Study in the Relationship between Angiogenic Factor and Expression of Cyclooxygenase and Nitric Oxide Synthase in Gastric Cancer

ABSTRACT

PURPOSE: Secretion of angiogenic factors from tumor cells is know to play an important role in neo-vascularization and metastasis. However, which angiogenic factor is related with the formation of neo-vasculature in gastric carcinomas is not well known. This study was performed to observe changes in the expression of vascular endothelial growth factor (VEGF), cyclooxygenase (COX), and nitric- oxide synthase (NOS). METHODS: Expressions of VEGF, COX, and NOS in thirty specimens resected from patients with a gastric carcinoma were investigated using the western blot method. Cultured MKN28 gastric cancer cells were treated with 100 ng/ml VEGF, and changes in the expression of COX and NOS were examined. Changes in VEGF expression were also investigated after treatment of the cells with inhibitors of COX and NOS. RESULTS: Expressions of VEGF, COX, and eNOS were increased up to 10, 60, and 30%, respectively, in tumors compared to surrounding normal tissues. VEGF-positive tumors showed a higher expression of COX-2. Human recombinant VEGF induced the expression of COX-2, but not eNOS, in the cultured MKN28 cells. The increase in expression was blocked with actinomycin D, the VEGF antibody, and anti-VEGF peptide. VEGF-induced expression of COX-2 was also blocked by pretreatment of cells with aspirin and indomethacin, suggesting that these anti-inflammatory drugs inhibit VEGF. The expression of eNOS was decreased by indomethacin in VEGF-treated cells, but COX-2 expression was not affected by inhibitors of NO production, N-arginine methylester (NAME). However, the protein level of VEGF was increased by indomethacin and NAME. CONCLUSION: This study showed that COX-2 and eNOS in gastric carcinomas seem to play an important role in the production of VEGF and that their expressions may also be affected by VEGF.