Window Effect And Experiment Study On Apoptosis Induction Of Nanosecond Pulsed Electric Fields On Tumor

Cancer is the main cause of people death. Traditional therapies are not satisfactory due to the limits of appropriateness, contraindication and side effects, etc. In fact, traditional therapies aim at killing caner cells or inhibiting tumor growth, patients can not heal in this way anyway. On the other hand, apoptosis induction could be another way to treat tumor because this way is very effective to make tumor shrink or disappear without any side effects. So, it is very important for tumor treatment to research method and mechanism of apoptosis induction.Based on the traditional Electrical Therapy (ET), this paper analyzed the common basic bioelectrical mechanism of all kinds of Pulsed Electric Fields (PEF) and then proposed the detailed method and mechanism of Nanosecond Pulsed Electric Fields (nsPEF) for apoptosis induction. The main achievements in this paper are as follows:â‘ Three cell models, Multilayer Dielectric Model (MDM), Equivalent Circuit Model (ECM) and electric field - electric circuit compound model, were proposed firstly. Calculation methods for transmembrane potential of cell inner and outer membrane of these three models were performed while exposing cancer cells to Electric Field (EF). Based on the calculation results, Window Effects (WE) of duration - intensity - transmembrane potential, duration - intensity - biomedical effects and conductivity - dielectric constant - transmembrane potential were brought forward, and this supported theory basics for nsPEF to induce cancer cells apoptosis.â‘¡A nsPEF generator sample was developed by technical combination of traditional Pulsed Power Technology (PPT), high power switcher technology and programmable voltage adjusting technology. This sample worked steadily and the parameters of its exponential decay output pulse, peak (0²5kV), duration (100ns¹Î¼s) and repeat rate (1¹00Hz), could be adjusted accurately. This supported hardware basics for nsPEF to induce cancer cells apoptosis.â‘¢Medical cell experiment to investigate the apoptosis and changes of the intracellular calcium concentration ([Ca²⁺]_i ) induced by nsPEF on human ovarian carcinoma cell line SKOV3 in vitro was carried on. SKOV3 cells were exposed to nsPEF (intensity of 10kV/cm, duration of 100ns, 1 Hz in 5 minutes). The results showed that early apoptotic rate of experimental group was significantly higher than that of the control group (P<0.01). The typical morphological features of apoptotic cells were observed by SEM and TEM. It was proved that nsPEF can mainly induced early apoptosis. The [Ca²⁺]_i was markedly increased by treatment with nsPEF (P<0.01), while the increase showed no relationship to the extracellular calcium concentration (P>0.05). One of the mechanisms of the apoptosis is that nsPEF can activate intracellular calcium and result in increase of [Ca²⁺]_i so as to induce apoptosis of SKOV3 cells.â‘£Medical animal experiment to research the apoptosis induction effects of nsPEF in vivo was performed. Tumor models in 20 female BALB/C nude mice were established by inoculating with human melanoma cells A375. These mice were randomly divided into treated group (exposed to exponential decay nsPEF with intensity of 20kV/cm, duration of 300ns and 1Hz in 5 minutes) and control group equally. 20 days later, compared with that of control group, tumor growth of treated group was effectively (P<0.01) inhibited, typical morphological apoptosis characteristics in ultrastructure were observed by TEM, expression of Caspase-3 and Caspase-3 mRNA were obviously increased using immunofluorescence and RT-PCR, respectively. These experiment results contributed evidence of tumor growth inhibition by nsPEF exposure in vivo. The mechanism was apoptosis induction effects of nsPEF on cancer cells by activating Caspase-3. This study presented the first in vivo evidence for apoptosis induction effects of nsPEF, and this supported possible tumor therapy utilizing nsPEF.In summary, apoptosis induction is the research focus to treat cancer with great possibility. At the same time, nsPEF is effective to induce cancer cells apoptosis and inhibit tumor growth in vivo, which shows bright future for nsPEF to treat local tumor.