MNNG/HOS CL#5 xenografts were established, treated, and monitored as described in Materials and Methods (n = 7/group). A. The growth curves of osteosarcoma xenografts under ZD6474 treatment. Data points represent an average from 7 mice (Bars, SD). A significant dose-dependent reduction of tumor volume was observed (**p < 0.01, two-way ANOVA). B. Tumor weights of xenografts after ZD6474 treatment (**p < 0.01, one-way ANOVA). C. The growth curves of osteosarcoma xenografts under ZD6474 or/and celecoxib treatment. Growth of tumors was significant slower in the ZD6474 and celecoxib combination treatment group than those in the control, ZD6474 or celecoxib single treatment groups (**p < 0.01, two-way ANOVA). D. Tumor weight of xenografts after ZD6474 or/and celecoxib treatment (**p < 0.01, one-way ANOVA). E. Picture of resected xenografts. F. TUNEL assays. The percentages of apoptotic cells (with green fluorescence) were presented as average ± SD (Left) (**p < 0.01, one-way ANOVA), and the representative pictures (×200) were displayed (Right).