Calcium electroporation for treatment of sarcoma in preclinical studies

// Anna Szewczyk 1 , Julie Gehl 2, 3, 4 , Malgorzata Daczewska 1 , Jolanta Saczko 5 , Stine Krog Frandsen 2, 4, * and Julita Kulbacka 5, * 1 Department of Animal Developmental Biology, Institute of Experimental Biology, University of Wroclaw, Wroclaw, Poland 2 Center for Experimental Drug and Gene Electrotransfer (C*EDGE), Department of Clinical Oncology and Palliative Care, Zealand University Hospital, Roskilde, Denmark 3 Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark 4 Department of Oncology, Herlev and Gentofte Hospital, University of Copenhagen, Herlev, Denmark 5 Department of Medical Biochemistry, Wroclaw Medical University, Wroclaw, Poland * These authors contributed equally to the work Correspondence to: Stine Krog Frandsen, email: stfra@regionsjaelland.dk Julita Kulbacka, email: julita.kulbacka@umed.wroc.pl Keywords: calcium electroporation; sarcoma; PMCA; calcium channels; cytoskeleton Received: November 22, 2017 Accepted: January 25, 2018 Published: January 30, 2018 ABSTRACT Calcium electroporation (CaEP) describes the use of electric pulses (electroporation) to transiently permeabilize cells to allow supraphysiological doses of calcium to enter the cytosol. Calcium electroporation has successfully been investigated for treatment of cutaneous metastases in a clinical study. This preclinical study explores the possible use of calcium electroporation for treatment of sarcoma. A normal murine muscle cell line (C2C12), and a human rhabdomyosarcoma cell line (RD) were used in the undifferentiated and differentiated state. Electroporation was performed using 8 pulses of 100 μs at 600–1000 V/cm; with calcium (0, 0.5, 1, and 5 mM). Viability was examined by MTS assay, intracellular calcium levels were measured, and expression of plasma membrane calcium ATPase (PMCA) was investigated using western blotting. Calcium/sodium exchanger (NCX1), ryanodine receptor (RyR1) expression and cytoskeleton structure (zyxin/actin) were assessed by immunofluorescence. CaEP efficiency on RD tumors was tested in vivo in immuno-deficient mice. CaEP was significantly more efficient in RD than in normal cells. Intracellular Ca 2+ levels after CaEP increased significantly in RD, whereas a lower increase was seen in normal cells. CaEP caused decreased expression of PMCA and NCX1 in malignant cells and RyR1 in both cell lines whereas normal cells exhibited increased expression of NCX1 after CaEP. Calcium electroporation also affected cytoskeleton structure in malignant cells. This study showed that calcium electroporation is tolerated significantly better in normal muscle cells than sarcoma cells and as an inexpensive and simple cancer treatment this could potentially be used in connection with sarcoma surgery for local treatment.