Preclinical Evaluation of Oncolytic HSV for Anaplastic Glioma Therapy

胶质瘤具有基因异质性，无论是在生物标志物的表达(或缺乏)方面，还是在它们支持转基因单纯疱疹病毒(HSV)载体的复制方面。除了基因表达谱(GEP)的异质性外，还发现了一种具有类似神经干细胞特性的胶质瘤细胞亚群，这些细胞被认为是胶质瘤复发的原因，并唯一地维持了肿瘤克隆。这种细胞亚群被称为脑肿瘤启动细胞或胶质瘤前体细胞(GPC)，在恶性胶质瘤的化疗耐药和放射耐药中起重要作用。这些GPC也可能表现出对单纯疱疹病毒基因工程感染或联合放射治疗的不同敏感性。基因工程HSV载体的抗肿瘤活性依赖于宿主肿瘤细胞支持HSV感染和复制的能力。明确y{1}34.5缺失的HSV载体和受体靶向的野生型HSV载体增强肿瘤杀伤的机制是提高临床疗效的关键。我们已经证明，IL-12在Ay[1}34.5 HSV背景中的表达导致了增强的抗肿瘤活性，这种增强效应是由免疫介导的。问题仍然是，这种益处是否也会在靶向病毒身上看到，在这种病毒中，病毒克服PKR反应的能力保持不变或恢复。 项目3有三个基本目标。目标1将确定由项目1和2设计的每个新突变HSV的相对溶瘤潜力，以使用不同的进入机制或克服固有的宿主反应。它们对胶质瘤细胞的抗肿瘤活性，单独或联合辐射，将与我们目前的Ay{1}34.5 HSV载体进行比较。这些研究将(I)确定哪些改良病毒最能感染细胞并克服自然宿主防御，(Ii)导致结合这些最佳特征的病毒的工程。目标2将集中于确定胶质瘤前体细胞亚群对溶瘤Ay{1}34.5单纯疱疹病毒和放射治疗的相对敏感性。针对CD133的HSV将被测试在GPC上的有效性，同时保持对正常神经胶质细胞的安全性。GPC和非GPC肿瘤细胞的GEP将进行比较，以揭示对HSV产生耐药性的潜在原因。AIM 3将完成整合了所有基因修改的基因工程HSV的临床前测试。

Gliomas are genotypically heterogeneous, both in biomarker expression (or lack thereof) and in their ability to support replication of genetically modified herpes simplex virus (HSV) vectors. In addition to heterogeneity in Gene Expression Profiles (GEP), a subpopulation of glioma cells has been identified that has properties resembling those of neural stem cells and these cells are believed to be responsible for glioma recurrence and to exclusively maintain the neoplastic clone. This subpopulation of cells, referred to as Brain Tumor-lnitiating Cells or Glioma Progenitor Cells (GPC), contribute significantly to chemoresistance and radioresistance of malignant gliomas. These GPC may also display differential susceptibility to oncolysis by genetically engineered HSV alone or combined with radiation. Anti-tumor activity of genetically engineered HSV vectors is dependent on the ability of the host tumor cell to support HSV infection and replication. A clear understanding of the mechanisms of enhanced tumor killing mediated by both y{1}34.5-deleted HSV and receptor-targeted wild-type HSV vectors is critical to achieve improved clinical efficacy. We have already shown that IL-12 expression in a Ay[1}34.5 HSV background results in enhanced anti-tumor activity and this enhanced effect is immune-mediated. The question remains whether this benefit would also be seen with a targeted virus in which the virus' ability to overcome the PKR response remains intact or is restored. Project 3 has three fundamental aims. Aim 1 will ascertain the relative oncolytic potential of each of the novel mutant HSV engineered by Projects 1 and 2 to use different entry mechanisms or to overcome innate host responses. Their antitumor activity on glioma cells, alone or combined with irradiation, will be compared with that of our current Ay{1}34.5 HSV vectors. These studies will (i) determine which modified viruses are best able to infect cells and overcome natural host defenses, and, (ii) lead to the engineering of viruses that combine these optimal features. Aim 2 will focus on defining the comparative susceptibility of a subpopulation of glioma progenitor cells to oncolytic Ay{1}34.5 HSV alone and with irradiation. HSV specifically targeted to CD133 will be tested for efficacy on GPC while retaining safety for normal neuroglial cells. GEP of GPC and non-GPC tumor cells will be compared to reveal potential causes for resistance to HSV. Aim 3 will complete preclinical testing of genetically engineered HSV that incorporate all genetic modifications.