Effects Of Chlorin-e6-SDT On The Proliferation Of Breast Cancer MDA-MB-231 Cells

Breast cancer is the leading cause of cancer death for women. Therapeutic means include operation, radiotherapy, chemotherapy, endocrine therapy and molecular targeted therapy. Its 5-years survival rate is 50%-60%. Nearly half of patients recur after first treatment. Chemotherapy is the main treatment for metastatic breast cancer, but its curative effect has reached a plateau. Although combination chemotherapy increases effect and extend disease free survival time, it exerts severe side effect and the life span can not be significantly extended. Endocrine therapy is regarded to be important as radiotherapy and chemotherapy. However, the effect of endocrine therapy depends on the state of estrogen receptor(ER), progesterone receptor (PR) and human epidermal growth factor receptor-2(Her-2). The survival time of patients with metastatic breast cancer is only 18-30 months. Seeking new treatments for metastatic breast cancer is a great challenge in cancer research.Sonodynamic therapy (SDT) is a promising approach for cancer therapy. As photodynamic therapy (PDT) (activating a tumor-localizing photosensitizers with light), SDT functions by activating a tumor-localizing sonosensitizing agent with ultrasound, which generates reactive oxygen species. Compared with the light, ultrasound can penetrate and focus on the deep tissue, which makes sonodynamic therapy become a highly potential approach for cancer therapy. Due to most photosensitizer simultaneously having sonodynamic effect, photosensitizers are usually applied as sonosensitizer for sonodynamic research. However, two problems remain to be solved in SDT research. The first is that the speed of those photosensitizers focusing on tumor tissue and clearing from normal tissue is slower, which includes high phototoxic side effect. The second is how to enhance the efficacy of sonodynamic therapy throngh combination with other treatments.Chlorin e6 is the degradation products of chlorophyll. It is siminlar to hematoporphyrin (HpD) in structure. Previous studies have shown that it can highly selectively focus on tumor tissue, clear quickly from nomal tissue, which let it have lower phototoxic side effect. As HpD, Chlorin e6 can be activated by light, and then produce photodynamic effect. The photodynamic effect of Chlorin e6 has been confirmed in cell and animal expereiment. Due to most photosensitizer simultaneously having sonodynamic effect, the first purpose of this study is to observe the SDT effect of Chlorin e6 on the proliferation of human breast cancer cells MDA-MB-231. Because some pre-clinical experiments have showed that adriamycin (ADM) can enhance the photodynamic effect of PDT and the synergistic effect might be associated with the combination sequence, the second purpose of this study is to explore whether ADM enhances the sonodynamic effect of chlorin e6 on the proliferation of human breast cancer cell MDA-MB-231 in vitro.PartⅠThe sonodynamic effect of chlorin-e6 on the proliferation of human breast cancer cells MDA-MB-231MDA-MB-231 and normal peripheral mononuclear cell(PMNC) were treated with ultrasound or chlorin-e6 alone and combined. Cell proliferation was determined by MTT assay and cell morphology was studied. Data are presented as mean±S.E.M. and analyzed by one-way ANOVA. Experiments between two group were analyzed by LSD or Tamhane.The following was the results of PartⅠ:1.1.0MHz ultrasound (1.0W/cm2～2.0W/cm2) and chlorin-e6 significantly inhibited the cell proliferation of both MDA-MB-231 and PMNC cells in a intensity-dependent and a dose-dependent manner respectively. The 50% inhibition of MDA-MB-231 and PMNC cell growth was 1.23W/cm2 and 1.25W/cm2 for ultrasound respectively and 0.38 mg/ml and 0.77mg/ml for chlorin-e6 respectively.2. Compared with treatment of ultrasound or chlorin-e6 alone, the combination treatment of ultrasound with chlorin-e6 significantly inhibited the proliferation of MDA-MB-231 cells(P<0.05), which exerted no significant inhibition in the cell growth of PMNC cells(P>0.05).3. The MDA-MB-231 cells were significantly damaged after sonodynamic effect of chlorin-e6.PartⅡAdriamycin enhances the sonodynamic effect of chlorin-e6 on proliferation of human breast cancer MDA-MB-231 in vitroMDA-MB-231 cells were treated with ultrasound/Chlorin e6 with or without ADM respectively. Cell proliferation was determined by MTT assay.. Data are presented as mean±S.E.M. and analyzed by one-way ANOVA. Experiments between two group were analyzed by LSD or Tamhane.The following was the results of PartⅡ:1.1.0MHz ultrasound, at the intensity of 0.5W/cm2～2.0W/cm2, inhibited the proliferation of MDA-MB-231 cells in a intensity-dependent manner. Chlorin-e6 and ADM, at the concentration of 0.05mg/ml～1.6mg/ml and 0.1μg/ml～0.4μg/ml, inhibited the proliferation of MDA-MB-231 cells in a dose-dependent manner, respectively.2. Compared with ultrasound (0.5W/cm2×1.0MHz×60s) or chlorin-e6 (0.05mg/ml～0.2mg/ml) alone, the inhibitory effect on the proliferation of MDA-MB-231 cells was significantly enhanced by the combination of ultrasound with chlorin e6 (P<0.05).3. Compared with ADM (0.1μg/ml～0.4μg/ml) or sonodynamic effect (0.5W/cm2×1.0MHz×60s) of chlorin e6 (0.1mg/ml) alone, the inhibitory effect on cell proliferation was significantly enhanced by the sonodynamic effect of chlorin e6 combined with ADM in MDA-MB-231 cells(P<0.05). This effect was schedule-dependent. The inhibitory effect was greater when ADM was added after sonodynamism than that when ADM was added before sonodynamism(P<0.05)CONCLUSION:Results of the present study demonstrated that the sonodynamic effect of chlorin-e6 exerted inhibitory effect on the cell proliferation of MDA-MB-231 cells. ADM enhanced the sonodynamic effect of chlorin e6 on the proliferation of human breast cancer MDA-MB-231 cells in vitro. Chlorin-e6 may be a promising sonosensitizing agent for the treatment of breast cancer.