Evaluating the role of Thrombospondin-1-CD47 mediated nitric oxide signaling in t

描述（由申请人提供）：癌症骨转移常见于许多晚期癌症，包括乳腺癌、前列腺癌和肺癌，引起剧烈疼痛、危及生命的高钙血症和神经压迫综合征。在稳态条件下，骨吸收破骨细胞受到严格调控，以实现健康的骨转换。然而，在骨转移中，肿瘤细胞分泌促进破骨细胞活性的可溶性因子，导致刺激局部肿瘤生长的生长因子的释放。这导致破骨细胞活化和肿瘤细胞增殖的“恶性循环”，引起肿瘤负荷增加和骨病变。血小板反应蛋白-1（TSP 1）是一种分泌性蛋白质，已知其主要作用是抑制血管生成。有证据表明，TSP 1通过其两个配体CD 36和CD 47调节一奥克西（NO）信号传导。NO的紧张水平对细胞存活至关重要。在病理条件下，NO信号通过iNOS上调。iNOS的具体调控途径尚未确定。TSP 1对NO的调节代表了用于治疗原发性和转移性癌症的有希望的新治疗靶点。我们建议评估TSP 1介导的NO信号在骨重建，无论是在健康和骨转移状态。我们发现，TSP 1缺陷的巨噬细胞表现出升高的iNOS转录水平和增加的NO活性。TSP 1耗竭的破骨细胞具有与失调的NO信号传导一致的分化缺陷。TSP 1-/-小鼠的骨体积显著增加，骨转换率降低，这是一种在给予泛NOS抑制剂后得以挽救的缺陷。我们已经发表了CD 47-/-小鼠也具有增加的骨量，伴有相关的破骨细胞缺陷。重要的是，我们发现，与它们在抗血管生成中的作用相反，骨转移细胞系C42 b和B16 F10具有增加的TSP 1表达。我们推测TSP 1与CD 47的连接通过抑制破骨细胞中的iNOS来调节NO信号传导，并且肿瘤衍生的TSP 1有助于增加骨转移中的肿瘤相关性骨质溶解。将使用小鼠模型和模拟物和抑制剂来评估健康和转移性骨重塑中的TSP 1/CD 47/NO信号传导轴以调节TSP 1/CD 47相互作用和NOS活性。 重要性：本研究训练计划中提出的研究将进一步了解骨重建和阐明TSP 1调节NO信号的作用。重要的是，我们将在病理条件下表征骨中的TSP 1/CD 47/NO信号传导，并对调节该信号传导途径的癌症治疗剂的脱靶效应提供有价值的见解。

DESCRIPTION (provided by applicant): Cancer metastasis to bone is common to many advanced cancers including breast, prostate, and lung cancers, causing severe pain, life-threatening hypercalcemia, and nerve compression syndromes. Under homeostatic conditions, bone-resorbing osteoclasts are tightly regulated for healthy bone turnover. In skeletal metastasis, however, tumor cells secrete soluble factors that promote osteoclast activity, resulting in the release of growth factors that stimulate local tumor growth. This leads to a "vicious cycle" of osteoclast activation and tumor cell proliferation, causing increased tumor burden and bone lesions. Thrombospondin-1 (TSP1) is a secreted protein that is known primarily for its role in inhibiting angiogenesis. There is evidence that TSP1 regulates nitric oxie (NO) signaling via two of its ligands, CD36 and CD47. Tonic levels of NO are critical for cell survival. Under pathological conditions, NO signaling is upregulated through iNOS. Specific regulatory pathways of iNOS have not been identified. TSP1 regulation of NO represents a promising novel therapeutic target for the treatment of primary and metastatic cancer. We propose to evaluate TSP1-mediated NO signaling in bone remodeling, both in healthy and bone metastatic states. We found that TSP1 deficient macrophages showed elevated iNOS transcript levels and increased NO activity. TSP1 depleted osteoclasts had differentiation defects consistent with misregulated NO signaling. TSP1-/- mice had significantly increased bone volume and reduced bone turnover, a defect rescued upon administration of a pan-NOS inhibitor. We have published that CD47-/- mice also have increased bone mass with associated osteoclast defects. Importantly, we found that, contrary to their roles in anti-angiogenesis, bone metastatic cell lines C42b and B16F10 have increased TSP1 expression. We hypothesize that TSP1 ligation of CD47 regulates NO signaling via inhibition of iNOS in osteoclasts and that tumor-derived TSP1 contributes to increased tumor-associated osteolysis in bone metastasis. The TSP1/CD47/NO signaling axis in healthy and metastatic bone remodeling will be evaluated using mouse models and mimetics and inhibitors to modulate TSP1/CD47 interaction and NOS activity. Significance: The research proposed in this research training plan will further the understanding of bone remodeling and elucidate the role of TSP1 regulation of NO signaling. Importantly, we will characterize the TSP1/CD47/NO signaling in bone under pathological conditions and provide valuable insight into the off-target effects of cancer therapeutics in trialto modulate this signaling pathway.