The methanol extract of Cirsium chanroenicum and the ethyl acetate eluted fraction inhibited cyclooxygenase-2 (COX-2)-mediated prostaglandin E2 (PGE2) and 5-lipoxygenase (5-LOX)-mediated leukotriene production in lipopolysaccharide-treated RAW 264.7 cells and in rat basophilic leukemia (RBL-1) cells treated with A23187calcium ionophore, respectively. Here, PTGS2 is linked to leukemia.