Current Gene Therapy (v.12, #2)

Background: The previous works about safety evaluation for constructed bladder tissue specific adenovirus are poorly documented. Thus, we investigated the biodistribution and body toxicity of bladder specific oncolytic adenovirus Ad-PSCAE-UPII-E1A (APU-E1A) and Ad-PSCAE-UPII-E1A-AR (APU-E1A-AR), providing meaningful information prior to embarking on human clinical trials. Materials and Method: Conditionally replicate recombinant adenovirus (CRADs) APU-E1A, APU-EIA-AR were constructed with bladder tissue specific UroplakinII(UPII) promoter to induce the expression of Ad5E1A gene and E1A-AR fusing gene, and PSCAE was inserted at upstream of promoter to enhance the function of promoter. Based on the cytopathic and anti-tumor effect of bladder cancer, these CRADs were intratumorally injected into subcutaneous xenografts tumor in nude mice. We then determined the toxicity through general health and behavioral assessment, hepatic and hematological toxicity evaluation, macroscopic and microscopic postmortem analyses. The spread of the transgene E1A of adenovirus was detected with RT-PCR and Western blot. Virus replication and distribution were examined with APU-LUC administration and Luciferase Assay. Results: General assessment and body weight of the animals did not reveal any alteration in general behavior. The hematological alterations of groups which were injected with 5x108 pfu or higher dose (5x109 pfu) of APU-E1A and APU-E1A-AR showed no difference in comparison with PBS group, and only slight increased transaminases in contrast to PBS group at 5x109 pfu of APU-E1A and APU-E1A-AR were observed. E1A transgene did not disseminate to organs outside of xenograft tumor. Virus replication was not detected in other organs beside tumor according to Luciferase Assay. Conclusions: Our study showed that recombinant adenovirus APU-E1A-AR and APU-E1A appear safe with 5x107 pfu and 5x108 pfu intratumorally injection in mice, without any discernable effects on general health and behavior.

Suicide gene therapy is an attractive strategy to selectively destroy cancer cells while minimizing unnecessary toxicity to normal cells. Since this idea was first introduced more than two decades ago, numerous studies have been conducted and significant developments have been made to further its application for mainstream cancer therapy. Major limitations of the suicide gene therapy strategy that have hindered its clinical application include inefficient directed delivery to cancer cells and the poor prodrug activation capacity of suicide enzymes. This review is focused on efforts that have been and are currently being pursued to improve the activity of individual suicide enzymes towards their respective prodrugs with particular attention to the application of nucleotide metabolizing enzymes in suicide cancer gene therapy. A number of protein engineering strategies have been employed and our discussion here will center on the use of mutagenesis approaches to create and evaluate nucleotide metabolizing enzymes with enhanced prodrug activation capacity and increased thermostability. Several of these studies have yielded clinically important enzyme variants that are relevant for cancer gene therapy applications because their utilization can serve to maximize cancer cell killing while minimizing the prodrug dose, thereby limiting undesirable side effects.

Hepatocellular carcinoma (HCC) is a malignancy with a high mortality. Gene therapy provides a promising way for the treatment of HCC. Efficient gene delivery system, suitable gene target and appropriate way of administration together determine the effect of gene therapy for HCC. In recent years, employing non-viral gene delivery systems in gene therapy for HCC has attracted a lot of attention. Compared with viral vectors, non-viral gene delivery systems are nearly non-immunogenic, relatively safer, less expensive to produce and can carry a good many of genetic materials. But the transfection efficiency of these vectors still needs to be improved. And the liver targeting is another problem that needs to be solved. Attaching ligands to the non-viral vectors to enhance the targeting ability to the specific receptor and targeting to molecular targets of HCC are the effective strategies. Adopting suitable ways of administration is also a factor that plays an important role to achieve liver targeting. This review introduced the advances in liver-targeted gene therapy by non-viral vectors including the efforts to overcome the low transfection efficiency and enhance the liver targeting effect.

Ex Vivo Gene Therapy and Vision by Kevin Gregory-Evans (103-115).
Ex vivo gene therapy, a technique where genetic manipulation of cells is undertaken remotely and more safely since it is outside the body, is an emerging therapeutic strategy particularly well suited to targeting a specific organ rather than for treating a whole organism. The eye and visual pathways therefore make an attractive target for this approach. With blindness still so prevalent worldwide, new approaches to treatment would also be widely applicable and a significant advance in improving quality of life. Despite being a relatively new approach, ex vivo gene therapy has already achieved significant advances in the treatment of blindness in pre-clinical trials. In particular, advances are being achieved in corneal disease, glaucoma, retinal degeneration, stroke and multiple sclerosis through genetic re-programming of cells to replace degenerate cells and through more refined neuroprotection, modulation of inflammation and replacement of deficient protein. In this review we discuss the latest developments in ex vivo gene therapy relevant to the visual pathways and highlight the challenges that need to be overcome for progress into clinical trials.

The discovery in the early 2000's that magnetic nanoparticles (MNPs) complexed to nonviral or viral vectors can, in the presence of an external magnetic field, greatly enhance gene transfer into cells has raised much interest. This technique, called magnetofection, was initially developed mainly to improve gene transfer in cell cultures, a simpler and more easily controllable scenario than in vivo models. These studies provided evidence for some unique capabilities of magnetofection. Progressively, the interest in magnetofection expanded to its application in animal models and led to the association of this technique with another technology, magnetic drug targeting (MDT). This combination offers the possibility to develop more efficient and less invasive gene therapy strategies for a number of major pathologies like cancer, neurodegeneration and myocardial infarction. The goal of MDT is to concentrate MNPs functionalized with therapeutic drugs, in target areas of the body by means of properly focused external magnetic fields. The availability of stable, nontoxic MNP-gene vector complexes now offers the opportunity to develop magnetic gene targeting (MGT), a variant of MDT in which the gene coding for a therapeutic molecule, rather than the molecule itself, is delivered to a therapeutic target area in the body. This article will first outline the principle of magnetofection, subsequently describing the properties of the magnetic fields and MNPs used in this technique. Next, it will review the results achieved by magnetofection in cell cultures. Last, the potential of MGT for implementing minimally invasive gene therapy will be discussed.

Dendritic cells (DCs) behave as antigenic or tolerogenic immune response inducers depending on the nature of their precursors, their differentiation pathway and their environment. As professional antigen presenting cells (APCs) it has been tempting to genetically modify them in order to improve their capacity to mount appropriate protective immune responses. Gene transfer may also be helpful to investigate fundamental issues about the DC biology. Of note, almost all strategies to deliver genes or interfering RNA into DCs have been used with different success rates. These methods are non-exhaustively presented and discussed here. We focused our attention on promising in vitro as well as in vivo lentiviral- mediated gene delivery solutions into murine or human DCs.