Development of Adaptive Resistance to Electric Pulsed Field Treatment in CHO Cell Line <i>In Vitro</i>

Abstract

Background: Pulsed electric field (PEF) treatment has increased over the last few decades. It has been successfully translated from in vitro studies into different medical treatments like electrochemotherapy, Irreversible Electroporation for tumor and cardiac tissue ablation and gene electrotransfer for gene therapy and DNA vaccination. PEF treatment is efficient but local and sometimes there is a need to repeat the treatment, e.g. due to partial response and recurrence of disease. It has been recently suggested that cells may become resistant to electroporation in repetitive treatments. In our study, we thus evaluated the possibility of developing adaptive resistance in cells exposed to PEF treatment. Methods: CHO cells were exposed to electroporation pulses, 8 x 100 μs at electric field 1000 V/cm, initially causing 80 % permeabilization and 80 % survival of cells, for 30 generations. Every 5 th generation was analyzed by determining permeabilization using propidium iodide assay and survival curve using colorimetric MTS test. Findings: No statistical difference between cells in control and cells exposed to PEF treatment was observed. The results of our study provide evidence that electroporation does not affect cells in a way that they would become less susceptible to pulsed electric field treatment. Interpretation: Our findings indicate pulsed electric field treatment can be used in repeated treatments with equal efficiency as the initial treatment. Funding Statement: Slovenian Research Agency (research core funding No. P2-0249). The research was in part supported by Medtronic. The work was performed within the network of research and infrastructural centers of University of Ljubljana, which is financially supported by Slovenian Research Agency through infrastructural grant IP-0510. Declaration of Interests: The authors have declared that no competing interests exist.