Abstract: Objective To explore the influence of bevacizumab（Avastin） on the growth and angiogenesis of RFP tagged osteosarcoma 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 Avastin 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. Immunohistochemical 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.