Spatial and Temporal Regulation of Angiogenesis

项目描述（申请人提供）：本项目从多个角度研究肿瘤血管的结构和功能：血管生成因子和内源性抑制剂在肿瘤和替代肿瘤血管中的作用和功能，这些因子诱导的基因表达及其在肿瘤血管生成中的作用，以及血管生成因子和血管生成对肿瘤进展的影响。该提案概述了一系列实验，重点关注主要血管生成细胞因子下游的主要信号通路之一，Akt通路，作为许多肿瘤血管异常的介质：它们的体积大，支撑力差，通透性增加和不稳定性。我们的初步数据表明，在生理性血管生成过程中，Akt信号的“开启”和“关闭”涉及到一个非常精确的开关。然而，当这种“关闭开关”被抑制时，生成的血管再现了肿瘤血管、其他血管异常血管和“母血管”的许多方面。“母血管”是德沃夏克博士创造的一个术语，用来描述VEGF-A和其他细胞因子过度表达形成的血管。该资助申请旨在探索Akt在“母血管”/“肿瘤血管”形成中的作用，以及下游Akt靶点对这些异常血管的个体特征和功能的影响。我们还提出探索新发现背后的机制，即TSP-1调节Akt信号。这个项目写了3年，使它能够融入这个项目项目的现有资助时间表。目的:1。验证Akt活性上调足以重现非肿瘤环境下异常血管的结构和功能的假设2。鉴定介导Akt影响3的下游信号通路。探讨血栓反应蛋白在Akt信号传导中的作用机制。

DESCRIPTION (provided by applicant): This program project focuses on the structure and function of tumor blood vessels from many angles: roles and functions of angiogenic cytokines and endogenous inhibitors in tumors and in surrogate tumor blood vessels, the gene expression induced by these factors and their role in tumor angiogenesis, and the impact of angiogenic cytokines and angiogenesis on tumor progression. This proposal outlines a series of experiments that focus on one of major signaling pathways downstream of the major angiogenic cytokines, the Akt pathway, as a mediator of many tumor blood vessel abnormalities: their large size, poor support, increased permeability and instability. Our preliminary data demonstrate that Akt signaling in physiological angiogenesis involves a very precise switching 'on' and 'off of the Akt signal. However, when this 'off switch is inhibited, the resulting vessels recapitulate many aspects of tumor blood vessels, vessels of other vascular anomalies and 'mother vessels', a term coined by Dr. Dvorak to describe blood vessels formed by overexpression of VEGF-A and other cytokines. This grant application seeks to explore the role of Akt in 'mother vessel'/'tumor vessel' formation, and the impact of downstream Akt targets on the individual features and functions of these abnormal blood vessels. We also propose to explore the mechanism behind our novel finding that TSP-1 modulates Akt signaling. This project is written for 3 years to enable it to fold into the existing funding schedule of this program project. Aims: 1. Test the hypothesis that upregulation of Akt activity is sufficient to recapitulate the structure and function of abnormal blood vessels reminiscent of tumor vessel in a non-tumor environment 2. Identify the downstream signaling pathways that mediate Akt affects 3. Explore the mechanisms of Thrombospondins on Akt signaling. COLLABORATING INSTITUTIONS (S): Massachusetts General Hospital, Boston, MA Children's Hospital, Boston, MA PROGRESS DURING THE CURRENT FUNDING PERIOD: This program has now completed its second year. During this period 17 publications have resulted from program related studies. A number of these have appeared in high impact journals and 11 list multiple authors who are part of this Program Project. Overall progress has been excellent. Project 1, "Structure and Function of New Blood Vessels," is directed by Dr. Harold Dvorak, in conjunction with Dr. Laura Benjamin. The studies under Specific Aim 1 where the investigators characterized new blood vessel induction by VEGF-A versus PIGF, VEGF-A/PIGF heterodynamers and FGF, are now completed and the work published in Nature Medicine. Specific Aim 2 is to employ inducible gene expression in mammary tumors to overexpress or not express the angiogenic factors studied under Specific Aim 1. These studies are underway and have resulted in two publications. Specific Aim 2 will use chip technology to profile genes that are differentially expressed in 'mother' vessels in response to local overexpression of VEGF-A or PIGF. Several novel genes have been characterized in the first two years of the project and many other potentially important genes also identified. Two manuscripts are in preparation describing this work. Project 2, Signaling Pathways that Determine Vascular Structure and Function, is the newly proposed project in this supplement and is considered in detail below. It is noted that Dr. Benjamin is a co-author of six of the 17 publications listed, several of which are very relevant to proposed supplement Project 2. Project 3, "Role of Placental Growth Factor in Normal and Neoplastic Skin Angiogenesis," is led by Dr. Michael Detmar. Specific Aim 1 is a study of the role of PIGF in skin vasculaturation and in experimental skin inflammation employing transgenic animal models. A novel transgenic mouse model for the targeted overexpression of human PIGF-2 in basal epidermal keratinocytes and other cells has been made. Studies of these animals have resulted in a paper published in Blood. Specific Aim 2 will employ these models to study chemically-induced skin cancer. Initial results suggest that PIGF plays a role in epithelial tumorigenesis. Specific Aim 3 will employ transfected PIGF and semaphorin D gene constructs to study the effects of modulating angiogenesis on the growth of human squamous cell carcinoma xenotransplants. Stably transfected cell lines have been obtained to pursue this aim and data are now being collected on these models. Project 4, "Inhibition of Angiogenesis by Thrombospondin-1," is led by Dr. Jack Lawler with the participation of Dr. R. Khosravi-far and Dr. S. Parangi. Specific Aim 1 seeks to characterize the CD36 receptor complex on endothelial cells to which TSP-1 binds. Specific Aim 2 will study mechanisms involved in TSP-1-induced apoptosis. Work is progressing on these aims, but appears quite preliminary. Dr. Lawler is co-author of three papers that report work on the ligand TSP-1 which have appeared in high impact journals. In addition, there are four cores (Administration, Morphology, Cell Biology, and Genomics) which are all operational and fulfill their role in the overall Program Project. Overall progress, as noted above, has been excellent.