Ceramide-Rich Platforms Functionalize Gemcitabine Uptake

我们的数据表明，在选择的环境中，酸性鞘磷脂酶（ASMase）/神经酰胺信号转导的激活在神经元中起着重要作用。 肿瘤内皮细胞通过放射和某些化学疗法协同直接肿瘤细胞损伤， 影响结果。ASMase是一种溶酶体水解酶，优先在内皮细胞中表达高达20倍 与其他哺乳动物细胞相比。从机制上讲，内皮ASMase激活在分钟内导致 形成质膜富含神经酰胺的平台（CRP），组织凋亡信号的大结构域 程序.支持我们的概念的研究表明，所有组织学的异种移植物，当植入 asmase-/-宿主小鼠变得对吉西他滨、紫杉醇、依托泊苷和高单剂量放射疗法具有抗性， 通过将腺病毒asmase基因递送至肿瘤微血管系统逆转了这种效应。我们最近 发现VEGF是内皮细胞ASMase的主要抑制剂，抗血管生成药物可以降低血管生成的抑制， ASMase，增强肿瘤对抗癌治疗的反应，但仅在特定条件下。我们发现 不论T1/2或抗血管生成类别，这些药物仅增强内皮细胞凋亡和肿瘤反应 如果安排在化疗前1- 2小时，因为ASMase仅可去抑制1- 2小时。基于这些 MSK肉瘤服务进行了一项II期试验，显示基于鞘脂的 贝伐珠单抗与常规同步定时相比改善了转移性肉瘤对胞苷的反应 类似物吉西他滨从38%至93%（p=0.0024; Tap和Kolesnick，未发表）。当前应用程序将 有助于建立短效抗血管生成药物的瞬时递送同时 增强吉西他滨诱导的内皮细胞和肿瘤细胞凋亡。这个最重要的假设是 应用是哺乳动物细胞中的主要核苷转运蛋白ENT 1，其是吉西他滨所需的 摄取，并不像普遍接受的那样组成性地“开启”，而是必须插入内皮细胞和肿瘤细胞上的CRP中 用于功能化。将在3个目标中探索吉西他滨作用的这种新的基于膜的机制 旨在研究内皮细胞和肉瘤细胞中ENT 1通过CRP功能化的机制， ASMase产生的CRP的VEGF抑制，以及增强内皮ASMase的药理学策略 在体内神经酰胺信号传导以改善ENT 1介导的吉西他滨摄取和细胞死亡。一个主要的概念是 探索的是吉西他滨诱导的内皮分泌的ASMase触发“旁观者”吉西他滨摄取 在肿瘤细胞中通过ENT 1。因此，这些研究可能定义了刺激ASMase/神经酰胺的失败 作为一种新的化学抗性的媒介。预计从研究中获得的信息 建议在这里将通知一个计划的后续临床试验的晚期肉瘤进行肉瘤 在MSK服务。

Our data indicate that in select settings activation of acid sphingomyelinase (ASMase)/ceramide signaling in tumor endothelial cells by radiation and certain chemotherapies synergizes with direct tumor cell damage to impact outcome. ASMase is a lysosomal hydrolase preferentially expressed in endothelial cells up to 20-fold compared with other mammalian cells. Mechanistically, endothelial ASMase activation leads within min to formation of plasma membrane ceramide-rich platforms (CRPs), macrodomains that organize apoptotic signaling programs. Support for our concept derives from studies showing xenografts of all histologies, when implanted in asmase-/- host mice become resistant to gemcitabine, paclitaxel, etoposide, and high single dose radiotherapy, effects reversed by exclusive adenoviral asmase gene delivery to tumor microvasculature. We recently discovered VEGF is the principal inhibitor of endothelial ASMase, and that anti-angiogenic drugs de-repress ASMase, amplifying tumor responses to anti-cancer therapies, but only under specific conditions. We found irrespective of t1/2 or anti-angiogenic class, these drugs enhance endothelial apoptosis and tumor response only if scheduled at 1-2h preceding chemotherapy, as ASMase can be de-repressed for only 1-2h. Based on these data, the MSK Sarcoma Service performed a Phase II trial that showed sphingolipid-based timing of bevacizumab vs. conventional synchronous timing improved metastatic sarcoma response to the cytidine analogue gemcitabine from 38 to 93% (p=0.0024; Tap and Kolesnick, unpublished). The current application will help establish the mechanism by which temporal delivery of a short-acting anti-angiogenic drug simultaneously enhances gemcitabine-induced endothelial and tumor cell apoptosis. The overarching hypothesis of this application is that the principal nucleoside transporter in mammalian cells, ENT1, required for gemcitabine uptake, is not constitutively “on” as generally accepted but must insert into CRPs on endothelial and tumor cells for functionalization. This new membrane-based mechanism of gemcitabine action will be explored in 3 aims designed to examine mechanism of ENT1 functionalization via CRPs in both endothelial and sarcoma cells, VEGF inhibition of ASMase-generated CRPs, and pharmacologic strategies to enhance endothelial ASMase- ceramide signaling in vivo to improve ENT1-mediated gemcitabine uptake and cell death. A major concept to be explored is that gemcitabine-induced ASMase secreted by endothelium triggers “bystander” gemcitabine uptake via ENT1 in tumor cells. As such, these investigations potentially define failure to stimulate ASMase/ceramide signaling as mediating a new form of chemoresistance. It is anticipated that information derived from studies proposed here will inform a planned follow up clinical trial for advanced sarcoma to be performed by the Sarcoma Service at MSK.