摘要Objective: To investigate the therapeutic effect and the related mechanism of oridonin on mice with prostate cancer. Methods: Sixty BALB/C male nude mice were selected. A model of RM-1 cell transplantation tumor of prostate cancer was built by the subcutaneous inoculation of RM-1 cells. After that, those 60 experimental mice were randomly divided into groups A, B and C. Each group had 20 mice. Mice in group A were treated with 0.2 mL of normal saline (0.9%) by intraperitoneal injection once a day; mice in group B received intraperitoneal injection of 1.875 mg/mL of oridonin once a day; and mice in group C received intraperitoneal injection of 7.5 mg/mL of oridonin once a day. Mice in the three groups were treated uninterruptedly for 5 weeks and were all killed. Then, tumors were excised and weighed to calculate their growth inhibitory rate, volume increment and anti-tumor rate. Thymus and spleen of mice in the three groups were collected to calculate the thymus and spleen index. Immunohistochemical staining was applied to observe the expression of caspase-3 in prostate cancer tissue of mice of the three groups. Results: The qualities and volume increment of tumors in groups B and C were significantly lower than those of group A (P < 0.05); the qualities and volume increment of tumors in groups C were evidently lower than those of group B (P < 0.05); the tumor volume increment and anti-tumor rate in group C were obviously higher than those of group B (P <0.05); the thymus and spleen indexes of groups B and C were distinctly higher than those of group A (P < 0.05); comparison of the thymus and spleen indexes between group B and group C showed no statistical differences (P > 0.05). Immumohistochemical staining revealed that the caspase-3 protein in prostate cancer tissue of mice of group A expressed negatively with colourless or light-colored karyon; while the caspase-3 protein in prostate cancer tissue of mice of group B expressed positively with dark-colored karyon, centralized distribution and granular sensation; and the caspase-3 in prostate cancer tissue of mice of group C showed strong positive expression with big and darker colored karyon and dense distribution. Conclusions:Oridonin can inhibit the growth of RM-1 prostate cancer cells effectively and have great therapeutic effects on RM-1 cell transplantation tumor of prostate cancer.