(A) MTT assay showed a decrease in EC metabolic activity, which oftentimes is linked to cell proliferation, after KDR knock-down (p<0.01), with no significant effect of FLT1 knock-down on metabolic activity. (B) In contrast, FLT1 ablation resulted in an increase in EC proliferation (p<0.01). Surprisingly, KDR knock-down did not affect EC proliferation. (C) A representative western blot showed that neither FLT1 or KDR ablation led to presence of cleaved caspase-3, a marker of apoptosis. There was also no effect of FLT1 or KDR knock-down on total caspase-3 expression (D).