Molecular mechanisms of osteoblastic bone metastasis: Role of endothelin-1

成骨细胞转移是癌症患者的一个重要临床问题。它们几乎总是出现在前列腺癌中，也经常出现在其他常见的恶性肿瘤中，比如乳腺癌。由于缺乏可复制的动物模型，成骨细胞转移的病理生理机制尚不清楚。在这个项目中，我们开发了一个成骨细胞骨转移的体内模型，该模型是可复制的，并允许对这种疾病的病理生理学进行研究。在这个模型中，引起成骨细胞转移的人类肿瘤细胞产生大量内皮素-1 (ET-1)，这是一种成骨细胞生长的刺激物，最近被发现与前列腺癌成骨细胞转移有关。该项目将描述新模型，严格测试ET-1在成骨细胞转移发生中的作用，并确定导致成骨细胞病变的其他因素。以下假设将被验证：1)人类乳腺癌细胞系ZR-75-1通过分泌一种或多种可溶性因子介导成骨细胞转移，这些因子局部刺激成骨细胞增殖和新骨形成。2)肿瘤产生的ET-1是前列腺癌和乳腺癌引起的成骨细胞转移的局部介质。阻断肿瘤产生的ET-1的作用或减少其产生将抑制成骨细胞骨转移的发生和进展。3)肿瘤中肿瘤产生的成骨刺激因子与破骨刺激因子的相对比例将决定骨内肿瘤的表型。4)相对于非骨部位，骨微环境促进肿瘤生成ET-1和其他成骨刺激因子。本文提出以下具体目的：1)探讨ET-1在成骨细胞转移中的作用。我们将在体外和体内研究ET-1对新骨形成的影响，并探讨内皮素受体A（ETA）和受体B （ETB）在介导内皮素对成骨细胞功能和成骨转移的影响中的相对重要性。2)与非骨部位相比，确定骨微环境是否诱导成骨因子的肿瘤生成。分子技术将应用于骨转移模型，以确定哪些成骨刺激因子是由骨微环境中的ZR-75-1细胞产生的，以及ET-1是否是主要因素。目的还将确定肿瘤生成成骨细胞刺激因子是否在骨微环境中相对于非骨部位增强。

Osteoblastic metastases represent a significant clinical problem for patients with cancer. They occur almost always in prostate cancer and frequently in other common malignancies such as breast cancer. The pathophysiology underlying osteoblastic metastases is unknown due to lack of a reproducible animal model of this disease. During this Program Project, we have developed an in vivo model of osteoblastic bone metastases which is reproducible and allows investigation into the pathophysiology of this disease. The human tumor cells which cause osteoblastic metastases in this model produce large amounts of endothelin-1 (ET-1), a stimulator of osteoblast growth, which recently has been linked to prostate cancer osteoblastic metastases. This project will characterize the new model, critically test the role of ET-1 in the genesis of osteoblastic metastases and identify other factors responsible for osteoblastic lesions. The following hypotheses will be tested: 1) The human breast cancer cell line, ZR-75-1, mediates osteoblastic metastases by the secretion of a soluble factor or factors which locally stimulate osteoblast proliferation and new bone formation. 2) Tumor- produced ET-1 is a local mediator of osteoblastic metastases caused by prostate and breast cancer. Blocking the effects of tumor-produced ET-1 or decreasing its production will inhibit the development and progression of osteoblastic bone metastases. 3) The relative ratio of tumor-produced osteoblast-stimulating factors to osteoclast-stimulating factors in a given tumor will determine the tumor phenotype in bone. 4) The bone microenvironment enhances tumor production of ET-1 and other osteoblast-stimulating factors, relative to non bone sites. The following specific aims are proposed: 1) To investigate the role of ET-1 in osteoblastic metastasis. The effect of ET-1 on new bone formation will be studied in vitro and in vivo and the relative importance of endothelin receptor A(ETA) and receptor B (ETB) in mediating the effects of endothelin on osteoblast function and osteoblastic bone metastases will be investigated. 2) To determine if tumor production of osteoblastic factors is induced in the bone microenvironment compared with nonbone sites. Molecular techniques will be applied to the bone metastases model to determine which osteoblast-stimulating factors are produced by the ZR-75-1 cells in the bone microenvironment and if ET-1 is the predominant factor. The aim will also determine if tumor production of osteoblast-stimulating factors are enhanced in the bone microenvironment relative to nonbone sites.