AIM:To explore the inhibitory action of recombinant human tumor necrosis factor-related apoptosis-inducing ligand(rhTRAIL) on mouse breast cancer. METHODS:Each mouse was inoculated 0.2 mL (1?106) D2F2 cells subcutaneously in the right lower limb and they were divided into five groups randomly. The control group was infused PBS 0.2 mL,while the low-dose,medium,high groups received purified rhTRAIL 2.5 mg/kg,5.0 mg/kg,10.0 mg/kg,respectively,the positive group was administered cyclophosphamide 30.0 mg/kg. Every group was operated by peritoneal injection once a day for fifteen days. The mice were weighed every day. The growth state was viewed and the size of the tumor was measured every 3 d to calculate the tumor volume and tumor suppression rate. All mice were killed after 15 d. The pathologic changes of the tumor were observed under light-microscopy and electronic microscopy. The cell cycle and apoptosis index of D2F2 cells were analyzed by flow cytometry. RESULTS:The body weight and tumor volume in low-dose,medium,high groups were lower than those in control group and the restriction effect was more significant than that in the control group (P