Bovine aortic endothelial cells (BAEC), established from the intima of bovine aorta as described , were maintained in DMEM supplemented with 5% calf serum, 100 U/ml penicillin, 100 μg/ml streptomycin, and 2 mM L-glutamine at 37° C in a humidified 10% CO2 chamber. JJ012 cell line and MPNST3 tumors given to us by the Singer lab at Memorial Sloan Kettering Cancer Center cells were maintained in DMEM containing glucose (4.5 g/L), glutamine (2 mM), penicillin (50 U/ml), and streptomycin (100 mg/ml) supplemented with 10% fetal bovine serum in a humidified 5% CO2 chamber.