Search

Evidence indicates that cyclooxygenase (COX)-2-derived prostaglandins (PGs) contribute to tumor growth by inducing angiogenesis. We investigated the role of COX-2 in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). COX-2 and vascular endothelial growth factor (VEGF) expressions were examined by immunohistochemistry in 24 HBV-associated HCC. Tumor micro-vessel density (MVD) was assessed using CD34 immunohistochemistry. Hep3B HCC cell line, which carries integrated HBV genome, was stably transfected with human COX-2 cDNA. COX-2 and VEGF expressions were determined by Western blot while PG level was determined by ELISA. The effects of PGs on VEGF expression were also investigated. Expression of COX-2 and VEGF in HCC cells were observed in 19 (79%) and 16 (67%) cases, respectively. Well-differentiated HCC expressed COX-2 more strongly than less-differentiated HCC (p

Evidence indicates that cyclooxygenase (COX)-2-derived prostaglandins (PGs) contribute to tumor growth by inducing angiogenesis. We investigated the role of COX-2 in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). COX-2 and vascular endothelial growth factor (VEGF) expressions were examined by immunohistochemistry in 24 HBV-associated HCC. Tumor micro-vessel density (MVD) was assessed using CD34 immunohistochemistry. Hep3B HCC cell line, which carries integrated HBV genome, was stably transfected with human COX-2 cDNA. COX-2 and VEGF expressions were determined by Western blot while PG level was determined by ELISA. The effects of PGs on VEGF expression were also investigated. Expression of COX-2 and VEGF in HCC cells were observed in 19 (79%) and 16 (67%) cases, respectively. Well-differentiated HCC expressed COX-2 more strongly than less-differentiated HCC (p0.001). COX-2 expression was found to correlate with VEGF expression and MVD (p=0.003 and 0.004, respectively). COX-2 overexpressing Hep3B clone had higher VEGF expression as compared to non-COX-2 expressing clone and parental cells. Treatment of the COX-2 overexpressing cells with a COX-2-selective inhibitor, NS-398 (10 microM), decreased PGE2 level and attenuated VEGF expression. Addition of PGE2 (10 microM) and the stable analog of PGI2, carbaprostacyclin (5 microM), to Hep3B cells also increased VEGF expression. Up-regulation of COX-2 correlates with VEGF expression and tumor angiogenesis in HBV-associated HCC. Moreover, COX-2 up-regulates VEGF expression in HCC cells, possibly via PGs production. Selective inhibition of COX-2 may block HCC associated angiogenesis and thus provides a rational approach for treatment of this malignancy.

Although gastric cancer with cyclooxygenase (COX)-2 overexpression is associated with poor prognosis, the mechanistic pathway remains unknown. We examined the associations between expressions of COX-2 and vascular endothelial growth factor (VEGF) in both gastric cancer cells and in human gastric cancer. The gastric cell line, Kato III, was transiently transfected with cox-2 expressing vector. The levels of COX-2, prostaglandin (PG) E 2 and VEGF expression were measured post-transfection. Additionally, expressions of COX-2 and VEGF in human gastric cancer were determined by immunohistochemistry in archive gastrectomy specimens. Tumor angiogenesis was assessed by the microvessel density (MVD), which was determined by anti-CD34 immunostaining. Transient transfection of Kato III with cox-2 was associated with increased COX-2 expression, higher PGE 2 production and upregulated VEGF expressions. Treatment with NS398, a specific COX-2 inhibitor, reduced VEGF expression in COX-2 expressing Kato III cells by 25%. Among the 67 gastric cancers examined, COX-2 overexpression was found in 45 (67%) cases whereas increased VEGF expression was detected in 46 (69%) cases. There was a significant association between COX-2 and VEGF expressions in gastric cancer (r=0.25, p=0.041). Additionally, tumor MVD was associated with both COX-2 (r=0.32, p=0.008) and VEGF (r=0.39, p=0.001) expressions. Our results showed that overexpression of COX-2 in both gastric cells and primary gastric cancer is associated with upregulation of VEGF and angiogenesis. Future studies should evaluate the potential anti-angiogenic effect of COX-2 inhibitors on human gastric cancer.

Although gastric cancer with cyclooxygenase (COX)-2 overexpression is associated with poor prognosis, the mechanistic pathway remains unknown. We examined the associations between expressions of COX-2 and vascular endothelial growth factor (VEGF) in both gastric cancer cells and in human gastric cancer. The gastric cell line, Kato III, was transiently transfected with cox-2 expressing vector. The levels of COX-2, prostaglandin (PG) E2 and VEGF expression were measured post-transfection. Additionally, expressions of COX-2 and VEGF in human gastric cancer were determined by immunohistochemistry in archive gastrectomy specimens. Tumor angiogenesis was assessed by the microvessel density (MVD), which was determined by anti-CD34 immunostaining. Transient transfection of Kato III with cox-2 was associated with increased COX-2 expression, higher PGE2 production and upregulated VEGF expressions. Treatment with NS398, a specific COX-2 inhibitor, reduced VEGF expression in COX-2 expressing Kato III cells by 25%. Among the 67 gastric cancers examined, COX-2 overexpression was found in 45 (67%) cases whereas increased VEGF expression was detected in 46 (69%) cases. There was a significant association between COX-2 and VEGF expressions in gastric cancer (r=0.25, p=0.041). Additionally, tumor MVD was associated with both COX-2 (r=0.32, p=0.008) and VEGF (r=0.39, p=0.001) expressions. Our results showed that overexpression of COX-2 in both gastric cells and primary gastric cancer is associated with upregulation of VEGF and angiogenesis. Future studies should evaluate the potential anti-angiogenic effect of COX-2 inhibitors on human gastric cancer.

