Endothelial-to-osteoblast transition in prostate cancer bone metastasis

描述(申请人提供)：具有致死潜能的前列腺癌(PCA)的一个明显特征是肿瘤细胞在去势环境中存活并发生骨形成表型的骨转移。我们最近证明了PCA诱导的异常骨过度生长促进了骨肿瘤的生长。因此，Pca细胞与其错误诱导的骨之间的双向相互作用在Pca在骨中的进展中起着至关重要的作用。通常认为，转移的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，对人骨转移标本的组织病理学分析表明，编织骨不是来自邻近的骨表面。因此，通过PCA转化为成骨细胞的细胞的来源尚未确定。我们的目的是确定前列腺癌在前列腺癌骨转移中诱导异位骨形成的细胞来源。 虽然成骨细胞性前列腺癌的骨转移在临床上很普遍，但缺乏 成骨性PCA模型用于PCA骨转移研究。我们的异种移植核最近成功地从患者样本中产生了形成骨形成的PCA异种移植物MDA-PCA-118b(PCA-118b)，为我们提供了一个破译PCA诱导成骨机制的模型。利用这种异种移植，我们的初步结果显示：(1)PCA-118b可以招募小鼠基质细胞进入肿瘤并将其转化为成骨细胞；(2)在PCA-118b中的成骨细胞也共表达内皮细胞标志物Tie2；(3)PCA-118b可以分泌包括BMP4和TGF？2在内的促进内皮细胞到间充质转化(EndMT)的因子；(4)BMP4或TGF？2能够转化内皮细胞表达成骨细胞特异性转录因子OSX；(5)在人前列腺癌骨转移标本中，我们检测到成骨细胞和内皮细胞标记物骨钙素和Tie2共表达的基质细胞。因此，我们推测，在PCa骨转移中错误诱导的骨起源于内皮细胞，这些内皮细胞在PCa分泌的因子诱导下经历EndMT和成骨细胞形成成骨细胞(OSB)。EndMT/OSB转换导致骨骼过度生长，从而支持骨骼的PCA进展。具体目标是： 目的1.确定在前列腺癌骨转移中诱导EndMT/OSB的肿瘤分泌因子。我们将确定与BMP4和转化生长因子2一起参与诱导EndMT/OSB的最小分泌因子集。 目的：探讨骨形态发生蛋白4和转化生长因子2在EndMT/OSB过程中对内皮细胞信号转导和转录程序的调节作用。RNA-SEQ和CHIP-SEQ将用于识别转录网络。 目的3.确定阻断PCA诱导的EndMT/OSB是否能抑制体内成骨细胞骨转移。 目的4.探讨EndMT/OSB在前列腺癌骨转移中的临床意义。 冲击力。成骨细胞的内皮来源将允许针对EndMT/OSB转换的关键步骤的策略，以抑制异常的骨形成，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.