| Objective: The objectives of this study are to establish a reliable animal model of mouse-transplanted prostate cancer, observing volume of tumor and the life span of mice, then evaluate the therapeutic efficacy of low frequency transduction magnetic field and magnetic field combined with radiotherapy and explore the mechanism of action.Methods: Adult male C57BL/6 mice, year at 6-7 weeks and weight from 18g-22g, 64 in all. Establish a reliable animal model of mouse-transplanted establish a reliable animal model of mouse-transplanted prostate cancer used mouse's prostate cancer cells RM-1. The tumor-bearing mice were fixed to A the control group, B the radiotherapy group, C the magnetic field combined with radiotherapy group and D the magnetic field group at random. There were 16 mice in each group, 8 for observing the volume of tumor and the other 8 for observing the life span. We found the mice prostatic carcinoma subcutaneouly and began to treated when the average gross tumor volume exceed to 250±20mm3: The mice of group B and C were exposed to 15Gy X-ray once and next the mice of group C and D were exposed to the 0.45T low frequency transduction magnetic fields for 2h/d and last 5 ds. The control group were not be coped. We recorded the the volume of the tumors every day and the live days of each rat. After the treatment the 8 mice in each group for volume observing were sacrificed at the next day of the end of the treatment. We got the tumors out and then they were cut into 4mm and dealed after several procedures, including fixed in 4% formalin, dehydrated by different concentrations of ethanol and then embedded in paraffin. Parts of the slices were stained with hematoxylin and eosin to observe the cellular necrosis. We put about 100mg tissue in the alcohol of 70% for flow cytometry to detect the cell cycle and apoptosis of tumor. And the rest mice were kept on observing for life span.Results: 1 The volume of tumors: the group A was 2278.90±553.29 mm3, the group B was 1583.03±350.53mm3, the group C was 1317.56±451.54mm3, and the group D was 2168.99±477.03 mm3. The inhibiting rates of tumor growth: the group B is 30.54%, the group C was 42.18%, the group D was 4.82%. The volume of group B and group C compare with group A, P<0.05.The volume of group D compare with group A, P>0.05.2 The apoptosis and cells growth cycle of the tumors were detected by FCM. The rate of apoptosis were : 6.85±1.10% for group A; 20.29±2.21% for group B; 23.30±2.53% for group C; and 7.54±3.05% for group D; group B and C compare with group A, P<0.05; and the group D compare with group A, P>0.05. The cell population of G1/G0 and G2/M stage in group B and C were increased obviously, but the S stage were decreased. It shows that the G1/G0 and G2/M stage of cell cycle were blocked.It has statistical significance compare group B and C to group A, P<0.05, but no statistical significance between group D and A, P>0.05.3 From the result of mice life span in different groups, we can see that the average life span was 21.25±2.72d and median life span was 21d in group A, 28.75±3.85d and 29d in group B, 26.75±7.21d and 27d in group C and 20.25±3.54d and 20d in group D. It has statistical significance that group B and group C compare with A, P < 0.05. There was no statistical significance for group D compare with group A, P>0.05.Conclusion: We established a reliable animal model of mouse-transplanted prostate cancer successfully; Our findings indicate that the magnetic field has not influence the growth of the tumour and the life span of tumor-bearing mice; In the course of the magnetic field combining with radiotherapy in therapying the tumors, the magnetic field didn't enhance the radiosensitiveness of tumor. It is the guidance for us to make more trails on the type, frequency, intensity and action time of magnetic field. |
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