To determine whether loss of either gene in endothelial cells affects the migration of tumor cells in this assay, primary lung iNOS null endothelial cells from global deletion animals, and VEGF-A conditional null (Gerber et al., 1999) primary lung endothelial cells (the latter treated ex vivo with cre recombinase-expressing virus, as above) were isolated. Here, NOS2 is linked to neoplasm.