Objective To explore the influence of bevacizumab ( Avastin) on the growth and angiogenesis of RFP-tagged os-teosarcoma orthotopic nude mice model of human osteosarcoma. Methods Twenty-one nude mice inoculated with human osteosarcoma cell line 143-B-RFP were randomly divided into three groups:control group, low dose Avastin group ( Avastin-L) and high dose Avas-tin group ( Avastin-H) . Avastin-L group and Avastin-H group received continuous 0. 2ml injection of 2. 0mg/kg or 5. 0mg/kg Avastin twice a week for 3 weeks, while control group was given an equal volume of saline. The body weight was recorded every 3 days. The in situ tumor size was measured to calculate the volume and the tumor inhibition rate every 7 days by fluorescence imaging system. Immu-nohistochemical En Vision method was used to detect the expression of CD34 in tumor tissue to evaluate the microvessel density ( MVD) . The vascular endothelial growth factor ( VEGF) levels of plasma and tumor tissue were measured by ELISA method. Results No significant difference was observed on body weight and lung metastasis rate among 3 groups ( P>0. 05) . Compared with control group, there were higher tumor inhibition rate, and lower tumor volume, MVD and VEGF levels of plasma and tumor tissue in both Avastin-L group and Avastin-H group (P<0. 05).The improvement effect of the above indexes were stronger in Avastin-H group versus Avastin-L group ( P<0. 05) . Conclusion Avastin can inhibit the growth and angiogenesis of human osteosarcoma, and reduce the VEGF level without influences on lung metastasis.%目的：探讨贝伐单抗（ Avastin）对人骨肉瘤143-B裸鼠移植瘤模型生长和血管生成的影响。方法将成功建立的红色荧光蛋白标记的人骨肉瘤143-B 裸鼠原位种植模型随机分为3组：对照组（生理盐水）、低剂量贝伐单抗组（ Avastin-L，2．0mg/kg）和高剂量贝伐单抗组（ Avastin-H，5．0mg/kg），每组7只。贝伐单抗每次腹腔注射0．2ml，1周2次，持续3周；对照组给予等体积生理盐水。每隔3天记录各组体质量，每隔7天用荧光影像系统测量原位肿瘤大小并计算抑瘤率；采用免疫组化En Vision法检测各组肿瘤组织中的CD34表达并计算微血管密度（ MVD）；酶联免疫吸附法检测各组血浆和肿瘤组织的血管内皮生长因子（ VEGF）的水平。结果3组实验裸鼠体质量及肺部转移率的差异无统计学意义（ P＞0．05）；与对照组相比，Avastin-L组和Avastin-H组的肿瘤体积减小， MVD、血浆及肿瘤组织的 VEGF水平降低，差异均有统计学意义（ P＜0．05）；Avastin-H组对上述指标的改善程度优于Avastin-L组（ P＜0．05）。结论 Avastin对人骨肉瘤143-B肿瘤生长有抑制作用，同时可降低血管生成及VEGF水平，但对肺部转移无明显抑制作用。
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