Performance of High Quality Minicircle DNA for In Vitro and In Vivo Gene Transfer.
ABSTRACT Plasmid DNA is frequently used particularly for nonviral gene therapy. Conventional plasmid DNA contains bacterial backbone and resistance gene sequences, as well as immunogenic CpG motifs. These components are not required for transgene expression. They represent a potential risk for safe clinical application and reduce gene transfer rates as well as transgene expression. To overcome these drawbacks, the minicircle technology is removing such sequences, to improve performance and also to reduce DNA size. Here, we show the effective production of luciferase, GFP, or lacZ-carrying minicircle DNA with high yield and reproducible high quality. They are used for lipofection or electroporation gene transfer into human melanoma and colon carcinoma cell lines. Comparison of respective parental plasmid and minicircle-mediated luciferase gene transfer shows improved luciferase expression by minicircle in all cell lines. This is not associated with increase in intracellular minicircle copy numbers after lipofection or electroporation. The minicircles rather mediate enhanced transgene mRNA transcription compared to their parental plasmids. In addition, FACS analysis revealed increase in counts of GFP positive cells after minicircle gene transfer, indicating higher gene transfer rates. Furthermore, minicircle showed also improved performance in vivo after jet-injection gene transfer. Therefore, availability of minicircles with reproducible high quality and sufficient amount makes them an applicable and effective alternative to conventional plasmid gene vectors.
- [Show abstract] [Hide abstract]
ABSTRACT: Nonviral gene therapy represents a realistic option for clinical application in cancer treatment. This preclinical study demonstrates the advantage of using the small-size MIDGE® DNA vector for improved transgene expression and therapeutic application. This is caused by significant increase in transcription efficiency, but not by increased intracellular vector copy numbers or gene transfer efficiency. We used the MIDGE-hTNF−alpha vector for high-level expression of hTNF-alpha in vitro and in vivo for a combined gene therapy and vindesine treatment in human melanoma models. The MIDGE vector mediated high-level hTNF-alpha expression leads to sensitization of melanoma cells towards vindesine. The increased efficacy of this combination is mediated by remarkable acceleration and increase of initiator caspase 8 and 9 and effector caspase 3 and 7 activation. In the therapeutic approach, the nonviral intratumoral in vivo jet-injection gene transfer of MIDGE-hTNF-alpha in combination with vindesine causes melanoma growth inhibition in association with increased apoptosis in A375 cell line or patient derived human melanoma xenotransplant (PDX) models. This study represents a proof-of-concept for an anticipated phase I clinical gene therapy trial, in which the MIDGE-hTNF-alpha vector will be used for efficient combined chemo- and nonviral gene therapy of malignant melanoma.Molecular oncology 05/2014; · 6.70 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Gene therapy provides a powerful tool for regulating cellular processes and tissue repair. Minicircle (MC) DNA are supercoiled DNA molecules free of bacterial plasmid backbone elements, and have been reported to enhance prolonged gene expression compared to conventional plasmids. Despite the great promise of MC DNA for gene therapy, methods for safe and efficient MC DNA delivery remain lacking. To overcome this bottleneck, here we report the development of a poly (β-amino ester) (PBAE)-based, biodegradable nanoparticulate platform for efficient delivery of MC DNA driven by an Ubc promoter in vitro and in vivo. By synthesizing and screening a small library of 18 PBAE polymers with different backbone and end-group chemistry, we identified lead cationic PBAE structures that can complex with minicircle DNA to form nanoparticles, and delivery efficiency can be further modulated by tuning PBAE chemistry. Using human embryonic kidney 293 cells and mouse embryonic fibroblasts as model cell types, we identified a few PBAE polymers that allow efficient MC delivery at levels that are comparable or even surpassing Lipofectamine 2000. The biodegradable nature of PBAE-based nanoparticles facilitates in vivo applications and clinical translation. When injected via intraperitoneal route in vivo, MC alone resulted in high transgene expression and a lead PBAE/MC nanoparticle formulation achieved a further 2-fold increase in protein expression compared to MC alone. Together, our results highlight the promise of PBAE-based nanoparticles as promising non-viral gene carriers for MC delivery, which may provide a valuable tool for broad applications of MC DNA-based gene therapy.ACS Nano 07/2013; · 12.03 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Minicircular DNA (mcDNA) biopharmaceuticals have recently risen as a valuable alternative for the development of a next generation of bioactive therapeutics because they are more efficient and safer than standard plasmid DNA (pDNA). To date, the relatively insufficient knowledge regarding mcDNA biosynthesis is currently hindering its manufacture in suitable amounts for clinical trial evaluations. Addressing this limitation is therefore mandatory to bring forth the full therapeutic potential of this cutting-edge technology. Herein, we describe for the first time, new processing parameters that improve the overall yield of mcDNA obtained from bacterial fermentations. We provide details for further in-line monitoring and optimization in view of the current good manufacturing guidelines. Our results show that by rising growth temperature to 42 ºC, an increase in the overall minicircle producer plasmid yield is attained, whilst biomass amounts are reduced. Moreover, by monitoring in real-time the dynamic recombination of parental plasmids to mcDNA, we found that this event is more efficient at specific time points, regardless of the growth temperature and inductor concentration used. These are important findings since mcDNA can be recovered with higher yields at these determined key stages. Indeed, the manipulation of these parameters resulted in a 2.21 fold increase in mcDNA production comparing with the established growth temperatures for this technology. Overall, our findings highlight that to achieve maximum productivity whilst attaining pharmaceutical-grade mcDNA preparations, process design and biosynthesis optimization must take into account key parameters such as temperature, inductor concentration and recovery time.Human Gene Therapy Methods 11/2013; · 1.64 Impact Factor