Transposon-based interferon gamma gene transfer overcomes limitations of episomal plasmid for immunogene therapy of glioblastoma

Abstract

Despite improvements in gene delivery technology, transient expression of plasmid DNA has limited the efficacy of nonviral vectors applied to cancer gene therapy. We previously developed plasmid DNA vectors capable of transgene integration and long-term expression in human glioblastoma cells by utilizing the Sleeping Beauty (SB) transposable element. In this study, we compared the efficacy of interferon gamma (IFN-g) immunogene therapy using episomal or SB vectors in a syngeneic GL261 glioma model. Gene delivery was achieved by intratumoral convection-enhanced delivery of DNA/polyethylenimine complexes. Only mice treated with SB transposase-encoding DNA to facilitate chromosomal integration exhibited a significant increase in survival (Po0.05). SBmediated intratumoral gene transfer caused sustained IFN-g expression assessed by reverse transcription-polymerase chain reaction, of both vector-derived and endogenous IFN-g, whereas expression following episomal plasmid gene transfer was undetectable within 2 weeks. Median survival was enhanced further when SB-mediated IFN-g gene transfer was combined with CpG oligodeoxynucleotides as adjuvant therapy. Prolonged survival positively correlated with tumor regression measured by in vivo bioluminescent imaging, and enhanced T-cell activation revealed by the ELISPOT assay. SB appears to improve the efficacy of cytokine gene therapy using nonviral vectors by enhancing the duration of transgene expression.

Nonviral Gene Delivery with the Sleeping Beauty Transposon System

“…Furthermore, PEI-based systemic delivery of the SB transposon system encoding the human indoleamine-2,3-dioxygenase (hIDO) gene was evaluated in the context of lung transplantation-associated chronic complications, and found to elicit a remarkable therapeutic response, as evidenced by near normal pulmonary function in lung allografts (H. Liu et al, 2006). Last, SBmediated gene transfer significantly increased survival of mice bearing human glioblastoma xenografts by expressing antiangiogenic gene products (Ohlfest et al, 2005a), and improved the efficacy of immunotherapy by facilitating sustained cytokine expression after local, intratumoral injections of vector-PEI complexes (Wu et al, 2007).…”

Inhibition of angiogenesis and suppression of colorectal cancer metastatic to the liver using the Sleeping Beauty Transposon System

“…Wu et al compared the efficacy of interferon-gamma immunogene therapy using non-integrating plasmid vectors vs SB plasmid vectors in a syngeneic glioma model. Only animals co-injected with SB transposase plasmid exhibited prolonged expression of interferon-gamma and a significant increase in survival (3 weeks), while expression in animals treated with transposon plasmid alone was undetectable after 1 week [53]. …”

Gene Therapy and Targeted Toxins for Glioma

“…IFNγ has been shown to upregulate the expression of MHCI, MHCII, and NK cell activating ligands in both human and murine GBM cell lines [199, 200]. Pre-clinical experiments have shown that intratumoral delivery of IFNγ using either adenoviral vectors [200]or transposon elements [201] enhances the recruitment of lymphocytes to the brain tumor site in orthotopic mouse models of GBM, but does not lead to long-term survival. A recent study using a canine spontaneous model of brain cancer, has demonstrated long-term survival following delivery of an adenoviral vector encoding IFNγ when used in combination with multiple vaccinations with autologous tumor cells mixed with CpG oligodeoxynucleotides.…”