The Study Of The Effects Of MSA On Proliferation And Apoptosis Of Human Breast Cancer Cell

Selenium is an essential micronutrient for human being shown to have general biological functions. Lacking selenium can lead to several kinds of disease, including some cancers, AIDS, bacterial infection, Keshan disease and infertility. The relationship between selenium and human health has absorbed more and more attentions, especially the relationship between selenium and breast cancer.As for the relationship between selenium and breast cancer, epidemiologic studies have found that selenium levels of toenail, serum, and cancer tissue in patients with breast cancer were significantly lower than in normal women. However, other epidemiological studies have shown no relationship between toenail selenium levels, serum selenium levels, or dietary selenium and breast cancer risk or incidence. The American Nurses'Health Study showed that selenium had no protective effect on breast cancer. Animal experiments indicated that selenium could inhibit the development of mouse breast cancer, however, others had the opposite conclusion. As reviewed above,we know that there have some issues about the effect of selenium on preventing breast cancer and the mechanism of anticancer.Breast cancer is one of the most frequent malignant tumors in women. There are 1.2 million new female patients with breast cancer every year, and 500,000 women died of this disease. In China, breast cancer accounts 7-10 percent among all of the malignant tumors, second only to uterine cervical cancer. But in recent years, breast cancer showed an ascendant tendency, and it might exceed the uterine cervical cancer in the future. In some big city, breast cancer has been the first morbility malignant tumor, it would seriously harm to the female health, influence the stabilization of family life and bring heavy burden to the society. People stand in awe of traditional chemical and surgery because of its side effects and harm to female .Our purpose is to find out a kind of drug which has a function of prophylaxis and treatment to breast cancer and has little side effect and high therapeutic effect.Organic selenium compounds are the agents of choice for chemopreventive studies. Some in vitro studies showed that MSA is the most efficiency chemical compound. But we knew little about the functions and mechanisms of selenium to breast cancer. The objectives of this study was to detect the effects of MSA on breast cancer cell-MCF-7, and to observe the influences of MSA on proliferation, morphous, growth, apoptosis and cell cycle, and then try to explore the mechanisms of selenium chemoprevention and to find out the evidences for new drug Se becoming a prophylaxis and treatment material for breast cancer.Applying random concurrent control research method,we cultured breast cancer cell line MCF-7 in vitro,and we observed the effects of MSA on breast cancer cell including morphous, growth, apoptosis and cell cycle. MTT-assay was used to measure the proliferation, optics microscope was applied to observe cell morphous and growth, and cell apoptosis ratio and cell cycle were determined by using flow cytometry. Data were analyzed by SPSS 11.0 soft ware and variance analysis was used to compare the difference between groups. P<0.05 was regarded to have statistical significance. We got the results and conclusions as follows:1. MSA could inhibit the proliferation of breast cancer cell in vitro in a dose and time dependent manner. After forty-eight hours, the inhibition did not strengthen any more. It might be because that the colony doubling time of MCF-7was 25±10h. It indicates that MSA may inhibit the mitoschisis of breast cancer cell,and inhibit its proliferation. Present study could not provide the precisely mechanism, but we presumed the possible mechanism as follows:(1)Selenium could regulate the expression of estrogen receptor. Lee so et al have found that MSA decreased the level of ERα, increased the level of ERβ, restrained the activity of ER and decreased the expression of ER regulating gene. Thus the affinity of female hormone to ER was low, the signal conduction way of ER was destroyed, and then the reproductive activity of human being breast cancer cell was restrained.(2)Our study found that MSA could step down proceeding of cell division through impeding the cell cycles. We considered that as the mechanism of Selenium inhibiting proliferation of breast cancer cell in vitro.2.MSA could induce the apoptosis of breast cancer cells during which nuclear fragment and disappearance could be observed. The apoptosis rate was dependent on MSA concentration and its action time. Apoptosis also named programmed cell death is a process of cell death during development and division. It participate in some pathological process and in maintenance of fluid balance. When apoptosis happened, cells show following features: chromatin pyknosis, cell nucleus spallation and disappearance, cytoplasm condense, cell body minification, cellular organ compression, mitochondria membrane potential loss and at last apoptotic body formation. In our study we observed apoptosis in breast cancer cell after treatment with MSA through light microscope and flow cytometry. We also observed that the apoptosis ratio increased with the concentration of MSA and the action time of MSA. So we concluded that MSA induced the apoptosis in some unknown ways.Malignant tumor cells can escape the normal regulation system and can grow fast with uncontrollable speed. One of our results was that MSA could inhibit the growth of breast cancer cells, which was consensus with the result obtained by El-Bayoumy K.MSA had double effects on breast cancer cells. On one hand, it could inhibit the cell growth, and on the other hand it could induce apoptosis. So, we concluded that MSA might inhibit cell growth through inducing apoptosis.It is a hotspot that Se can induce tumor cells apoptosis. Se could induce the apoptosis of prostate carcinoma, lung cancer and esophageal carcinoma. But the study on its effect of apoptosis induction in breast cancer was little. We suggested in our study that Se could induce apoptosis of breast cancer cells.The mechanisms of Selenium inducing apoptosis might include follows:(1)expression of genes association with apoptosis including BRCA1,P53,Apo-3,c-jun,cdk5,cyclinD1could be changed by stimulation with Se. (2) Selenium could suppress the phosphorylation of Akt, and then induce the apoptosis. (3) some signal transduction ways such as MAPK signal way,PKC signal way,signal way association with transcription factors and ribosome s6 protein . Neera et al have found that sodium selenite could induce apoptosis through inhibiting the expression and the activity of NF-ΚB and PKC. But its mechanism still was unclear and need further study.3. When stimulating with MSA, cell cycle was blocked at G1 stage and the number of cell at s stage was reduced. So, MSA could effect the cell cycle through inhibiting the transformation from G1 stage to S stage, obstructing the process of cell cycle, reducing the synthesis of DNA , and suppressing the cell reproduction. Selenium could affect cell cycle through regulating the expression of gene association with the cycle nodal points , including cyclins, CDKs, transcription activating factors and serine/threonine kinase. We still could not understand its deep mechanism, and we would focus on it in the future.In our study, when stimulating the breast cancer cells in vitro with MSA, we could observe that the reproduction and growth have been inhibited, the cellular morphous have been changed, the apoptosis has been induced and the cellular cycle has been affected. We hope that MSA could become a new way for prevention and therapy of breast cancer. Although some studies on its mechanism have been carried out, we were still uncertain. The effect of MSA on molecule and gene needed further study. In addition, we could exploit the compound of Selenium which was highly effective with lower poison. In order to prevent the deficiency of Selenium, people should take care of its intake, and should keep rational diet. Intake of trace elements could reduce the risk of breast in women and could raise the quality of life. We think that Selenium might expand a new field in prevention and therapy of breast cancer.