In vivo antitumor activity of the ephrinB2-specific scFvs on BxPC3 xenograft. (A) Groups of SCID mice (n = 10) bearing BxPC3 tumors were treated intravenously with either B11 or 2B1 at a total dose of 20 mg/kg or with an equal volume of PBS in alternating days starting when tumors were macroscopically noticeable. Tumor volumes were measured with calipers about twice a week and mean tumor volume was represented versus time for each group. Bars correspond to SD (*P < .001, **P < .01 versus PBS control). (B) BxPC3 tumor tissues excised on day 2 after treatments from mice injected with either PBS or 2B1 or B11 as indicated, were stained with H&E or by IHC using Abs anti-caspase 3–active to assess apoptosis (brown, apoptotic cells; magnification, 200×), anti-Ki67 to assess proliferation (brown, proliferating cells; magnification, 200×), anti-CD34 to evaluate blood vessel density (brown, endothelial cells; magnification, 200×), and anti-LYVE-1 to measure lymphatic vessel density (brown, lymphatic endothelial cells; magnification, 200×). Representative examples of tumor sections in each experimental condition are shown in the photographs. Results are shown as the percentages of the positive cells or areas relative to the total number of cells or areas quantified with the AxioVison software. Each data point is derived from 3 tumors and corresponds to the mean ± SD. *P < .001, **P > .01 versus PBS control. (C) Higher magnifications of CD34-positive blood vessels from BxPC3-bearing mice treated with PBS (left panel) or B11 (right panel). Arrowheads point to filopodial protrusions in untreated tumor vessels.