PET imaging of heat-inducible suicide gene expression in mice bearing head and neck squamous cell carcinoma xenografts

Abstract

The ability to achieve tumor selective expression of therapeutic genes is an area that needs improvement for cancer gene therapy to be successful. One approach to address this is through the use of promoters that can be controlled by external means, such as hyperthermia. In this regard, we constructed a replication-deficient adenovirus that consists of a mutated herpes simplex virus 1 thymidine kinase (mTK) fused to enhanced green fluorescent protein (EGFP) under the control of the full-length human heat shock (HS) 70b promoter. The virus (AdHSmTK-EGFP) was evaluated both in vitro and in vivo in oral squamous cell carcinoma SCC-9 cells for expression of both mTK and EGFP. The in vitro expression of mTK-EGFP was validated using both 3 H-penciclovir and fluorescence-activated cell sorting assays. These studies show that specific expression could be achieved by heating the cells at 41 1C for 1 h, whereas little expression was observed using high doses of virus without hyperthermia. The vector was also evaluated in vivo by direct intratumoral injection into mice bearing SCC-9 xenografts. These studies demonstrated tumor expression of mTK-EGFP after ultrasound heating of the tumors by radioactive biodistribution assays, histology and microPET imaging. These in vivo results, which demonstrate HS-inducible transgene expression using PET imaging, provide a means for noninvasive monitoring of heat-induced gene therapy in local tumors, such as oral squamous cell carcinomas.

Gene Therapy of Carcinoma Using Ultrasound-Targeted Microbubble Destruction

“…Despite their promise, these studies are disadvantaged by the requirement for surgical access to inject gene vectors directly into the tumor, which is not always technically feasible and limits the possibility of multiple treatments. Alternatively, if viral gene therapy vectors are delivered systemically, transduction of nontarget tissues may occur, resulting in adverse side effects (Parryl et al 2009). Viral vectors also elicit an immune response that can limit their effectiveness and prevent repeated delivery (Nayak and Herzog 2010).…”

Ultrasound-targeted microbubble destruction in gene therapy: A new tool to cure human diseases

“…Currently, viral vectors are the favored clinical approach, but transduction of non-target tissues may occur, resulting in adverse side effects. 61 Furthermore, viral vectors can elicit an immune response that could limit their effectiveness and prevent repeated delivery. 62 Thus, an ideal gene therapy method for cancer treatment would be non-viral and capable of specifically targeting and destroying tumor cells after delivery while leaving healthy tissue and organs unaffected.…”

A siRNA system based on HSP70 promoter results in controllable and powerful gene silencing by heat‐induction

“…Conversely, vector‐based siRNA drugs have the ability to be stably introduced when used in a gene‐therapy with one single treatment . In clinical settings, an ideal siRNA expression system should have three advantages: (I) It can be induced to initiate siRNA expression by exogenous signals or drugs in times of need; (II) It can precisely command siRNA expression based on the dose, time and dependence of the given inducer; (III) Under normal circumstances the expression of triggered siRNA is on a relatively low level, while after induction, it can be significantly increased . As a consequence, the siRNA expression is under control and may be terminated at any time when the treatment is successfully completed, or when side effects emerge.…”