Mechanisms of tumor escape from anti-angiogenic therapy

描述（由申请人提供）：实体瘤需要新的血管生长超过几立方毫米。肿瘤血管复杂且功能失调，多种细胞类型可合并形成肿瘤血管系统。在一个引人注目的例子中，一些肿瘤细胞可以直接整合在血管结构内或形成携带血液和流体的肿瘤细胞内衬导管（称为血管拟态，VM）。我们最近分离出了一种新的血管样肿瘤细胞亚群，并通过表达血管细胞粘附分子CD 31进行鉴定。这些CD 31+肿瘤细胞不表达VEGF受体，它们下调神经嵴转录因子/CD 31阻遏物AP-2 α，并且它们在移植到小鼠中时形成肿瘤血管。此外，CD 31+肿瘤细胞不响应VEGF抑制，并且在用VEGF中和抗体攻击的肿瘤中富集。在目标1中，我们将使用来自人和小鼠细胞系的CD 31-和CD 31+肿瘤细胞的克隆群体以及自发性小鼠黑色素瘤模型来确定CD 31在肿瘤中形成灌注血管结构中的功能作用。目的2是使用细胞消融策略和尖端肿瘤灌注研究来确定CD 31+肿瘤细胞如何介导逃避抗血管生成治疗。在目标3中，我们将定义神经嵴特异性AP-2 α的缺失如何控制CD 31表达并产生VM感受态肿瘤细胞。为此，我们将使用遗传缺失和过表达研究以及活体显微镜观察植入小鼠耳中的VM感受态肿瘤细胞。在完成我们的研究目标后，我们将阐明CD 31+肿瘤细胞如何与宿主血管形成功能性连接，产生和维持这种独特亚群的分子机制，以及这些血管样肿瘤细胞如何介导逃避抗血管生成治疗。

DESCRIPTION (provided by applicant): Solid tumors require new blood vessels to grow beyond a few cubic millimeters. Tumor blood vessels are complex and dysfunctional and multiple cell types may coalesce to form the tumor vasculature. In a striking example, some tumor cells may directly integrate within vascular structures or form tumor cell-lined conduits that carry blood and fluid (termed vascular mimicry, VM). We have recently isolated and characterized a novel subpopulation of vascular-like tumor cells identified by expression of the vascular cell adhesion molecule, CD31. These CD31+ tumor cells do not express VEGF receptors, they down-regulate the neural crest transcription factor/CD31 repressor AP-2alpha, and they form tumor blood vessels when engrafted in mice. Furthermore, CD31+ tumor cells do not respond to VEGF inhibition and are enriched in tumors challenged with VEGF neutralizing antibodies. In aim 1 we will use clonal populations of CD31- and CD31+ tumor cells we have derived from human and mouse cell lines and a spontaneous mouse melanoma model to determine the functional role of CD31 in forming perfused vascular structures in tumors. Aim 2 is to use cell ablation strategies and cutting-edge tumor perfusion studies to determine how CD31+ tumor cells mediate escape from anti-angiogenic therapy. In aim 3 we will define how loss of the neural crest specifer AP-2alpha controls CD31 expression and generates VM-competent tumor cells. For this aim, we will use genetic deletion and over- expression studies and intravital microscopy to visualize VM-competent tumor cells implanted in the mouse ear. Upon completion of our study aims, we will clarify how CD31+ tumor cells form functional connections with the host vasculature, the molecular mechanisms that generate and maintain this unique subpopulation, and how these vascular like tumor cells mediate escape from anti-angiogenic therapy.