Ceramide in angiogenic integrin signaling

描述(申请人提供)：血管生成，即新的毛细血管的萌发，对癌症的生长是必不可少的。在小鼠模型中，抑制整合素av-beta3/av-beta5，在血管生成中至关重要的细胞表面受体，诱导内皮细胞凋亡，干扰血管生成，抑制脑瘤生长。整合素av-beta3/av-Beta5抑制在癌症治疗中的潜在作用随着对RGDfV的鼓舞人心的反应而变得明显。RGDfV是一种整合素功能阻断肽，在成人复发胶质瘤患者中完成了I期临床试验。尽管av-beta3/av-beta5整合素抑制在癌症治疗中的应用日益增多，尤其是对脑肿瘤的治疗，但这种抑制的分子机制还不是很清楚，因此无法为未来的试验设计合理的联合治疗方法。我们已经证明，整合素抑制会增加细胞内神经酰胺，这是一种促凋亡的脂质第二信使。目前尚不清楚这种神经酰胺增加是否是整合素av-beta3/av-Beta5抑制所需的抗血管生成作用所必需的。我们最近的数据表明，酸性鞘磷脂酶在这一机制中起着关键作用。我们推测，酸性鞘磷脂酶产生的神经酰胺增加和整合素-av-beta3/av-Beta5抑制所诱导的神经酰胺增加是内皮细胞凋亡和RGDfV体内抗脑瘤作用所必需的。我们的具体目标是：1)确定神经酰胺、整合素av-beta3/av-Beta5与细胞凋亡的分子相互作用；2)比较RGDfV在WT和ASMase缺陷小鼠脑内肿瘤模型中的抑制作用。在体外，我们将使用ASMase缺陷的或有能力的内皮细胞在玻璃连蛋白上，比较它们的神经酰胺和对RGDfV的凋亡反应。在体内，我们将在ASMase基因敲除小鼠和野生型小鼠身上植入颅内肿瘤，并确定RGDfV或对照治疗组小鼠在存活率、肿瘤生长和血管生成方面的差异。Av-beta3/av-beta5整合素介导的内皮细胞凋亡中需要酸性鞘磷脂酶的证明将是神经酰胺在整合素信号转导中的因果作用的第一个证据。整合素信号中神经酰胺代谢的要求提供了将整合素抑制药物与优化神经酰胺反应的药物相结合的分子基础，从而提高了抗癌疗效。

DESCRIPTION (provided by applicant): Angiogenesis, the sprouting of new capillaries, is essential for cancer growth. Inhibition of integrins av-beta3/av-beta5, cell surface receptors critical in angiogenesis, induces endothelial apoptosis, disrupts angiogenesis and inhibits brain tumor growth in a mouse model. The potential utility of integrin av-beta3/av-beta5 inhibition in cancer therapy is becoming apparent with the encouraging responses to RGDfV, an integrin-function-blocking peptide that completed a phase-I clinical trial in adults with recurrent gliomas. Despite the emerging use of av-beta3/av-beta5 integrin inhibition in cancer therapy, especially against brain tumors, the molecular mechanism of this inhibition is poorly understood, precluding rational design of combination therapies for future trials. We have shown that integrin inhibition increases intracellular ceramide, a pro-apoptotic lipid second messenger. It is not known whether this ceramide increase is required for the anti-angiogenic action of integrin av-beta3/av-beta5 inhibition. Our recent data suggest that acid sphingomyelinase is critical in this mechanism. We hypothesize that the ceramide increase, generated by acid sphingomyelinase and induced by integrin- av-beta3/av-beta5 inhibition is required for endothelial apoptosis and for the effect of RGDfV against brain tumors in vivo. Our Specific Aims are: 1) To determine molecular interactions between ceramide, integrins av-beta3/av-beta5 and apoptosis, and 2) To compare the inhibitory effect of RGDfV in WT and ASMase deficient mice using an intracranial mouse brain tumor model. In vitro we will use ASMase-deficient or -competent endothelial cells plated on vitronectin and compare their ceramide and apoptotic responses to RGDfV. In-vivo we will implant intracranial brain tumors in ASMase knockout mice and wild type littermates and determine differences in survival, tumor growth and angiogenesis in RGDfV- or control-treated mice between the groups. Demonstration of a requirement for acid sphingomyelinase in av-beta3/av-beta5 integrin-mediated endothelial apoptosis will be the first evidence for a causal role of ceramide in integrin signaling. Requirement for ceramide metabolism in integrin signaling has potentially far-reaching implications by providing a molecular rationale for combining integrin-inhibiting drugs with agents geared to optimize the ceramide response, resulting in improved anti-cancer efficacy.