The Expression Of MiR-218 In Breast Cancer And The Biological Function Of MiR-218

Objective: Breast cancer is one of the common malignant tumor.In China,the incidence of breast cancer among the first of women malignant tumor.The incidence of breast cancer in urban and rural areas were rising both.The early diagnosis and individual treatment of breast cancer is the key to achieve good prognosis.So searching for the diagnostic and prognostic markers and molecular targets is still a hot spot of current research.A number of studies have shown that miRNA related to the occurrence of tumor development closely.In recent years,the study show that miR-218 can participate in the occurrence and development of tumor through a variety of signal transduction pathways.At present,the function of miR-218 in breast cancer is not fully clear.In our study,the expression levels of miR-218 in breast cancer tissues and the corresponding adjacent tissues were detected by quantitative real-time polymerase chain reaction.The expression of miR-218 was up-regulated in MCF-7 breast cancer cells by the application of lipofectaminesome transfection method,to research the effect on proliferation,apoptosis and cell cycle distribution of MCF-7 breast cancer cells.The target genes of miR-218 was predicted by the online target gene prediction software,and the result was confirmed by the following experiment.Providing a new method for the diagnosis and treatment of breast cancer.Methods:1 The 34 cases of breast cancer tissues and the corresponding adjacent tissues were collected between november 2013 to november 2014 from the first hospital of hebei medical university.After in vitro,the specimens were put in liquid nitrogen rapidly,and then put into-80? refrigerator.Before the operation,all of the patients have not been accepted radiotherapy,chemotherapy and endocrine therapy.2 The expression levels of miR-218 in breast cancer tissues and the corresponding adjacent tissues were detected by quantitative real-time polymerase chain reaction.3 Selecting breast cancer MCF-7 cell for cell culture,using the culture solution of PRMI 1640.4 The transfection of MCF-7 cells was conducted by lipofectaminesome transfection method.The experimental group were transfected with miR-218mimic;The negative control group were transfected with miR-218 negative control;The blank control group were transfected with equal lipofectamine2000 only.5 The expression levels of miR-218 in the experimental group,negative control group,and the blank control group were detected by qRT-PCR.6 1day,2day,3day,4day and 5day after transfection of MCF-7 cells,OD value were detected and the growth curve were drawn,in order to observe the effects of miR-218 on cell proliferation.7 The apoptosis and cell cycle distribution were examined by flowcytometry(FCM)after transfection with miR-218,in order to compare the difference between control group and experimental group.8 The target genes of miR-218 were predicted by online target gene prediction software TargetScan and MiRanda.9 The expression levels of BMI1 mRNA in the experimental group,negative control group,and the blank control group were detected by qRT-PCR.10 The expression levels of BMI1 mRNA in breast cancer tissues and the corresponding adjacent tissues were detected by qRT-PCR.11 The results of the experimental data were analysied by SPSS 19.0 and GraphPad Prism 5.0 software.The data of normal distribution show as mean±standard deviation,the data of non-normal distribution show as P50(P25,P75),the comparison between the paired samples using Wilcoxon rank and inspection,correlation analysis were conducted with Spearman test,the comparison between two independent samples using the t test.Thecomparison of multiple sets of data using analysis of variance.Comparison between two groups using the LSD-t test.P < 0.05 is considered difference was statistically significant.Results:1 The expression level of miR-218 in breast cancer tissues [43.89(10.78,100.89)]was significantly lower than that in corresponding adjacent tissues[171.14(58.59,343.31)](P < 0.01).2 The expression level of miR-218 in experimental group was significantly higher than that in the negative control group and the blank control group(P < 0.01),there was no statistically significant difference between the negative control group and the blank control group(P > 0.05).3 The proliferation ability of experimental group was inhibited(P <0.05).4 The proportion of G1-stage cells was decreased while the proportion of S-stage cells was increased,and the apoptosis rate was increased of experimental group(all P < 0.01).5 BMI1 could be the potential target gene of miR-218 through the online target gene prediction software TargetScan and MiRanda.6 The expression level of BMI1 mRNA in experimental group was significantly lower than that in the negative control group and the blank control group(P < 0.01),there was no statistically significant difference between the negative control group and the blank control group(P > 0.05).7 The expression level of BMI1 mRNA in breast cancer tissues [0.0078(0.0035,0.0131)] was significantly higher than that in corresponding adjacent tissues [0.0053(0.0031,0.0076)](P < 0.05).The expression level of miR-218 and BMI1mRNA were negatively correlated(r =-0.419,P < 0.05).Conclusions:1 The expression level of miR-218 is down-regulated in breast cancer tissues.Prompting miR-218 may play the role of tumor suppressor genes in the initiation and progression of breast cancer.2 Over expression of miR-218 may inhibit breast cancer MCF-7 cellproliferation,promote cell apoptosis,and affect cell cycle distribution.3 BMI1 could be the potential target gene of miR-218.Discussing the relationship between BMI1 and miR-218 may provide a new way to the diagnosis and treatment of breast cancer,and to clarify anticancer mechanism of miR-218.