Calcium Electroporation: Evidence for Differential Effects in Normal and Malignant Cell Lines, Evaluated in a 3D Spheroid Model

Stine Krog Frandsen; Laure Gibot; Moinecha Madi; Julie Gehl; Marie-Pierre Rols

doi:10.1371/journal.pone.0144028

Calcium Electroporation: Evidence for Differential Effects in Normal and Malignant Cell Lines, Evaluated in a 3D Spheroid Model

PLoS One. 2015 Dec 3;10(12):e0144028. doi: 10.1371/journal.pone.0144028. eCollection 2015.

Authors

Stine Krog Frandsen¹, Laure Gibot^{2

3}, Moinecha Madi^{2

3}, Julie Gehl¹, Marie-Pierre Rols^{2

3}

Affiliations

¹ Center for Experimental Drug and Gene Electrotransfer, Department of Oncology, Copenhagen University Hospital Herlev, 2730 Herlev, Denmark.
² CNRS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.
³ Université de Toulouse, UPS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.

Abstract

Background: Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill efficacy-and normal cell sensitivity.

Methods: Using a 3D spheroid cell culture model we have tested the effect of calcium electroporation and electrochemotherapy using bleomycin on three different human cancer cell lines: a colorectal adenocarcinoma (HT29), a bladder transitional cell carcinoma (SW780), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n).

Results: The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (p<0.0001) or electrochemotherapy using bleomycin (p<0.0001). Strikingly, the size of normal fibroblast spheroids was neither affected after calcium electroporation nor electrochemotherapy using bleomycin, indicating that calcium electroporation, like electrochemotherapy, will have limited adverse effects on the surrounding normal tissue when treating with calcium electroporation. The intracellular ATP level, which has previously been shown to be depleted after calcium electroporation, was measured in the spheroids after treatment. The results showed a dramatic decrease in the intracellular ATP level (p<0.01) in all four spheroid types-malignant as well as normal.

Conclusion: In conclusion, calcium electroporation seems to be more effective in inducing cell death in cancer cell spheroids than in a normal fibroblast spheroid, even though intracellular ATP level is depleted in all spheroid types after treatment. These results may indicate an important therapeutic window for this therapy; although further studies are needed in vivo and in patients to investigate the effect of calcium electroporation on surrounding normal tissue when treating tumors.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adenosine Triphosphate / metabolism
Calcium / metabolism*
Cell Line, Tumor
Electroporation*
Humans
Models, Biological*
Spheroids, Cellular*

Substances

Adenosine Triphosphate
Calcium

Grants and funding

SKF—grant, University of Copenhagen, The experimental work was performed during the Short-Term Scientific Mission (Grant ECOST-STSM-TD1104-14339) under the networking efforts of COST Action TD1104; LG—grant, ANR Astrid PIERGEN, ANR-12-ASTR-0039-01; MM—grant, Department de Mayotte; JG—research fellow of the Royal Swedish Academy of Science supported by the Acta Oncologica Foundation; MPR—ANR Astrid PIERGEN, ANR-12-ASTR-0039-01. Research was conducted in the scope of the EBAM European Associated Laboratory. This report is the result of networking efforts of COST Action TD1104 (http://www.electroporation.net). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.