Retro-inverso CendR peptide-mediated polyethyleneimine for intracranial glioblastoma-targeting gene therapy

The development of nonviral gene delivery vectors offers the potential to provide effective treatment for glioblastoma in the form of gene therapy. Here, we report the use of retro-inverso C-end rule (CendR) peptide _D(RPPREGR) as a targeting ligand to prepare a _D(RPPREGR)- PEG-PEI gene vector. _D(RPPREGR) peptide specifically recognized the neuropilin-1 receptor that was overexpressed on U87 glioma cells, and showed enhanced tumor spheroid penetration ability. Compared with parental RGERPPR, _D(RPPREGR) possessed improved biological stability and had a higher affinity for U87 glioma cells; it also showed enhanced penetration of the tumor spheroid. mPEG-PEI/pDNA and _D(RPPREGR)-PEG-PEI/pDNA complexes were prepared and MTT assay results revealed that the cytotoxicity of _D(RPPREGR)-PEG-PEI complexes was significantly lower than that of PEI complexes, with cell survival rates above 80%. Qualitative and quantitative in vitro transfection results revealed that _D(RPPREGR)-PEG-PEI complex transfection efficiencies were 1.9 times higher than those of mPEG-PEI. Fluorescent imaging and frozen sections of brain tissue demonstrated that the _D(RPPREGR) modification improved the in vivo transfection efficiency of mPEG-PEI in nude mice bearing U87 gliomas. An antiglioblastoma assay revealed that _D(RPPREGR)-PEG-PEI carrying the therapeutic gene pORF-hTRAIL significantly prolonged the survival time of intracranial U87 glioma-bearing mice from 25 to 30 days. Therefore, _D(RPPREGR)-PEG-PEI appears to be suitable for use as a safe and efficient gene delivery vehicle with potential applications in glioblastoma gene therapy.