Electroporation outperforms in vivo-jetPEI for intratumoral DNA-based reporter gene transfer

Liesl Jacobs,Kevin Hollevoet,Nick Geukens,Paul Declerck,Elien De Smidt

doi:10.1038/s41598-020-75206-2

Abstract

Intratumoral delivery of drug-encoding plasmid DNA (pDNA) enables localised in vivo expression of biological drugs, offering an attractive alternative to conventional protein treatment. However, this requires physical or chemical methods to enhance the low transfection efficiency of naked pDNA. Electroporation and complexation with the polycation in vivo-jetPEI are both evaluated in the clinic for intratumoral pDNA delivery, but lack head-to-head comparison. This study therefore compared both methods for intratumoral DNA-based reporter gene transfer in a subcutaneous mouse tumour model. Intratumoral electroporation resulted in strong reporter expression that was restricted to the tumour area and persisted for at least ten days. Intratumoral expression after injection of pDNA-jetPEI complexes was two to three logs lower, did not exceed the background in most mice, and lasted less than five days even with repeated dosing. Remarkably, reporter expression was primarily detected in the lungs, presumably due to leakage of pDNA-jetPEI complexes into the systemic circulation. In conclusion, electroporation enabled more efficient, prolonged and tumour-specific reporter expression compared to intratumoral injection of pDNA complexed with in vivo-jetPEI. These results favour the use of electroporation for intratumoral DNA-based gene transfer, and suggest further optimisation of pDNA-jetPEI complexes is needed to improve their efficacy and biosafety.

Highlights

Gene transfer of biological drugs presents an attractive alternative to conventional treatment modalities
PDNA is much less immunogenic, is easier to produce and has no defined restrictions regarding the size of the transgene. plasmid DNA (pDNA) presents a convenient expression platform for biological drugs, yet its low transfection efficiency requires physical or chemical methods to enhance in vivo pDNA uptake[1,2]
Most results to date are based on the use of viral vectors[2], despite recent progress with intratumoral pDNA delivery[3,7,8,14]

Summary

Introduction

Gene transfer of biological drugs presents an attractive alternative to conventional treatment modalities. While recent studies demonstrated promising results with mRNA, including fast but transient gene expression, most preclinical and clinical data have been reported with viral vectors. The latter enable robust and prolonged production of the transgene, with oncolytic viruses giving the additional advantage of tumour-specific cell killing and immune activation. Electroporation, for example, employs localised electrical pulses to generate transient pores in cell membranes[5] Cationic carriers such as the commercially available polyethylenimine in vivo-jetPEI form complexes with pDNA, thereby protecting it against degradation and promoting cellular entry by e ndocytosis[6]. The current study compares intratumoral electrotransfer of naked reporter pDNA with intratumoral injection of reporter pDNA complexed with in vivo-jetPEI in mice

Methods

Results

Conclusion