Dep-1 inhibits proliferation, transmigration, and capillary-like tube formation of ECs. (A) EC migration of transfected HUVECs was assessed in a modified Boyden chamber assay in the presence of 50 ng/mL VEGF₁₆₅. Migrated cells were fixed, stained, and quantified by microscopic counting. Overexpression of DEP-1 significantly decreased EC migration toward VEGF₁₆₅ compared with mock-transfected cells. Data are mean ± SEM. **P < .01. (B) ³H-thymidine incorporation in HUVECs transfected with plasmids overexpressing either wild-type DEP-1, a mutant lacking phosphatase activity (C → S), or mock. After 24 hours of culture in full growth medium, ³H-thymidine (1 μCi/well) uptake of proliferating cells was measured (20 hours). Overexpression of DEP-1 significantly inhibited cell growth. Data are mean (cpm) ± SEM. **P < .01. (C) Capillary-like tube formation of HUVECs transfected with plasmids either overexpressing wild-type DEP-1, the C → S mutated form lacking phosphatase activity, or mock. Transfected cells were seeded on Matrigel in the presence of 1% FCS and analyzed 24 hours after seeding. Tubular-like structures were quantified as described in “In vitro Matrigel tube-formation assay.” DEP-1 inhibited capillary-like tube formation dependent on phosphatase activity. Data are mean ± SEM. *P < .05. **P < .01. DEP-1 indicates wild-type; and C → S, inactivated tyrosine phosphatase resulting from cysteine to serine mutation in the catalytic domain.