Oncolytic Adenoviruses Armed with Thymidine Kinase Can Be Traced by PET Imaging and Show Potent Antitumoural Effects by Ganciclovir Dosing

Replication-competent adenoviruses armed with thymidine kinase (TK) combine the concepts of virotherapy and suicide gene therapy. Moreover TK-activity can be detected by noninvasive positron emission-computed tomography (PET) imaging, what could potentially facilitate virus monitoring in vivo. Here, we report the generation of a novel oncolytic adenovirus that incorporates the Tat8-TK gene under the control of the Major Late Promoter in a highly selective backbone thus providing selectivity by targeting the retinoblastoma pathway. The selective oncolytic TK virus, termed ICOVIR5-TK-L, showed reduced potency compared to a non-selective counterpart. However the combination of ICOVIR5-TK-L with ganciclovir (GCV) induced a potent antitumoural effect similar to that of wild type adenovirus in a preclinical model of pancreatic cancer. Although the treatment with GCV provoked a reduction in the viral yield, both in vitro and in vivo, a two-cycle treatment of virus and GCV resulted in an enhanced antitumoral response that correlated with high TK-activity, based on microPET measurements. Thus, TK-expressing oncolytic adenoviruses can be traced by PET imaging providing real time information on the activity of the virus and its antitumoral potency can be optimized by GCV dosing.

携带胸苷激酶（thymidine kinase，TK）的复制型腺病毒融合了溶瘤病毒疗法与自杀基因疗法的双重理念。此外，其TK活性可通过无创正电子发射计算机断层显像（positron emission tomography-computed tomography，PET）检测，有望实现体内病毒的无创监测。本研究构建了一种新型溶瘤腺病毒：该病毒以高度选择性的腺病毒骨架为载体，将Tat8-TK融合基因置于主要晚期启动子（Major Late Promoter）的调控之下，通过靶向视网膜母细胞瘤通路实现病毒的选择性复制。这款命名为ICOVIR5-TK-L的选择性溶瘤TK病毒，其复制活性相较于非选择性对照病毒有所减弱。然而，在胰腺癌临床前模型中，ICOVIR5-TK-L与更昔洛韦（ganciclovir，GCV）联合给药时，可诱导出与野生型腺病毒相当的强效抗肿瘤效应。尽管更昔洛韦处理在体外与体内均会导致病毒滴度下降，但基于微型正电子发射计算机断层显像（microPET）的检测结果显示，病毒与更昔洛韦的两周期联合治疗可增强抗肿瘤应答，且该应答与高水平的TK活性密切相关。综上，表达TK的溶瘤腺病毒可通过PET显像实现实时追踪，获取病毒活性的实时信息，且可通过调整更昔洛韦给药剂量优化其抗肿瘤效能。