Objectives and methods : Previous mechanistic studies suggest the cyclooxygenase-2 (COX-2) inhibitors represent the good candidates against tumor progression. MeOH extract of the stem barks of Euonymus alatus induced the strong inhibition of COX-2. A phenolic compound responsible for the anti- COX-2 known to involve in tumor adhesion and invasion has been studied through the methanol extracts. The compound, rosmarinic acid (ROS-A) was an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid. ROS-A showed a strong inhibitory effect of COX-2 activity in a concentration-dependent manner. Then we have measured the IL-1${eta}$, IL-6 and TNF-${alpha}$ production related the immune regulation, induction of inflammatory related genes. Results and Conclusions :Hep3B cells produce proinflammatory cytokines of IL-1${eta}$, IL-6 and TNF-${alpha}$ while ROS A inhibited the cytokines production. Since IL-1${eta}$, IL-6 and TNF-${alpha}$ need the transcription factors such as nuclear factor- ${kappa}$B (NF-${kappa}$B) and activated protein-1 (AP-1), we measured the transcription factors. ROS-A inhibited the activation of p65, p50, c-Rel subunits of NF-${kappa}$B and AP-1 transcription factors. These findings indicate that ROS A from the stem bark of E. alatus inhibits proliferation in metastatic cancer cells. It was suggested that stem barks of E. alatus could be suitable for anti-cancer drugs.