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Cyclooxygenase-2 ( COX-2) plays an important role in the carcinogenesis and progression of gastric cancer. It has been demonstrated that COX-2 overexpression depends on different cellular pathways, involving both transcriptional and post-transcriptional regulation. Micro RNAs (mi RNAs) are small, noncoding RNAs that function as post-transcriptional regulators. Here, we characterize miR-101 expression and its role in the regulation of COX-2 expression, which in turn, will provide us with additional insights into the potential therapeutic benefits of exogenous mi R-101 for treatment of gastric cancer. Our results showed that mi R-101 levels in gastric cancer tissues were significantly lower than those in the matched normal tissue ( P < 0.01). Furthermore, lower levels of mi R-101 were associated with increased tumor invasion and lymph node metastasis ( P < 0.05). We also found an inverse correlation between mi R-101 and COX-2 expression in both gastric cancer specimens and cell lines. Significant decreases in COX-2 mRNA and COX-2 levels were observed in the pre-mi R-101-infected gastric cancer cells. One possible mechanism of interaction is that mi R-101 inhibited COX-2 expression by directly binding to the 3′- UTR of COX-2 m RNA. Overexpression of mi R-101 in gastric cancer cell lines also inhibited cell proliferation and induced apoptosis in vitro, as well as inhibiting tumor growth in vivo. These results collectively indicate that mi R-101 may function as a tumor suppressor in gastric cancer, with COX-2 as a direct target. [ABSTRACT FROM AUTHOR]

Objective: To investigate the regulative roles of the gastrin receptor antagonist proglumide and the specific cyclooxygenase (COX)-2 inhibitor NS-398 on the proliferation and apoptosis of gastric cancer cells., Methods: Human gastric cancer cells of the line MKN-45 were routinely cultured in RPMI-1640 medium supplemented with 10% heat-inactivated fetal calf serum. Subconfluent cell cultures were treated with proglumide at a final concentration of 5 mmol/L, NS-398 at a final concentration of 10.0 micromol/L, or proglumide in combination with NS-398 for 48 h. The growth and proliferation of MKN-45 cells were analyzed with MTT assay. Flow cytometric analysis was used to detect the apoptosis of the gastric cancer cells. RT-PCR and Western blotting were used to detect the expression of apoptosis-inhibited gene bcl-2 mRNA and protein., Results: The apoptosis rates of the cells treated by proglumide, NS-398, and combination of two agents were 24.7% +/- 3.2%, 26.7% +/- 3.4%, and 36.1% +/- 4.6% respectively, all significantly higher than that in the control group (1.6% +/- 0.6%, all P < 0.01). The apoptosis rates of the MKN-45 cells treated with proglumide combined with NS-398 was significantly greater than those of the cells treated by the two agents alone (both P < 0.05). Treatment with proglumide and NS-398 significantly reduced the bcl-2 mRNA and protein expression in the MKN-45 cells (P < 0.05)., Conclusion: Both proglumide and NS-398 inhibit the proliferation and induce the apoptosis of human gastric cells. This apoptosis may be mediated by down-regulation of the expression of apoptosis-inhibited gene bcl-2. Co-treatment with proglumide and NS-398 have synergistic anticancer role.

Objective: To investigate COX-2 expression in patients with gastric cancer and its relationship with angiogenesis and clinicopathologic features of gastric cancer., Methods: COX-2 expression and CD34-stained microvessel density (MVD) were detected by immunohistochemical methods in specimens from 96 patients with gastric cancer. The correlations among COX-2 expression, MVD and clinicopathologic features were analyzed., Results: The COX-2 positive rate and MVD in gastric cancer were significantly higher than those in the normal gastric mucosa (80.2% vs. 13.3%; 32.5+/- 8.3 vs. 13.1+/- 2.4, all P< 0.01). The COX-2 positive rate and MVD in the patients with stage III and IV were significantly higher (91.4% and 34.9+/- 8.7 respectively, P< 0.01), than that in the patients with stage I and II. The COX-2 positive rate and MVD in the cases with lymph node metastasis were 87.9% and (35.0+/- 8.5) respectively, higher than those in the cases without lymph node metastasis (P< 0.05). The Spearman rank correlation test showed a significant correlation between COX-2 expression and tumor MVD (r=0.311, P< 0.01)., Conclusions: COX-2 plays an important role in gastric cancer angiogenesis. COX-2 and angiogenesis induced by COX-2 contribute to tumor invasion and lymph node metastasis.