Study of effects of nanosecond pulsed electric fields on cancer cell by using in vitro and ex vivo assay

Pulsed electric fields (PEFs) were applied on solid tumors obtained by embryonic chick assay. The mean weight of the pulse-treated tumors was significantly smaller than that of controls; tumor growth was constricted by nsPEFs application. The nsPEFs were applied to the tumor cell suspension to examine the effect of nsPEFs application in detail. The viability of tumor cells was measured by the WST-1 assay (water soluble tetrazolium salts) in advance. In increasing the charging voltage and the number of applied pulses, the viability of pulse-treated cells was significantly smaller than that of controls which were not exposed to nsPEFs. By using a flow cytometry with Apoptotic/Necrotic/Healthy Cells Detection Kit, it was confirmed that apoptosis was induced and necrosis slightly occurred in cell by nsPEFs application. In addition, it was confirmed that equal or more apoptosis in cells were induced by nsPEFs application than anisomycin application as a positive control. In other words, it was also confirmed that apoptosis was induced. In the same way, an ex vivo assay was performed on pulse-applied solid tumors obtained by embryonic chick assay. Apoptosis was induced and necrosis hardly occurred in ex vivo. It was also confirmed that the number of apoptosis induced cells by nsPEFs was equal or more than control as with in vitro. Therefore, application of nsPEFs is a potential measure of anti-tumor effect by apoptosis.