Knockdown Of C-myc Expression By SiRNA Inhibits MCF-7 Breast Cancer Cells Growth And Induces The Cells Apoptosis

Objective: To evaluate the effect of small interferring RNA(siRNA) targeting c-myc gene on the proliferation and apoptosis of MCF-7cells and on the expression of c-myc target gene.Methods: SiRNA targeting c-myc gene was transfected into MCF-7 cells by Lipofectimine^TM2000. The c-myc mRNA expression level was detected by Real-time quantitive PCR, and the c-myc protein expression level was tested by Western Blotting.MTT assay was used to assess the proliferation of the cells. Fluorescence- activated cell sorter analysis was used to determine apoptosis of the cells. C-myc and its target gene expression levels were assessed by Multiplex PCR.Results: (1) MCF-7 cells were transfected with c-myc siRNA about 98.1±0.003% at 6 hours after transfection.(2) The expression levels of c-myc mRNA in MCF-7 cells were suppressed by up to 50±0.028%and 85±0.042%at 24 and 48 hours after transfection respectively.(3)The corresponding decrease of c-myc protein expression level in MCF-7 cells was found . The suppressive rates were 52% and 93% at 24 and 48 hours after transfection respectively.(4)The growth rate of MCF-7 cells began to decline after transfecting with c-myc siRNA 24 hours later . The growth rate of MCF-7 cells was suppressed markedly at 24 and 48 hours after transfection ,and the suppression rates were 23.6% and 35.6% respectively .(5)The apoptosis rates of MCF-7 cells were 28.85±0.65%,51.2±0.52%and 80.8±1.32% at 24,48 ,72hours after transfection respectively,and were significantly higher than those in the blank control (p<0.05, <0.05and <0.05 respectively).(6)The expression levels of c-myc target gene( such as DHFR,hTERT,ODC,cdc25a,cad,HMG-I/Y,C/EBPa,p53,cyclinD1and cyclinD2 ) in MCF-7 cells were also decreased when the c-myc expression was suppressed by siRNA.Conclusions: (1)Lipofectamine^TM2000 transfected siRNA for c-myc gene into...