Current Gene Therapy (v.15, #1)

Preface: by Ignacio Anegon, Tuan H. Nguyen (1-2).

Effects of APC De-Targeting and GAr Modification on the Duration of Luciferase Expression from Plasmid DNA Delivered to Skeletal Muscle by Maria C. Subang, Rewas Fatah, Ying Wu, Drew Hannaman, Jason Rice, Claire F. Evans, Yuti Chernajovsky, David Gould (3-14).
Immune responses to expressed foreign transgenes continue to hamper progress of gene therapy development. Translated foreign proteins with intracellular location are generally less accessible to the immune system, nevertheless they can be presented to the immune system through both MHC Class I and Class II pathways. When the foreign protein luciferase was expressed following intramuscular delivery of plasmid DNA in outbred mice, expression rapidly declined over 4 weeks. Through modifications to the expression plasmid and the luciferase transgene we examined the effect of detargeting expression away from antigen-presenting cells (APCs), targeting expression to skeletal muscle and fusion with glycine-alanine repeats (GAr) that block MHC-Class I presentation on the duration of luciferase expression. De-targeting expression from APCs with miR142-3p target sequences incorporated into the luciferase 3'UTR reduced the humoral immune response to both native and luciferase modified with a short GAr sequence but did not prolong the duration of expression. When a skeletal muscle specific promoter was combined with the miR target sequences the humoral immune response was dampened and luciferase expression persisted at higher levels for longer. Interestingly, fusion of luciferase with a longer GAr sequence promoted the decline in luciferase expression and increased the humoral immune response to luciferase. These studies demonstrate that expression elements and transgene modifications can alter the duration of transgene expression but other factors will need to overcome before foreign transgenes expressed in skeletal muscle are immunologically silent.

MicroRNAs: Association with Radioresistant and Potential Uses of Natural Remedies as Green Gene Therapeutic Approaches by Subramanion L. Jothy, Yeng Chen, Soundararajan Vijayarathna, Jagat R. Kanwar, Sreenivasan Sasidharan (15-20).
Radiotherapy plays an essential primary role in cancer patients. Regardless of its significant advances in treatment options, tumor recurrence and radio-resistance in cancer cells still occur in a high percentage of patients. Furthermore, the over expression of miRNAs accompanies the development of radio-resistant cancer cells. Consequently, miRNAs might serve as therapeutic targets for the treatment of radio-resistance in cancer cells. The findings of the current research also signify that the use of a natural anti-miRNA substance could inhibit specific miRNAs, and, concurrently, these natural remedies could exhibit radioprotective activity against the healthy cells during radiotherapy. Therefore, in this review, we have reported the association of miRNAs with radio-resistance and the potential uses of natural remedies as green gene therapeutic approaches, as well as radioprotectors against the adverse effects of irradiation on healthy cells during radiotherapy.

Transfection of CXCR-4 Using Microbubble-Mediated Ultrasound Irradiation and Liposomes Improves the Migratory Ability of Bone Marrow Stromal Cells by Gong Wang, Zhongxiong Zhuo, Qian Zhang, Yali Xu, Shengzheng Wu, Lu Li, Hongmei Xia, Yunhua Gao (21-31).
Bone marrow stromal cells (BMSCs) have proven useful for the treatment of various human diseases and injuries. However, their reparative capacity is limited by their poor migration and homing ability, which are primarily dependent on the SDF-1/CXCR4 axis. Most subcultured BMSCs lack CXCR4 receptor expression on the cell surface and exhibit impaired migratory capacity. To increase responsiveness to SDF-1 and promote cell migration and survival of cultured BMSCs, we used a combination of ultrasound-targeted microbubble destruction (UTMD) and liposomes to increase CXCR4 expression in vitro. We isolated and cultured rat BMSCs to their third passage and transduced them with recombinant plasmid pDsRed-CXCR4 using microbubble-mediated ultrasound irradiation and liposomes. Compared to some viral vectors, the method we employed here resulted in significantly better transfection efficiency, CXCR4 expression, and technical reproducibility. The benefits of this approach are likely due to the combination of “sonoporation” caused by shockwaves and microjet flow resulting from UTMD-generated cavitation. Following transfection, we performed a transwell migration assay and found that the migration ability of CXCR4-modified BMSCs was 9-fold higher than controls. The methods we describe here provide an effective, safe, non-viral means to achieve high levels of CXCR4 expression. This is associated with enhanced migration of subcultured BMSCs and may be useful for clinical application as well.

Controlled Gene Delivery Can Enhance Therapeutic Outcome for Cancer Immune Therapy for Melanoma by Shawna A. Shirley, Cathryn G. Lundberg, Fanying Li, Niculina Burcus, Richard Heller (32-43).
Effective delivery still remains a major hurdle in the development of gene based therapies. While technological advances have occurred that have improved delivery in general, there is still a need for controlled delivery in order to achieve therapeutic effects. Gene electrotransfer (GET) can be utilized to accomplish this. Careful selection of parameters used for delivery such as amplitude, duration and number of pulses as well as plasmid construct can be manipulated in order to achieve appropriate levels of local expression. Previously we have shown that direct delivery of the therapeutic cytokine, interleukin 12 (IL-12), to tumors using electrotransfer can generate local and systemic anti-tumor effects in pre-clinical and clinical studies. Using this model we hypothesized that modulating local gene expression using GET can affect therapeutic outcome. To test this, we used multiple GET protocols and plasmids to achieve varying levels of local IL-12 expression. We found that high local gene expression did not give rise to a better therapeutic outcome. This suggests the level and possibly the duration of gene expression are important in mediating the host immune response against melanoma. These data also emphasize the importance of considering the desired immune outcome of the therapy when selecting parameters for GET.

