Noninvasive and Local Delivery of Adenoviral-Mediated Herpes Simplex Virus Thymidine Kinase to Treat Glioma Through Focused Ultrasound-Induced Blood-Brain Barrier Opening in Rats

Adenoviral-mediated gene therapy has been shown great prospects for tumor treatment. However, it is still a great challenge for its application in the glioma. A main cause is the blood-brain barrier (BBB) limits the delivery of adenoviral vectors, greatly compromising their efficacy. Here, we used focused ultrasound (FUS) induced microbubble cavitation to locally and reversibly open BBB for enhancing gene delivery. In this study, Ad-CMV-TK-IRES-EGFP (Ad-HSV-TK-EGFP) carrying the herpes simplex virus thymidine kinase (HSV-TK) and EGFP transgenes was chose as gendicine and Ad-CMV-IRES-EGFP (Ad-EGFP) as the control. The in vitro experiments showed that Ad-HSV-TK-EGFP had a high infection efficiency for C6 glioma cells, producing good tumor cell killing effects when these cells were exposed to more than 10 μg/ml ganciclovir (GCV). Taking advantage of FUS-induced BBB opening, Ad-HSV-TK-EGFP could be effectively delivered into the brain tumors, getting the overexpression of HSV-TK gene in the tumor cells. After exposure to GCV, the significantly stronger anti-tumor efficacy and longer survival time were observed in tumor-bearing mice treated with Ad-HSV-TK-EGFP + FUS than those treated with Ad-EGFP + FUS or only Ad-HSV-TK-EGFP. Histological examination indicated that the reduced expression level of Ki67 proteins and the increased apoptotic tumor cells in tumor xenografts, causing the inhibition of tumor growth. In conclusion, our study provided a new strategy to efficiently and locally deliver recombinant adenoviral vector-mediated HSV-TK gene into the brain to treat glioma.