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 Ca2+ 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.
Highlights
Rhabdomyosarcoma is the malignant tumor derived from myoblasts and mainly affects children and young adults
We have previously shown that calcium electroporation (CaEP) significantly decreased sarcoma cells viability and led to apoptotic cell death
We have confirmed these results by showing higher toxicity of calcium electroporation on sarcoma cells (RD) compared to normal muscle cells (C2C12)
Summary
Rhabdomyosarcoma is the malignant tumor derived from myoblasts and mainly affects children and young adults. Due to the most frequent localization in muscle tissue, tumor resection often impacts functional outcomes [1, 2]. The function of muscle fibers is based on electrical stimulation and calcium signaling [3]. Calcium plays a crucial role in physiological processes such as cell cycle, proliferation, differentiation, apoptosis, and necrosis [4]. The concentration of calcium ions [Ca2+] in the cytoplasm is maintained in the range of 10–100 nM, while the extracellular Ca2+ concentration is 1–2 mM. Drastic increases in intracellular calcium ion concentration may affect cytoskeleton structure and mitochondria function, which cause cell swelling and in consequence lead to cell death [6]
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