Dll4 overexpression in tumor cells inhibits tumor growth. Weight of Dll4 and control BL41 tumors removed 3 weeks (A) and 6 weeks (B) after subcutaneous injection of BL41 tumor cells in NOD/SCID mice. Weight of Dll4 and control MOPC315 tumors removed 12 days after subcutaneous injection of MOPC315 tumor cells in BALB/c mice (C). Solid bars represent individual tumor weights and striped bars represent group means plus or minus SEM (A,B: n = 10; C: n = 13).