Effect Of 5-Aza-2'-deoxycytidine On Biological Behaviors Of Human Breast Cancer Cell Line MCF-7

AIM: To explore the effect of methylation inhibitor, 5-Aza-2'-deoxycytidine (5-Aza-CdR) on the growth,cell cycle and expression of RASSF1AmRNA of human breast cancer MCF-7 cells, in order to investigate the mechanism and to provide principle of its application in clinically treating breast cancer.METHODS: Human breast cancer MCF-7 cells were treated with 0.4, 1.6, 6.4, 25.6,and 102.4μmol/L 5-Aza-CdR, respectively. Then the growth of the cells were observed by MTT assay.The cell cycle and apoptosis were analyzed by flow cytometry. The expression of the tumor suppressor gene RASSF1AmRNA was detected by reverse transcription polymerase chain reaction (RT-PCR).RESULTS: After 5-Aza-CdR treatment, malignant degree and activeness of human breast cancer MCF-7 cells reducesed while response time and the concentration increased.Then the cells displayed early apoptosis and necrotized at a concentration of 102.4μmol/L. MTT assay showed after 0.4μmol/L 5-Aza-CdR treatment for 1 day, survival rate of breast cancer MCF-7 cells was 96.33±0.91%, while the survival rate was 88.03±0.45% and 82.93±3.33% respectively after treatment for 5 day or at a concentration of 102.4μmol/L.5-Aza-CdR inhibited the proliferation of human breast cancer MCF-7 cells in a time- and concentration-dependent manner(P<0.05).FCM with PI staining indicated the number of G0/G1 and human breast cancer MCF-7 cells treated with 5-Aza-CdR at a concentration of 6.4μmol/L for 3 days was increased significantly(P <0.05) while the number of S cells was decreased(P<0.05) compared to control group, and 5-Aza-CdR blocked the cell cycle at G0/G1 phase. Obviously, the apoptosis rate increased to 11.8±0.30% after treatment of 0.4μmol/L5-Aza-CdR while the apoptosis rate of control group was 6.5±0.10% (P <0.01).The effect above was in a concentration-dependent manner.RT-PCR demonstrate that RASSF1A gene was reactivated by 5-Aza-CdR in breast cancer cells not expressing RASSF1AmRNA.CONCLUSION: 5-Aza-CdR can inhibit the growth, blocked the cell cycle at G0/G1 phase ,and promote the apoptosis of human breast cancer MCF-7 cells by eliminating the methylation status of RASSF1A promoter.