AIM: To develop an in vitro intact cell-based assay for screening selective cyclooxygenase inhibitors. METHODS: Human cyclooxygenase-1 (hCOX-1) and cyclooxygenase-2 (hCOX-2) genes were cloned from human monocyte cell line THP-1 cells and expressed in Spodoptera frugiperda (sf9) insect cell line by Bac-to-Bac baculovirus expression systems. Infected sf9 cells were harvested 24 h post-infection (hpi), and distributed to a 24-well plate, preincubated with various nonsteroidal anti-inflammatory drugs, and challenged with 10 mmol/L arachidonic acid; the cyclooxygenase activity was assessed indirectly by prostaglandin E2-specific radioimmunoassay. RESULTS: Polymerase chain reaction detection demonstrated that hCOX-1 and hCOX-2 were transposed to the bacmid. Western blot analysis showed that infected sf9 cells could express hCOX-1 and hCOX-2 proteins. Radioimmunoassay demonstrated that both recombinant proteins functioned well in sf9 cells. CONCLUSION: Human cyclooxygenase-1 and cyclooxygenase-2 were successful AIM: To develop an in vitro intact cell-based assay for screening for selective cyclooxygenase inhibitors. METHODS: Human cyclooxygenase-1 (hCOX-1) and cyclooxygenase- 2 (hCOX-2) genes were cloned from human monocyte cell line THP-1 cells and expressed in Spodoptera frugiperda (sf9) insect cell line by Bac-to-Bac baculovirus expression systems. Infected sf9 cells were harvested for 24 h post-infection (hpi), and distributed to a 24-well plate, preincubated with various nonsteroidal anti- inflammatory drugs, and challenged with 10 mmol / L arachidonic acid; the cyclooxygenase activity was endogenous to prostaglandin E2-specific radioimmunoassay. RESULTS: Polymerase chain reaction detection demonstrated that hCOX-1 and hCOX-2 were transposed to the bacmid. showed that infected sf9 cells could express hCOX-1 and hCOX-2 proteins. Radioimmunoassay said that both recombinant proteins functioned well in sf9 cells. CONCLUSION: Human cyclooxygenase-1 and cyclooxygenas e-2 were successful