RESUMO
Objective To observe the effect of DNA methyltransferase 1 (DNMT1 ) gene silencing by RNA interfering technology on the proliferation and apoptosis of HeLa cells. Methods Recombinant plasmid pshRNA-DNMT1-A, B and C were respectively transfected into HeLa cells by lipofectamine 2000, while cells transfected plasmid vector pSilencer3.1-HI and cells untreated as control groups. RT-PCR was adopted to select the recombinant plasmid which showed the most optimal inhibition effect. RT-PCR and western blotting was used to detected the mRNA and protein expression of DNMT1 in HeLa cells transfected for 24, 48 and 72 hours. Cell counting kit-8 (CCK-8 ) assay was used to investigate the proliferation of the HeLa cells after transfection, while apoptosis was detected by flowcytometry(FCM ) method. Results Three DNMT1-targeted short hairpin RNA (shRNA) A,B and C were successfully inserted into the plasmid vector PShRNA, and the coding sequences of the obtained shRNA were consistent with the designed fragments. The results indicated that both recombinant plasmid pshRNA-DNMT1-A and B could effectively knock down the expression of DNMT1 gene in human cervical cancer cells, of which pshRNA-DNMTI-B was the better choice. While no effect of pshRNA-DNMTI-C was seen. BT-PCR results showed that the relative mRNA expression of DNMT1 gene in Helm cells transfected with pshRNA-DNMT1 for 24, 48 and 72 hours were 0.406±0.057,0.191±0.036 and 0.104±0.015, which were significantly lower than that in Helm cells transfected by empty vector and non-transfected cells (0.520±0.020, 0.537±0.041, respectively, P ＜ 0.05 ). The western blotting analysis manifested that the relative expression of DNMT1 protein of Helm cells transfected by pshRNA-DNMT1 for 24, 48 and 72 hours were 0.197±0.024, 0.075±0.015, 0.040± 0.013, which were significantly lower than that in transfected cells by empty vector and non-transfected cells (0.273±0.010, 0.283±0.016, respectively, P ＜0.05). The CCK-8 results showed that the cell survival rates of HeLa cells transfected by pshRNA-DNMT1 for 24, 48, 72, 96 and 120 hours were 70.8%, 64.8%, 51.6%, 45.3% and 38.0%, there were statistically different compared with cells transfected by empty vector and non-transfected cells at different time-points (P ＜ 0.01 ). The results of FCM indicated that the apoptesis rate of HeLa cells trandected with pshRNA-DNMTI for 24, 48 and 72 hours were (17.7± 1.3 ) %, (35.3±1.3 ) %, (47.6±1.6 ) %, which were significantly higher than empty vector transfected cells and non-transfected cells [(4.9±0.5 ) %, (5.1±0.7 ) %, respectively, P ＜ 0.05]. Conclusions DNMT1 can be successfully silenced by RNA interfering in cervical Helm cells. Downregulation of DNMT1 can inhibit cervical cancer cells proliferation and induce cell apoptosis.