞标志物骨钙素和Tie 2的基质细胞。因此，我们假设PCa骨转移中的错误诱导的骨来源于内皮细胞，所述内皮细胞由PCa分泌因子诱导以经历EndMT和成骨细胞生成以形成成骨细胞（OSB）。EndMT/OSB转化导致骨过度生长，支持骨中的PCa进展。具体目标是： 目标1.鉴定在PCa骨转移中诱导EndMT/OSB的肿瘤分泌因子。我们将确定参与诱导EndMT/OSB的分泌因子以及BMP 4和TGF？2的最小集合。 目标2.确定在EndMT/OSB过程中BMP 4和TGF <$2如何调节内皮细胞的信号转导和转录程序。RNA-seq和ChIP-seq将用于鉴定转录网络。 目标3.确定阻断PCA诱导的EndMT/OSB是否抑制体内成骨细胞骨转移。 目标4。检查EndMT/OSB在人PCa骨转移中的临床相关性。 冲击成骨细胞的内皮起源将允许靶向EndMT/OSB转化的关键步骤的策略，以抑制异常骨形成，从而抑制骨中的PCa进展。

DESCRIPTION (provided by applicant): A distinct feature of prostate cancer (PCa) with lethal potential is the ability of tumor cells to survive in a castrated environment and develop metastases in bone with a bone-forming phenotype. We recently demonstrated that PCa-induced aberrant bone overgrowth promotes tumor growth in bone. Thus, bi-directional interaction between the PCa cells and their mis-induced bone plays a critical role in PCa progression in bone. It is generally assumed that the metastatic PCa cells induce new bone formation by stimulating the proliferation of resident osteoblasts in the bone marrow. However, histopathological analyses of human bone metastasis specimens showed that woven bone was not from the adjacent bone surface. Thus, the origin of cells that were converted into osteoblasts by PCa is yet to be determined. Our objective is to identify the cell origin for the PCa-induced ectopic bone formation in PCa bone metastasis. While osteoblastic PCa bone metastasis is prevalent in the clinical setting, there is a lack of osteogenic PCa models for PCa bone metastasis study. Our xenograft core has recently successfully generated a bone forming PCa xenograft MDA-PCa-118b (PCa-118b) from a patient sample, providing us with a model to decipher the mechanism of PCa-induced bone formation. Using this xenograft, our preliminary results showed that (1) PCa-118b recruits mouse stromal cells into the tumors and converts them into osteoblasts; (2) Osteoblasts in PCa-118b also co-express the endothelial cell marker Tie2; (3) PCa-118b secretes factors, including BMP4 and TGF¿2, which have been shown to promote endothelial-to-mesenchyme transition (EndMT); (4) BMP4 or TGF¿2 are able to convert endothelial cells to express osterix (OSX), an osteoblast- specific transcription factor; and (5) In human PCa bone metastasis specimens, we detected stromal cells that co-express osteoblast and endothelial cell markers, osteocalcin and Tie2, respectively. Thus, we hypothesize that mis-induced bone in PCa bone metastasis originates from endothelial cells that were induced by PCa- secreted factors to undergo EndMT and osteoblastogenesis to form osteoblasts (OSB). The EndMT/OSB conversion leads to bone overgrowth that supports PCa progression in bone. The Specific Aims are: Aim 1. Identify tumor-secreted factors that induce EndMT/OSB in PCa bone metastasis. We will determine a minimal set of the secretory factors together with BMP4 and TGF¿2 that are involved in inducing EndMT/OSB. Aim 2. Determine how BMP4 and TGF¿2 regulate the signal transduction and transcriptional program of endothelial cells during EndMT/OSB. RNA-seq and ChIP-seq will be used to identify the transcriptional network. Aim 3. Determine whether blocking PCa-induced EndMT/OSB inhibits osteoblastic bone metastasis in vivo. Aim 4. Examine the clinical relevance of EndMT/OSB in human PCa bone metastasis. Impact. The endothelial origin of osteoblasts will allow for strategies to target the key steps of the EndMT/OSB conversion for suppression of aberrant bone formation and thus, PCa progression in bone.