AIM:To observe the expression of cyclooxygenase-2(COX-2)and to investigate the association between COX-2expression and infection with cytotoxic-associated gene A(cagA)positive strain Helicobacter pylori(Hp)in humangastric cancer,and subsequently to provide fresh ideas forthe early prevention of gastric cancer.METHODS:32 Specimens of gastric cancer andcorresponding adjacent normal gastric mucosa were obtainedfrom patients who had undergone surgical operations ofgastric cancer.All the samples including 1 case of stomachmalignant lymphoma and 31 cases of gastric adenocarcinomawere confirmed by pathology diagnosis.The expression ofCOX-2 in 32 specimens of gastric cancer and correspondingadjacent normal gastric mucosa was quantitativelydetermined and analyzed with Flow Cytometry,and the levelsof COX-2 protein were compared between specimens withcagA~+ Hp infection and those without cagA~+ Hp infection.The cagA gene in 32 specimens of gastric cancer wasdetected by polymerase chain reaction(PCR)method.RESULTS:Twenty-seven of 32(84 %)specimens of gastriccancer showed over-expression of COX-2,compared withthe adjacent normal gastric mucosa,cagA~+ gene weredetected from 19 specimens of gastric cancer,but not fromthe other 13 specimens.The levels of COX-2 protein in 19specimens of gastric cancer with cagA~ Hp infection(thenumber of positive cells was 73.82±18.2)were significantlyhigher than those in the 13 specimens without cagA~+ Hpinfection(the number of positive cells was 35.92±22.1).CONCLUSION:COX-2 is overexpressed in gastric cancerand cagA~+ Hp infection could up-regulate the expression ofCOX-2 in gastric cancer in human.There may also existanother way or channel to regulate the expression of COX-2 in gastric cancer in addition to cagA~+ Hp infection.Therefore,applying COX-2 selective inhibitors could be aneffective and promising way to prevent gastric cancer. AIM: To observe the expression of cyclooxygenase-2 (COX-2) and to investigate the association between COX-2 expression and infection with cytotoxic-associated gene A (cagA) positive strain Helicobacter pylori (Hp) in humangastric cancer, and subsequently to provide fresh ideas forthe early prevention of gastric cancer. METHODS: 32 Specimens of gastric cancer andcorresponding adjacent normal gastric mucosa were obtained from patients who had undergone surgical operations of gastric cancer. All the samples including 1 case of stomach malignant lymphoma and 31 cases of gastric adenocarcinomawere confirmed by pathology diagnosis. The expression of COX-2 in 32 specimens of gastric cancer and corresponding adjacent normal gastric mucosa was quantitatively determined and analyzed with Flow Cytometry, and the levels of COX-2 protein were compared between specimens with cagA ~ + Hp infection and those without cagA ~ + Hp infection The cagA gene in 32 specimens of gastric cancer wasdetected by polymerase chain reaction (P CR) method .RESULTS: Twenty-seven of 32 (84%) specimens of gastriccancer showed over-expression of COX-2, compared with the adjacent normal gastric mucosa, cagA ~ + gene weredetected from 19 specimens of gastric cancer, but not fromthe other 13 specimens. These levels of COX-2 protein in 19specimens of gastric cancer with cagA ~ Hp infection (then ofmber of positive cells was 73.82 ± 18.2) were significantlyhigher than those in the 13 specimens without cagA ~ + Hpinfection (the number of positive cells was 35.92 ± 22.1) .CONCLUSION: COX-2 is overexpressed in gastric cancers cagA ~ + Hp infection could up-regulate the expression of COX-2 in gastric cancer in human.There may also be existanother way or channel to regulate the expression of COX-2 in gastric cancer in addition to cagA ~ + Hp infection.Therefore, applying COX-2 selective inhibitors could be aneffective and promising way to prevent gastric cancer.