Objective To detect the expression of Mcl-1 gene in gastric cancer cell lines SGC7901 and MGC-803, and to screen the most effective Mcl-1-targeted siRNA sequence. Methods Mcl-1 expression was evaluated in human gastric cancer cell lines SGC7901 and MGC-803 by RT-PCR. Four segments of siRNAs (siRNA1, siRNA2, siRNA3 and siRNA4) targeting Mcl-1 mRNA and a no-sense control segment were designed by bioinformatic technology . Mcl-1 specific siRNAs were transfected transiently into SGC7901 and MGC-803 cells by using lipofectamine 2000 . After transfected 24 , 48 and 72 h , quantitative real-time PCR was applied to detect the mRNA expression of Mcl-1 and western-blot analysis was applied to detect the protein expression. Results Mcl-1 gene was expressed in both SGC7901 and MGC-803 cells. Overall, siRNA1 exhibited the best inhibitory effect after being transfected for 48h. The inhibition rate of mRNA level in SGC7901 group and MGC-803 group was 73.8%and 67.6%, and the inhibition rate of protein level in SGC7901 group and MGC-803 group was 79.3%and 96.1%. Conclusion Mcl-1 specific siRNA sequences were successfully designed, and siRNA1 was selected as the most effective sequence, which can simultanandeously inhibit the expression of Mcl-1 in GC7901 and MGC-803 cells.

Objective To investigate the effect of inhibiting Mcl-1 gene expression on the biological behavior of gas-tric cancer cell MGC-803 by using a small interference RNA (siRNA). Methods Synthesized siRNA targeting Mcl-1(Mcl-1 siRNA group) was transfected into MGC-803 cells. On the other hand, MGC-803 cells transfected with negative siRNA (Mcl-1siRNA-NC group), MGC-803 cells transfected with Lipofectamine 2000(liposomes control group)and vacant MGC-803 cells(blank control group)were used as controls. Proliferation of MGC-803 cells after transfection of Mcl-1 siRNA was investigated by MTT assay. After 48 h transfection of Mcl-1 siRNA, flow cytometry (FCM) was used to examine the apoptosis cells and cell cycle in all four groups. Polycarbonate membrane transwell chamber was used for evaluating the invasion and migration of the cell line. Results The absorbance of MGC-803 cells decreased greatly after transfected with Mcl-1siRNA for 24、48 and 72 h compared to those in control groups (P＜0.05);After transfected 48 h, apoptosis rate in Mcl-1siRNA group was higher than in the blank control group, liposomes control group and Mcl-1siRNA-NC group (%:19.61 ± 1.66 vs 3.69±0.37 vs 3.54±0.47 vs 3.68±0.55,F=12.230, P＜0.05),G0/G1 [(41.03±1.86)%] and G2/M phase ratio [(1.80± 0.46)%] in Mcl-1 siRNA group were lower than in the three control groups, S phase ratio [(57.17±1.72)%] in siRNA group was higher than in three control groups (P＜0.05). The number of transmembrane cells in Mcl-1 siRNA group in polycarbonate mem-brane transwell chamber experiment (42.00 ± 4.00,76.33 ± 3.51 respectively) were less than in blank control group (79.33 ± 3.51,108.00 ± 3.61 respectively), liposome control group (74.67 ± 2.52,110.67 ± 4.04 respectively) and negative control group (77.33 ± 3.06,109.33 ± 4.51 respectively). However, there was no significant difference in above index among the control groups. Conclusion Inhibitiing Mcl-1 expression can effectively suppress growth, invasion and migration, but promote apoptosis in gastric cancer cells.