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

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

Human gene therapy has made significant advances in less than two decades. Within this short period of time, gene therapy has proceeded from the conceptual stage to technology development and laboratory research, and finally to clinical trials for the treatment of a variety of deadly diseases. Cardiovascular disease, cancer, and stroke are leading causes of death worldwide. Despite advances in medical, interventional, radiation and surgical treatments, the mortality rate remains high, and the need for novel therapies is great. Gene therapy provides an efficient approach to disease treatment. Notable advances in gene therapy have been made for genetic disorders, including severe combined immune deficiency, chronic granulomatus disorder, hemophilia and blindness, as well as for acquired diseases, including cancer and neurodegenerative and cardiovascular diseases. However, lack of an efficient delivery system to target cells as well as the difficulty of sustained expression of transgenes has hindered advancements in gene therapy. Ultrasound targeted microbubble destruction (UTMD) is a promising approach for target-specific gene delivery, and it has been successfully investigated for the treatment of many diseases in the past decade. In this paper, we review UTMD-mediated gene delivery for the treatment of cardiovascular diseases, cancer and stroke.

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

RNAi is a powerful tool for gene-specific knockdown and gene therapy. However, the imprecise expression of siRNA limits the extensive application of RNAi in gene therapy. Here we report the development of a novel controllable siRNA expression vector pMHSP70psil that is initiated by HSP70 promoter. We determined the efficiency of the controllable siRNA system by targeting the gama-synuclein (SNCG) gene in breast cancer cells MCF-7. The results show that the controllable siRNA system can be induced to initiate siRNA expression by heat-induction. The silencing effect of SNCG occurs at a relatively low level (10.1%) at 37°C, while it is significantly increased to 69.4% after heat induction at 43°C. The results also show that the controllable siRNA system inhibits proliferation of cancer cells by heat-shock. Therefore, this RNAi strategy holds the promise of the high efficiency in gene knockdown at targeted times and locations, avoiding systemic side effects. It provides, for the first time, an approach to control siRNA expression by heat-shock.

Gene therapy of carcinoma using ultrasound-targeted microbubble destruction

When microbubble contrast agents are loaded with genes and systemically injected, ultrasound-targeted microbubble destruction (UTMD) facilitates focused delivery of genes to target tissues. A mouse model of squamous cell carcinoma was used to test the hypothesis that UTMD would specifically transduce tumor tissue and slow tumor growth when treated with herpes simplex virus thymidine kinase (TK) and ganciclovir. UTMD-mediated delivery of reporter genes resulted in tumor expression of luciferase and green fluorescent protein (GFP) in perivascular areas and individual tumor cells that exceeded expression in control tumors (p=0.02). The doubling time of TK-treated tumors was longer than GFP-treated tumors (p=0.02), and TK-treated tumors displayed increased apoptosis (p=0.04) and more areas of cellular drop-out (p=0.03). These data indicate that UTMD gene therapy can transduce solid tumors and mediate a therapeutic effect. UTMD is a promising nonviral method for targeting gene therapy that may be useful in a spectrum of tumors.

Modular strategies for PET imaging agents

In recent years, modular and simplified chemical and biological strategies have been developed for the synthesis and implementation of positron emission tomography (PET) radiotracers. New developments in bioconjugation and synthetic methodologies, in combination with advances in macromolecular delivery systems and gene-expression imaging, reflect a need to reduce radiosynthesis burden in order to accelerate imaging agent development. These new approaches, which are often mindful of existing infrastructure and available resources, are anticipated to provide a more approachable entry point for researchers interested in using PET to translate in vitro research to in vivo imaging.