Expression Of SIRT3 In Breast Cancer And Its Effect On Proliferation Of Breast Cancer Cells

Background and ObjectiveBreast cancer is the highest incidence of malignancy in women worldwide,accounting for 23% of total cancer cases and 14% of cancer deaths.In China,the incidence of breast cancer was increasing year by year,and tend to younger,breast cancer is one of the greatest threat to women's health.What's more,Due to the lack of appropriate screening measures or improper treatment,the mortality of breast cancer in China is gradually increased.Therefore,deep research of the pathogenesis of breast cancer is necessary.With the research of molecular biology mechanism becoming more and more mature in the field of oncology,molecular targeted therapy show its unique advantages increasingly.Silent information regulators(Sirtuins)are considered to play an important role in regulating aging.Sirtuins consists of seven members,SIRT1-SIRT7.SIRT3 as a mitochondrial deacetylase,is an important member of the Sirtuins family.In recent years,SIRT3 has not only been involved in the regulation of body life,but also plays an important role in tumorigenesis and development.Recent studies have shown that the expression of SIRT3 in hepatocellular carcinoma cells is significantly lower than that in adjacent tissues,and high expression of SIRT3 can prolong the overall survival(OS)and RFS.In addition,the high expression of SIRT3 can inhibit cell growth and induce apoptosis of hepatocellular cancer cells.What's more,in lung adenocarcinoma,gastric cancer,pancreatic cancer,the expression of SIRT3 was down-regulated,overexpression of SIRT3 inhibited cell growth and induced cell death.On the contrary,other studies have shown that SIRT3 knockdown in oral squamous cell carcinoma,esophageal cancer,and bladder cancer significantly inhibits tumorigenesis and promotes tumor progression.It was found that the mechanism of SIRT3 in different types of tumors remains to be further studied.The current research on the role of SIRT3 in breast cancer is not yet complete,in this study,SIRT3 was used as a target to study the expression of SIRT3 in breast cancer tissues by immunohistochemistry,Western blot is used to examine the expression of SIRT3 in breast cancer cells,and detect the expression of SIRT3 on RNA level by RT-PCR to explore the role of SIRT3 in the development of breast cancer.Through the correlation analysis and survival analysis of SIRT3 and clinicopathological features to explor the relationship between SIRT3 and the prognosis of breast cancer.At last,to investigate the effect of SIRT3 on the proliferation of breast cancer cells under the overexpression and knockdown conditions of SIRT3 gene,to explore the function and properties of SIRT3 in cancer cells,and to research whether SIRT3 is expected to be a potential target for treatment of breast cancer.Methods1.tissue microarray and immunohistochemical method were used to examine the expression of SIRT3 in breast cancer tissues.The expression of SIRT3 in breast cancer was observed and the correlation between the expression of SIRT3 and clinicopathological features was analyzed.All cases were studied by both univariate and multivariate analysis.2.cell culture technique and Western blot method were used to examine the expression of SIRT3 in breast cancer cell line EMT6 and breast fibroblast cell line MEFs.3.The expression of SIRT3 message RNA in breast cancer cell line EMT6 and breast fibroblast cell line MEFs were measured based on Realtime PCR.4.The effect of SIRT3 on the proliferation of breast cancer cells EMT6 was observed through MTT assay.Results1.The positive expression rate of SIRT3 protein in breast cancer tissue(84.72%,122/144)was obviously lower than that in normal tissue(96.63%,86/89)(t=7.572,P<0.05).SIRT3 expression were associated with the age,lymph node metastasis,TNM stage,HER-2 expression(P<0.05).While it was not related with Pathological grade,invasion depth,ER or PR expression(P>0.05).Univariante analysis revealed that the expression of SIRT3,lymph node metastasis,TNM stage and HER-2 expression were associated with the survival rate.COX stepwise proportional hazaids analysis showed that the expression of SIRT3 and TNM stage were independent prognostic factors.2.The Western blot showed that the expression rate of SIRT3 protein in breast cancer cell(0.220±0.173)was lower than that in normal cell(0.850±0.086)(t=7.133,P=0.002,P<0.01).3.The expression of the message RNA level of SIRT3 in breast cancer cell(0.520±0.069)was lower than that in normal cell(0.886±0.034)(t=4.729,P=0.009,P<0.01).4.MTT assay showed that the proliferation rate of SIRT3 was significantly higher than that of the control group when SIRT3 in knockdown condition.While the proliferation rate of SIRT3 overexpression was slow down.The difference was statistically significant.ConclusionsDownregulated SIRT3 expression in breast tumor and cancer cell line,SIRT3 may inhibit the development of breast cancer.Upregulation of SIRT3 gene can inhibit breast cancer cell proliferation.