Contribution of osteocytes to the musculoskeletal effects of Multiple Myeloma

摘要 多发性骨髓瘤(MM)的特征是支持骨髓中恶性浆细胞的生长 通过增加血管生成。尽管在治疗方面取得了重大进展，但由于多发性骨髓瘤频繁发生，多发性骨髓瘤仍无法治愈 治疗难治的多发性骨髓瘤细胞复发。此外，多发性骨髓瘤会导致一种毁灭性的骨病， 骨折风险增加，生活质量下降。这项建议的长期目标是改善临床 通过确定多发性骨髓瘤生长、治疗反应和骨骼的靶向机制来研究多发性骨髓瘤的预后 毁灭。其基本原理来自于前一个资助期的研究表明，骨细胞(OTS) 是支持多发性骨髓瘤的多发性骨髓瘤微环境(TME)中丰富而持久的信号源 生长和促进骨破坏；靶向OT-MM细胞相互作用减少MM生长和 改善骨骼健康。在导致这一应用的研究中，我们发现MM细胞上调了这种表达 成纤维细胞生长因子23在OTS中的表达，发现OTS支持血管生成并促进耐药 以波特佐米为基础的疗法。这项建议的具体目标是评估针对当地的效果 来源于OTS的FGF23可以减少肿瘤生长，修复受损的骨骼，并改善对治疗的反应 中心假设是OT衍生的FGF23促进多发性骨髓瘤的进展、骨破坏和 FGF23共受体α-Klotho介导的局部TME自分泌和旁分泌信号的难治性疾病 (αKL)。这一假设将在三个具体目标中得到检验：(1)确定OT衍生的FGF23的贡献 通过干扰旁分泌和/或自分泌FGF23-αKL信号通路抑制MM肿瘤生长和骨病；(2) 确定OT衍生的血管内皮生长因子A(VEGFA)的影响，VEGFA是 FGF23等骨源性促血管生成因子对MM-TME病理性血管生成的影响； (3)确定FGF23和FGF23靶基因乙酰肝素酶(HPSE)在TME诱导中的作用 MM细胞对基于Bortezomib的治疗的抵抗力。这些目标的实现将结合以下几个方面： 在体外、体内和计算机方法方面的创新，包括细胞特有的遗传工具、药理学 方法：人多发性骨髓瘤异种移植和免疫抑制的多发性骨髓瘤小鼠模型，多发性骨髓瘤原代细胞 患者，scRNAseq分析，以及MM患者遗传/临床数据库的挖掘。

Summary Multiple myeloma (MM) is characterized by the growth of malignant plasma cells in the bone marrow supported by increased angiogenesis. Despite significant advances in treatments, MM remains incurable due to frequent relapses originating from MM cells refractory to therapy. Further, MM induces a devastating bone disease, increasing fracture risk and decreasing quality of life. The long-term goal of this proposal is to improve clinical outcomes in MM by defining targetable mechanisms underlying MM growth, responses to therapy, and bone destruction. The rationale stems from work from the previous funding period demonstrating that osteocytes (Ots) are an abundant and long-lived source of signals in the MM tumor microenvironment (TME) that supports MM growth and promote bone destruction; and that targeting Ot-MM cell interactions decreases MM growth and improves bone health. In studies leading to this application, we found that MM cells upregulate the expression of Fibroblast growth factor (FGF) 23 in Ots and discovered that Ots support angiogenesis and promote resistance to Bortezomib-based therapies. The specific goal of this proposal is to evaluate the efficacy of targeting local FGF23 derived from Ots to decrease tumor growth, repair damaged bone, and improve responses to therapy in MM. The central hypothesis is that Ot-derived FGF23 promotes MM progression, bone destruction, and refractory disease via local TME autocrine and paracrine signals mediated by the FGF23 co-receptor α-Klotho (αKL). This hypothesis will be tested in three specific aims: (1) Determine the contribution of Ot-derived FGF23 to MM tumor growth and bone disease by interfering with paracrine and/or autocrine FGF23-αKL signaling; (2) Determine the impact of Ot-derived Vascular endothelial growth factor A (VEGFA), a downstream target of FGF23, and other osteocyte-derived pro-angeogenic factors on the pathological angiogenesis in the MM-TME; and (3) Determine the role of FGF23 and the FGF23 target gene Heparanase (HPSE) on TME-induced resistance to Bortezomib-based therapies in MM cells. These aims will be pursued using a combination of innovative in vitro, in vivo, and in silico approaches, including cell-specific genetic tools, pharmacological approaches, human MM xenograft and immunocompentent mouse models of MM, primary cells from MM patients, scRNAseq analysis, and mining of MM patient genetic/clinical databases.