ROLE OF BETA 3 INTEGRIN IN SKELETAL METASTASIS

描述(由申请人提供)：仅在美国，骨转移每年影响35万人。我们发现，整合素3整体敲除小鼠可以防止肿瘤相关的骨丢失和骨转移，这一发现与肿瘤细胞在分别表达AIIB？3和av？3的血小板和破骨细胞中上调整合素途径的模型一致。血小板和破骨细胞都是宿主细胞，对骨环境中肿瘤细胞的生长和存活至关重要。靶向骨转移的一个问题是，所有组织中整合素亚单位的缺失都可以增强与肿瘤相关的血管生成，这很可能是由于整合素存在于肿瘤环境中的内皮细胞和激活的巨噬细胞上。因此，对av？3的药理抑制可能具有不良的促癌作用，而对aib？3的抑制可能会导致出血。为了避免这些种系基因敲除的问题，我们用组织靶向的Cre转基因小鼠产生了带有loxP位点的整合素基因的小鼠，并在血小板和髓系(巨噬细胞和破骨细胞)谱系中删除了该基因。作为调节血小板和破骨细胞中3整合素功能的替代方法，我们将研究3整合素激活受体P2Y12和3整合素刺激蛋白CD47在血小板和破骨细胞功能以及骨转移中的作用。为了避免全球整合素抑制的负面影响，并寻找新的治疗靶点，我们将研究这些可能赋予细胞类型特异性和减少副作用的整合素刺激途径。我们的中心假设是，阻断血小板和髓样细胞中的整合素刺激通路将扰乱骨中肿瘤的生长和肿瘤驱动的骨溶解。因此，我们的具体目标是：1.明确血小板和髓样细胞上的整合素在骨转移和骨微环境中肿瘤生长过程中的作用。2.探讨整合素β3上游激活剂P2Y12在骨转移和肿瘤骨溶解过程中对血小板和髓系细胞的作用。3.评价整合素刺激蛋白CD47作为治疗靶点消除骨转移和肿瘤骨溶解的作用。在相对健康的癌症患者中使用的干预策略必须具有临床上最小的副作用。因此，该项目的总体目标是设计新的新辅助治疗策略，通过靶向激活血小板和破骨细胞的整合素途径来预防骨转移。这些研究将在3整合素途径中确定最佳的药物靶点，副作用最小，克服普遍的3整合素抑制问题，同时预防或减少骨转移。

DESCRIPTION (provided by applicant): Bone metastases affect 350,000 people per year in the United States alone. We found that the integrin ¿3 global knockout mouse was protected from tumor-associated bone loss and bone metastasis, a finding consistent with the model that tumor cells highjack the ¿3 integrin pathways in platelets and osteoclasts, which express express aIIb¿3 and av¿3, respectively. Both platelets and osteoclasts are host cells that are critical for the growth and survival of tumor cells in the bone environment. A problem with targeting ¿3 for bone metastasis is that deletion of the ¿3 integrin subunit in all tissues can enhance tumor-associated angiogenesis, most likely as a result of ¿3 integrin present on the endothelium and on activated macrophages in the tumor environment. Therefore, pharmacologic inhibition of av¿3 may have adverse procancer effects and inhibition of aIIb¿3 causes bleeding. To obviate these issues of the germline ¿3 knockout we generated mice with a ¿3 integrin gene flanked by loxP sites and deleted the gene in platelets and myeloid (macrophage and osteoclast) lineages using tissue-targeted Cre transgenic mice. As alternative approaches to modulating ¿3 integrin function in platelets and osteoclasts, we will investigate the roles of the ¿3 integrin activating receptor, P2Y12, and a ¿3-integrin stimulating protein, CD47, on platelet and osteoclast function and during bone metastasis. In order to avoid the negative effects of global ¿3 integrin inhibition and to identify novel therapeutic targets, we will study these ¿3 integrin stimulatory pathways that may confer cell type specificity and reduce side effects. Our central hypothesis is that blockade of ¿3 integrin stimulatory pathways in platelets and myeloid cells will disrupt tumor growth in bone and tumor-driven osteolysis. Thus, our Specific Aims are to: 1. Define the role of ¿3 integrins on platelets and myeloid cells during metastasis to bone and tumor growth in the bone micro-environment. 2. Evaluate the role of the upstream activator of ¿3 integrin P2Y12 on platelets and myeloid cells during skeletal metastasis and tumor osteolysis. 3. Evaluate the role of CD47, a ¿3 integrin stimulatory protein, as a therapeutic target to abrogate bone metastasis and tumor osteolysis. Intervention strategies to be used in relatively healthy patients with cancer must have side effects that are clinically minimal. Thus the over-arching goal of this project is to design novel neoadjuvant treatment strategies to prevent bone metastasis through targeting ¿3 integrin pathways active on platelets and osteoclasts. These studies will lead to identification of optimal drug targets within the ¿3 integrin pathway with minimal side effects that overcome the problem of generalized ¿3 integrin inhibition, while preventing or decreasing bone metastasis.