Delivery of Hypoxia and Glioma Dual-Specific Suicide Gene Using Dexamethasone Conjugated Polyethylenimine for Glioblastoma-Specific Gene Therapy

Abstract

Gene therapy has been considered a promising approach for glioblastoma therapy. To avoid side effects and increase the specificity of gene expression, gene expression should be tightly regulated. In this study, glioma and hypoxia dual-specific plasmids (pEpo-NI2-SV-Luc and pEpo-NI2-SV-HSVtk) were developed by combining the erythropoietin (Epo) enhancer and nestin intron 2 (NI2). In the in vitro studies, pEpo-NI2-SV-Luc showed higher gene expression under hypoxia than normoxia in a glioblastoma-specific manner. The MTT and caspase assays demonstrated that pEpo-NI2-SV-HSVtk specifically induced caspase activity and cell death in hypoxic glioblastoma cells. For in vivo evaluation, subcutaneous and intracranial glioblastoma models were established. Dexamethasone-conjugated-polyethylenimine (PEI-Dexa) was used as a gene carrier, since PEI-Dexa efficiently delivers plasmid to glioblastoma cells and also has an antitumor effect due to the effect of dexamethasone. In the in vivo study in the subcutaneous and intracranial glioblastoma models, the tumor size was reduced more effectively in the pEpo-NI2-SV-HSVtk group than in the control and pSV-HSVtk groups. In addition, higher levels of HSVtk gene expression and TUNEL-positive cells were observed in the pEpo-NI2-SV-HSVtk group compared with the control and pSV-HSVtk groups, suggesting that pEpo-NI2-SV-HSVtk increased the therapeutic efficacy in hypoxic glioblastoma. Therefore, pEpo-NI2-SV-HSVtk/PEI-Dexa complex may be useful for glioblastoma-specific gene therapy.

Enhanced blood–brain barrier penetration and glioma therapy mediated by a new peptide modified gene delivery system

“…However, the therapeutic efficiency is of high demand to be enhanced. Till now, variety of non-viral gene delivery systems including polyplexes [2,4,16], liposomes [3,17], micelles [18], and nanobubbles [19], have been reported for glioma gene therapy. Among these systems, dendrigraft poly-L-lysines (DGL) was proved to be a potential gene delivery vector due to its cationic, monodispersed, well-defined, biodegradable and biocompatible properties [20] and easy modification of targeting ligands such as a choline derivate [4].…”

Peptide Micelle-Mediated Delivery of Tissue-Specific Suicide Gene and Combined Therapy with Avastin in a Glioblastoma Model

“…Suicide genes such as the herpes simplex virus thymidine kinase (HSVtk) gene have been delivered using delivery vectors such as adenoviral vectors . In addition to viral vectors, nonviral vectors have also been evaluated for the delivery of the HSVtk gene in glioblastoma animal models . Nonviral vectors include cationic polymers, liposomes, and peptides .…”

“…Recently, Avastin was approved for use in glioblastoma therapy in the United States . The glioma and hypoxia dual‐specific HSVtk, pEpo–NI2–SV–HSVtk, was previously developed by combining the erythropoietin (Epo) enhancer and the nestin intron 2 (NI2) . The Epo enhancer increased the transcription level in hypoxic tissue.…”

“…Solid tumors such as glioblastoma have a hypoxic region in their core, because of lack of blood supply. The Epo enhancer responds to the low‐oxygen concentration in the core of the tumors and enhances gene expression . NI2 was reported to increase gene expression in neural stem cells or glioblastoma .…”

“…Therefore, the dual‐specific expression vector may be useful for the treatment of glioblastoma with specific enhancement of gene expression in hypoxic glioblastoma tissue. Our previous report showed that pEpo–NI2–SV–HSVtk induced gene expression specifically in hypoxic glioblastoma cells and enhanced the therapeutic efficacy of glioblastoma gene therapy …”