A CEST-MRI Reporter Gene for Image Guided Oncolytic Virotherapy

 描述（由申请人提供）：许多癌症的高度侵袭性和大多数全身化疗的毒性代表了癌症治疗的重大挑战，并限制了其有效性。克服这些挑战的一种非常有希望的治疗方法是使用溶瘤病毒，其选择性地仅杀死癌细胞，而不伤害周围的正常细胞。溶瘤病毒可以在肿瘤中原位产生子代，并到达远端恶性细胞，因此代表了治疗侵袭性癌症如多形性胶质母细胞瘤（GBM）的理想策略。此外，溶瘤病毒可以被工程化以表达化学治疗剂，从而提供多模式的靶向药物递送。最后，溶瘤病毒可以引发针对病毒感染的肿瘤细胞的强烈免疫应答。然而，溶瘤病毒疗法的优化及其临床转化目前受到缺乏方法来监测这些治疗策略的成功和成像肿瘤内病毒递送、复制和传播的阻碍。 我们建议开发和优化MRI报告基因，可以被工程化到溶瘤病毒，并允许溶瘤病毒治疗的非侵入性成像。我们最近已经证明，由于酰胺可交换的赖氨酸质子，用编码富赖氨酸蛋白（LRP）的人工基因工程化的溶瘤单纯疱疹病毒（oHSV）在病毒感染的急性阶段产生的化学交换饱和转移（CEST）MRI对比度显著高于从用对照、非LRP表达病毒感染的肿瘤获得的对比度。然而，将CEST oHSV报告基因方法转化到临床用于oHSV治疗的纵向成像将需要成像和报告基因技术的改进。我们假设，具有更高交换率特异性的改进CEST MRI方法将使病毒感染和复制能够在OV肿瘤治疗的整个过程中被连续监测。为了检验这一假设，我们将首先量化oHSV治疗期间的内源性肿瘤CEST对比度和质子交换率（目的1）。接下来，我们将优化频率标记交换转移（FLEX）和可变延迟多脉冲（VPEST）CEST MRI方法，以分别对快速交换的LRP酰胺质子和缓慢交换的内源性酰胺质子进行选择性成像（目标2）。最后，我们将在临床相关的小鼠GBM肿瘤模型中分别使用即时早期和晚期基因病毒启动子来纵向成像病毒感染和复制（目的3）。

 DESCRIPTION (provided by applicant): The highly invasive nature of many cancers and the toxicity of most systemic chemotherapies represent significant challenges for cancer therapies and limit their effectiveness. A very promising therapeutic approach for overcoming these challenges is the use of oncolytic viruses that selectively kill only cancer cells, while sparing te surrounding normal cells. Oncolytic viruses can generate progeny on-site that spread throughout the tumor and reach distal malignant cells, thus representing an ideal strategy for treating invasive cancers such as glioblastoma multiforme (GBM). In addition, oncolytic viruses can be engineered to express chemotherapeutics and thereby provide multimodal, targeted drug delivery. Finally, oncolytic viruses can elicit a strong immune response against viral infected tumor cells. However, the optimization of oncolytic virotherapies and their clinical translation is currently hindered by the lack of methods to monitor the success of these therapeutic strategies and image intratumoral viral delivery, replication and spread. We propose to develop and optimize a MRI reporter gene that can be engineered into oncolytic viruses and allow for the non-invasive imaging of oncolytic virotherapy. We have recently demonstrated that an oncolytic Herpes Simplex Virus (oHSV) engineered with an artificial gene encoding for a Lysine-Rich Protein (LRP) generated Chemical Exchange Saturation Transfer (CEST) MRI contrast, due to the amide exchangeable lysine protons, at acute stages of viral infection that was significantly higher than the contrast obtained from tumors infected with control, non-LRP expressing virus. Translation of the CEST oHSV reporter gene method to the clinic for longitudinal imaging of oHSV therapy will, however, require improvements in the imaging and reporter gene technology. We hypothesize that improved CEST MRI methods with greater exchange rate specificity will enable viral infection and replication to be monitored longitudinall throughout OV tumor therapy. To test this hypothesis we will first quantify the endogenous tumor CEST contrast and proton exchange rate during oHSV therapy (Aim 1). Next we will optimize Frequency Labeled Exchange Transfer (FLEX) and Variable Delay Multi-Pulse (VDMP) CEST MRI methods to selectively image the fast exchanging LRP amide protons and the slow exchanging endogenous amide protons, respectively (Aim 2). Finally, we will use immediate early and late gene viral promoters to longitudinally image viral infection and replication, respectively, in clinically relevant mouse GBM tumor models (Aim 3).