Ubiquitin-
proteasome pathway (UPP) is the major system for the selective degradation of cellular
proteins that play key roles in cellular processes. Previous study indicated that
ubiquitin-
proteasome inhibitor MG-132 could inhibit growth of some
carcinoma. However, anti-
carcinoma mechanism of
MG-132 is unclear. Our objective was to investigate mechanisms of growth inhibitory effect of
MG-132 on gastric
carcinoma cells. Gastric
carcinoma cell SGC-7901 was treated with
ubiquitin-
proteasome inhibitor MG-132. Cell growth suppression was evaluated with 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium
bromide (MTT) assay.
DNA synthesis was evaluated by (3)H-thymidine ((3)H-TdR) incorporation. Activity of
telomerase was examined by telomeric repeat amplification protocol (TRAP) PCR-ELISA. Cell cycle and apoptosis were detected by flow cytometry (FCM).
DNA fragment analysis was used to confirm the presence of apoptosis. Expression of p27kip1 and
survivin was detected using the western blot method. After exposed to
MG-132, the growth and value of (3)H-TdR incorporation of gastric
carcinoma cells were obviously inhibited. TRAP PCR-ELISA showed that light absorption of cells gradually decreased after exposed to 5 microM of
MG-132 for 24, 48, 72 and 96 h (P < 0.01). The percentage of cells at G(0)/G(1) phase was increased and that at S and G(2)/M phase was decreased (P < 0.01). The ratio of apoptotic cells treated with 5 microM
MG-132 for 96 h was 53.7 +/- 6.4%.
Agarose electrophoresis showed marked ladders. Moreover, expression of p27kip1 of cells was increased and expression of
survivin was decreased. Our results suggest that
MG-132 inhibits
telomerase activity, induces apoptosis and G(1) arrest which is associated with upregulated p27kip1 expression and downregulated
survivin expression in gastric
carcinoma cells.