| Objective:The aim of the present study is to investigate the inhibitory efficacy of alternating micro-current at intermediate frequency on human breast cancer in vitro and in vivo, and explore the underlying mechanisms. At the same time, the micro-current was combined with chemotherapy to examine if the treatment sensitivity could be increased, thus evaluate the potential applicability of intermediate-frequency, alternating micro-current as a novel therapeutic modality for malignant tumors.Methods:1 Effects of intermediate-frequency, alternating micro-current in MCF-7 tumor cells:The human breast cancer cell lines MCF-7 were exposed to the intermediate-frequency alternating micro-current. The cell growth was detected with MTT assay, and apoptosis of cells was tested by flow cytometry. The pH value and temperature of the microenvironment surrounding the cells, and reactive oxygen species and calcium ions intracellular were measured. Morphology of the cells were observed by transmission electron microscopy.2 Effects of combining intermediate-frequency, alternating micro-current with chemotherapy in MCF-7 tumor cells:The cells were exposed to the intermediate frequency alternating micro-current, epirubicin, methotrexate and cisplatin separately and in combinations. Use MTT assay and Annexin V/PI staining to test the proliferation of cell and viability. In addition, we observe the uptake of chemotherapy drugs into cells by confocal microscopy and the cell morphology was observed by transmission electron microscopy.3 Effects of intermediate-frequency, alternating micro-current in an animal tumor model: The tumor-bearing mice model was established by injecting breast cancer cell lines MCF-7 inoculums into the subcutaneous tissue of the right hind limb of BALB/c nude mouse. The animals were randomly divided into the following four groups:control group, electrical stimulation group, chemotherapy group (epirubicin), electrical stimulation combined with chemotherapy group. Eepirubicin (7.5 mg/kg) was injected intraperitoneally in the model mice, and the day after injection, alternating micro-current at the frequency of 200 kHz was applied in the model mice for 30 min per day, and they were treated 3 times in all. Tumor volumes were measued to evaluate the effects of treatment. After the mice were sacrificed, the tumors and other tissues were analyzed by histopathology (HE staining).Results:1 The result of MTT assay showed that the intermediate frequency alternating micro-current exhibited inhibitory effect on MCF-7 cells (inhibition ratio:～9%). Annexin V/PI stainning showed that compared with control cells, the intermediate frequency alternating micro-current increased apoptosis cells (0.86%±0.74% vs.11.43%±6.01%), and necrotic cells were also increased (4.52%±1.58% vs.9.14%±1.71%).The intermediate frequency alternating micro-current exhibited no obvious effect on the pH value and temperature (pH value of 7.5 and uniform in the media, temperature increased only 1.1℃) surrounding the cells. Where as, it could increase the level of reactive oxygen species significantly, but had no significant effect on the concentration of calcium intracellular. The cells exposed to the electrical stimulation varied a lot, including nuclear expansion, cytoplasm and nucleoplasm loose, organelles degeneration, multivesicular body forming and so on.2 The results of MTT and Annexin V/PI stainning showed that the intermediate frequency alternating micro-current could enhance the efficacy and sensitivity of chemotherapy. The cell survival rate of the combination therapy group was reduced (～38.66%), while the control group was significantly higher (～94.04%), and the survival rates of cells in electrical stimulation group and chemotherapy group were 71.87% and 87.79%, separately. We also observed that micro-current could facilitate the uptake of chemotherapy drugs into the cells.3 The results of experiment in vivo showed that the intermediate frequency alternating micro-current had inhibitory effects on tumor growth in nude mice, and it could enhance the effect of chemotherapy. Histological analysis showed that electrical stimulation had no significant side effects, except for some mild skin inflammation.Conclusions:The intermediate frequency alternating micro-current can inhibit the proliferation of MCF-7 cells and has inhibitory effect on human breast cancer. The underlying mechanisms may be due to the increase of intracellular reactive oxygen species and changes of cell morphology after the electrical stimulation. In addition, The results indicate that combining chemotherapy with the intermediate frequency alternating micro-current may increase chemotherapeutic efficacy and sensitivity without increasing treatment related toxicity. The intermediate frequency alternating micro-current may be explored as a new tumor treatment modality. It could be used clinically not only by means of anti-tumor lonely, but also as effective sensitizers for chemotherapeutic agents. On the other hand, it is necessary to further study the underlying mechanisms, and more experiments in vivo and clinical trails are needed. |
PDF Full Text Request