The effect of concurrent radiation and calcium in two cancer cell lines

Sammanfattning: Introduction: Calcium is an important ubiquitous second messenger regarding the maintenance of cellular homeostasis, and is therefore tightly regulated. Calcium induces cell death when internalised into cancer cells after permeabilization of the cell membrane by electroporation. It is established that radiation causes damage to the lipids and proteins of the cell membrane; and ionizing radiation also causes permeabilization of the cell membrane by peroxidation of the phosphor-lipid layer. Purpose: To investigate the survival of two cancer cell lines exposed to high levels of calcium in combination with radiation. Materials and Methods:Two human cancer cell lines were used in this study; H69 (small cell lung cancer) and SW780 (bladder cancer). Using an x-ray system (Gulmay D3100, Gulmay medical) 30.000 cells in 50 µl hepes buffer with or without 5mM CaCl2 was irradiated in open air with x-rays of 100 kVp and half value layer (HVL) of 5.2 mm aluminum in the dose range of 0-16 Gy. The survival rate was first and foremost assessed using a MTS viability assay, however clonogenic assay was also used to assess the survival after irradiation performed with a Varian 2300iX Clinic linear accelerator (Varian Medical Systems,Inc., Palo Alto, CA). To verify the given dose, GAFCHROMICTM EBT3 dosimetry film and TLD were used. Result: No difference in cell viability of SW780 and H69 cells treated with or without calcium in combination with radiation could be detected when using MTS viability assay to determine the cell survival rate. No dose response was obtained. When using clonogenic assay, the result displayed no difference in viability of the cells treated with or without calcium, however a cellular response to an increased absorbed dose could be distinguished. Results from measurements performed with EBT3 dosimetry film and TLDs assured the dose delivery to the cells in this study. Conclusion: The effect of concurrent radiation and calcium could not be investigated properly due to the method chosen for determination of cell survival. It is therefore necessary to continue to investigate the effect of calcium in combination with radiotherapy, tentatively using clonogenic assay to determine cell viability after treatment, before further conclusions are drawn.