Reduced vascular perfusion in tumors overexpressing Dll4. CD31 immunostaining, lectin perfusion, and nuclear staining of DII4-overexpressing and control BL41 and MOPC315 tumors (A). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in mice bearing Dll4 or control BL41 tumors: (B) Representative images showing tumor enhancement (blue = lowest, red = highest) and contrast kinetics (red line = arterial input; white line = k_ep, green line = K^trans) of forward blood-plasma transfer to the tumor extravascular space (K^trans) and reverse plasma transfer from the tumor extravascular space to the blood (k_ep); (C) Quantification of K^trans and k_ep from DCE-MRI. Bars represent the mean plus or minus SEM (n = 3).