The Effect Of ¹²⁵I Seeds Interstitial Brachytherapy For Transplanted Human Lung Adenocarcinoma In Nude Mice

Objective: The purpose of this study was to examine the effects of irradiation by I-125 seed in human lung cancer xenograft model and to determine underlying the mechanisms involved,with a focus on angiogenesis.We investigate 125I-induced cell apoptosis,suppressing proliferation and angiogenesis and the possible role of HIF-1? and VEGF in the process of ¹²⁵I brachytherapy in lung carcinoma.Methods: The 40 mice bearing A549 lung adenocarcinoma xenografts were randomly separated into 4 groups: control group?n = 10?,sham seed?0 MBq?implant group?n =10?,¹²⁵I seed?22.2 MBq?implant group?n = 10?and ¹²⁵I seed?29.6 MBq?implant group?n = 10?,respectively.¹²⁵I seed brachytherapy groups were respectively embeded by 18 G implant needle with different activities of ¹²⁵I seeds: 0,22.2 and 29.6 MBq.The body weight and tumor volume,were recorded every four days till the end of study.The tumor volume?V?was calculated by the following formula: V?mm3?=L×W2×1/2?L,length of tumor;W,width of tumor?.After 30 days of treatment,time courses of tumor growth was generated.All mice were humanely sacrificed,and tumors were harvested and weighed followed by fixed in 4% paraformaldehyde?PFA?or flash frozen on liquid nitrogen.Tumor sections were stained using H&E to investigate the histology of the xenografts.The microvessel density,proliferative index and apoptotic index were evaluated by quantitative morphometric analysis of the expression of CD34,proliferating cell nuclear antigen?Ki-67?and in situ terminal transferase-mediated fluorescein deoxyUTP nick end labeling?TUNEL?,respectively.The changes in the expression of hypoxia inducible factor-1??HIF-1??and vascular endothelial growth factor?VEGF?were assessed by real-time PCR and western blot analysis.Results:?1?After embedding of ¹²⁵I seeds,the tumor volums in 22.2 MBq group and29.6 MBq group were significantly smaller than that in control group at 4 time points on the 44 th,48th,52 th,54th days?all P<0.05?;no significant difference was found between 0MBq group and control group?P>0.05?;no significant difference was found between 22.2MBq group and 29.6 MBq group?P>0.05?.?2?The histological appearance of the tumors showed that in 0 MBq and control groups,the cancer cells were densely arranged with large darkly stained nuclei and obvious karyokinesis.Meanwhile,the cancer cells around the ¹²⁵I seed in 22.2 MBq group and 29.6 MBq group revealed broad necrosis after treatment.?3?We examined tumor cell apoptosis using the TUNEL assay.There was statistically significant difference in apoptotic indices between 22.2 MBq and 29.6 MBq groups and control group?P < 0.05,both?;The study can show that there are no significant difference was found between 0 MBq group and control group,and 22.2 MBq and 29.6 MBq groups?P>0.05,both?.?4?The proliferation indices were significantly decreased in 22.2 MBq group and 29.6 MBq group compared with control group?P < 0.05,both?.However,there was no significant difference in the proliferation indices between 0m Ci groupand control group?P>0.05?.The immunohistochemical CD34-positive staining demonstrated MVD in 22.2 MBq group and 29.6 MBq group were decreased significantly compared with that in the control group?all P<0.05?;no significant difference was found between 0 MBq group and control group?P>0.05?.no significant difference was found between 22.2 MBq group and 29.6 MBq group?P>0.05?.?5?The expression of VEGF and HIF-1? m RNA in 22.2 MBq group and 29.6 MBq group were significantly lower than that in the control group,and the difference was statically significant?all P<0.05?;no significant difference was found between 0 MBq group and control group?P>0.05?;no significant difference was found between 22.2 MBq group and 29.6 MBq group?P>0.05?.?6?VEGF and HIF-1? protein after ¹²⁵I seed brachytherapy were also decreased obviously in 22.2 MBq group and 29.6 MBq group when compared with control group,and the difference was statically significant?all P<0.05?;no significant difference was found between 0 MBq group and control group?P>0.05?;no significant difference was found between 22.2 MBq group and 29.6 MBq group?P>0.05?as well.Conclusions: Our study showed that ¹²⁵I seed radiation can elicit significant anticancer effects by inhibiting proliferation and inducing apoptosis in nude mice of the human lung adenocarcinoma xenografts.In the tumor microenvironment,reducing the levels of HIF-1? and VEGF induced by ¹²⁵I seed might be the underlying molecular mechanisms to inhibit angiogenesis,so as to exert anti-tumor effects.