title: Calcium Electroporation: Evidence for Differential Effects in Normal and Malignant Cell Lines, Evaluated in a 3D Spheroid Model.
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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Center for Experimental Drug and Gene Electrotransfer, Department of Oncology, Copenhagen University Hospital Herlev, 2730 Herlev, Denmark.
authors.forename: Stine Krog
authors.initials: SK
authors.lastname: Frandsen
authors.affiliation: CNRS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.|Université de Toulouse, UPS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Gibot
authors.affiliation: CNRS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.|Université de Toulouse, UPS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.
authors.forename: Moinecha
authors.initials: M
authors.lastname: Madi
authors.affiliation: Center for Experimental Drug and Gene Electrotransfer, Department of Oncology, Copenhagen University Hospital Herlev, 2730 Herlev, Denmark.
authors.forename: Julie
authors.initials: J
authors.lastname: Gehl
authors.affiliation: CNRS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.|Université de Toulouse, UPS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Rols
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D018274:Electroporation; D006801:Humans; D008954:Models, Biological; D018874:Spheroids, Cellular
chemical_list: D000255:Adenosine Triphosphate; D002118:Calcium