Inhibition of endothelial cell growth by BMP6 in the AngioKit model. Immunostaining with monoclonal anti-CD31 antibody. (A) Shown are medium control (RPMI-1640), positive control (vascular endothelial growth factor), negative control (suramin) and BMP6 in concentrations of 4, 0.8, 0.16 and 0.032 μg/ml, respectively. Original magnification ×40. (B) Boxplot summarizing the CD31 ELISA results. BMP6 significantly inhibits tubule formation down to the level of the negative control.