Objective To study the efficacy of RNA interference targeting 5-LOX on 5-LOX and VEGF expression as well as the growth of tumor xenografts in the nude mice,in order to evaluate the value of the clinical application.Methods SW1990 cells were injected into the back of BALB/c nude mice.Once the visible tumors were evidenced about 100mm3,the animals were divided randomly into 4 groups (6 animals/group) and treated with shRNA1 and shRNA2 targeting 5-LOX,negatrve control shRNA (shNC) or control LipofectamineTM 2000 (Lipo) by intratumoral injection.Observing the effect of the shRNA on the growth of tumor xenografts,investigating the expression of 5-LOX and VEGF by immunohistochemistry and RT-PCR.Results Two nude mice were dead in shNC group and Lipo group because of the wasting disease.Other nude mice had no changes in body weight,spirit,appetite,and activity.The growth of tumor xenografts was suppressed potently when administered with shRNA.Compared with shNC and Lipo group,the mean tumor size in groups treated with shRNA was reduced markedly at every point of test time.Between two treat groups,they did not have significant difference.5-LOX and VEGF were both expressed in the pancreatic cancer tissue.The level of the 5-LOX expression in shRNA groups was stronger than that in shNC or Lipo group.The VEGF had the game situation.Between the two treat groups,the difference was not significant.Conclusions RNA interference targeting 5-LOX can inhibit the growth of tumor tumor xenografts in the nude mice by depressing the expression of 5-LOX directly and depressing the expression of VEGF indirectly.