(A) Wild type mice injected s.c. with B16 tumor cells mixed with Gr1+CD11b+ cells enriched from tumor-bearing Ceacam1−/− mice (Ceacam1−/− +B16) or WT mice (C57BL/6+B16) or B16 alone (B16 control). Data represent mean ± SEM, *0.01< P ≤0.05, *** P ≤ 0.001 (n=6 mice per group from three independent experiments). (B) Blood vessels in tumors were counted from mice in (A) after 17 days. More than 8 fields of view were analyzed. Data represent mean ± SEM. **0.001< P ≤ 0.01, ***P ≤ 0.001. (C) Immunohistochemistry staining (anti-CD31 antibody) of mouse B16 tumor tissue collected from mice in (A) after 17 days. (D) Gr1+CD11b+ cells were depleted by anti-Gr1 Ab, and compared to untreated animals. Data represent mean ± SEM. *0.01< P ≤0.05, **0.001< P ≤ 0.01, NS (no significance) (n=8 mice per group from two independent experiments). (E) Frozen tumor tissue harvested after 17 days were stained with anti-CD31 antibody. Data represent mean ± SEM. ***P ≤ 0.001. (F) Immunohistochemistry staining (anti-CD31) of mouse B16 tumor tissue collected from mice in (D) after 17 days of treatment with anti-CD31 antibody. Bar = 200µm.