Cyclooxygenase (COX-2) has been recently suggested to play a role in hepatocarcinogenesis. However, the exact pathway by which COX-2 affects the growth of hepatocellular carcinoma (HCC) is not clear. This study investigated the effects of a specific COX-2 inhibitor, NS-398, on the cell proliferation and apoptosis of COX-2-expressing and non-expressing HCC cell lines. In addition, the modulatory effect of NS-398 on apoptosis-regulating gene expression was examined. Semi-quantitative/quantitative reverse transcription-polymerase chain reaction and Western blot showed that Hep3B and HKCI-4 cells expressed COX-2 mRNA and protein, but HepG2 cells did not. NS-398 suppressed cell proliferation and induced apoptosis in the two COX-2-expressing cell lines in a dose-dependent manner, but not in HepG2 cells. Fas ligand mRNA and protein expression were increased by the treatment with NS-398 (10 micro M) in COX-2-expressing cell lines. The expressions of Fas and Bcl-2 family genes (Bax, Bcl-2, Bcl-xL, Bcl-xS) were not affected by NS-398 treatment in all three cell lines. In conclusion, specific COX-2 inhibitor suppresses cell proliferation and induces apoptosis in HCC cell lines that express COX-2. Our finding suggests that COX-2 inhibition may offer a new approach for HCC chemoprevention.

Cyclooxygenase (COX-2) has been recently suggested to play a role in hepatocarcinogenesis. However, the exact pathway by which COX-2 affects the growth of hepatocellular carcinoma (HCC) is not clear. This study investigated the effects of a specific COX-2 inhibitor, NS-398, on the cell proliferation and apoptosis of COX-2-expressing and non-expressing HCC cell lines. In addition, the modulatory effect of NS-398 on apoptosis-regulating gene expression was examined. Semi-quantitative/quantitative reverse transcription-polymerase chain reaction and Western blot showed that Hep3B and HKCI-4 cells expressed COX-2 mRNA and protein, but HepG2 cells did not. NS-398 suppressed cell proliferation and induced apoptosis in the two COX-2-expressing cell lines in a dose-dependent manner, but not in HepG2 cells. Fas ligand mRNA and protein expression were increased by the treatment with NS-398 (10 micro M) in COX-2-expressing cell lines. The expressions of Fas and Bcl-2 family genes (Bax, Bcl-2, Bcl-xL, Bcl-xS) were not affected by NS-398 treatment in all three cell lines. In conclusion, specific COX-2 inhibitor suppresses cell proliferation and induces apoptosis in HCC cell lines that express COX-2. Our finding suggests that COX-2 inhibition may offer a new approach for HCC chemoprevention.

Overexpression of cyclooxygenase-2 (COX-2) is associated with loss of apoptosis, enhancement of proliferation and tumorigenesis. The role of promoter methylation in the transcriptional silencing of cox-2 gene in human gastric cancer is less determined. We investigated 5 gastric cancer cell lines and 58 primary gastric carcinomas for the presence of promoter hypermethylation in cox-2 gene. Combined methylation-specific polymerase chain reaction analysis and bisulfite sequencing analysis revealed that the cox-2 promoter was methylated in 2 of the gastric cancer cell lines. Treatment with 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor, induced COX-2 expression in the methylated gastric cancer cell line. Among the 58 primary gastric cancers, hypermethylation was detected in 25 (43.1%) cases. However, none of the normal gastric tissues showed methylation in cox-2. Promoter hypermethylation was associated with loss of protein expression as determined by immunostaining (p=0.005). Our results indicate that hypermethylation of the CpG island in the cox-2 gene is a major mechanism that mediates transcriptional silencing in a subset of gastric cancers. Thus, gastric cancers with methylation in cox-2 may not be good candidates for treatment with specific COX-2 inhibitors.

Overexpression of cyclooxygenase-2 (COX-2) is associated with loss of apoptosis, enhancement of proliferation and tumorigenesis. The role of promoter methylation in the transcriptional silencing of cox-2 gene in human gastric cancer is less determined. We investigated 5 gastric cancer cell lines and 58 primary gastric carcinomas for the presence of promoter hypermethylation in cox-2 gene. Combined methylation-specific polymerase chain reaction analysis and bisulfite sequencing analysis revealed that the cox-2 promoter was methylated in 2 of the gastric cancer cell lines. Treatment with 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor, induced COX-2 expression in the methylated gastric cancer cell line. Among the 58 primary gastric cancers, hypermethylation was detected in 25 (43.1%) cases. However, none of the normal gastric tissues showed methylation in cox-2. Promoter hypermethylation was associated with loss of protein expression as determined by immunostaining (p=0.005). Our results indicate that hypermethylation of the CpG island in the cox-2 gene is a major mechanism that mediates transcriptional silencing in a subset of gastric cancers. Thus, gastric cancers with methylation in cox-2 may not be good candidates for treatment with specific COX-2 inhibitors.