Attenuating bone metastases by inhibiting Ror2 signaling and osteoblast senescence

在晚期乳腺癌患者中，骨转移是一种常见的、毁灭性的晚期事件。在骨微环境中，乳腺癌细胞通过刺激破骨细胞介导的骨吸收和抑制成骨细胞介导的骨形成来干扰生理性骨重塑，导致溶骨病。虽然抗骨吸收治疗有效减轻骨破坏，但由于疾病无法治愈，溶骨性病变仍然存在。我们小组和其他人最近的研究表明，以治疗方式影响骨重塑可以减少乳腺癌在骨中的归巢和骨微环境中的转移性生长。此外，增强骨形成的药物可以防止乳腺癌引起的骨破坏，这是一个意想不到的发现，具有很大的翻译价值。为了在这个优先项目的第二个资助期内继续这项新颖和创新的研究，我们的目标是确定前所未有的骨合成代谢线索，以减轻骨转移负担，从而减少病理性骨破坏。在这种情况下，我们做了有趣的观察，非规范的Wnt信号，抑制骨形成。使用一套全面的体内和体外方法，我们发现酪氨酸激酶样孤儿受体2 （Ror2）受体减少成骨细胞分化和骨形成。从机制上讲，成骨细胞中ror2缺乏会损害白细胞介素6 （IL-6）信号传导，IL-6是成骨细胞分化的负调节因子，是骨转移中介导病理性细胞串扰的关键细胞因子，也是衰老相关分泌表型（SASP）的重要组成部分。有趣的是，当乳腺癌刺激成骨细胞采用SASP时，缺乏ror2的成骨细胞对产生氧化应激诱导的SASP具有抗性。这些发现让我们假设，抑制Ror2信号并因此导致成骨细胞衰老可能会减轻乳腺癌引起的骨破坏。为了解决这一假设，我们提出1)确定Ror2在成骨细胞中在乳腺癌骨转移中的作用，2)研究乳腺癌细胞诱导的Ror2介导的成骨细胞衰老，以及3)减少Ror2信号和衰老以减轻转移性骨疾病。在实验方面，我们将采用新的基于寡核苷酸的基因沉默方法，结合最先进的小鼠遗传学、转移模型和最新的骨成像和质量检测技术。机制见解将通过细胞和分子生物学方法阐明，并通过在我们的研究中实施患者样本来确保研究结果的临床相关性。该项目是原创的，有望扩大对骨病理中非规范Wnt信号的认识，并可能为开发潜在的未来干预措施来治疗乳腺癌诱导的骨病患者揭示新的靶点。

Bone metastases are a frequent and devastating late-stage event in patients with advanced breast cancer. In the bone microenvironment, breast cancer cells disturb physiological bone remodeling by stimulating osteoclast-mediated bone resorption and suppressing osteoblast-mediated bone formation, leading to an osteolytic disease. Although anti-resorptive treatments are efficient to attenuate bone destruction, osteolytic lesions remain with the disease being incurable. Recent studies by our group and others demonstrate that affecting bone remodeling in a therapeutic manner reduces breast cancer homing to bone and metastatic growth in the bone microenvironment. Furthermore, pharmacological augmentation of bone formation protects from breast cancer-induced bone destruction, an unsuspected finding of great translational value. To continue this novel and innovative line of research during the second funding period of this priority program, we aim to identify unprecedented bone anabolic cues to alleviate bone metastatic burden, thereby reducing pathological bone destruction. In this context, we made the interesting observation that non-canonical Wnt signaling, inhibits bone formation. Using a comprehensive set of in vivo and in vitro approaches we uncovered that receptor of tyrosine kinase-like orphan receptor 2 (Ror2) diminishes osteoblast differentiation and bone formation. Mechanistically, Ror2-deficiency in osteoblasts impairs interleukin 6 (IL-6) signaling, which is a negative regulator of osteoblast differentiation, a key cytokine mediating the pathological cellular crosstalk in bone metastases and an important component of the senescence-associated secretory phenotype (SASP). Interestingly, while breast cancer stimulates osteoblasts to adopt a SASP, Ror2-deficient osteoblasts are resistant to develop an oxidative stress-induced SASP. These findings let us to hypothesize that inhibition of Ror2 signaling and consequently osteoblast senescence might attenuate breast cancer-induced bone destruction. To address this hypothesis, we propose to i) determine the role of Ror2 in osteoblasts in breast cancer bone metastases, ii) investigate breast cancer cell-induced Ror2-mediated osteoblast senescence, and iii) reduce Ror2 signaling and senescence to alleviate metastatic bone disease. Experimentally, we will use novel oligonucleotide-based gene silencing approaches combined with state-of-the-art mouse genetics, metastases models and the latest technology of bone imaging and quality testing. Mechanistic insights will be elucidated using cell- and molecular biology approaches and clinical relevance of the findings will be ensured by implementing patient samples in our investigations. This project is original and expected to expand the knowledge on non-canonical Wnt signaling in bone pathology and may reveal novel targets for the development of potential future interventions to treat patients with breast cancer-induced bone disease.