Mechanisms of thymide phosphorylase angiogenesis

描述（由申请人提供）：我们的研究重点是血管生成因子PD-ECGF（血小板来源的内皮细胞生长因子），这是肿瘤上皮细胞和基质细胞产生的几种多肽因子之一，可促进肿瘤血管生成活性。人PD-ECGF cDNA序列与人胸腺嘧啶磷酸化酶（TP）相同，TP是一种催化胸腺嘧啶转化为胸腺嘧啶和2-脱氧核糖-1-磷酸（dR-1-P）的酶。当来自转染TP的细胞时，肿瘤异种移植物生长更快，血管化程度更高，并且有广泛的临床数据表明，人类实体瘤中TP表达升高与微血管密度增加、肿瘤侵袭性增加和患者预后差有关。与VEGF和其他细胞因子不同，TP不是直接血管生成，而是由于其催化活性而起作用。在之前的资助期内，我们明确了TP在肿瘤和单核细胞中的转录调节机制，获得了TP的血管生成作用是由2-脱氧核糖（2dR）介导的确凿证据，该2-脱氧核糖是由dR-1-P在细胞内形成，然后从表达TP的细胞中释放出来，表明2dR是人内皮细胞（HUVEC）的趋化因子，首次提供了2dR对HUVEC中整合素相关信号通路影响的数据。鉴定并合成了TP活性和TP诱导的HUVEC迁移抑制剂。我们建议在下一个资助期扩展这些研究，具体到：1)确定2dR的作用是否通过其激活VEGF受体-2和/或VEGF受体-3介导；2)验证微血管内皮细胞（EC），特别是淋巴内皮细胞对2dR的高度反应的假设；3)确定2dR是否作用于内/外和/或外/内整合素信号通路；4)确定2dR是否保护EC免于凋亡；5)确定EC中是否存在特异性的2dR受体；6)利用肿瘤中含有人EC的人肺癌异源移植小鼠模型，评估靶向TP的药物单独使用和与VEGF抑制剂联合使用的体内抗血管生成和抗肿瘤活性。本项目的长期目标是明确TP抗血管生成作用的分子机制，并确定靶向TP介导的血管生成途径是否是治疗癌症的可行方法。这一信息可能会导致新的癌症药物治疗。

DESCRIPTION (provided by applicant): Our studies have focused on the angiogenic factor PD-ECGF (platelet-derived endothelial cell growth factor), one of several polypeptide factors that are produced by tumor epithelial and stromal cells and that promote tumor angiogenic activity. Sequencing of the of human PD-ECGF cDNA revealed it to be identical to human thymidine phosphorylase (TP), an enzyme which catalyzes the conversion of thymidine to thymine and 2-deoxyribose-1-phosphate (dR-1-P). Tumor xenografts grew more rapidly and were more highly vascularized when derived from cells that were transfected with TP, and there are extensive clinical data correlating elevated TP expression in human solid tumors with increased microvessel density, increased tumor invasiveness, and poor patient prognosis. Unlike VEGF and other cytokines, TP is not directly angiogenic, rather its effects are due to its catalytic activity. In the previous grant period, we defined the mechanisms regulating TP transcription in tumors and in monocytes, obtained definitive evidence that the angiogenic actions of TP are mediated by 2-deoxyribose (2dR) which is formed intracellularty from dR-1-P and then released from cells expressing TP, showed that 2dR is a chemotactic factor for human endothelial cells (HUVEC), provided the first data illustrating an effect of 2dR on integrin-related signaling pathways in HUVEC, and identified and synthesized an inhibitor of TP activity and of TP-induced HUVEC migration. We propose to extend these studies in the next grant period, specifically to: 1) determine if 2dR's actions are mediated by its activation of the VEGF receptor-2 and/or VEGF receptor-3; 2) test the hypothesis that microvascular endothelial cells (EC), and lymphatic EC in particular, will be highly responsive to 2dR; 3) determine if 2dR acts on inside/out and/or outside/in integrin signaling pathways; 4) determine if 2dR protects EC from apoptosis; 5) determine if there is a specific 2dR receptor in EC, and 6) use a human lung cancer heterotransplant mouse model in which tumors contain human EC to evaluate the in vivo anti- angiogenic and anti-tumor activities of agents targeting TP, alone and in combination with a VEGF inhibitor. The long term objectives of this project are to define the molecular mechanisms regulating the anti- angiogenic actions of TP, and to determine whether targeting TP-mediated angiogenic pathways is a viable therapeutic approach to treat cancer. This information could lead to new drug treatments for cancer.