Combination therapy of sDll4-Fc and sEphB4Alb inhibits RT2 tumor growth with greater efficacy than either molecule alone. A, Average tumor volumes developed by 13.5-week old RT2 male mice previously treated for 3.5 weeks with drug vehicle (PBS, i.p. 3×/wk, control group), sEphB4-Alb (10 mg/kg i.p., 3×/wk), sDll4-Fc (10 mg/kg i.p. 3×/wk), or combination of sEphB4-Alb and sDll4-Fc (10 mg/kg, i.p. 3×/wk for both). The results were obtained from two independent trials involved 6 animals per treatment group and per trial. B, Sections of tumors harvested at the end of the experiment mentioned in A were immunostained with PECAM (red) and DAPI (blue) as described in Fig. 1B. C. Sections of tumors harvested at the end of the experiment mentioned in A were stained as described in Fig. 1C. D, Tumor vessel functionality evaluated by lectin perfusion as described in Fig. 1D. Perfusion in normal pancreas tissue was also analyzed and shown on the bottom left. The data were analyzed using Mann-Whitney-Wilcoxon test. Error bars represent SEM. * P < 0.05 and ** P < 0.01 were considered significant and highly significant, respectively.