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

描述(申请人提供)：癌症转移到骨是常见的许多晚期癌症，包括乳腺癌、前列腺癌和肺癌，导致剧烈疼痛、危及生命的高钙血症和神经压迫综合征。在动态平衡条件下，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，导致释放刺激局部肿瘤生长的生长因子。这会导致破骨细胞激活和肿瘤细胞增殖的“恶性循环”，导致肿瘤负担增加和骨骼损伤。凝血酶敏感蛋白-1(TSP1)是一种分泌型蛋白，主要以抑制血管生成而闻名。有证据表明，TSP1通过其两个配体CD36和CD47调节一氧化氮(NO)信号。NO的紧张性水平对细胞生存至关重要。在病理条件下，NO信号通过iNOS上调。诱导型一氧化氮合酶的具体调控途径尚未确定。TSP1对NO的调节是治疗原发癌和转移癌的一个很有前途的新靶点。我们建议评估TSP1介导的NO信号在骨重建中的作用，无论是在健康状态还是骨转移状态。我们发现，TSP1缺乏的巨噬细胞表现出iNOS转录水平升高和NO活性增加。TSP1缺失的破骨细胞存在与NO信号失控一致的分化缺陷。TSP1-/-小鼠显著增加了骨体积，降低了骨转换，这一缺陷在给予PAN-NOS抑制剂后得到修复。我们已经发表，CD47-/-小鼠也有骨量增加并伴随破骨细胞缺陷。重要的是，我们发现，骨转移细胞系C42b和B16F10在抗血管生成方面的作用相反，它们增加了TSP1的表达。我们假设TSP1连接CD47通过抑制破骨细胞中的iNOS来调节NO信号，并且肿瘤来源的TSP1有助于增加骨转移中肿瘤相关的骨溶解。TSP1/CD47/NO信号轴在健康和转移性骨重塑中的作用将通过小鼠模型、模拟物和抑制剂来调节TSP1/CD47的相互作用和NOS活性。 意义：本研究培训计划中提出的研究将加深对骨重建的理解，并阐明TSP1对NO信号的调节作用。重要的是，我们将描述病理条件下骨骼中TSP1/CD47/NO信号的特征，并在实验中为癌症治疗的非靶点效应提供有价值的见解，以调节这一信号通路。

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.