Author: Hansen EL1, Sozer EB2, Romeo S3, Frandsen SK1, Vernier PT2, Gehl J1.
Affiliation: 1Center for Experimental Drug and Gene Electrotransfer, Department of Oncology, Copenhagen University Hospital Herlev, Copenhagen, Denmark. 2Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, Virginia, United States of America. 3Institute for Electromagnetic Sensing of the Environment (IREA), Italian National Research Council, Naples, Italy.
Conference/Journal: PLoS One.
Date published: 2015 Apr 8
Other:
Volume ID: 10 , Issue ID: 4 , Pages: e0122973 , Special Notes: doi: 10.1371/journal.pone.0122973 , Word Count: 247
Abstract
BACKGROUND:
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). 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.
METHODS:
In 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.
RESULTS:
Both 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).
CONCLUSIONS:
Calcium electroporation dose-dependently reduced cell survival and intracellular ATP. Increasing extracellular calcium allows the use of a lower electric field.
GENERAL SIGNIFICANCE:
This study supports the use of calcium electroporation for treatment of cancer and possibly lowering the applied electric field in future trials.
PMID: 25853661