Exploiting Caveolae-Dependent Albumin Endocytosis to Optimize Therapy in Pancreatic Cancer

 描述（由申请方提供）：胰腺癌（PC）是一种以治疗耐药和预后差为特征的疾病。迫切需要发现新的治疗方法，并确定现有的治疗方法是否对某些患者无效。最近，在吉西他滨中加入白蛋白结合型紫杉醇（Abraxane（r））已被证明可以提高PC的缓解率和生存率，但代价是增加了毒性。白蛋白结合型紫杉醇是一种白蛋白结合的化疗药物，据推测其通过小窝/gp 60介导的白蛋白内吞作用进入细胞。小窝是50-100 nM的膜内陷，负责内吞作用、胆固醇稳态和信号转导。小窝蛋白-1（Caveolin-1，Cav-1）是小窝的主要结构成分，基因敲低Cav-1可消除小窝。我们的初步数据表明，Cav-1在PC中过度表达并与预后不良相关，并赋予致癌特性，包括迁移、侵袭和对治疗的抵抗。我们的数据还表明，Cav-1的表达是重要的白蛋白和白蛋白结合型紫杉醇进入PC细胞的细胞内运输。因此，我们假设Cav-1水平调节进入，并可以预测白蛋白结合型紫杉醇的反应。此外，我们寻求通过鉴定增加白蛋白结合型紫杉醇功效的其他策略和通过测试新的白蛋白结合型化疗剂来改善白蛋白结合型紫杉醇。我们的具体目标包括：（1）确定Cav-1表达是否介导白蛋白摄取和对白蛋白结合型紫杉醇的应答;（2）确定Cav-1表达是否介导对新的白蛋白结合型化疗剂的应答;和（3）测试改善对白蛋白结合型紫杉醇的应答的策略。我们将通过分析白蛋白和白蛋白结合型紫杉醇摄取、细胞毒性测定和细胞凋亡途径的激活来测试Cav-1水平是否影响PC细胞系组中对白蛋白结合型紫杉醇的应答。我们将在体内扩展这些研究，以评估Cav-1的丢失是否会改变对白蛋白结合型紫杉醇的反应，使用患者来源的异种移植物和PC的本地小鼠模型。此外，我们将确定肿瘤、基质和血液中的Cav-1水平是否预测从接受白蛋白结合型紫杉醇的PC患者获得的样品中对白蛋白结合型紫杉醇的响应。此外，我们将测试看起来比白蛋白结合型紫杉醇上级的新型白蛋白-化疗缀合物，并确定Cav-1水平是否也调节它们的反应。最后，我们将测试增加Cav-1表达以进一步使细胞对白蛋白结合型紫杉醇敏感的其他策略。如果成功，这些研究将确定Cav-1对于白蛋白进入PC肿瘤细胞中是重要的，并且决定对白蛋白结合的化疗的应答。此外，这些研究可以通过预测哪些肿瘤可能从白蛋白结合型紫杉醇中受益，通过基于Cav-1表达的分层治疗来实现治疗的个性化。最后，这些研究旨在通过靶向Cav-1/小窝依赖性白蛋白内吞途径首次完善PC中的现有疗法。

 DESCRIPTION (provided by applicant): Pancreatic adenocarcinoma (PC) is a disease typified by resistance to therapy and poor outcomes. There is a pressing need to discover new therapies and determine whether existing therapies will be ineffective in certain patients. Recently, the addition of nab-paclitaxel (Abraxane(r)) to gemcitabine has been shown to improve response rates and survival in PC, at the expense of added toxicity. Nab-paclitaxel is an albumin-bound chemotherapeutic which has been hypothesized to enter the cell through caveolae/gp60-mediated albumin endocytosis. Caveolae are 50-100 nM membrane invaginations responsible for endocytosis, cholesterol homeostasis, and signal transduction. Caveolin-1 (Cav-1) is the principal structural component of caveolae, and genetic knockdown of Cav-1 ablates caveolae. Our preliminary data indicate that Cav-1 is over-expressed and associated with poor prognosis in PC, and confers oncogenic properties including migration, invasion, and resistance to therapy. Our data also suggest that Cav-1 expression is important for intracellular transport of albumin and nab-paclitaxel into PC cells. Thus, we hypothesize that Cav-1 levels regulate entry and can predict response to nab-paclitaxel. In addition, we seek to improve upon nab-paclitaxel by identifying other strategies which increase nab-paclitaxel efficacy and by testing novel albumin-conjugated chemotherapeutics. Our specific aims include: (1) To determine whether Cav-1 expression mediates albumin uptake and response to nab-paclitaxel; (2) To determine whether Cav-1 expression mediates response to novel albumin-conjugated chemotherapeutics; and (3) To test strategies to improve response to nab-paclitaxel. We will test whether Cav-1 levels affect response to nab-paclitaxel in a panel of PC cell lines through analysis of albumin and nab- paclitaxel uptake, cytotoxicity assays, and activation of apoptotic pathways. We will extend these studies in vivo to assess whether loss of Cav-1 alters response to nab-paclitaxel using patient-derived xenograft and autochthonous mouse models of PC. In addition, we will determine whether Cav-1 levels in tumor, stroma, and blood predict response to nab-paclitaxel in samples obtained from patients with PC receiving nab- paclitaxel. Furthermore, we will test novel albumin-chemotherapy conjugates that appear superior to nab- paclitaxel and determine whether Cav-1 levels also regulate their response. Lastly, we will test other strategies to increase Cav-1 expression in order to further sensitize cells to nab-paclitaxel If successful, these studies will establish that Cav-1 is important for albumin entry in PC tumor cells and dictates response to albumin- bound chemotherapies. Furthermore, these studies could allow personalization of therapy by predicting which tumors are likely to benefit from nab-paclitaxel, by stratifying therapy based on Cav-1 expression. Finally, these studies are designed to be the first to refine an existing therapy in PC through targeting of the Cav-1/caveolae-dependent albumin endocytic pathway.