Abstract
BackgroundElectroporation, a method for increasing the permeability of membranes to ions and small molecules, is used in the clinic with chemotherapeutic drugs for cancer treatment (electrochemotherapy). Electroporation with calcium causes ATP (adenosine triphosphate) depletion and cancer cell death and could be a novel cancer treatment. This study aims at understanding the relationship between applied electric field, calcium concentration, ATP depletion and efficacy.MethodsIn three human cell lines — H69 (small-cell lung cancer), SW780 (bladder cancer), and U937 (leukaemia), viability was determined after treatment with 1, 3, or 5 mM calcium and eight 99 μs pulses with 0.8, 1.0, 1.2, 1.4 or 1.6 kV/cm. Fitting analysis was applied to quantify the cell-killing efficacy in presence of calcium. Post-treatment intracellular ATP was measured in H69 and SW780 cells. Post-treatment intracellular ATP was observed with fluorescence confocal microscopy of quinacrine-labelled U937 cells.ResultsBoth H69 and SW780 cells showed dose-dependent (calcium concentration and electric field) decrease in intracellular ATP (p<0.05) and reduced viability. The 50% effective cell kill was found at 3.71 kV/cm (H69) and 3.28 kV/cm (SW780), reduced to 1.40 and 1.15 kV/cm (respectively) with 1 mM calcium (lower EC50 for higher calcium concentrations). Quinacrine fluorescence intensity of calcium-electroporated U937 cells was one third lower than in controls (p<0.0001).ConclusionsCalcium electroporation dose-dependently reduced cell survival and intracellular ATP. Increasing extracellular calcium allows the use of a lower electric field.General SignificanceThis study supports the use of calcium electroporation for treatment of cancer and possibly lowering the applied electric field in future trials.
Highlights
Electroporation is a method used to generate increased porousness of cell membranes by applying permeabilising electric pulses [1]
Increasing extracellular calcium allows the use of a lower electric field
This study supports the use of calcium electroporation for treatment of cancer and possibly lowering the applied electric field in future trials
Summary
Electroporation is a method used to generate increased porousness of cell membranes by applying permeabilising electric pulses [1]. Reversible electroporation, where cell membranes reseal after transient permeabilisation, is used in the clinic in combination with chemotherapeutic drugs for local treatment of malignant tumours (electrochemotherapy) [9,10,11]. Irreversible electroporation (IRE) [13] is another electroporation based therapy, where stronger electric fields are used to kill cancer cells through irreversible membrane permeabilisation. Electroporation, a method for increasing the permeability of membranes to ions and small molecules, is used in the clinic with chemotherapeutic drugs for cancer treatment (electrochemotherapy). This study aims at understanding the relationship between applied electric field, calcium concentration, ATP depletion and efficacy
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