Anticancer effect of combined application of ionizing radiation and electrochemotherapy on human breast cancer cells

Cancer, a complex disease, ranks first among the causes of death worldwide. Chemotherapy is a systemic treatment method for cancer, and it can be effective if the drugs easily pass through the plasma membrane and reach their intracellular targets. Cell membrane resistance to chemotherapy drugs is one of the most important factors preventing the success of cancer therapy. In recent years, electric field pulses are also applied with the use of chemotherapy drugs (electrochemotherapy). In electrochemotherapy (ECT) treatment, the application of short-term and high-intensity electrical pulses to cells or tissues creates nanometer-sized temporary pores in the cell membrane, causing the cell membranes to become permeable to molecules such as DNA, RNA, drugs, dyes and antibodies. Thus, by providing effective treatment with lower doses of chemotherapeutic agents, the side effects of the drugs are minimized. The efficacy of ECT with different chemotherapeutic drugs has been demonstrated in many in vivo and in vitro studies. However, many studies claim that ionizing radiation (IR) can alter the efficiency of ECT. In the literature review, no study was found on the effect of ECT and ECT+IR on the anticancer activity of methotrexate in MCF-7 breast cancer cells. Our aim in this study is to investigate the effectiveness of ECT on the activity of methotrexate and to examine the effect of IR on ECT efficiency in the treatment of MCF-7 breast cancer. MCF-7 (breast cancer) cell line was used in the study. Cancer cells were treated with different treatments method such as electroporation (EP), Methotrexate (MTX), MTX+EP (ECT), 140 kV X-ray (IR_140kV), 500 kV X-ray (IR_500kV), ECT +IR_140kV (140 kV X-ray 10 min after ECT) and ECT+IR_500kV (500 kV X-ray 10 min after ECT). In ECT, 8 square wave pulse trains of 100 μs length, 800 V/cm intensity and 1 Hz repetition frequency were used. MTT analysis method was used to determine the effectiveness of the treatments applied. There was a significant decrease in MCF-7 cancer cell viability (%) (p<0.05) when the MTX, EP, IR_140kV, IR_500kV and ECT treatment groups were compared with the control group in terms of cancer cell viability 24 hours after treatment. ECT has been the most effective treatment among these treatments, reducing cancer cell viability to 58.78%. In order to examine the effect of radiation on ECT treatment, the ECT+IR_140kV and ECT+IR_500kV groups were compared with the ECT group. A significant decrease in cell viability was observed in both groups that underwent X-ray after ECT compared to the ECT group (p<0.05). In addition, while MCF-7 cell viability decreased to 46.38% in the 140 kV X-ray group after ECT, the cell viability decreased to 35.89% in the 500 kV X-ray group. This shows that high voltage X-ray applied after ECT can cause further cell inhibition. In conclusion, our data show that ECT therapy is much more effective than standard chemotherapy in MCF-7 breast cancer cells. In addition, ionizing radiation applied after ECT significantly increased the effectiveness of ECT treatment.