Calcium delivery via electroporation significantly enhances cell death in vitro

Abstract

The intracellular/intratumoral delivery of chemotherapeutic drugs using electroporation has been widely investigated as a promising modality for cancer treatment. Recently it has been discovered that calcium ion delivery via electroporation can also kill cancerous cells without posing harm to neighbour healthy tissue. The increase of intracellular calcium concentration can significantly induce cell death and tumour necrosis, thus calcium electroporation is considered to be an effective alternative to electrochemotherapy using anticancer drugs such as bleomycin or cisplatin [1]. Cell death is induced by the sudden change in calcium concentration inside the cell which is related to ATP depletion, lipase and protease activity, the production of reactive oxygen species, non-specific pore opening, etc [2]. Despite the plethora of investigations performed, the true mechanism behind calcium electroporation remains unclear. In addition, electroporation parameters for effective calcium delivery to cells have to be determined. In this research we have analysed Chinese hamster ovary cell viability and metabolic activity using two different assays: cell clonogenic and MTT. The cells were exposed to different CaCl2 concentration (0, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5 mM) media and electroporation pulses (1; 2; 4 HV). After the application of high voltage electric pulses (1200 V/cm, 100 μs), cell viability as well as metabolic activity (after 0.5, 12, 24 h) decrease with increasing calcium concentration. As our results have shown it is possible to obtain 20 - 100 % cell death depending on the electroporation parameters and calcium concentrations used. In addition to this the increase in cell viability after electroporation application was observed at lower calcium concentrations (in the range of 0,1 – 0,5 mM), which shows that low calcium levels can stimulate cell survival. [...]