Abstract: Objective To observe the inhibitory effect of toosendanin on tumor growth in nude mice bearing ovarian cancer and its mechanism. Methods Nude mice were randomLy divided into groups, and ovarian cancer cells were transplanted for modeling. Cyclophosphamide 0.4mL/d (10g/L) was injected intraperitoneally in positive group. In the experimental groups 1, 2 and 3, toosendanin 1, 10 and 20 mg/kg were dissolved in 0.02 mL/g normal saline for intraperitoneal injection once a day for 15 days. The tumor volume, mass and HE staining results were compared after treatment. Apoptotic indexes were detected by TUNEL method. The expressions of P53, Bax, Bcl-2 and caspase-9 were detected by RT-PCR. The expressions of P53, Bax, Bcl-2 and caspase-9 were detected by Western-blot method. Results Tumor volume and mass were the highest in the model group (P < 0.05), and apoptotic index was the lowest (P < 0.05). Tumor tissue in the model group had high cell density, disordered arrangement, hyperchromatic nuclei and obvious atypia. In experiment 1, 2, positive group and experiment 3 group, the cells were loosely arranged, the size of tumor cells was different, the nuclei were light stained and the nucleoli were small. Flake necrosis and apoptotic cells could be found in the tumors. The differences in the expression of Bax, Bcl-2 and caspase-9 and the expression of p-P53/P53 were statistically significant (P < 0.05). The differences between the experimental group and the positive group were similar, and the differences between the other two groups were statistically significant (P < 0.05). Conclusion Toosendanin can inhibit the growth of ovarian cancer in nude mice and promote the apoptosis of tumor cells.

Key words: Azadirachtin, Ovarian cancer, Tumor, Inhibition, Mechanism