Interactions of the angiopoietin and PD-ECGF pathways in tumor angiogenesis

描述（由申请人提供）：靶向肿瘤血管生成的药物可以提高晚期恶性肿瘤患者的应答率和生存率，尽管应答的患者比例通常很低。最近的临床试验表明，大多数晚期胰腺外分泌癌对血管生成抑制剂无效，这可能是由于这些肿瘤的低血管性和其他生物学特征。与更常见的外分泌胰腺癌相比，起源于胰腺神经内分泌细胞的恶性肿瘤，称为胰腺神经内分泌肿瘤（PNET），缺乏促结缔组织增生的纤维炎性囊，且血管化程度高。虽然转移性PNET不能通过手术或化疗治愈，但在小鼠模型和随机III期临床试验中可以看到PNET对抗血管生成药物的客观反应。由于胰腺癌通常表达多种血管生成因子，本研究的目的是确定针对不同血管生成因子的抑制剂组合在PNET小鼠模型中是否有效。待研究的抑制剂包括我们合成的一种新型的、高度特异性的口服小分子血管生成因子胸苷磷酸化酶（TP）抑制剂，以及两种高度特异性的中和血管生成因子血管生成素-1 （Ang-1）和Ang-2的肽体。本提案的第二个目标是确定TP的作用，以及我们的TP抑制剂在体内的作用机制。这一目标包括基于意想不到的发现血管生成素/TIE系统和TP之间的直接联系的研究，在肿瘤相关巨噬细胞（tam）的一个亚群中被称为TEMs（表达tie2的单核细胞/巨噬细胞）。这些研究可以为胰腺癌的新疗法奠定基础，并且可以很容易地外推到其他实体肿瘤类型。具体目的是：1)在正常小鼠和荷瘤小鼠体内进行AEAC的药代动力学和药效学（PK/PD）研究，确定其是否产生宿主毒性；2)测定AEAC联合使用血管生成素和/或VEGF途径抑制剂时的抗血管生成和抗肿瘤活性；3)确定TP和AEAC在体内的作用机制，包括对肿瘤内皮细胞下游信号事件的影响以及对血管形态和正常化的影响，并确定TP在体内是否受Ang-2的调控；4)利用遗传学方法评估TP对肿瘤血管化和体内进展的影响，包括对胰腺癌细胞和肿瘤基质细胞的操纵，特别是tam和tem。在体内使用的模型中，有一种遗传小鼠模型（Pdx1- Cre；Men1小鼠），该模型有条件地敲除胰腺内分泌细胞中的Men1基因。这些小鼠的胰腺内分泌肿瘤在遗传起源和表型上都与人类疾病非常相似，包括血管生成因子的表达增加，并且对血管生成抑制剂的治疗有反应。

DESCRIPTION (provided by applicant): Drugs that target tumor angiogenesis can increase response rates and survival in patients with advanced malignancies, although the percentage of patients responding is generally low. Recent clinical trials suggest that most advanced pancreatic exocrine carcinomas are refractory to angiogenesis inhibitors, and this may be due to the hypovascularity and other biological features of these tumors. In contrast to the more common exocrine pancreatic cancers, malignancies originating from neuroendocrine cells in the pancreas, called pancreatic neuroendocrine tumors (PNET), lack a desmoplastic fibroinflammatory capsule and are highly vascularized. While metastatic PNET are not cured by surgery or chemotherapy, objective responses of PNET to anti-angiogenic agents have been seen in mouse models and in randomized phase III clinical trials. Since pancreatic cancers often express multiple angiogenic factors, an objective of this proposal is to determine if combinations of inhibitors targeting different angiogenic factors are effective in mouse models of PNET. The inhibitors to be studied include a novel, highly specific, orally available small molecule inhibito of the angiogenic factor thymidine phosphorylase (TP) which we have synthesized, and two highly specific peptibodies which neutralize the angiogenic factors angiopoietin-1 (Ang-1) and Ang-2. The second objective of this proposal is to determine the role of TP, and the mechanisms of action of our TP inhibitor, in vivo. Included in this objective are studies that are based on the unexpected discovery of a direct link between the angiopoietin/TIE system and TP, observed in a subset of tumor-associated macrophages (TAMs) called TEMs (TIE2-expressing monocytes/ macrophages). These studies could form the basis for new therapies to treat pancreatic cancer, and could be readily extrapolated to other solid tumor types. The specific aims are: 1) to conduct pharmacokinetic and pharmacodynamic (PK/PD) studies of AEAC in normal and tumor-bearing mice, and to determine if it produces host toxicity; 2) to determine the anti- angiogenic and antitumor activities of AEAC when used in combination inhibitors of angiopoietin and/or VEGF pathways; 3) to determine the mechanisms of action of TP and AEAC in vivo, including effects on downstream signaling events in tumor endothelial cells and effects on vasculature morphology and normalization, and to determine if TP expression is regulated in vivo by Ang-2; and 4) to use genetic approaches to assess the effect of TP on tumor vascularization and progression in vivo, including the manipulation of the pancreatic cancer cells and tumor stromal cells, particularly TAMs and TEMs. Among the in vivo models to be used is a genetic mouse model which has a conditional knockout of the Men1 gene in the endocrine pancreatic cells (Pdx1- Cre;Men1 mice). These mice develop pancreatic endocrine tumors that closely mimic the human disease both in genetic origin and phenotype, including increased expression of angiogenic factors, and respond therapeutically to treatment with angiogenesis inhibitors.