Role of Dickkopf-1 as a mediator of inflammation in osteotropic cancers

Dickkopf-1 （DKK-1）是wnt信号的抑制因子，是成骨细胞分化的关键调控因子。在嗜骨性恶性肿瘤中，如乳腺癌和前列腺癌，DKK-1水平升高，与骨转移的发生有关，在某些情况下，与预后不良有关。近年来，DKK-1作为肿瘤生物学中的一个重要因子受到越来越多的关注，除了其对成骨细胞的作用外，它还可能介导wnt不依赖的机制并与不同的信号通路相互作用。在µBone的第一个资助期，我们观察到DKK-1的基因敲低而不是细胞外中和导致促炎细胞因子如IL-1β、CXCL8和CXCL1的抑制，以及抑制成骨性前列腺癌细胞系PC3的迁移。一致地，蛋白质的亚细胞分离显示DKK-1主要存在于细胞核和相关膜中。考虑到炎症在骨转移中的重要作用，这些数据指向了DKK-1和炎症之间的新联系，作为一个新的潜在治疗靶点。我们在第二个µBone资助期的项目旨在确定DKK-1在早期和晚期骨转移的促炎反应中的作用，以及它是否以及如何维持肿瘤微环境中局部细胞类型（如肿瘤细胞、成骨细胞和骨髓细胞）之间的对话。为了解决这个问题，我们将应用一组综合方法，包括遗传和药物调节DKK-1和细胞系和原代细胞中的炎症介质，以评估它们的双向相互作用。此外，我们将在不同的处理和细胞类型的组合上进行直接和间接的共培养和迁移试验。斑马鱼和小鼠模型，包括在成骨细胞和髓细胞中具有全局和细胞类型特异性敲除DKK-1的转基因小鼠系，代表了我们研究的另一个中心方面。在这里，大量的读数包括实时成像，FACS， ELISA和组织学将揭示局部和系统机制的不同方面。最后，研究人员将使用来自嗜骨性恶性肿瘤患者的临床样本来评估DKK-1的局部和全身表达，并研究其潜在的相关性。这些综合分析将潜在地揭示免疫系统和DKK-1之间新的调节相互作用，因此将有助于详细了解DKK-1是否适合作为癌症骨转移的治疗靶点。

Dickkopf-1 (DKK-1) is an inhibitor of Wnt-signaling and best known as a key regulator of osteoblastic differentiation. In osteotropic malignancies, such as breast and prostate cancer, DKK-1 levels are increased, associated with the occurrence of bone metastases and, in some cases, linked to a poor prognosis. In recent years, DKK-1 has attained increasing attention as an important factor in tumor biology, which, in addition to its well-established effects on osteoblasts, may also mediate Wnt-independent mechanisms and interact with distinct signaling pathways.In the first funding period of µBone, we observed that a genetic knockdown of DKK-1 but not extracellular neutralization leads to a suppression of proinflammatory cytokines such as IL-1β, CXCL8, and CXCL1 as well as inhibited migration of the osteotropic prostate cancer cell line PC3. Consistently, subcellular fractioning of proteins revealed a predominant presence of DKK-1 in the nucleus and associated membranes. Given the key importance of inflammation in bone metastases, these data point towards the identification of a novel link between DKK-1 and inflammation as a new potential therapeutic target. Our project for the second µBone funding period aims at identifying the contribution of DKK-1 as a mediator of a proinflammatory response to early and late stages of bone metastases and if and how it sustains the dialogue between local cell types within the tumor microenvironment such as tumor cells, osteoblasts, and myeloid cells required for metastatic development. To address this question we will apply a comprehensive panel of methods comprising genetic and pharmaceutical modulation of DKK-1 and inflammatory mediators in cell lines and primary cells to assess their bidirectional interaction. In addition, we will perform direct and indirect co-culture and migration assays upon varying treatments and combinations of the cell types. Zebrafish and mouse models including transgenic mouse lines with global and cell type-specific DKK-1 knockouts in osteoblasts and myeloid cells represent an additional central aspect of our investigations. Here, an extensive number of readouts including live imaging, FACS, ELISA, and histology will uncover different aspects of local and systemic mechanisms. Finally, clinical samples from patients with osteotropic malignancies will be used to assess local and systemic expression of DKK-1 and to investigate potential correlations. These comprehensive analyzes will potentially reveal novel regulatory interactions between the immune system and DKK-1 and will therefore contribute to a detailed understanding if DKK-1 is suitable a therapeutic target in cancer metastasis to bone.