Effecting of inhibiting ubiquitin-proteasome pathway on proliferation and apoptosis of gastric carcinoma cells

Objective To investigate the effects of inhibiting ubiquitin proteasome pathway(UPP) on proliferation of gastric carcinoma cells and the possible mechanism was discussed. Methods The gastric carcinoma cell strain SGC 7901 was treated with MG 132 to inhibit its UPP specially. The effect of growth suppression on cells was evaluated with MTT assay. Cell cycle and apoptosis were detected by flow cytometry(FCM). DNA fragment analysis was used for confirming the presence of apoptosis. The activity of telomerase was examined by TRAP PCR ELISA. Expression of p27kip1 was detected by immunocytochemical technique. Results MG 132 had great inhibitory effect on the growth of SGC 7901 cells. The FCM analysis showed that the ratio of G0/G1 phase of control group was (46.3±4.1)%, the ratio of G0/G1 phase of SGC 7901 cells treated with MG 132 increased to (72.1±5.0)% ( P 0.01) and obviously apoptotic sub G1 peak was noticed. Agarose electrophoresis showed marked ladder. TRAP PCR ELISA showed that light absorptions(value A ) of SGC 7901 cells treated with MG 132 after 24 h, 48h, 72 h and 96 h were 0.197 ± 0.007 , 0.081± 0.005, 0.074±0.004 and 0.063±0.002 respectively, light absorptions of control group were 1.801 ±0.048, 1.887±0.072, 2.047±0.085 and 2.131±0.076 respectively. The activity of telomerase was greatly inhibited ( P 0.01). Expression of p27kip1 was positive in plasma of SGC 7901 cells and it was positive in plasma and nuclei of cells treated with MG 132. Conclusions MG 132 can significantly inhibit proliferation of SGC 7901 cells and induce its apoptosis. The mechanisms may possibly relate to enhancing expression of p27kip1, G1 blocking and inhibiting the activity of telomerase.