Immunobiology of Pediatric Tumors

我们之前已经证明，尤因氏肉瘤通过TRAIL受体激动剂对细胞凋亡非常敏感。绝大多数尤文氏肉瘤细胞系表达TRAIL-受体2 (TR2)，大多数细胞在TR2受体与单克隆抗体或天然TRAIL配体连接后24小时内发生凋亡。此外，异种移植模型表明，抗tr2是一种抗体内生长的尤文氏肉瘤的活性剂。在此基础上，我们已经启动了抗tr2治疗儿童实体瘤的I期临床试验，该试验目前正在进行中。尽管有这些有希望的临床前数据，我们也注意到少数尤因肿瘤细胞系对抗tr2不敏感，我们观察到抗tr2无法治愈大多数已建立的尤因异种移植物的动物。因此，我们试图了解限制尤文氏肉瘤对TR2靶向药物敏感性的因素。值得注意的是，在这项工作的背景下，基于TRAIL的杀伤是免疫系统根除肿瘤的主要途径之一，因此我们对该系统的兴趣既基于抗tr2直接临床应用的可能性，也基于通过TRAIL受体信号优化细胞死亡的可能性，这也可以提高这些肿瘤免疫治疗的有效性。该项目在2008财年的主要成就是发表了一篇论文，证明了caspase 8在致敏尤因斯肉瘤细胞TRAIL介导的细胞死亡中的重要性，并确定了caspase 8在尤因斯肉瘤临床样本中的表达是异质性的（Lissat等人，Am J Path 2007; 170:1917）。这是一项合作工作，我们的项目通过提供50多个尤因肿瘤的caspase 8表达分析做出了贡献，这是本报告的基本要素。因此，我们已经证明，TRAIL介导的尤因斯肉瘤杀伤的全部益处，无论是通过moAb还是通过细胞溶解细胞，只有在确保caspase 8表达的情况下才能实现。我们进一步证明了干扰素γ是caspase 8表达的主要调节因子，并且Ewings肉瘤细胞暴露于干扰素γ会导致caspase 8大幅上调，并增加对抗trail受体治疗的敏感性。因此，我们将寻求将干扰素纳入我们正在进行的抗tr2临床试验，并将寻求将基于TRAIL的疗法与免疫疗法相结合，这些疗法可以将干扰素局部递送到肿瘤部位，从而可能相互协同。

We have previously demonstrated that Ewings sarcomas are exquisitively sensitive to apoptosis via TRAIL receptor agonists. The vast majority of Ewings sarcoma cell lines express TRAIL-Receptor 2 (TR2) and most cells undergo apoptosis within 24 hours of ligation of the TR2 receptor with either monoclonal antibody or the natural TRAIL ligand. Moreover, xenograft models show that anti-TR2 is an active agent against Ewings sarcomas growing in vivo. On this basis, we have initiated a Phase I clinical trial of anti-TR2 in childhood solid tumors and this trial is currently proceeding. Despite this promising preclinical data, we have also noted that a minority of Ewings tumor cell lines are not sensitive to anti-TR2 and we observed that anti-TR2 was unable to cure most animals with established Ewings xenografts. Therefore, we have sought to understand the factors that limit sensitivity of Ewings sarcoma to TR2 targeted agents. It is important to note in the context of this work, that TRAIL based killing is one of the primary pathways through which the immune system eradicates tumors and therefore our interest in this system is based both upon the possibility for direct clinical application with anti-TR2 as well as the possibility that optimizing cell death via TRAIL receptor signaling could also improve the effectiveness of immune based therapies for these tumors. The primary accomplishment for this project during FY2008 was the publication of a manuscript demonstrating the importance of caspase 8 in sensitizing Ewings sarcoma cells TRAIL mediated cell death and identifying that caspase 8 expression in Ewings sarcoma clinical samples is heterogeneous (Lissat et al, Am J Path 2007; 170:1917). This was a collaborative work and our program contributed by providing the analysis of more than 50 Ewings tumors for caspase 8 expression which was a fundamental element of this report. Thus, we have demonstrated that the full benefit of TRAIL mediated killing in Ewings sarcoma, whether delivered via a moAb or via a cytolytic cell, can only be accomplished if caspase 8 expression is assured. We have further demonstrated that interferon gamma is a primary regulator of caspase 8 expression and that exposure of Ewings sarcoma cells to interferon gamma results in substantial caspase 8 upregulation and increased sensitivity to anti-TRAIL receptor therapies. We therefore will seek to incorporate interferon into our ongoing clinical trial of anti-TR2 and will seek to combine TRAIL based therapies with immune therapies that can deliver interferon locally to the tumor site and therefore potentially synergize with each other.