GATA1 and breast carcinoma: Neutralization of secreted VEGF by a VEGF neutralizing antibody abolished the ability of the conditioned medium from GATA1-overexpressing breast cancer cells to increase HUVEC proliferation (Figure 2B and Supplementary Figure S2C, S2D), suggesting that GATA1-mediated enhancement of VEGF expression in the conditioned medium is responsible for HUVEC proliferation.