Heat Activated Gene Therapy Using Radiomimetic CdtB

描述（由申请人提供）：中心假设是有效的癌症基因治疗可以使用高毒性转基因来实现，该转基因从热诱导启动子可控地表达。 为了测试这一点，将细胞致死膨胀毒素B（Cdt B）（三联细菌蛋白毒素的细胞毒性组分）置于腺病毒载体中，所述腺病毒载体处于经修饰的人HSP 70 B热休克启动子的控制下，所述热休克启动子在41.0 ℃或更高温度下热休克之前非常沉默。 目的1是优化使用这种可热激活的CdtB基因疗法在兔VX 2脑肿瘤模型中建立局部肿瘤控制并延长动物生存期。 目的二是递送具有组织透化剂的腺病毒载体，所述组织透化剂增加间隙空间以促进载体在整个实体瘤中扩散，以确定这是否增加治疗功效。 据推测，使用透化剂将增加被感染以表达CdtB的肿瘤细胞的分数，以更有效地控制肿瘤并允许成功治疗更大的肿瘤。 目的三是阐明CdtB旁观者杀伤机制。 治疗功效取决于旁观者杀死与感染并表达CdtB转基因的那些细胞相邻的细胞。 虽然CdtB旁观者杀伤已在体外和体内观察到，很少有人知道它。实验将确定旁观者杀伤是由一个自由扩散的细胞外信号介导的，或者如果细胞间的接触和间隙连接通讯是必要的。 测定还将确定旁观者细胞是否通过细胞凋亡或其他死亡机制死亡，并将鉴定启动旁观者杀伤的信号。 一些肿瘤，例如，多形性胶质母细胞瘤、胰腺肿瘤等对常规放疗和化疗更难治疗，使得难以实现局部肿瘤控制。 此外，许多肿瘤以高频率局部复发，并且手术通常是不可能的和/或放射治疗选择是有限的，因为周围的正常组织已经积累了它们的耐受辐射剂量。 因此，需要能够改善原发性和复发性癌症的局部控制的补充疗法。 这项拟议的研究将测试热激活CdtB基因疗法的潜力，以帮助满足这一需求。

DESCRIPTION (provided by applicant): The central hypothesis is that effective cancer gene therapy can be achieved using a highly toxic transgene that is expressed controllably from a heat-inducible promoter. To test this, cytolethal distending toxin B (CdtB), the cytotoxic component of a tripartite bacterial proteotoxin, was placed into an adenovirus vector under control of a modified human HSP70B heat shock promoter that is extremely silent until heal shocked at 41.0 degrees C or higher. Aim 1 is to optimize using this heat-activatable CdtB gene therapy to establish local tumor control in a rabbit VX2 brain tumor model and to protract animal survival. Aim two is to deliver the adenovirus vectors with tissue permeabilizing agents that increase the interstitial space to promote vector diffusion throughout solid tumors to ascertain if this increases treatment efficacy. It is postulated that using the permeabilizers will increase the fraction of tumor cells that get infected to express CdtB to control tumors more efficiently and permit larger tumors to be treated successfully. Aim three is to explicate the mechanisms of CdtB bystander killing. Treatment efficacy is dependent upon bystander killing of cells adjacent to those infected with and expressing the CdtB transgene. Although CdtB bystander killing has been observed in vitro and in vivo, little is known about it. Experiments will determine if bystander killing is mediated by a freely diffusible extracellular signal or if cell-cell contact and gap junction communication are requisite. Assays will also establish if the bystander cells die by apoptosis or other death mechanisms and will identify the signals that initiate bystander killing. Some tumors, e.g., glioblastoma multiforme, pancreatic tumors, etc. are more refractory to conventional radiotherapy, and chemotherapy, making local tumor control difficult to achieve. Additionally, many tumors recur locally with high frequency and surgery is often impossible and/or radiotherapy options are limited because surrounding normal tissues have accrued their tolerance radiation dose. Consequently, complementary therapies that can improve local control for primary and recurrent cancers are needed. The proposed study will test the potential of heat-activated CdtB gene therapy to help satisfy this need.