Re-setting the Endothelial Ceramide Rheostat

描述（申请人提供）：我们最近的研究探索了抗血管生成通过增强微血管功能障碍的鞘脂信号来介导肿瘤治疗的生化机制，包括一些抗癌药物和高单剂量放疗（SDRT）。本应用程序的研究是基于观察到内皮细胞比任何哺乳动物细胞产生更多的酸性鞘磷脂酶（ASMase），并利用它来指示细胞凋亡。我们发表的数据表明，ASMase快速易位到内皮细胞膜外小叶可诱导鞘磷脂水解为促凋亡的第二信使神经酰胺，从而引发细胞凋亡。我们的初步数据表明，微血管功能障碍级联随之而来，包括急性灌注缺陷（通过动态MRI和Hoechst 33342染料外渗测量）和缺氧（通过EPR血氧仪测量），并且这种血管功能障碍抑制肿瘤干细胞DNA损伤修复，以增强SDRT的治愈。该应用假设神经酰胺介导的细胞凋亡强度、血管功能障碍程度和肿瘤治愈概率之间存在直接关系。我们建议验证这一机制，并尝试通过药物或基因上调ASMase信号来提高肿瘤的治愈。具体来说，我们将研究抗血管生成药物是否通过激活ASMase来实现放射增敏（Aim 1），通过腺病毒ASMase基因治疗直接靶向内皮神经酰胺信号，在肿瘤血管中特异性过表达ASMase，是否会比抗血管生成药物更有效地实现放射增敏（Aim 2），以及ASMase定向治疗是否通过急性血管损害来实现肿瘤的治愈（Aim 3）。因此，我们提出了一种新的抗血管生成放射致敏的病理生理模型，其中神经酰胺信号的强度不是内皮生物学的静态功能，而是由肿瘤细胞分泌的血管生成因子动态调节的，并且在药理学上是可处理的。认识到内皮神经酰胺变阻器对srt的肿瘤治疗是必需的，表明了提高内皮神经酰胺信号传导强度的治疗潜力。实际上，在重新设置ASMase激活的条件下，结合蚂蚁- VEGF策略几乎可以立即应用于临床。此外，拟议的研究探索了通过腺病毒基因治疗直接进入神经酰胺生物学，在新血管生成的血管中过度表达asmase，从而对肿瘤治疗产生更大影响的潜力。

DESCRIPTION (provided by applicant): Our recent studies explore a biochemical mechanism by which anti-angiogenesis enhances sphingolipid signaling of microvascular dysfunction to mediate tumor cure by anti-neoplastic therapies, including some anti- cancer drugs and high single dose radiotherapy (SDRT). The studies proposed in this application are predicated on the observation that endothelium make more acidic sphingomyelinase (ASMase) than any mammalian cell and uses it to signal apoptosis. Our published data show that rapid ASMase translocation to the external leaflet of the endothelial cell plasma membrane induces sphingomyelin hydrolysis to the pro- apoptotic second messenger ceramide therein, triggering apoptosis. Our preliminary data indicate a cascade of microvascular dysfunction ensues, which includes acute perfusion defects (measured by Dynamic MRI and Hoechst 33342 dye extravasation) and oxygen deprivation (measured by EPR oximetry), and that this vascular dysfunction represses DNA damage repair in tumor stem cells to enhance cure by SDRT. It is the hypothesis of this application that there is a direct relationship between the intensity of ceramide-mediated apoptosis, the extent of vascular dysfunction, and the probability of tumor cure. We propose to validate this mechanism and attempt to enhance tumor cure by pharmacologic or genetic up-regulation of ASMase signaling. Specifically, we will examine whether radiosensitization by anti-angiogenic drugs occurs by dialing up ASMase activation (Aim 1), whether directly targeting endothelial ceramide signaling via adenoviral asmase gene therapy to overexpress ASMase specifically in tumor vasculature will radiosensitize more effectively than anti-angiogenic drugs (Aim 2), and whether tumor curability with ASMase-directed therapies occurs via acute vascular compromise (Aim 3). As such, we propose a new pathophysiologic model for anti-angiogenic radiosensitization, in which intensity of the ceramide signal is not a static function of endothelial biology, but rather is dynamically regulated by angiogenic factors secreted by tumor cells and is pharmacologically tractable. Recognition that an endothelial Ceramide Rheostat is obligate for tumor cure for SDRT suggests the therapeutic potential of turning up the intensity of endothelial ceramide signaling. Practically, combining ant- VEGF strategies under conditions that re-set ASMase activation can be taken to the clinic almost immediately. Furthermore, the proposed studies explore the potential for greater impact on tumor cure by directly accessing ceramide biology using adenoviral gene therapy to overexpress asmase exclusively in neo-angiogenic vasculature.