Safety and Efficacy of Tumor-Targeted Interleukin 12 Gene Therapy in Treated and Non-Treated, Metastatic Lesions by Jeffry Cutrera, Glenn King, Pamela Jones, Kristin Kicenuik, Elias Gumpel, Xueqing Xia, Shulin Li (44-54).
The ability to control the immune system to actively attack tumor tissues will be a marvelous weapon to combat the persistent attack of cancer. Unfortunately, safe and effective methods to gain this control are not yet available as cancer therapies. To overcome the impediments to this control, tumor-targeted (tt) Interleukin 12 (IL-12) plasmid DNA can be safely delivered to accessible tumors, and these treatments can induce antitumor immune responses in both the treated and untreated tumors. Here, electroporationmediated ttIL-12 pDNA treatments are shown to be safe and well tolerated in a dose escalation study in canines bearing naturally-occurring neoplasms. The final patient in the dose-escalation study received up to 3,800 ?g pDNA distributed among five separate squamous cell carcinoma tumors in doses equivalent to those administered in a Phase I trial with wildtype IL-12 pDNA. Not a single severe adverse event occurred in any patient at any of the five dose levels, and only minor, transient changes were noted in any tested parameter. Clinical response analysis and immune marker mRNA detection of treated and non-treated lesions suggest that ttIL-12 pDNA treatments in only a few tumors can elicit antitumor immune responses in the treated lesions as well as distant metastatic lesions. These observations and results demonstrate that ttIL-12 pDNA can be safely administered at clinical levels, and these treatments can affect both treated and nontreated, metastatic lesions.

Microfluidics is a compelling technology that shows considerable promise in applications ranging from gene expression profiling to cell-based assays. Owing to its capacity to enable generation of single droplets and multiple droplet arrays with precisely controlled composition and a narrow size distribution, recently microfluidics has been exploited for delivery of genes. This article provides an overview of recent advances in microfluidic gene delivery, and speculates the prospects for further research. The objectives of this article are to illustrate the potential roles played by microfluidics in gene delivery research, and to shed new light on strategies to enhance the efficiency of gene therapy.

Preclinical Evaluation of Efficacy and Safety of an Improved Lentiviral Vector for the Treatment of β-Thalassemia and Sickle Cell Disease by Olivier Negre, Cynthia Bartholomae, Yves Beuzard, Marina Cavazzana, Lauryn Christiansen, Celine Courne, Annette Deichmann, Maria Denaro, Edouard de Dreuzy, Mitchell Finer, Raffaele Fronza, Beatrix Gillet-Legrand, Christophe Joubert, Robert Kutner, Philippe Leboulch, Leila Maouche, Anais Paulard, Francis J. Pierciey, Michael Rothe, Byoung Ryu, Manfred Schmidt, Christof von Kalle, Emmanuel Payen, Gabor Veres (64-81).
A previously published clinical trial demonstrated the benefit of autologous CD34+ cells transduced with a selfinactivating lentiviral vector (HPV569) containing an engineered β-globin gene (βA-T87Q-globin) in a subject with β thalassemia major. This vector has been modified to increase transduction efficacy without compromising safety. In vitro analyses indicated that the changes resulted in both increased vector titers (3 to 4 fold) and increased transduction efficacy (2 to 3 fold). An in vivo study in which 58 β-thalassemic mice were transplanted with vector- or mock-transduced syngenic bone marrow cells indicated sustained therapeutic efficacy. Secondary transplantations involving 108 recipients were performed to evaluate long-term safety. The six month study showed no hematological or biochemical toxicity. Integration site (IS) profile revealed an oligo/polyclonal hematopoietic reconstitution in the primary transplants and reduced clonality in secondary transplants. Tumor cells were detected in the secondary transplant mice in all treatment groups (including the control group), without statistical differences in the tumor incidence. Immunohistochemistry and quantitative PCR demonstrated that tumor cells were not derived from transduced donor cells. This comprehensive efficacy and safety data provided the basis for initiating two clinical trials with this second generation vector (BB305) in Europe and in the USA in patients with β-thalassemia major and sickle cell disease.

Regulatory elements of the osteopontin (opn) gene are attractive candidates for expressiontargeted gene therapy because numerous malignant cancers are marked by opn overexpression. The maximum opn promoter (Popn)-driven reporter intensity obtained for tested cancer cell lines was as strong (102.69%) as positive-control transfections. At the same time, Popn-driven reporter expression was reduced by ~90% in non-cancer cell lineages. Deletion analysis of the -922 bp region opn promoter did not confirm published reports of a repressor area within 922 bases upstream of the transcriptional start site. Further enhancements to targeting and expression were obtained through incorporation of single-nucleotide polymorphisms (SNPs) into the promoter sequence. It was found that the SNPs -443C, -155GG, -66T led to increased Popn-driven transfection in cancer cells (fold increase of 1.23 ~ 3.48), with a concomitant decrease in reporter expression in normal controls (fold change of 0.69). Further investigations to confirm a correlation between endogenous opn mRNA levels and Popn-driven reporter expression produced a surprising lack of correlation (R2=0.24). However, taking into account opn mRNA splicing variants showed a strong negative correlation between mRNA levels of the variant opn-a and P opn-driven transgene activity (R2=0.95). These data have implications on how future searches for expression-targeting promoters should be conducted.