Platelets promote growth of ovarian cancer

描述(申请人提供)：血小板计数升高是许多癌症患者的常见发现，包括卵巢癌患者。卵巢癌和血小板增多症患者的预后比类似癌症分期和血小板计数正常的患者更差。我们已经证明，无论是在体外还是在卵巢癌小鼠模型中，血小板都能促进癌细胞的增殖；减少血小板计数可以减少卵巢癌细胞诱导的小鼠原位肿瘤的大小。为了探讨血小板对癌细胞生长促进作用的机制，我们在体外使用了针对血小板的阻断试剂，发现血小板的激活和转化生长因子β1的释放在血小板对癌细胞的增殖作用中起着重要的作用。在这个项目中，我们将使用卵巢癌小鼠模型和卵巢癌患者的组织样本，在体内研究血小板和癌细胞之间的相互作用。我们的假设是，在血小板和癌细胞之间存在一个反馈回路。癌细胞分泌ADP并激活血小板，而血小板分泌促进癌细胞增殖的转化生长因子？1。在具体的 目的1、利用转基因小鼠或药物试剂，研究阻断血小板表面ADP受体是否会阻断血小板对小鼠原位肿瘤的促生长作用。在特定的目标2中，我们将针对血小板分泌的转化生长因子1、癌细胞上的转化生长因子1受体或转化生长因子1受体信号来评价转化生长因子1在血小板-癌细胞相互作用中的作用。我们将使用血小板特异性的转化生长因子受体缺陷小鼠、抑制物RNA或抗转化生长因子受体信号的药物来进行这些实验。为了使血小板与肿瘤细胞在肿瘤内发生相互作用，血小板必须退出循环，进入肿瘤微环境。我们已经在小鼠的移植肿瘤中显示了血管外的血小板的存在。在具体目标3中，我们将利用免疫荧光和电子显微镜对人和小鼠卵巢癌组织标本中的血小板退出肿瘤微循环的机制进行研究。我们将确定血小板外渗的途径，并评估血小板对中性粒细胞外渗的依赖性。我们这项研究的目的是评估使用抗血小板试剂作为一种有效的抗癌治疗的可能性。

DESCRIPTION (provided by applicant): Elevated platelet counts are a common finding in many cancer patients, including patients with ovarian cancer. Patients with ovarian cancer and thrombocytosis have a worse prognosis compared to patients with similar stages of cancer and normal platelet counts. We have shown that platelets promote proliferation of cancer cells both in vitro and in the murine models of ovarian cancer; and reducing platelet counts decreased the size of orthotopic tumor induced in mice by ovarian cancer cells. To identify the mechanisms of the growth- enhancing effect of platelets on cancer cells, we used blocking reagents against platelets in vitro, and found that platelet activation and release of TGF¿1 are important for the proliferative effect of platelets on cancer cells. In this project, we will study the interaction between platelets and cancer cells in vivo, using both murine models of ovarian cancer and tissue samples obtained from patients with ovarian cancer. Our hypothesis is that there is a feedback loop between platelets and cancer cells. Cancer cells secrete ADP and activate platelets, and platelets secrete TGF¿1 that promotes proliferation in cancer cells. In the specific aim 1, we will investigate whether blocking ADP receptors on platelets would disrupt the growth promoting effect of platelets on orthotopic tumors in mice, using genetically modified mice or pharmacologic reagents. In the specific aim 2, we will target TGF¿1 secretion from platelets, TGF¿1 receptor on cancer cells, or TGF¿1 receptor signaling to evaluate the role of TGF¿1 on the platelet-cancer cell interaction. We will use platelet-specific TGF¿1 deficient mice, inhibitor RNAs, or pharmacologic reagents against TGF¿ receptor signaling to conduct these experiments. For the interaction between platelets and cancer cells to occur inside the tumors, platelets should exit circulation and enter into tumor microenvironment. We have shown the presence of platelets outside of blood vessel inside the implanted tumors in mice. In the specific aim 3, we will study the mechanisms of platelet exit from tumor microcirculation using immunofluorescence and electron microscopy on human and murine ovarian cancer tissue samples. We will identify the route of platelet extravasation, and evaluate the dependency of platelets on neutrophils for extravasation. The goal of our studies in this grant proposal is to evaluate the possibility of using anti-platelet reagents as an effective anticancer therapy.