| Ojective:To discuss the effectiveness and scientific in nude mice bearing SW480 tumor treated with Iodine-125 brachytherapy.Methods:Taked the male nude mice of BLAB/c-nu/nu inoculated with human colon adenocarcinoma(SW480) cell as animal model. To be implanted iodine-125 seeds,the animal were divided into two groups (n=24), control groups and experiment group then randomly divided into 4 groups again (n=6).control group:to be implanted empty seeds, without iodine-125 radioelement(OmCi); experiment group:to be implanted iodine-125 seeds (0.4mCi),We observe the condition of tumor growth after implanted iodine-125. we killed 6 nude mice of each group in 7th,14th,21th,28th day after implantation, then we tested these implanted tumors by flow cytometer, transmission electron microscopy immunohistochemical and TUNEL respectively. Results:With the accumulation of radiation time, the tumor cells cycle in experiment group was blocked in G2/M phase.we can observe the early-mid-late period cell apoptosis in the experiment group by TEM,rare cell apoptosis were found in the control group. PCNA in the experiment group was significantly lower expression than it in corresponding control group after 1st week.(P＜0.05). TUNEL was used to detect apoptosis in situ. After the second week, the apoptosis index in the experiment group were significantly higher than the control group.Conclusions:1.one of the important biological mechanism to restrain the colon adenocarcinoma (SW480)is the iodine-125 seeds continuous low-dose radiationwas to block the cell cycle in G2/M phase and the proliferating cell nuclear antigen was inhibited.2. The continuous radiation in a low-doses with the iodine-125 seeds could induced cell apoptotic and exist the relationship of time-effect.
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