Dickkopf-1 as a critical determinant of malignant bone disease

转移性骨病仍然是许多恶性肿瘤（包括乳腺癌、前列腺癌和皮肤癌）的临床相关并发症。除了增强的成骨细胞骨吸收，受损的成骨细胞功能也可能有助于转移性病变。Dickkopf-1（DKK-1）是一种Wnt抑制剂，通过抑制成骨细胞功能与多发性骨髓瘤中骨病变的发展相关。我们先前已经表明，DKK-1在乳腺癌组织中高度表达，并在受影响患者的血清中升高。作为医生-科学家（Gerok）项目的一部分，我们确定了前列腺癌组织中DKK-1表达的升高，以及诊断时DKK-1水平低的前列腺癌患者的生存率显著提高。在体外，具有高水平DKK-1的乳腺癌和前列腺癌细胞系抑制成骨细胞分化，这可以通过阻断DKK-1来逆转。基于这些结果，我们假设DKK-1是骨转移形成的关键决定因素，是乳腺癌生存的合适预后标志物，也是骨恶性肿瘤的潜在治疗靶点。我们在第二个资助期的具体目标是：（I）使用预后乳腺癌组织阵列评估DKK-1的预后价值（II）分析DKK-1在癌症和骨细胞相互作用中的作用通过使用RNAi和过表达构建体调节DKK-1在体外培养MSC，破骨细胞;（III）确定DKK-1在乳腺癌鼠模型中的治疗潜力通过在乳腺癌和黑素瘤细胞系中稳定过表达和抑制DKK-1，以及通过使用单克隆抗体抑制DKK-1，来治疗（皮下、胫骨内和心内肿瘤模型）;（IV）使用在骨骼发育后具有条件性DKK-1整体缺失或在成骨细胞中特异性缺失DKK-1的小鼠，阐明非肿瘤来源的DKK-1在癌症进展中的作用。将使用显微CT、发光成像和组织学确定肿瘤生长和骨破坏。此外，DKK-1抑制的骨合成代谢作用将使用骨组织形态计量学、血清骨重建标志物和成像进行全面研究。这些研究将有助于阐明DKK-1信号通路在骨转移中的分子机制和治疗潜力。

Metastatic bone disease remains a clinically relevant complication of many malignancies including those of breast, prostate and skin. In addition to enhanced osteoclastic bone resorption, impaired osteoblast function may also contribute to metastatic lesions. Dickkopf-1 (DKK-1) is a Wnt inhibitor and associated with the development of bone lesions in multiple myeloma by inhibiting osteoblast function. We have previously shown that DKK-1 is highly expressed in breast cancer tissue and elevated in the serum of affected patients. As part of a physician-scientist (Gerok) project, we identified elevated DKK-1 expression in prostate cancer tissue and significantly better survival in patients with prostate cancer, who had low levels of DKK-1 at the time of diagnosis. In vitro, breast and prostate cancer cell lines with high levels of DKK-1 inhibit osteoblast differentiation, which can be reversed by blocking DKK-1. Based on these results, we hypothesize that DKK-1 is a critical determinant of the formation of skeletal metastases and is a suitable prognostic marker for breast cancer survival and a potential therapeutic target in osteotropic malignancies. Our specific aims for the second funding period are to: (I) assess the prognostic value of DKK-1 using a prognostic breast cancer tissue array (from the NCI) and serum analyses of a well-characterized cohort of breast cancer patients; (II) analyze the role of DKK-1 in the mutual interaction of cancer and bone cells (MSC, osteoclasts) in vitro by modulating DKK-1 using RNAi and overexpression constructs; (III) determine the therapeutic potential of DKK-1 in murine models of breast cancer (subcutaneous, intratibial and intracardiac tumor models) by stably over-expressing and inhibiting DKK-1 in breast cancer and melanoma cell lines, and by inhibiting DKK-1 using a monoclonal antibody; (IV) clarify the role of non-tumor derived DKK-1 in cancer progression using mice with a conditional global deletion of DKK-1 after skeletal development or a deletion of DKK-1 specifically in osteoblasts. Tumor growth and bone destruction will be determined using micro-CT, luminescence imaging, and histology. Furthermore the bone anabolic effects of DKK-1 inhibition will be comprehensively studied using bone histomorphometry, serum bone remodeling markers and imaging. These studies will help to clarify the molecular mechanisms and therapeutic potential of modifying DKK-1 signaling in bone metastasis.