MRI-guided ultrasonic heating allows spatial control of exogenous luciferase in canine prostate

The need for efficient and controlled delivery is one of the major obstacles to clinical use of gene therapy. In this study, we investigated the use of magnetic resonance imaging-monitored ultrasound (US) to induce expression of luciferase after local injection of the construct Ad-HSP-Luc, an adenoviral vector containing a transgene encoding firefly luciferase under the control of the human hsp70B promoter. The hsp promoter allows induction of the associated transgene only in areas that are subsequently heated after infection. US imaging was used to guide the injection of purified virus into both lobes of the prostates of three beagles. At 48 h after injection, the left lobe of the prostate was heated using a 1.5-MHz US transducer driven by a multichannel radiofrequency system and employing an magnetic resonance imaging guidance system. High levels of luciferase expression were observed only in areas exposed to ultrasonic heating. This study demonstrates the feasibility of using ultrasonic heating to control transgene expression spatially using a minimally-invasive approach.