The role of extracellular matrix quality in the prediction of metastasis-induced skeletal fragility and response to immunotherapy

转移性骨病(MBD)是晚期实体恶性肿瘤患者常见且致命的并发症。 免疫检查点抑制物(ICIS)如程序性细胞死亡蛋白-1(PD-1)已经使癌症发生了革命性的变化 过去十年的治疗；然而，ICIS对MBD的积极影响因一些免疫- 相关的骨骼不良事件(IrSAE)，包括形成新的骨损伤，增加骨吸收， 和脊椎压缩骨折。骨骼、免疫和免疫之间的动态和多方向相互作用 肿瘤细胞(OIO)可以改变骨细胞外基质(ECM)的质量，影响骨 机械完整性，并影响治疗反应，但OIO目前在MBD中检查不足。受体 核因子kappa-β激活物(RANK)及其配体(RANKL)可被认为是 然而，它们在综合信息系统环境中的作用仍未得到探索。转移性前列腺癌(PCA)细胞，成骨 成骨细胞和活化的T细胞通过产生与RANK结合的RANKL独立地触发骨溶解 关于骨吸收破骨细胞(OCS)。我们假设RANK/RANKL和PD-1信号的调制在 OIO可能在抑制破骨细胞活性的同时支持T细胞的激活，从而降低恶化的风险 骨ECM的质量和机械完整性，并产生协同抗癌功效。因此，我们将(1) OIO相关细胞外基质生物标记物在人转移性骨组织中的表达及其预后 评价RANKL和PD-1联合阻断对骨细胞外基质的影响 PCa骨转移(BM)小鼠模型的质量、机械完整性和抗癌效果。身体 腰椎中含有溶骨性、骨硬化性和混合性的人松质骨核 转移性病变将被压缩至失效，以测量骨力学特性。基于 对于损伤的破坏载荷的分布，将选择适当的阈值来创建二进制测量 骨骼脆弱的症状。将提取与OIO相关的骨ECM生物标记物及其翻译后修饰 从每一处损伤中。使用混合效应多项Logistic回归模型，最小一组生物标志物 预测将获得骨脆性。我们将在不同的模型中进一步验证这些基于OIO的生物标记物 溶骨性和骨硬化性PCa BM，并评价抗RANKL在减轻骨脆性的效果 抗PD1治疗的设置。这项研究的结果将扩大目前对 转移瘤及其治疗对骨基质质量和力学完整性的影响。与OIO相关的ECM标记 调节病变异质性和预测脆性将提供新的与功能相关的分子信息 这可以推动翻译工作。此外，免疫介导的骨重建和骨修复的机制 联合阻断RANKL和PD-1可缓解骨脆性，有助于风险适应性选择 正在进行的和后续的治疗。

Metastatic bone disease (MBD) is a frequent and fatal complication in patients with advanced solid malignancies. Immune checkpoint inhibitors (ICIs) such as programmed cell death protein-1 (PD-1) have revolutionized cancer therapy over the past decade; however, the positive impact of ICIs in MBD is attenuated due to some immune- related skeletal adverse events (irSAEs), including the formation of new bone lesions, increased bone resorption, and vertebral compression fractures. The dynamic and multidirectional interactions between bone, immune, and tumor cells (osteoimmuno-oncology, OIO) can alter bone extracellular matrix (ECM) quality, influence bone mechanical integrity, and affect response to therapy, but OIO is currently underexamined in MBD. Receptor activator of nuclear factor kappa-β (RANK) and its ligand (RANKL) may be considered as key orchestrators of OIO yet their role in the setting of ICIs remain unexplored. Metastatic prostate cancer (PCa) cells, bone-forming osteoblasts, and activated T-cells trigger osteolysis independently by producing RANKL which binds to RANK on bone-resorbing osteoclasts (OCs). We hypothesize that modulation of RANK/RANKL and PD-1 signaling in OIO may support T-cell activation while inhibiting osteoclastic activity, thereby decreasing risk for worsening bone ECM quality and mechanical integrity and produce synergistic anticancer efficacy. Thus, we will (1) Characterize the expression of OIO-related ECM biomarkers in metastatic human bone and develop a prognostic signature of bone fragility; and (2) Evaluate the effects of combined RANKL and PD-1 blockade on bone ECM quality, mechanical integrity, and anti-cancer efficacy in mouse models of PCa bone metastases (BM). Cadaveric human trabecular bone cores from the lumbar vertebrae containing osteolytic, osteosclerotic, and mixed metastatic lesions will be compressed to failure for measurements of bone mechanical properties. Based on the distribution of the failure loads of the lesions, an appropriate threshold will be selected to create a binary measure of bone fragility. OIO-related bone ECM biomarkers and their posttranslational modifications will be extracted from each lesion. Using mixed effects multinomial logistic regression models a minimum set of biomarkers that predict bone fragility will be obtained. We will further validate these OIO-based biomarkers in distinct models of osteolytic and osteosclerotic PCa BM and assess the efficacy of anti-RANKL in mitigating bone fragility in the setting of anti-PD1 therapy. The results of this study will extend the current understanding of the effects of metastases and its treatment on bone matrix quality and mechanical integrity. OIO-related ECM markers that regulate lesion heterogeneity and predict fragility will provide new molecular information of functional relevance that can drive translational efforts. Moreover, the mechanisms of immune-mediated bone remodeling and mitigation of bone fragility by combined blockade of RANKL and PD-1 can aid in risk-adapted selection for ongoing and subsequent therapies.