GENE THERAPY TARGETING HYPOXIC GLIOMA CELLS

放射治疗是恶性胶质瘤患者的主要治疗方式，在大多数患者中，放射治疗明显有益。然而，这些患者的总体治疗结果令人沮丧，大多数多形性胶质母细胞瘤（GBM）患者在诊断后一年内死亡。脑肿瘤中缺氧细胞的存在是放射治疗的主要障碍，因为这些细胞对辐射诱导的损伤具有众所周知的抵抗力。因此，我们建议设计一种基因治疗方法，在放射治疗过程中杀死缺氧的脑肿瘤细胞。待递送至肿瘤细胞的DNA构建体在启动子的增强子区域中含有低氧响应元件（HRE）和自杀基因。在缺氧条件下，转录复合物缺氧诱导因子-1（HIF- 1）在细胞中积聚并结合HRE。这反过来又激活了相邻的启动子，并导致下游自杀基因的表达，从而杀死细胞。这个项目有两个目标。首先是研究几种细胞或肿瘤内特征如何影响这种基因治疗策略。第二是研究基因治疗是否增强肿瘤细胞的辐射反应。我们提出了四个具体目标来实现这些目标。1)研究HIF-1与脑肿瘤和正常脑组织氧合状态的关系; 2）评估低pH和非循环脑肿瘤细胞中的自杀基因; 3）揭示和研究特定自杀基因在缺氧条件下产生的旁观者效应（BE）; 4）确定缺氧和好氧细胞中自杀基因的表达是否增强其对辐射的反应。

Radiation is a primary treatment modality for patients with malignant gliomas, and in most patients radiation therapy is clearly beneficial. However, the overall outcome of therapy for these patients is dismal, and most patients with glioblastoma multiforme (GBM) die within a year of diagnosis. The presence of hypoxic cells in brain tumors is a major obstacle for radiation therapy, because these cells are notoriously resistant to radiation-induced damage. Therefore, we propose to devise a gene therapy approach for killing hypoxic brain tumor cells during the course of radiation therapy. The DNA construct to be delivered to the tumor cells contains hypoxia-responsive elements (HREs) in the enhancer region of the promoter and a suicide gene. Under hypoxic conditions, the transcriptional complex hypoxia inducible factor-1 (HIF- 1) builds up in cells and binds to HREs. This, in turn, activates the adjacent promoter and causes expression of the downstream suicide gene that kills the cell. This project has 2 goals. The first is to investigate how several cellular or intratumoral characteristics impact on this gene therapy strategy. The second is to investigate whether the gene therapy enhances the radiation response of the tumor cells. We propose 4 specific aims to accomplish these goals. 1) investigate the relationship between HIF-1 and oxygenation status in brain tumor and normal brain; 2) evaluate suicide genes under low pH and in noncycling brain tumor cells; 3) reveal and investigate any bystander effect (BE) produced by specific suicide genes under hypoxic conditions; 4) determine whether expression of suicide genes in hypoxic and oxic cells enhances their response to radiation.