Sound Of The Original Porphyrin Ix Mediated Photodynamic Therapy Of Human Breast Cancer Mda-mb-231 Cell Apoptosis And Its Mechanism

Breast cancer is one of the malignant tumors, which can seriously threat to human health and life and the incidence of a disease, and mortality is rising year by year. Until now, the scientists in medical profession has not yet to find an effective cure method. Therefore, breast cancer prevention research appears more urgent. In recent years, It has appeared some cancer treatment of physical therapy, ultrasonic activation of acoustic sensitive agent antineoplastic therapy Sonodynamic dynamic therapy (SDT) is one of them. SDT refers to the synergistic effect on cell killing by the combination of sonosensitizers and ultrasound, which is based on the tumor-specific accumulation of a sonosensitizer that induces cell death after irradiation of ultrasound with specific frequency and intensity. Ultrasound can penetrate into small volumes and activate sonosensitizers. Therefore, SDT has been developed as a promising approach for cancer treatment.On the background of our previous results, this study is supported by the ministry of education of specialized research fund for the doctoral program of higher education. It was discussed that the mechanism of cell death and the p38MAPK signal activation in human breast cancer cell MDA-MB-231by PpIX-SDT, which may provide some useful information for the clinical treatment of breast cancer by SDT. we detect the kinetics of protoporphyrin IX in MDA-MB-231 cells following various concentration and different times with fluorospectro photometer. The cytotoxicity of sonosensitizer and ultrasound were evaluated by MTT assay. The localization of the sonosensitizer in MDA-MB-231 cells was evaluated by Laser confocal microscope. The reactive oxygen species and mitochondria membrane potential were analysed with Flow cytomety and expression of protein was analysed by western blotting technique. Research results are as follows:1. Our findings suggested that the kinetics of protoporphyrin IX in MDA-MB-231 cells was dynamic change trend and the peak concentration was at 2 hour. Therefore, the optimal ultrasound irradiation was for 2 hour.2. Under the ultrasonic frequency of 1.074MHz, the effect of various ultrasounds on cell survival is intensity dependence, namely, the greater the ultrasound intensity is, the the lower cell survival rates is. Therefore,3W/cm2 ultrasonic intensity is the threshold value in this study.3. In addition, the cell rates reduced along with the increase of PpIX concentration. When the PpIX concentration is 1μM, the concentration is threshold value in this study. It is showed that the effect of 1μM PpIX combined with 3W/cm2 ultrasonic intensity on MDA-MB-231 cells is obvious compared with 1μM PpIX only and 3W/cm2 ultrasonic intensity only. SDT showed obious damage effect on cell morphology, such as, adherent rate reduced and cell debris increased.4. Effect of intensities combined with PpIX on survival rate of MDA-MB-231 cells is not time dependence. Maybe, the cells damaged and the cell cycle blocked, that have not been repaired thoroughly in 24 h.5. Our finding suggested that apoptosis is one of the death types of MDA-MB-231 cells mediated by SDT and it is caspase-dependence.6. Mitochondria may be one of the major treatment targets for protoporphyrin IX.The ROS production by SDT can damage the MDA-MB-231 cells, inhibit the cell growth, change the membrane permeability and reduce the mitochondrial membrane potential. We also find that ROS inhibitors suppress the caspase-3 activation and apoptosis occurrence. The present study suggested that cell apoptosis induced by SDT was concerned with mitochondrial function damage and ROS is probably the upstream factors of apoptosis initiation.7. In this study, we find that p38 MAPK phosphorylation activation may be involved in the aopotosis induced by PpIX-SDT in MDA-MB-231 cells. When the p38 MAPK phosphorylation activation was suppressed, the cell death rates and expression of caspase-3 were reduced. Our previous study indicated that ROS production induced by ultrasound combined with PpIX can participate in the process of apoptosis and inhibit the cell growth. The present study suggested that ROS inhibitors can reduced the level of p38 MAPK phosphorylation expression, which comfirm that ROS may be related to p38MAPK signal pathway.